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MCAS Cell biology, mitosis, meiosis, fertilization
Different types of cells in the human body undergo mitosis at different rates. Which of the following statements best explains why skin cells frequently undergo mitosis?
A. Skin cells contain molecules of DNA.
B. Skin cells constantly need to be replaced or repaired.
C. Skin cells have large numbers of sensory nerve receptors.
D. Skin cells constantly need to produce antibodies to fight off infections.
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Mice with the same parents can have different traits. Which of the following
best explains how most of these differences occur?
A. Gametes join by binary fission.
B. Cells divide by asexual reproduction.
C. Genes assort independently during meiosis.
D. Spontaneous mutations occur during mitosis.
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Which of the following is always part of normal sexual reproduction?
A. The male produces gametes by mitosis.
B. An offspring looks identical to the parents at birth.
C. The female carries only one fertilized egg at a time.
D. An offspring receives half its chromosomes from each parent.
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Various MCAS questions may be related to bacteria.
a. Identify the process that bacteria cells use to reproduce.
b. Describe two similarities between the process that skin cells use for cell division and the process that you identified in part (a).
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2015 MCAS
The illustration below shows one chromosome pair in a zygote. The zygote was produced by sexual reproduction.
Assuming normal meiosis and fertilization occurred, which illustration shows the egg and sperm that produced this zygote?
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The diagram below shows a plant cell at a particular stage in the cell cycle. This stage occurs immediately after which cellular process?
A. crossing over
B. DNA replication
C. fertilization
D. mitosis
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2016 MCAS
Which of the following must occur before mitosis can begin?
A. DNA must be replicated in the nucleus.
B. RNA must move to the center of the nucleus.
C. Chromosomes must attach to the cell membrane.
D. Ribosomes must move to opposite sides of the cell.
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Each summer, up to 40% of the lobsters in a certain area lose one of their claws due to injury. By late fall, the missing claw usually begins to grow back. Which of the following describes the process by which lobsters grow new claws?
A. Lysosomes fuse together to recycle matter to build a new claw.
B. Mitotic cell division adds new cells to rebuild the lobster’s claw.
C. Facilitated diffusion moves body cells from the remaining claw to the new claw.
D. Cellular respiration creates nutrients to enlarge existing cells in the lobster’s claw.
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2014 MCAS
Sharks typically reproduce sexually. A particular female shark, however, gave birth in a zoo despite having no recent contact with a male shark.
a. Identify the type of cell division that produces eggs and sperm in animals such as sharks.
b. Describe what normally happens during fertilization in animals such as sharks. Be sure to identify the end product of fertilization.
Female sharks can store sperm after mating and then wait to fertilize their eggs.
Scientists investigated whether the female shark in the zoo did this.
c. Describe how DNA analysis can determine if the shark reproduced using stored sperm or if she reproduced asexually. Be sure to include the source(s) of DNA being analyzed and the results of the analysis in your answer.
d. Explain why sexual reproduction is important for the long-term survival of shark species.
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2016 MCAS open response question
The diagram below represents a plant cell with three structures labeled X, Y, and Z.
Plant cells and fungal cells have many of the same types of organelles. Structures X and Y are found in both plant cells and fungal cells. Structure Z is found in plant cells, but not in fungal cells.
a. Identify structure Y and describe its main function.
b. Identify structure Z and explain how plants use this structure to survive.
c. Explain how fungi can survive without structure Z
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Each summer, up to 40% of the lobsters in a certain area lose one of their claws due to injury. By late fall, the missing claw usually begins to grow back. Which of the following describes the process by which lobsters grow new claws?
A. Lysosomes fuse together to recycle matter to build a new claw.
B. Mitotic cell division adds new cells to rebuild the lobster’s claw.
C. Facilitated diffusion moves body cells from the remaining claw to the new claw.
D. Cellular respiration creates nutrients to enlarge existing cells in the
lobster’s claw.
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2017 MCAS
The diagram below shows a chloroplast and some of the components of the reactions that occur in chloroplasts.
Which of the following is a product of the reactions that take place in a chloroplast?
A. hydrogen gas B. nitrate C. oxygen gas D. protein
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In which of the following ways does the plasma membrane regulate the entry of molecules into a cell?
A. The membrane allows only certain molecules to move into the cell.
B. The membrane destroys most molecules so that they do not enter the cell.
C. The membrane changes only certain molecules into ions before they move into the cell.
D. The membrane allows most molecules to transfer energy to the cell without entering the cell.
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Many animals have either internal or external skeletons that provide support and structure. Which of the following parts of plant cells play a similar role?
A. cell membranes
B. cell walls
C. chloroplasts
D. cytoplasm
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Sample response: Sharks typically reproduce sexually.
Meaningless words in food science
4 meaningless words: toxin, natural, organic, and GMO
Archived for my students. From The Logic of Science, 8/16/2016
News articles and blog posts are often full of buzzwords that are heavy on emotional impact but light on substance, and for scientific topics such as nutrition, health, medicine, and agriculture, four of the most common buzzwords are “toxins,” “natural,” “organic,” and “GMO.”
These words are used prolifically and are typically stated with clear implications (“toxin” and “GMO” = bad; “natural” and “organic” = good).
The problem is that these words are poorly defined and constantly misused.
They are often used in a way that shifts them into the category of what are referred to as “weasel words,” meaning that their use gives the impression that the author said something concrete and meaningful, when in fact the statement was a null sentence that lacked any real substance.
“Toxins”
Our society seems to be obsessed with “toxins.” The internet is full of purveyors of woo selling everything from expensive fruit cleanses to “earthing” mats, all with the intended purpose of ridding your body of vaguely defined “toxins.”
The problem is simply that there is no such thing as a “toxin.” All matter is made of chemicals (excluding subatomic particles for a minute), and essentially all chemicals are safe at a low enough dose and toxic at a high enough dose (i.e., the dose makes the poison).
So there are toxic doses not toxic chemicals. Even water becomes lethally toxic at a high enough dose (Garigan and Ristedt 1999). So this idea that something is going to rid your body of “toxins” doesn’t make any sense, because the chemicals themselves are not “toxins,” and they only become toxic at a high enough dose.
Take formaldehyde, for example. I often hear people talk about it as a “toxin,” but the reality is that it is an inevitable bi-product of normal biological processes. So not only is it in many fruits and vegetables, but it is actually produced by your body! The chemical itself is not dangerous, but it can become dangerous at a high enough dose.
To be clear, I’m not saying that we shouldn’t pay attention to what we put into our bodies. Of course we should, but we need to evaluate chemicals based on the dose at which they become toxic, not simply based on whether or not they are present.
Addendum (16-Aug-16): “Toxin” does have an actual biological meaning in the context of chemicals that are released by microscopic organisms. These are often toxic to individual cells at incredibly low doses because a cell itself is so small. So when I talked about “toxins” in the post, I was referring to the notion that certain chemicals are automatically dangerous for you as an organism, rather than on a cell by cell basis.
“Natural”
The definition of “natural” seems obviously to be, “found in nature,” but that’s actually a lot more ambiguous and arbitrary than it sounds. First, let’s deal with why this definition is arbitrary, and the best way to explain that is by talking about chemical compounds.
Everything around you is made of chemicals (including you)
In chemistry, a compound is simply the combination of two or more different elements. So most of the things that are around you are in fact chemical compounds (there are several thousand compounds that make your body, for example).
Now, many people like to distinguish between “natural” and “synthetic” chemicals, where “natural” chemicals can be found in nature, while “synthetic” ones were produced in a lab, but that distinction is arbitrary. A chemical is a chemical, and on a molecular level, there is nothing that separates natural and synthetic chemicals.
All chemical compounds are made by stringing different elements together, and there is no inherent difference between nature stinging elements together and scientists stringing elements together. We can make acids in the lab and you can find acids in nature, we can make chemicals that are poisonous at anything but a low dose in the lab, and you can find chemicals that are poisonous at anything but a low dose in nature, etc.
The fact that something was synthesized in a lab doesn’t make it any more dangerous or any safer than a chemical that was found in nature.
Consider, for example, acetylsalicylic acid and salicylic acid. One of those is natural and the other is synthetic.
Can you tell which? No, and neither could a chemist. If you showed those two molecules to a chemist who had no prior information about those chemicals, there is no way they she could tell you which was natural and which was synthetic, because that distinction is arbitrary.
In all likelihood though, she would know which is which because these are two very well-known compounds. Salicylic acid is the compound in willow bark that gives it medicinal value, and acetylsalicylic acid is the synthetic version of it that we all know as aspirin.
Further, we switched to the synthetic version largely because straight salicylic acid has a lot of unpleasant side effects like gastrointestinal problems (Hedner and Everts 1997).
To be clear, aspirin has side effects as well (as do all chemicals), but they tend to be less severe, and the point is, once again, that simply being natural doesn’t automatically make something better. Indeed, asserting that something is better because it is natural is a logical fallacy known as an appeal to nature.
Moving beyond the arbitrariness of what is natural, the typical definition of “found in nature” doesn’t apply to some things that most people would intuitively think of as natural.
Take apples, for example. They’re natural, right? Not so much. The fruit that we know as an apple does not grow in nature. As I will talk about more later, essentially all of our crops have been modified by thousands of years of careful breeding, so, technically speaking, they aren’t natural.
The situation is even more problematic when we talk about actions rather than objects. People often say things like, “we should do X, because X is natural,” but what on earth does that mean?
