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Simple DIY masks could help flatten the curve. We should all wear them in public.
Also see How do viruses spread? Airborne vs non-airborne
Jeremy Howard writes
When historians tally up the many missteps policymakers have made in response to the coronavirus pandemic, the senseless and unscientific push for the general public to avoid wearing masks should be near the top.
The evidence not only fails to support the push, it also contradicts it. It can take a while for official recommendations to catch up with scientific thinking. In this case, such delays might be deadly and economically disastrous.
It’s time to make masks a key part of our fight to contain, then defeat, this pandemic. Masks effective at “flattening the curve” can be made at home with nothing more than a T-shirt and a pair of scissors. We should all wear masks — store-bought or homemade — whenever we’re out in public.
At the height of the HIV crisis, authorities did not tell people to put away condoms. As fatalities from car crashes mounted, no one recommended avoiding seat belts. Yet in a global respiratory pandemic, people who should know better are discouraging Americans from using respiratory protection.
… There are good reasons to believe DIY masks would help a lot. Look at Hong Kong, Mongolia, South Korea and Taiwan, all of which have covid-19 largely under control. They are all near the original epicenter of the pandemic in mainland China, and they have economic ties to China.
Yet none has resorted to a lockdown, such as in China’s Wuhan province. In all of these countries, all of which were hit hard by the SARS respiratory virus outbreak in 2002 and 2003, everyone is wearing masks in public.
George Gao, director general of the Chinese Center for Disease Control and Prevention, stated, “Many people have asymptomatic or presymptomatic infections. If they are wearing face masks, it can prevent droplets that carry the virus from escaping and infecting others.”
My data-focused research institute, fast.ai, has found 34 scientific papers indicating basic masks can be effective in reducing virus transmission in public — and not a single paper that shows clear evidence that they cannot.
Studies have documented definitively that in controlled environments like airplanes, people with masks rarely infect others and rarely become infected themselves, while those without masks more easily infect others or become infected themselves.
Masks don’t have to be complex to be effective. A 2013 paper tested a variety of household materials and found that something as simple as two layers of a cotton T-shirt is highly effective at blocking virus particles of a wide range of sizes.
Oxford University found evidence this month for the effectiveness of simple fabric mouth and nose covers to be so compelling they now are officially acceptable for use in a hospital in many situations. Hospitals running short of N95-rated masks are turning to homemade cloth masks themselves; if it’s good enough to use in a hospital, it’s good enough for a walk to the store.
The reasons the WHO cites for its anti-mask advice are based not on science but on three spurious policy arguments.
First, there are not enough masks for hospital workers.
Second, masks may themselves become contaminated and pass on an infection to the people wearing them.
Third, masks could encourage people to engage in more risky behavior.
None of these is a good reason to avoid wearing a mask in public.
Yes, there is a shortage of manufactured masks, and these should go to hospital workers. But anyone can make a mask at home by cutting up a cotton T-shirt, tying it back together and then washing it at the end of the day. Another approach, recommended by the Hong Kong Consumer Council, involves rigging a simple mask with a paper towel and rubber bands that can be thrown in the trash at the end of each day.
… the idea that masks encourage risky behavior is nonsensical. We give cars anti-lock brakes and seat belts despite the possibility that people might drive more riskily knowing the safety equipment is there. Construction workers wear hard hats even though the hats presumably could encourage less attention to safety. If any risky behavior does occur, societies have the power to make laws against it.
Papers about effectiveness of basic masks #masks4all
About the author – Jeremy Howard is a distinguished research scientist at the University of San Francisco, founding researcher at fast.ai and a member of the World Economic Forum’s Global AI Council.
Simple DIY masks could help flatten the curve. We should all wear them in public.
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More reason to wear face masks:
Experts said the choir outbreak is consistent with a growing body of evidence that the virus can be transmitted through aerosols — particles smaller than 5 micrometers that can float in the air for minutes or longer.
The World Health Organization has downplayed the possibility of transmission in aerosols, stressing that the virus is spread through much larger “respiratory droplets,” which are emitted when an infected person coughs or sneezes and quickly fall to a surface.
But a study published March 17 in the New England Journal of Medicine found that when the virus was suspended in a mist under laboratory conditions it remained “viable and infectious” for three hours — though researchers have said that time period would probably be no more than a half-hour in real-world conditions.
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Nell Greenfieldboyce writes
the question of whether or not the coronavirus can be “airborne” is extremely contentious right now — and it’s a question that has real implications for what people should do to avoid getting infected.
… a committee of independent experts convened by the National Academies of Sciences, Engineering, and Medicine has weighed in, in response to a question from the White House Office of Science and Technology Policy about whether the virus “could be spread by conversation in addition to sneeze/cough-induced droplets.”
“Currently available research supports the possibility that SARS-CoV-2 could be spread via bioaerosols generated directly by patients’ exhalation,” says a letter from the committee chair. By bioaerosols, they are referring to fine particles emitted when someone breathes that can be suspended in the air rather than larger droplets produced through coughs and sneezes.
Even if additional research shows that any virus in such tiny particles is viable, researchers still won’t how much of it would need to be inhaled to make someone sick. But the committee experts also caution that uncertainty about all this is almost a given—because there’s currently no respiratory virus for which we know the exact proportion of infections that come from breathing the virus in versus coming into contact with droplets in the air or on surfaces.
“I personally think that transmission by inhalation of virus in the air is happening,” says Linsey Marr, an aerosol scientist at Virginia Tech. But she says so far, health experts have largely discounted the possibility of transmitting this coronavirus in this way.
“From an infection prevention perspective, these things are not 100% black and white. The reason why we say ‘droplet’ versus ‘airborne’ versus ‘contact’ is to give overall guidance on how to manage patients who are expected to be infectious with a specific pathogen,” said Dr. Hanan Balkhy, assistant director-general for antimicrobial resistance at WHO, in an interview with NPR earlier this week.
As an expert who worked to contain an outbreak of the deadly MERS coronavirus in Saudi Arabia, she believes that this new virus should behave similarly to other severe coronaviruses — and that means, unless health-care workers are doing invasive procedures like putting in breathing tubes, the virus is expected to primarily spread through droplets.
Droplets are larger respiratory particles that are 5 to 10 micrometers in size. Those are considered “big,” even though a 5 micrometer particle would still be invisible to the naked eye. Traditionally, those droplets are thought to not travel more than about three feet or so after exhalation. That would mean the virus can only spread to people who get close to an infected person or who touch surfaces or objects that might have become contaminated by these droplets. This is why public health messages urge people to wash their hands and stand at least 6 feet away from other people.
An “airborne” virus, in contrast, has long been considered to be a virus that spreads in exhaled particles that are tiny enough to linger in the air and move with air currents, letting them be breathed in by passersby who then get sick. Measles is a good example of this kind of virus — an exhaled measles pathogen can hang suspended in a room for a couple hours after an infected person leaves.
The reality of aerosol generation, however, is far more complex than this “droplet” versus “airborne” dichotomy would suggest, says Marr. People produce a wide range of different-sized particles of mucus or saliva. These particles get smaller as they evaporate in the air and can travel different distances depending on the surrounding air conditions.
“The way the definitions have been set up, this “droplet” vs “airborne” distinction, was first established in the 1950s or even earlier,” says Marr. “There was a more limited understanding of aerosol science then.”
Even a 5 micrometer droplet can linger in the air. “If the air were perfectly still, it would take a