Generally, I hear people say that it means what our ancestors did, but that raises the obvious question of how far back do we have to go for something to be natural? Are we talking about 200 years ago? 1,000 years ago? 10,000 years ago? etc. This definition is horribly ambiguous.
To get around this problem, some people say that natural actions are those that are found in the animal kingdom, but that is also an extremely problematic definition for a number of reasons.
First, how widespread does it need to be in the animal kingdom? Is it simply required to find one animal that does it? Further, there are lots of human actions that most people think of as natural, even though other animals don’t do them. For example, we cook our food. Does that making cooking unnatural?
Finally, this definition is fundamentally flawed because we are just highly evolved animals, so doesn’t that make everything that we do natural? Actually think about this for a second. I think that we can all agree that structures like bird nests and beaver dams are natural, but those are not structures that just form spontaneously in nature. Rather, they are carefully and deliberately constructed by an animal who uses materials to make them.
Nevertheless, if I make a wooden table, most people would agree that the table is unnatural, but how on earth is that any different from a beaver dam? The beaver is an animal that took materials found in nature and combined them to make a new structure, and I am an animal that took materials found in nature and combined them to make a new structure. What’s the difference?
Further, we can logically extend this to all human structures. When you get right down to it, all of the parts of a skyscraper came from nature, and there is no logical reason to say that a beaver combining sticks and mud to make a dam is natural but me combing two metals to make steel is unnatural. Again, the definition of natural is completely arbitrary and functionally meaningless.
“GMO”
GMO stands for “Genetically Modified Organism,” and you may think that this has a very clear and precise definition…but it really doesn’t. Before reading the rest of this, try to come up with a definition of it yourself, then see how that definition holds up.
The most general line of thought would be that a GMO is exactly what is says: “an organism whose genes have been altered,” but that definition is much too broad.
Every living organism has a genetic code that has been altered from its ancestral state by millions of years of evolution. If you really think about it, we are all just heavily modified cyanobacteria (cyanobacteria [or some similar organisms] where most likely the first living cells).
Now you may think that I am stretching things a bit here, and perhaps I am, but “nature” does all sorts of crazy things like hybridizing species (as plants do frequently) and even stealing the DNA from one organism and inserting it into the genetic code of another.
For example, at some point in the evolution of the sweet potato, it managed to modify its genetic code by inserting bacterial genes into its DNA. In other words, it is a transgenic species whose genetic code is a combination of the genes of several species. Shouldn’t that make it a GMO?
Further, this is not limited to sweet potatoes, because bacteria themselves are well known for their ability to incorporate the DNA of other species into their own genomes. So nature is constantly doing the types of things that most people would associate with GMOs, and foods like sweet potatoes really are transgenic species.
Nevertheless, you can try to qualify the term GMO by saying that GMOs are, “organisms that have been genetically modified by humans,” but that definition is also fraught with problems. Beyond the fact that it is totally arbitrary (see the “natural” section), it also would encompass all modern agriculture.
Those delicious fruits that you know as watermelons don’t exist in nature (at least not in their current form). Similarly, natural bananas are small and full of giant seeds, and wild corn does not produce those nice juicy husks that you slather in butter and salt. Both our livestock and crops have been genetically modified through years selective breeding, and they contain genetic codes that aren’t found in nature.
[All the “natural” corn we eat has been extensively genetically modified by thousands of years of artificial selection.]
At this point, people often try to add something about moving genes between species, but that just creates more problems. First, nature does that as well…
Second, that would also include lots of “non-GMO” crops such as pluots, plumcots, tangelos, etc. all of which are hybrids that used selective breeding to combine the DNA of two different species.
Given the problems with that definition, you might try defining a GMO as an organism that is “modified by humans via a method other than selective breeding,” but that definition includes mutation breeding, which is typically not considered to be a GMO.
This method uses chemicals or UV radiation to randomly mutate organisms’ DNA in order to produce new and useful traits (i.e., it makes genetic modifications via inducing mutations). However, this method typically does not receive the label “GMO,” and in some cases, even farms that label themselves as “organic” can us crops that were produced by this method.
This leaves us with the outrageous definition that a GMO is, “an organism whose DNA was modified by humans via a method other than selective breeding or mutation breeding,” but at that point we have tacked so many arbitrary qualifiers onto the term, that the term itself is essentially meaningless.
“Organic”
Finally, let’s talk about the term “organic.” This is perhaps the greatest marketing term ever coined, and the problem with it is not that a definition doesn’t exist, but rather that the definition is arbitrary and most people don’t use it correctly (to be clear, I am talking specifically about organic farming practices, not organic chemistry.)
Here is a question for you, true or false, organic farming doesn’t use pesticides?
Organic farmers absolutely use pesticides, and many of those pesticides are toxic at comparable doses to the pesticides used in traditional farming.
Indeed, organic pesticides have can harm wild species, pollute waterways, and do all of the other harmful things that traditional pesticides can do (Bahlai et al. 2010). In fact, one of the most common organic pesticides is “Bacillus thuringiensis (Bt) toxin,” which is the exact same chemical that GMO corn produces (i.e., Bt maize).
So one the one hand, organic farmers use Bt liberally, and on the other hand, they demonize corn that produces Bt. Are you starting to see why this is arbitrary ?
So if organic crops use potentially dangerous pesticides just as much as traditional crops, then what exactly does it take for a crop to be considered organic? Generally speaking, they have to be grown without synthetic pesticides (“natural” are fine) and without the use of GMOs (some countries place additional requirements like no petroleum-based fertilizers). …
Yet distinction between “natural” and “synthetic” chemicals is arbitrary and all chemicals are safe at a low dose and toxic at a high enough dose… and the term GMO is really arbitrary. So, since the definition of organic relies on those other terms, the “organic” label is itself arbitrary.
To put this another way, organic crops are not automatically healthier or more nutritious than traditional crops. Indeed, reviews of the literature have been unable to find consistent and compelling evidence that organic food is healthier (Smith-Spangler et al. 2012; Galgano et al. 2015).
Now, at this point, you may be thinking that organic crops aren’t healthier, but surely they are better for the environment. However, that is also a misnomer. Some practices that are typically associated with organic farming are better for the environment, but those practices are sometimes included in non-organic farming as well, and organic farming has serious drawbacks, such as the fact that it often uses far more land and resources than traditional farming (Tuomisto et al. 2012).
As a result, you can’t make a blanket statement like, “organic farming is better for the environment” because in many cases it isn’t.
The point is that simply saying that something is “organic” doesn’t actually tell you anything useful about how healthy it is or whether or not it was grown in a sustainable way.
Also see https://thelogicofscience.com/2015/11/16/the-real-frankenfoods/
Citations
Bahlai et al. 2010. Choosing organic pesticides over synthetic pesticides may not effectively mitigate environmental risk in soybeans. PLoS ONE 5:e11250.
Doucleff. 2015. Natural GMO? Sweet potato genetically modified 8,000 years ago. NPR: Food and Culture
Garigan and Ristedt 1999. Death from hyponatremia as a result of acute water intoxication in an Army basic trainee. Military Medicine 164:234–238.
Galgano et al. 2015. Conventional and organic foods: A comparison focused on animal products. Cogent Food and Agriculture 2: 1142818.
Hedner and Everts 1997. The early clinical history of salicylates in rheumatology and pain. Clinical Rheumatology 17:17–25.
Ruishalme. 2015. Natural assumptions. Thoughtscapism.com. Accessed 15-Aug-16
Smith-Spangler et al. 2012. Are organic foods safer or healthier than conventional alternatives? A systematic review. Annals of Internal Medicine 157:348–366.
Tuomisto et al. 2012. Does organic farming reduce environmental impacts? A meta-analysis. Journal of Environmental Management, 112:309–320.
Wilcox. 2011. Mythbusting 101: Organic farming > conventional agriculture. Scientific American.
Related articles
Meaningless words in food science
Nutrients
Organic food and farming
Meaningless words in food science
What we need to know about healthy diets
Healthy meal generator
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MCAS Anatomy and Physiology
Feb 2016 MCAS. Mature red blood cells in mammals contain the protein hemoglobin but do not contain a nucleus. The nucleus is lost as the red blood cell matures.
Which of the following can be concluded about mammalian red blood cells from this information?
A. The cells store their DNA in ribosomes.
B. The cells have no functionality once the nucleus is lost.
C. The cells divide by meiosis to produce more red blood cells.
D. The cells perform transcription and translation before the nucleus is lost.
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Secretions from the pancreas contain compounds called lipases. Lipases increase the rate of digestion of lipids. Lipases are an example of which of the following?
A. enzymes
B. hormones
C. nucleic acids
D. simple sugars
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Each part of the human digestive system has a specific function. Which of the
following activities best models the role of the esophagus?
A. shaking a small piece of chalk in a plastic bottle
B. cutting a clay cube into smaller and smaller cubes
C. squeezing a small greased ball through plastic tubing
D. placing a small piece of egg in dilute hydrochloric acid
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Here are some problems associated with four organs of the human digestive system.
1 Acid inside this organ begins to dissolve some of its tissue lining.
2 An infection prevents the movement of nutrients through this organ’s walls into the bloodstream.
3 Inflamed tissue prevents the smooth passage of food through this organ
after swallowing.
4 Swelled-up veins make eliminating wastes from this organ difficult.
Which organ is most likely the stomach?
A. organ 1 . B. organ 2 C. organ 3 D. organ 4
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Feb 2016 MCAS: At high altitudes, air is less dense than at sea level because of decreased air pressure. This means that a person who ascends to high altitudes takes in fewer oxygen molecules per breath.
a. Describe and explain an immediate response that occurs in the respiratory system when a person first reaches high altitudes.
b. Describe and explain an immediate response that occurs in the circulatory system when a person first reaches high altitudes.
If a person lives at high altitudes for an extended period of time, other body responses occur. One response is an increase in the number of red blood cells.
c. Explain how this response is helpful to the body.
At high altitudes, air temperature is also generally colder than at sea level.
d. Describe and explain one internal body response that occurs when a person has been outside long enough for his core temperature to drop.
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The heart is part of the circulatory system.The heart is part of the circulatory system.
a. Describe the primary function of the heart.
Medical researchers are working on developing artificial hearts. Three of the many requirements for the design of an artificial heart are listed below.
• An artificial heart must connect to the pulmonary artery (artery connected to the lungs).
• An artificial heart must connect to the superior vena cava and inferior vena cava(large veins).
• An artificial heart must be able to function at different speeds when a person is exercising and is at rest.
b. Describe how each of the requirements listed above would help the body of an individual with an artificial heart function normally.
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In the human heart, a group of cells in the wall of the right atrium produces nerve impulses that stimulate cardiac muscle. What do these nerve impulses directly control?
A. the amount of oxygen in the blood
B. the release of platelets into the blood
C. the speed at which the heart pumps blood
D. the path blood takes when it leaves the heart
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Low blood pressure can be life-threatening. To help maintain a stable blood pressure, receptors in the heart detect changes in blood pressure. Information about blood pressure changes is then sent to the brain. If blood pressure is too low, the brain sends a message to the heart to beat faster. Based on this information, which of the following systems are directly involved in keeping blood pressure stable?
A. circulatory, muscular, nervous
B. circulatory, immune, skeletal
C. excretory, immune, muscular
D. excretory, nervous, skeletal
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When astronauts are in low-gravity environments, their bodies begin to release stored calcium. As a result, which of the following most likely occurs when an astronaut returns to Earth?
A. The risk of inflamed tendons increases.
B. The chance of breaking a bone increases.
C. The stomach’s level of functioning decreases.
D. The blood’s ability to carry oxygen decreases.
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During exercise, a person’s muscles need a constant supply of ATP. To meet this need, the rate of which of the following processes increases?
A. cellular respiration
B. mitosis
C. protein synthesis
D. transcription
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Feb 2016 MCAS. When astronauts are in low-gravity environments, their bodies begin to release stored calcium. As a result, which of the following most likely occurs when an astronaut returns to Earth?
A. The risk of inflamed tendons increases.
B. The chance of breaking a bone increases.
C. The stomach’s level of functioning decreases.
D. The blood’s ability to carry oxygen decreases.
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Feb 2016 MCAS. An altered form of the structural protein collagen causes a condition in which bones are weak and break easily. Which of the following are components of collagen?
A. amino acids . B. fatty acids . C. monosaccharides . D. nucleotides
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Secretions from the pancreas contain compounds called lipases. Lipases increase the rate of digestion of lipids. Lipases are an example of which of the following?
A. enzymes B. hormones C. nucleic acids D. simple sugars
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Feb Biology MCAS 2016
The axons of some vertebrate neurons are wrapped with special cells called Schwann cells, as shown below.
Which type of signal jumps from node to node between the Schwann cells to move down the axon?
A. a digital pulse B. a magnetic pulse
C. an electrical signal D. a glycoprotein signal
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Base your answers to questions 35 through 37 on the diagram below
and on your knowledge of biology.
35. The process represented in the diagram best illustrates
(1) cellular communication
(2) muscle contraction
(3) extraction of energy from nutrients
(4) waste disposal
36. Which statement best describes the diagram?
(1) Nerve cell X is releasing receptor molecules.
(2) Nerve cell Y is signaling nerve cell X.
(3) Nerve cell X is attaching to nerve cell Y.
(4) Nerve cell Y contains receptor molecules for substance A.
37. A drug is developed that, due to its molecular shape, blocks the action of substance A. Which shape would the drug molecule most likely resemble?
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Base your answers to questions 56 through 58 on the diagram below.
56 In region F, there is a space between nerve cells C and D.
Cell D is usually stimulated to respond by:
(1) a chemical produced by cell C moving to cell D
(2) the movement of a virus from cell C to cell D
(3) the flow of blood out of cell C to cell D
(4) the movement of material through a blood vessel that forms between cell C and cell D
57 If a stimulus is received by the cells at A, the cells at E will most likely use energy obtained from a reaction between
(1) fats and enzymes (3) glucose and oxygen
(2) ATP and pathogens (4) water and carbon dioxide
58 State one possible cause for the failure of muscle E to respond to a stimulus at A.
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A high respiratory rate usually indicates that a person’s body needs more
A. antibodies.
B. carbon dioxide.
C. oxygen.
D. platelets.
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The human skeletal system has many important functions, including movement. As a person ages, movement can become difficult. Ligaments become less elastic and cartilage is damaged.
a. Considering the function of ligaments, explain why less elastic ligaments could cause movement to be difficult.
b. Considering the function of cartilage, explain why damaged cartilage could cause movement to be difficult.
c. Identify two functions of the skeletal system besides movement.
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Which of the following structures transmits nerve impulses between the
brain and most motor and sensory neurons?
A. carotid artery
B. diaphragm
C. esophagus
D. spinal cord
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2009 MCAS
The hormones glucagon and insulin are produced by the pancreas and regulate the amount of glucose in the blood. Glucagon stimulates liver cells to release glucose into the blood, whereas insulin stimulates body cells to absorb glucose from the blood.
a. Describe and explain what will happen in the body to regulate the amount of glucose in the blood shortly after a person eats a sugary snack.
b. Describe and explain what will happen in the body to regulate the amount of glucose in the blood after a person has not eaten for several hours.
c. Discuss how your answers to parts (a) and (b) relate to the concept of homeostasis.
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Laboratory tests can be used to evaluate how well a person’s liver is working. One test measures how well the liver removes a substance called bilirubin from the blood. Based on this information, which of the following describes bilirubin?
A. an antibody
B. an energy source
C. a vitamin
D. a waste product
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Which of the following statements describes a function of the human brain?
A. It produces ATP for organs but not for muscles.
B. It controls voluntary actions but not involuntary actions.
C. It is responsible for removing toxic compounds from the blood.
D. It is the main center for sensory and motor processing in the body.
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In humans, the first seven pairs of rib bones are connected to the sternum (breastbone) by cartilage. Which of the following statements describes the main reason why cartilage is important in these bone-to-bone connections?
A. The cartilage keeps the bones from touching the heart.
B. The cartilage pulls on the ribs to draw air into the lungs.
C. The cartilage makes the rib cage flexible enough to expand during breathing.
D. The cartilage provides a location for the diaphragm muscle to attach to the lungs.
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The diagram below shows a system in the human body. Four parts of the system are
numbered.
Which of the following correctly identifies the four numbered parts?
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Growth hormone, estrogen, and thyroxine are some hormones secreted by endocrine glands. What is the role of these hormones?
A. to generate nerve impulses
B. to regulate body functions
C. to directly supply energy to cells
D. to directly remove toxins from the body
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2014 MCAS question on anatomy and homeostasis
The human body works to keep its blood glucose level within a narrow range. The hormones insulin and glucagon have important roles in this process: insulin decreases the blood glucose level, and glucagon increases the blood glucose level. Many different factors, including exercise, can affect a person’s blood glucose level.
a. Describe how a healthy person’s blood glucose level most likely changes after 45 minutes of intense exercise. Explain your answer.
b. Based on your answer to part (a), describe how a healthy person’s body responds to restore homeostasis with regard to blood glucose after exercising.
c. Describe another example of how exercise disrupts homeostasis in the body and how the body responds to restore homeostasis.
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MCAS Ecology
Feb 2016 MCAS: In the past, coyotes lived throughout the western prairies and central Rocky Mountains in North America. Over time, the coyotes’ range has expanded. Humans have tried trapping and hunting coyotes to decrease their numbers. However, biologists currently estimate the number of coyotes to be at an all-time high. Which of the following statements best explains why the number of coyotes continues to increase despite increases in death rates due to hunting and trapping?
A. Coyote lifespan is increasing, so only the oldest coyotes encounter hunters or trappers.
B. Coyote birth rates remain high, so more coyotes are added to the population than are removed.
C. Coyotes are migrating more often, so male coyotes have more fights over territories.
D. Coyotes have to compete with more species, so the coyote emigration rate has increased.
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Feb 2016 MCAS.
Here are the ecological roles of several organisms in a rainforest ecosystem.
fig tree – producer
jaguar – secondary consumer
mango tree – producer
monkey – primary consumer
toucan bird – primary consumer
a. In your Student Answer Booklet, draw a food web that includes all the organisms listed here. . Make sure the arrows represent the correct direction of energy flow.
Decomposers, such as bacteria, are not listed here:
b. Describe the role of decomposers in the rainforest ecosystem.
c. Describe what would most likely happen to producer populations and consumer populations if all decomposers in an ecosystem were removed. Explain your answer for each type of population.
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Spring 2017
The graph below shows the changes in the population size of a mammal
species introduced onto an isolated island in 1957.
Which of the following conclusions is best supported by the data?
A. Every year, more individuals were born than died.
B. A predator of this mammal was removed from the island in 1990.
C. The population decreases were the result of low immigration rates.
D. In the 1980s, the mammal’s population size stayed around its carrying capacity.
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The graph below shows changes that occurred in the size of a population of animals over a year.
Which of the following is best supported by the graph?
A. Between month 1 and month 5, the immigration rate was zero.
B. Between month 4 and month 6, a predator was introduced into the ecosystem and increased the death rate.
C. Between month 5 and month 7, the birth and emigration rates decreased and the death and immigration rates increased.
D. Between month 8 and month 12, the birth and immigration rates equaled the death and emigration rates.
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A female Hymenoepimecis wasp will temporarily paralyze a spider and then lay an egg on the spider’s abdomen. After the paralysis wears off, the spider resumes its normal activity. When the egg hatches, the larva grows by sucking its required nutrients from the spider. What type of relationship exists between the spider and the Hymenoepimecis wasp?
A. commensalism
B. mutualism
C. parasitism
D. predator-prey
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Spring 2017
A food web is shown below:
An organism in the food web is labeled X.
a. Identify and describe the ecological role of organism X in the food web.
b. Identify the organism in the food web whose population size would likely increase the
most if the bat became extinct. Explain your answer.
There are many types of relationships between organisms, including competitive and
predator-prey relationships.
c. Identify two organisms in the food web that have a competitive relationship. Explain your answer.
d. Identify two organisms in the food web that have a predator-prey relationship. Explain your answer.
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Which of the following statements best explains why introduced species often threaten native species in an ecosystem?
A. Introduced species often have less genetic diversity than native species.
B. Introduced species often lack natural predators in their new environment.
C. Introduced species often form mutualistic relationships with native species.
D. Introduced species often cause short-term droughts in their new environment.
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Spring 2017
Red lionfish have been introduced into the Caribbean Sea and the Gulf of Mexico. The red lionfish are predators that compete with native fish for space and food, causing coral reef fish population sizes to decrease. Government and environmental groups are encouraging coastal communities to catch red lionfish and serve them at restaurants.
Which of the following best explains how catching and eating red lionfish could help preserve coral reefs?
A. Reef fish will learn that red lionfish are no longer dangerous.
B. Red lionfish will return to their native habitats to avoid being caught.
C. Humans will fill the role of predator and control the red lionfish population.
D. Restaurants that serve red lionfish will attract more tourists to visit coral reefs.
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Approximately 250 million years ago, over 90% of species living in the oceans became extinct. Which of the following conditions most likely contributed to this mass extinction?
A. changes in global climate
B. evolution of new parasite species
C. mutation of species’ DNA sequences
D. increases in the rates of photosynthesis
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Biologists studied a population of lizards. They found that small lizards had trouble defending their territories and that large lizards were more likely than small or medium lizards to be preyed upon by owls. Which of the following graphs represents the most likely distribution for body size in this lizard population?
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MCAS 2014 Open Response
The Elk Mortality graph shows changes in elk mortality with wolves present and without
wolves present.
a. Summarize what the Elk Mortality graph shows about elk mortality from November to April with wolves present and without wolves present.
Based on these data, scientists can estimate the size of scavenger populations through the winter. The graph below shows the size of a scavenger population with wolves present and without wolves present.
b. Explain the cause of these data patterns for the scavenger population.
c. Describe one way that the wolves’ effect on the elk population could benefit organisms other than scavengers in the ecosystem.
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In a certain population, the death rate is greater than the birth rate from year 1 to year 2, and the immigration rate equals the emigration rate. Which of the following graphs represents this information?
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Many individuals in wild animal populations die at a young age. Which of the following factors most directly limits lifespan and therefore has a large effect on a species’ population size?
A. low birth rate
B. low immigration rate
C. high prey numbers
D. high predator numbers
MCAS Bacteria Viruses and Fungi
Spring 2017 MCAS. Show all your work (diagrams, tables, or computations) in your Student Answer Booklet. If you do the work in your head, explain in writing how you did the work. Write your answer in the space provided in your Student Answer Booklet.
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A population of S. epidermidis decreases the population sizes of other types of bacteria on the skin.
a. Describe one way decreasing the population sizes of other bacteria on the skin helps the S. epidermidis population.
b. Identify the process that S. epidermidis cells use to reproduce.
c. Describe two similarities between the process that skin cells use for cell division and the process that you identified in part (b).
When S. epidermidis moves from the skin into the body, it behaves like an invasive species entering a new ecosystem.
d. Will the S. epidermidis population size decrease, increase, or stay the same after the bacteria enter the body? Using your knowledge of invasive species, explain your answer
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Spring 2017
Topics: Biochemistry, Protista, Classification
Diatoms are marine organisms with unique cell walls that contain the element silicon. Which of the following are two common elements found in the cells of diatoms?
A. aluminum and magnesium
B. helium and hydrogen
C. mercury and neon
D. nitrogen and phosphorus
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The human body contains diverse types of bacteria. Scientists estimate that the average healthy adult human body is home to at least 10,000 species of bacteria. In fact, there are about 10 times more bacterial cells than human cells in the human body.
Many bacterial populations are important to the normal functioning of human body systems. For example, some bacteria in the digestive system produce substances the human body cannot produce. These substances help the body break down and absorb nutrients. However, bacteria that help the human body in one location can cause serious illness if introduced to a different part of the body.
8. This bacteria, S. epidermidis, can sometimes infect wounds. The symptoms of the infection include swelling, pain, pus, skin that is warm to the touch, and redness at the
infection site. Based on the symptoms, which of these human body systems work together to restore homeostasis?
A. circulatory system and immune system
B. immune system and reproductive system
C. skeletal system and respiratory system
D. respiratory system and nervous system
9. Which of the following is a characteristic that distinguishes viruses from B. thetaiotaomicron and S. epidermidis?
A. Viruses lack mitochondria.
B. Viruses lack genetic material.
C. Viruses are unable to accumulate mutations.
D. Viruses are unable to reproduce outside of host cells.
10. Which of the following best explains how antibiotic resistance spreads through
some populations of S. epidermidis?
A. All S. epidermidis cells exposed to antibiotics respond by developing mutations.
B. Some S. epidermidis cells exposed to antibiotics survive and pass their genes on to their offspring.
C. Exposure to antibiotics causes S. epidermidis cells to learn simple behaviors that help the cells survive.
D. Exposure to antibiotics causes an increase in the respiration rate of S.epidermidis cells living on the skin.
11. Which of the following describes one way B.thetaiotaomicron helps in digestion?
A. It breaks down lipids into fatty acids.
B. It breaks down proteins into amino acids.
C. It breaks down polysaccharides into simpler sugars.
D. It breaks down nucleic acids into nitrogenous bases.
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Mini-essay question:
A population of S. epidermidis decreases the population sizes of other types of bacteria on the skin.
a. Describe one way decreasing the population sizes of other bacteria on the skin helps the S. epidermidis population.
b. Identify the process that S. epidermidis cells use to reproduce.
c. Describe two similarities between the process that skin cells use for cell division and the process that you identified in part (b).
When S. epidermidis moves from the skin into the body, it behaves like an invasive species entering a new ecosystem.
d. Will the S. epidermidis population size decrease, increase, or stay the same after the bacteria enter the body? Using your knowledge of invasive species, explain your answer.
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Feb 2016 MCAS. Medicines called antifungals are used to treat infections caused by fungi. One way antifungals work is by targeting cell parts that are present in fungal cells but not in human cells.
c. Identify one cell part other than a ribosome or a plasma membrane that human cells and fungal cells have in common.
d. Describe what would happen to a human cell if the cell part you identified in part (c) were affected by an antifungal. Explain your answer based on the function of the cell part.
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MCAS Biochemistry questions
Sample Questions
Feb 2016 Bio MCAS
ATP molecules in cells undergo a process called hydrolysis. The equation below represents this process.
ATP + H2O → ADP + Pi [ + energy ]
( Pi = inorganic phosphate)
What always happens within cells as a result of ATP hydrolysis?
A. Water is produced.
B. Chemical energy is released.
C. Phosphorus atoms are used up.
D. Carbohydrate building blocks are formed.
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An English doctor is given credit for developing the modern terrarium in the 1800s. The doctor kept some plants in a sealed glass jar containing soil and air. The plants survived in the sealed jar for four years. What two processes allowed the plants to cycle nutrients and survive in the sealed jar?
A. meiosis and fertilization
B. mutualism and commensalism
C. photosynthesis and cellular respiration
D. asexual reproduction and sexual reproduction
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Scientists use satellite data to produce images such as the one below, showing the density of plants across Earth’s different land areas. Scientists study these images to determine how plant density changes during a year. They can then use this information to help predict carbon dioxide concentrations in the atmosphere in different locations and at different times of the year.
Which of the following best explains why scientists can predict carbon dioxide concentrations from plant density data?
A. Plants add carbon dioxide to theatmosphere during germination.
B. Plants add carbon dioxide to the atmosphere during transpiration.
C. Plants remove carbon dioxide from the atmosphere during photosynthesis.
D. Plants remove carbon dioxide from the atmosphere during cellular respiration.
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Which of the following are mainly cycled through the processes of photosynthesis and cellular respiration?
A. carbon and sulfur
B. carbon and oxygen
C. nitrogen and sulfur
D. nitrogen and oxygen
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Some diseases decrease the activity of certain enzymes in the mitochondria of cells. Which of the following is the most direct result of this decreased enzyme activity?
A. The cells are not able to divide by mitosis.
B. The cells are not able to move water by diffusion.
C. The cells produce less ATP by cellular respiration.
D. The cells produce fewer sugars by photosynthesis.
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Feb 2017 MCAS.
Some bacteria produce cellulase, a substance that speeds up the breakdown
of cellulose in plant cell walls. Cellulase is an example of which of the following?
A. a carbohydrate B. an enzyme C. a hormone D. an organelle
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Feb 2017 MCAS. Protein pumps actively transport ions across a cell’s plasma membrane. What molecule directly supplies the energy required for this transport?
A. ATP B. cholesterol C. oxygen D. tRNA
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Spring 2017
Collagen is found in connective tissue throughout the human body. Collagen is made of three amino acid chains that are twisted around one another. Which of the following best explains why collagen is classified as a protein?
A. It is found in a tissue.
B. It is made up of amino acids.
C. It is made up of twisted chains.
D. It is found throughout the human body
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Spring 2017
Which of the following is a characteristic that distinguishes
viruses from B. thetaiotaomicron and S. epidermidis?
A. Viruses lack mitochondria.
B. Viruses lack genetic material.
C. Viruses are unable to accumulate mutations.
D. Viruses are unable to reproduce outside of host cells.
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Which of the following describes one way B. thetaiotaomicron helps in digestion?
A. It breaks down lipids into fatty acids.
B. It breaks down proteins into amino acids.
C. It breaks down polysaccharides into simpler sugars.
D. It breaks down nucleic acids into nitrogenous bases.
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A scientist is trying to determine how closely related two species of plants are. Which of the following would be most useful for the scientist to compare?
A. the root depths of the plants
B. the leaf structures of the plants
C. the genetic sequences of the plants
D. the nutrient requirements of the plants
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Spring 2017 . Which of the following best describes how enzymes affect chemical reactions?
A. They speed up the rate of reactions.
B. They change the reactants into ions.
C. They dissolve the products of
reactions.
D. They take the place of one of the
reactants.
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The diagram below shows a chloroplast and some of the components of the
reactions that occur in chloroplasts.
Which of the following is a product of the reactions that take place in a chloroplast?
A. hydrogen gas
B. nitrate
C. oxygen gas
D. protein
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In which of the following ways does the plasma membrane [lipid bilayer] regulate the entry of molecules into a cell?
A. The membrane allows only certain molecules to move into the cell.
B. The membrane destroys most molecules so that they do not enter the cell.
C. The membrane changes only certain molecules into ions before they move into the cell.
D. The membrane allows most molecules to transfer energy to the cell without entering the cell.
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Spring 2017
In a cell, a phosphate group is added to ADP to form ATP. Which of the
following best describes the importance of the formation of ATP?
A. It connects amino acids.
B. It provides energy for the cell.
C. It creates new polysaccharides.
D. It catalyzes chemical reactions.
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The energy that primary consumers use for metabolism and growth comes
directly from which of the following sources?
A. organic compounds synthesized by producers
B. organic compounds released by decomposers
C. organic compounds stored in carnivore tissues
D. organic compounds absorbed from the environment
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Which of the following statements describes a difference between
photosynthesis and cellular respiration in plants?
A. Photosynthesis occurs only during the day, whereas cellular respiration occurs only at night.
B. Photosynthesis involves only one reaction, whereas cellular respiration involves many steps.
C. Photosynthesis occurs only in cells containing chlorophyll, but cellular respiration occurs in all cells.
D. Photosynthesis converts light energy into chemical energy, but cellular respiration converts light energy into heat energy
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During the processes of respiration and photosynthesis in plant cells, what are the three primary elements that cycle between the mitochondria and chloroplasts?
A. carbon, iron, and sulfur
B. hydrogen, carbon, and oxygen
C. carbon, nitrogen, and phosphorus
D. hydrogen, oxygen, and potassium
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Which of the following happens when a phosphate-phosphate bond in an ATP molecule is broken?
A. Energy is released in a cell.
B. Light energy is absorbed in a plant cell.
C. Water is transported into an animal cell.
D. Lysosome contents are released in a cell.
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Some cell types contain thousands of mitochondria. These cells are likely
to use large amounts of which of the following?
A. ATP
B. carbon dioxide
C. DNA
D. nitrogen
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The table below provides information about the composition and function of four
important molecules in living organisms.
Which of the molecules in this table is a carbohydrate?
A. 1
B. 2
C. 3
D. 4
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Question 23 is an open-response question.
• BE SURE TO ANSWER AND LABEL ALL PARTS OF THE QUESTION.
• Show all your work (diagrams, tables, or computations) in your Student Answer Booklet. If you do the work in your head, explain in writing how you did the work. Write your answer to question 23 in the space provided in your Student Answer Booklet.
●23 Catalase is an enzyme that protects cells from damage by helping convert the toxin hydrogen peroxide (H O2 2) into water (H O2 ) and oxygen (O2). A student is investigating how different pH values and different temperatures affect catalase activity. The table below shows the student’s data.
a. Identify the test tube that most likely has physical conditions similar to the conditions in human cells. Explain your answer.
b. Describe how catalase activity changes as pH decreases. Use data from the table to support your answer.
c. Describe how catalase activity changes as temperature increases. Use data from the table to support your answer.
d. Explain why temperature affects catalase activity in the way you described in part (c)
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The body structure of a reef-building coral consists of a hard skeleton covering soft tissue. Which of the following elements is most common in the coral’s soft tissue?
A. carbon
B. chlorine
C. sodium
D. zinc
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The growth of most plants is limited by the amount of nitrogen available. Which of the following effects does low nitrogen availability most likely have on the carbon cycle?
A. More carbon dioxide is taken up by plants.
B. Carbon dioxide is trapped in the soil around plants.
C. Less carbon dioxide is removed from the atmosphere.
D. Carbon dioxide is converted to carbonates by bacteria.
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Which process do elk and other Yellowstone animals use to convert energy in their food into ATP?
A. cellular respiration
B. filtration
C. osmosis
D. photosynthesis
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Which of the following will most likely change when an enzyme is added to a reaction?
A. the pH of the reaction
B. the rate of the reaction
C. the products of the reaction
D. the temperature of the reaction
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Cellulose is a compound found in plants. It is made of a long
chain of molecules with ringed structures. The molecules contain
mostly carbon, hydrogen, and oxygen atoms in a ratio of approximately
1 carbon : 2 hydrogen : 1 oxygen.
To which category of biological molecules does cellulose belong?
A. carbohydrates
B. nucleic acids
C. phospholipids
D. proteins
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Some types of bacteria are able to perform photosynthesis. These bacteria must therefore contain which of the following in their membranes?
A. chlorophyll
B. glucose
C. mitochondria
D. ribosomes
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What directly supplies the energy needed to actively transport sodium ions across the plasma membrane of a cell?
A. ATP B. DNA C. enzyme D. lipids
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Photosynthesis is most likely to occur in which of the following cells?
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Many farm animals eat hay, which is made by cutting and drying plants such as ryegrass and timothy grass. Scientists analyzed the composition of hay after it was cut and again after it was dried. The amounts of which common biological elements would have decreased the most as the hay dried?
A. sulfur and calcium
B. phosphorus and zinc
C. oxygen and hydrogen
D. nitrogen and chlorine
MCAS Genetics questions
What is the genetic material in the
chromosomes of an animal’s cells?
A. DNA
B. glucosamine
C. RNA
D. transcriptase
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An enzyme moves along a strand of DNA and produces a new nucleic acid strand. Part of the new strand is shown below.
GUACUCGGCAAUUUCGCA
Which of the following cellular processes created the new strand?
A. active transport
B. crossing over
C. replication
D. transcription
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A mutation occurs in an individual, but the individual’s phenotype does not change. Which of the following statements describes what most likely occurred to produce this result?
A. The mutation deleted a portion of a coding section of the DNA.
B. The mutation caused a portion of a coding section of the DNA to repeat.
C. The mutation affected a nucleotide in the DNA, but the mutation did not affect the sequence of amino acids synthesized.
D. The mutation translocated a group of nucleotides in the DNA, but the mutation did not change the number of base pairs in the DNA.
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In rabbits, a single gene with two alleles codes for ear shape. Two rabbits, each with a homozygous genotype, are mated. The female rabbit has straight ears and
the male rabbit has floppy ears. All the offspring have straight ears. Which of the following conclusions about rabbit genetics is best supported by the results of the cross
A. Offspring rabbits receive alleles only from their mothers.
B. The allele for straight ears is dominant to the allele for floppy ears.
C. Alleles in female rabbits are always more dominant than alleles in male rabbits.
D. The allele for straight ears and the allele for floppy ears are on different chromosomes.
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Reading: People may be Rh-positive or Rh-negative for their blood types. Rh-positive individuals have Rh factors, or markers, on the surface of their red blood cells. Rh-negative individuals do not have these markers. Several genes code for Rh factors.
The D allele, which codes for one type of Rh marker, is responsible for the majority of Rh-positive phenotypes. Because of this, the D and d alleles are often used to describe Rh blood type inheritance.
Determining Rh blood type inheritance is especially important when an Rh-negative woman is pregnant. If the baby is Rh-positive, the woman is treated with a special medicine so she does not produce antibodies that attack the baby’s red blood cells.
Questions:
a. Using the given allele symbols, identify the genotype of an Rh-negative woman.
b. Draw Punnett squares to represent all the different crosses in which an Rh-negative woman could have an Rh-positive baby.
c. For each Punnett square you drew in part (b), determine the percent chance that the baby will be Rh-positive.
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Feb 2016 MCAS.
The stored information in DNA codes for which of the following?
A. proteins
B. simple sugars
C. mitochondria when energy is needed
D. large vacuoles when nutrients are abundant
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Feb 2016 MCAS.
A type of golden brown coat color in horses is called palomino. Several pairs of palomino horses are mated. The results of the crosses are here:
Coat Color – Percent of Offspring
palomino 50% reddish-brown 25% creamy white 25%
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Feb 2016 MCAS. Which of the following is the most likely inheritance pattern of coat color in horses?
A. complete dominance
B. incomplete dominance
C. polygenic inheritance
D. sex-linked inheritance
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Which of the following statements explains the importance of enzymes that check for and repair mistakes during DNA replication?
A. The enzymes replace the DNA with RNA.
B. The enzymes speed up the rate of RNA synthesis.
C. The enzymes remove many recessive gene copies from the nucleus.
D. The enzymes prevent many genetic mutations from being expressed.
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Feb 2016 MCAS. (42) Four boys have the same biological mother and father. What percentage of each boy’s chromosomes come from the mother?
A. 0% . B. 25% . C. 50% . D. 100%
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Feb 2017 MCAS. A red-eyed male fruit fly is crossed with a heterozygous red-eyed female fruit fly. The expected results for the cross are shown in the table below.
Which of the following describes this inheritance pattern and the allele that codes for red eye color in fruit flies?
A. The inheritance pattern is sex-linked, and the allele for red eye color is dominant.
B. The inheritance pattern is sex-linked, and the allele for red eye color is recessive.
C. The inheritance pattern is codominant, and the allele for red eye color masks the allele for white eye color.
D. The inheritance pattern is codominant, and the alleles for red eye color and
white eye color are expressed equally
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The diagram below represents a biological process involving DNA.
What process is represented?
A. fertilization . B. mutation . C. replication . D. translation
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Feb 2017. The bacterium E. coli is a model organism used by many scientists for genetic and biochemical research. Which of the following statements helps explain why E. coli is so frequently used for research?
A. It has a large nucleus and a long generation time.
B. It has hundreds of chromosomes and a long lifespan.
C. It has a simple cell structure and reproduces rapidly.
D. It has many kinds of organelles and reproduces sexually.
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Spring 2017 MCAS
In tigers, the allele for orange fur is dominant to the allele for white fur. If two heterozygous tigers mate and produce offspring, what is the probability of an individual offspring having white fur?
A. 0 . B. 1/4 . C. 1/2 . D. 1.0
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Spring 2017 MCAS
The diagram below represents structures and processes involved in protein synthesis in an animal cell. Four parts of the diagram are labeled W, X, Y, and Z.
Which part of the diagram represents transcription?
A. part W B. part X C. part Y D. part Z
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Spring 2017
A particular species of moth can have green or yellow scales on its wings. The scale color is controlled by a single gene with two alleles, the green allele and the yellow allele. When moths that are homozygous for green scales are mated with moths that are homozygous for yellow scales, 100% of the offspring have green scales. Based on this information, how do the alleles for scale color interact?
A. The green allele is dominant to the yellow allele.
B. The green allele is recessive to the yellow allele.
C. The green allele and the yellow allele are codominant.
D. The green allele and the yellow allele are incompletely dominant.
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Spring 2017
Lipids, carbohydrates, and DNA all exist in human cells as long molecular chains. Which of the following describes how DNA differs from lipids and carbohydrates?
A. Only DNA has carbon atoms.
B. Only DNA is found in the cytoplasm.
C. Only DNA is needed to create new cells.
D. Only DNA contains genetic information.
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Spring 2017
For a new liver cell to form, DNA replication is necessary because it ensures that the newly formed cell has which of the following?
A. two copies of the original cell’s DNA
B. an identical copy of the original cell’s DNA
C. a rearranged copy of the original cell’s DNA
D. only the best parts of the original cell’s DNA
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Spring 2017
A scientist is studying the inheritance of two genes, gene R and gene P, in dogs. Each gene is located on a different chromosome. Gene R has two alleles, R and r, and gene P has two alleles, P and p.
What are the expected probabilities for the genotypes of gametes produced by a dog with the genotype RrPp?
A. 50% Rr and 50% Pp
B. 50% RP and 50% rp
C. 50% Rp, 25% rP, and 25% rp
D. 25% RP, 25% Rp, 25% rP, and 25% rp
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Spring 2017
The diagram below shows a parent cell and the daughter cells that are produced
after the parent cell divides.
Which of the following best describes the daughter cells?
A. They are a result of transcription.
B. They are a result of binary fission.
C. They have half the number of lipids that the parent cell has.
D. They have half the number of chromosomes that the parent cell has.
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Spring 2017
In humans, an X-linked recessive allele (Xb) causes red-green colorblindness. Which of the following crosses could produce a female who is red-green colorblind?
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Spring 2017
Which of the following describes a mutation in a parent that could change the phenotype of its future offspring?
A. a mutation in the RNA of a skin cell
B. a mutation in the DNA of a liver cell
C. a mutation in the RNA of a brain cell
D. a mutation in the DNA of a sperm cell
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Spring 2017
The chromosomes of a human female are shown below. The chromosomes are
arranged in pairs. The 23rd pair, labeled XX, is the sex chromosomes.
Which of the following would the female normally pass on to her child?
A. all 46 of the chromosomes
B. 23 chromosomes, one from each pair
C. a random set of any 23 of the chromosomes
D. the first 11 chromosome pairs, plus one sex chromosome
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Spring 2017: These are open-response questions.
Instructions: Show all your work (diagrams, tables, or computations) in your Student Answer Booklet. If you do the work in your head, explain in writing how you did the work. Write your answer in the space provided in your Student Answer Booklet.
A certain genetic disorder is caused by a single base mutation in the DNA of a certain gene. The mutation changes the amino acid glutamate (Glu) to aspartate (Asp).
a. Identify the type of macromolecule (carbohydrate, lipid, nucleic acid, protein) that changes when Glu changes to Asp. Explain your answer.
A portion of the amino acid sequence that includes this mutation is shown below.
Val-Ser-Ala-Arg-Asp
The sample of DNA below is being analyzed to determine if a patient has the genetic disorder.
3’ CAA-TCG-CGG-TCT-CTT 5’
b. Determine the mRNA sequence from the patient’s DNA sequence.
c. Using the information in the codon table below, determine the amino acid sequence that is coded for by the mRNA sequence you determined in part (b).
d. Determine whether the patient has the genetic disorder. Explain your answer.
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A newly discovered gene has two alleles, A and a.
Scientists hypothesize that the alleles show incomplete dominance.
Which of the following statements provides evidence for incomplete dominance?
A. Analysis of the DNA shows that only males have genotype AA.
B. Individuals with genotype aa survive only a few days after birth.
C. Individuals with genotype AA and individuals with genotype Aa both have the same phenotype.
D. Crosses between two individuals with genotype Aa result in three different phenotypes among the offspring.
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A single gene with two alleles codes for the fruit color (red and yellow) of tomato plants. Two tomato plants heterozygous for fruit color are crossed. The table below shows the results of the cross. Based on the results, what is the most likely inheritance pattern of the alleles for fruit color?
A. The alleles for red color and for yellow color are polygenic.
B. The alleles for red color and for yellow color are codominant.
C. The allele for red color is recessive to the allele for yellow color.
D. The allele for red color is dominant to the allele for yellow color.
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In Labrador retrievers, the black fur allele (B) is dominant to the brown fur allele (b).
A black male dog and a brown female dog are mated and have a litter of eight puppies. Five puppies are black and three puppies are brown. What are the genotypes of the parent dogs?
A. BB and Bb
B. Bb and Bb
C. Bb and bb
D. BB and bb
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Based on the results of genetic crosses, Mendel concluded that the alleles for seed color and seed shape in pea plants assorted independently. Which of the following statements best explains why the alleles for each trait assorted independently in Mendel’s experiments?
A. The alleles were all recessive.
B. The alleles were all dominant.
C. The alleles were on separate chromosomes.
D. The alleles were inherited in a sex-linked manner.
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Scientists compared the DNA sequence of a gene in four mammals. A portion of the gene’s DNA sequence in each mammal is shown below.
Based on the sequence data, which of the mammals are most closely related to each other?
A. mammals 1 and 2
B. mammals 1 and 3
C. mammals 2 and 4
D. mammals 3 and 4
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2014 MCAS Open response question
The inheritance patterns for some traits in guinea pigs are listed in the table below.
a. Identify the phenotype of a guinea pig with the genotype HhBBrr.
b. Using allele symbols in the table above, identify the genotype of a guinea pig that is
recessive for hair length, heterozygous for hair color, and homozygous dominant for hair texture.
Suppose the guinea pigs from parts (a) and (b) are crossed.
c. Identify the percent of offspring that will have black hair. To support your answer, draw a Punnett square for the hair color trait.
d. Considering only hair length, identify the expected phenotype ratio of the offspring.
Draw a Punnett square to support your answer.
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Fat How it gets made and broken down
How does fat get made?
We eat to (a) have building materials for our cells, and (b) to get energy for chemical reactions in our cells.
Excess protein or carbohydrates get broken down, and rebuilt as fat molecules, usually triglycerides.
What happens to fat when it is broken down?
Eventually, broken down fat turns into CO2 and H2O. The H2O stays in your body as regular water, and excess water is removed by sweating and urination. The CO2 is removed as you exhale.
When you lose weight, where does it go? Turns out, most of it is exhaled.
Myth: Fat gets burned, and turned into “energy” or heat.
Reality: Fat is made of atoms. Those atoms get broken apart and rearranged into other molecules.
To lose weight, we must break triglycerides into smaller molecules. We need oxygen to do this. Part of this process is oxidation.
Doesn’t happen all in one step.
Some fats get converted to Aceryl-CoA and glycolysis intermediates, but even these will eventually break down int into CO2 and H2O.
When a triglyceride is oxidized the process consumes many molecules of oxygen while producing carbon dioxide (CO2) and water (H2O) as waste products.
So, for example, to burn 10 kilograms (22 lbs.) of fat, a person needs to inhale 29 kg (64 lbs.) of oxygen….
burning that fat will produce 28 kg (62 lbs.) of carbon dioxide and 11 kg (24 lbs.) of water.
“None of this biochemistry is new, but for unknown reasons it seems nobody has thought of performing these calculations before,” study authors Ruben Meerman and Andrew Brown of the University of New South Wales in Australia, said…. during weight loss, 84 percent of the fat that is lost turns into CO2 and leaves the body through the lungs, whereas the remaining 16 percent becomes water, according to the study.
“These results show that the lungs are the primary excretory organ for weight loss. The water formed may be excreted in the urine, feces, sweat, breath, tears or other bodily fluids, and is readily replenished,” the researchers said.
The calculations also show the frightening power of, for example, a small muffin over an hour of exercise: At rest, a person who weighs 154 pounds (70 kg) exhales just 8.9 mg of carbon with each breath. Even after an entire day, if this person only sits, sleeps, and does light activities, he or she exhales about 200 grams of carbon, the researchers calculated. A 100 g muffin can cover 20 percent of what was lost.
On the other hand, replacing one hour of rest with exercise such as jogging, removes an additional 40 g of carbon from the body, the researchers said. Even if one traces the fates of all the atoms in the body, the secret to weight loss remains the same: In order to lose weight, one needs to either eat less carbon or exercise more to remove extra carbon from the body.
– Exhaled Pounds: How Fat Leaves the Body, Bahar Gholipour, Live Science, 12/14
Reference: When somebody loses weight, where does the fat go?
BMJ 2014; 349 doi: https://doi.org/10.1136/bmj.g7257 (Published 16 December 2014)
Abstract: When somebody loses weight, where does the fat go?
Considering the soaring overweight and obesity rates and strong interest in this topic, there is surprising ignorance and confusion about the metabolic process of weight loss among the general public and health professionals alike. We encountered widespread misconceptions about how humans lose weight among general practitioners, dietitians, and personal trainers (fig 1⇓). Most people believed that fat is converted to energy or heat, which violates the law of conservation of mass. We suspect this misconception is caused by the “energy in/energy out” mantra and the focus on energy production in university biochemistry courses. Other misconceptions were that the metabolites of fat are excreted in the faeces or converted to muscle. We present a novel calculation to show how we “lose weight.”
Learning standards
Massachusetts Curriculum Frameworks: Biology
8.MS-PS1-1. Develop a model to describe that (a) atoms combine in a multitude of ways to produce pure substances which make up all of the living and nonliving things that we encounter, (b) atoms form molecules and compounds that range in size from two to thousands of atoms, and (c) mixtures are composed of different proportions of pure
substances.
HS-LS1-6. Construct an explanation based on evidence that organic molecules are primarily composed of six elements, where carbon, hydrogen, and oxygen atoms may combine with nitrogen, sulfur, and phosphorus to form monomers that can further combine to form large carbon-based macromolecules.
Clarification Statements:
• Monomers include amino acids, mono- and disaccharides, nucleotides, and fatty acids.
• Organic macromolecules include proteins, carbohydrates (polysaccharides), nucleic acids, and lipids.
Disciplinary Core Idea Progression Matrix: PS1.A Structure of matter
That matter is composed of atoms and molecules can be used to explain the properties of substances, diversity of materials, how mixtures will interact, states of matter, phase changes, and conservation of matter.
Evolutionary Origin of the Turtle Shell
This intro is lightly adapted from thelogicofscience.com
Many people mistakenly believe that there are two fundamentally different types of evolution: microevolution and macroevolution. They argue that microevolution does actually occur, but only produces small changes within a species or “kind” of animal.
For example, they’re okay with the concept that all finches evolved from a common ancestor, all crows evolved from a common ancestor, all ducks evolved from a common ancestor, etc.
However, they draw the line roughly at the taxonomic level of family (e.g., ducks are in the Anatidae family), and they argue that evolution beyond that level (what they call macroevolution) is impossible and has never and can never happen. Thus, they dismiss the notion that finches, crows, and ducks all share a common ancestor.
However, this distinction is completely arbitrary and meaningless: the exact same evolutionary mechanisms that caused the evolution of finch species could (and indeed did) cause the evolution of all birds. In other words, macroevolution is simply the accumulation of microevolutionary steps, and one inherently leads to the other.
Here is a visual explanation. The image below shows a hypothetical pathway through which turtles could have evolved from their lizard-like ancestors.
Several of these images are renderings of actual fossils: B6 = Milleretta, A15 = Eunotosaurus, C22 = Odontochelys, B30 = Proganochelys, D37 = Chelydra [modern turtles]; these are just screen shots from Dr. Tyler Lyson’s excellent video.
This full progression is, of course, what creationists would consider to be macroevolution, and creationists are adamant that today’s turtle families were uniquely created and did not evolve from a lizard-like ancestor. However, because they accept microevolution, most creationists would have no problem with any particular pair of images, and they would accept that A1 could evolve into B1, B1 could evolve into C1, etc.
In other words, each pair of images shows “microevolution” (which creationists almost universally accept), but when we string all of those steps together, we get “macroevolution” (which they say is impossible).
You can probably see where I am going with this, but just to be sure, I will state it explicitly. If you are going to say that macroevolution is impossible and turtles could not have evolved from lizard-like ancestors, then which step do you think is impossible?
Please show me which step could not have occurred, and justify that claim. Additionally, please explain the obvious transitional fossils.
Remember, B6, A15, C22, B30, and D37 are actual fossils, and they perfectly match the expectations for what a transitional fossil should look like (details here).
So, if turtles and their lizard like ancestors were uniquely created kinds, then at what point in this progression do lizard-like reptiles end and turtles begin?
Image from “Evolutionary Origin of the Turtle Shell” by Tyler Lyson
Step-by-step
And here is the amazing video
Continued from “The Logic of Science”
Some people will likely be inclined to ignore my questions and harp instead on the fact that this pathway is hypothetical, but that argument completely misses the point in several ways.
First, this pathway is only partially hypothetical because B6, A15, C22, B30, and D37 are actual fossils that we have found.
Additionally, of course the pathway is partially hypothetical. We will never find every single one of these steps, and we don’t need to:
Evolution is very much like the visible light spectrum. Each color gradually fades into the next color without a clear breaking point.
In other words, there is a point along the spectrum that is clearly red, and there is a point that is clearly blue, and there is a point that is clearly violet, but there is a spectrum of change in between those points – and it is not possible to pick an exact point where the blue ends and violet begins, just as you cannot pinpoint the exact step at which the reptile becomes a turtle as we know it.
Reference
Evolutionary Origin of the Turtle Shell, By Tyler R. Lyson, Gabe S. Bever, Torsten M. Scheyer, Allison Y. Hsiang, Jacques A. Gauthier
Current Biology, Published Online: May 30, 2013
DOI: https://doi.org/10.1016/j.cub.2013.05.003
Healthy diets
How to construct a healthy diet
Vegan sources of protein
Healthy plant-based diets – “A diet based on fruits, vegetables, tubers, whole grains, and legumes; and it excludes or minimizes meat (including chicken and fish), dairy products, and eggs, as well as highly refined foods like bleached flour, refined sugar, and oil.”
Forksoverknives.com/plant-based-primer-beginners-guide-starting-plant-based-diet
https://www.drmcdougall.com/forums/viewtopic.php?f=22&t=48602
Changes to the American diet over the last century
Old American diet
* Near the start of the 20th century, Americans each ate about 120 lbs if meat per year. By 2007, we ate about 222 lbs.
* About 1913, Americans ate about 40 lbs of processed sugar per person. By 1999, it had increased to 147 lbs per person.
* About 1909, Americans ate about 294 lbs of dairy products per person. By 2006, that number was over double…605 lbs of dairy per person!!
* This information came from the companion book to Forks Over Knives.
Write about health effects due to these changes
http://veggiesforme.com/2011/09/14/shocking-rate-of-increase-of-consumption-of-meat-dairy-and-sugar/
How lose weight and stay healthy
Plant-based diet
This is not the same as vegan or vegetarian!
Give meals flavor with spices, not fats, oils, or sugar.
Think of high calorie density foods (nuts, avocado, oils) as condiments. So can you have a slice of avocado on a bean and rice burrito? Sure! But don’t sit down with guacamole and a bag of corn chips.
Calorie dilution allows people to fill their stomach with fewer calories.
The China Study
The China Study, T. Colin Campbell, 2005
The China Study examines the relationship between the consumption of animal products (including dairy) and chronic illnesses such as coronary heart disease, diabetes, breast cancer, prostate cancer, and bowel cancer. The authors conclude that people who eat a predominantly whole-food, plant-based diet—avoiding animal products as a main source of nutrition, including beef, pork, poultry, fish, eggs, cheese, and milk, and reducing their intake of processed foods and refined carbohydrates—will escape, reduce, or reverse the development of numerous diseases.
The book is loosely based on the China–Cornell–Oxford Project, a 20-year study—described by The New York Times as “the Grand Prix of epidemiology”—conducted by the Chinese Academy of Preventive Medicine, Cornell University, and the University of Oxford. (Wikipedia)
Dean Ornish Diet – tba
Ornish is known for his lifestyle-driven approach to the control of coronary artery disease (CAD) and other chronic diseases. He promotes lifestyle changes including a whole foods, plant-based diet, smoking cessation, moderate exercise, stress management techniques including yoga and meditation, and psychosocial support. Ornish does not follow a strict vegetarian diet and recommends fish oil supplements; the program additionally allows for the occasional consumption of other animal products. (Wikipedia)
The Engine 2 Diet/Rip Esselstyn
– Details tba
Jeff Novick diet
The Five Pillars of Healthy Eating: “A Common Sense Approach To Nutrition”
1) Plant-Centered – Center your plate and your diet around minimally processed plant foods (fruits, vegetables, starchy vegetables, roots/tubers, intact whole grains, and legumes (beans, peas & lentils).
2) Minimally Processed – Enjoy foods as close to “as grown in nature” with minimal processing that does not detract from the nutritional value &/or add in any harmful components.
3) Calorie Dilute – Follow the principles of calorie density choosing foods that are calorie adequate, satiating and nutrient sufficient.
4) Low S-O-S – Avoid/minimize the use of added Salts/sodium, Oils/Fats and Sugars/sweeteners
5) Variety – Consume a variety of foods in each of the recommended food groups.
from The Healthy Eating Placemat A Visual Guide To Healthy Eating
Also see
Jeff Novick A Common Sense Approach To Sound Nutrition
This excerpt from an interview summarizes Jeff Novick’s view:
Consume a variety of foods in each of the recommended food groups. Now, if there were ten of us in the room, we could each implement these pillars slightly differently and still each have a healthy diet and great health results. That’s because when we look at the research evidence, there’s no one specific diet that is “best.”
Instead, there are common denominators across healthy diets that combine to make up a healthy dietary pattern, and these are reflected in my five guidelines/principles of healthy eating.
What foods do you recommend that people incorporate into their diets? The healthiest foods are minimally processed fruits, vegetables, starchy vegetables, roots/tubers, intact whole grains, and legumes. These should make up most—if not all—of our daily calories. I recommend that people start right where they are and just keep adding in more of these foods each day.
It seems today that the topic of nutrition and health has become a war with sides drawn and no discussion. I am disappointed in the conversation I see happening on social media because a lot of it is very judgmental, confrontational, and elitist.
The message out there seems to be that if the food you eat is not fresh, organic, local, shade-grown, GMO-free, and picked yourself or picked up at a local farmer’s market or purchased from some elite health food store, then all blended together in some expensive hi-tech blender, you are not doing well enough. And, if you buy any frozen or canned foods, you might as well be eating bacon and cheeseburgers.
We need to have compassion, not only for the animals and the environment, but also for our fellow humans, particularly in the way we treat each other, especially those who may not follow the exact same dietary pattern we do.
source: An interview with healthy eating expert Jeff Novick, posted on Jewishfoodherocom, Dec. 2015
Jeff Novick’s Healthy Eating Placemat
Do vegetarians need to engage in protein combining?
Protein combining is a dietary theory for protein nutrition that purports to optimize the biological value of protein intake. According to the theory, vegetarian and vegan diets provide insufficient content of essential amino acids, making protein combining necessary. The theory has been roundly discredited by major health organizations. Studies on essential amino acid contents in plant proteins has shown that vegetarian and vegans in fact do not need to complement plant proteins in each meal to reach the desired level of essential amino acids as long as their diets are varied. The terms complete and incomplete are misleading in relation to plant protein. Protein from a variety of plant foods, eaten during the course of a day, supplies enough of all essential amino acids when caloric requirements are met.
https://en.wikipedia.org/wiki/Protein_combining
Do humans need meat? Is veganism safe?
Studies are clearly honing in on the idea that the typical American diet is harmful, and that plant-based diets are much healthier. Just remember that this isn’t the same as being vegan or vegetarian. Plant-based diets allow for a small amount of meat on a regular basis (red meat, fowl, seafood, etc.)
From this BBC article, Zaria Gorvett writes
Recent concern about the nutritional gaps in plant-based diets has led to a number of alarming headlines, including a warning that they can stunt brain development and cause irreversible damage to a person’s nervous system.
Back in 2016, the German Society for Nutrition went so far as to categorically state that – for children, pregnant or nursing women, and adolescents – vegan diets are not recommended, which has been backed up by a 2018 review of the research.
… there are several important brain nutrients that simply do not exist in plants or fungi. Creatine, carnosine, taurine, EPA and DHA omega-3 (the third kind can be found in plants), haem iron and vitamins B12 and D3 generally only occur naturally in foods derived from animal products, though they can be synthesised in the lab or extracted from non-animal sources such as algae, bacteria or lichen, and added to supplements.
Others are found in vegan foods, but only in meagre amounts; to get the minimum amount of vitamin B6 required each day (1.3 mg) from one of the richest plant sources, potatoes, you’d have to eat about five cups’ worth (equivalent to roughly 750g or 1.6lb).
… though the body can make some of these vital brain compounds from other ingredients in our diets, this ability isn’t usually enough to make up for these dietary cracks. For all of the nutrients listed above, vegetarians and vegans have been shown to have lower quantities in their bodies. In some cases, deficiency isn’t the exception – it’s completely normal.
For now, the impact these shortcomings are having on the lives of vegans is largely a mystery. But a trickle of recent studies have provided some clues – and they make for unsettling reading.
“I think there are some real repercussions to the fact that plant-based diets are taking off,” says Taylor Wallace, a food scientist and CEO of the nutrition consulting firm Think Healthy Group. “It’s not that plant-based is inherently bad, but I don’t think we’re educating people enough on, you know, the nutrients that are mostly derived from animal products.”
How a vegan diet could affect your intelligence, BBC, Future
Is cheese bad for us? Is dairy bad for us?
Every food group is okay in moderation.
Great News, America: Cheese Isn’t Bad for You, Gilad Edelman, Wired magazine, 2/22/2021
The best evidence for the benign impact of cheese comes from long-term cohort studies that tracked the health and eating habits of tens or hundreds of thousands of people. A 2011 paper published in the New England Journal of Medicine analyzed three cohorts that together tracked 120,877 US adults over several decades.
The authors found that foods like potatoes, processed meats, and refined grains were associated with weight gain over time, while yogurt, fruit, and nuts were associated with weight loss. Cheese was right in the middle: On average, eating more or less of it had essentially no effect on weight.
That finding has held up in more recent research. A 2018 analysis of a study of 2,512 men in Wales, for example, showed a mild inverse relationship between cheese consumption and body mass after five years, meaning eating cheese was associated with weight loss, though that effect faded at the 10-year mark.
A meta-analysis of 37 randomized clinical trials found that increased dairy consumption overall led to increased lean muscle mass and decreased body fat.
“There’s almost no evidence that cheese causes weight gain—and in fact, there’s evidence that it’s neutral at worst,” says Dariush Mozaffarian, the lead author of the 2011 paper and dean of the Tufts Friedman School of Nutrition Science and Policy.
Related articles
Nutrients
Organic food and farming
Meaningless words in food science
What we need to know about healthy diets
Healthy meal generator
External related articles
Low-Fat Vegan Diets By Sharon Palmer, RDN Today’s Dietitian
Lack of exercise is a major cause of chronic diseases
Learning Standards
Massachusetts Health Framework
Students will gain the knowledge and skills to select a diet that supports health and reduces the risk of illness and future chronic diseases. PreK–12 Standard 4
Through the study of Improving Nutrition students will
3.1 Identify the key nutrients in food that support healthy body systems (skeletal, circulatory) and recognize that the amount of food needed changes as the body grows
3.2 Use the USDA Food Guide Pyramid and its three major concepts of balance, variety, and moderation to plan healthy meals and snacks
3.3 Recognize hunger and satiety cues and how to make food decisions based upon these cues.
3.8 List the functions of key nutrients and describe how the United States Dietary Guidelines relate to health and the prevention of chronic disease throughout the life span.
3.9 Describe a healthy diet and adequate physical activity during the adolescent growth spurt.
3.20 Identify and analyze dietary plans, costs, and long-term outcomes of weight management programs.
3.21 Identify how social and cultural messages about food and eating influence nutrition choices.
Benchmarks for Science Literacy, American Association for the Advancement of Science
Increased knowledge about nutrition has led to the development of diets containing the variety of foods that can help people live longer and healthier lives. 8F/M7** (SFAA)
2016 Massachusetts Science and Technology/Engineering Curriculum Framework
HS-LS1-2. Develop and use a model to illustrate the key functions of animal body systems, including (a) food digestion, nutrient uptake, and transport through the body; (b) exchange of oxygen and carbon dioxide; (c) removal of wastes; and (d) regulation of
body processes.
KaiserScience 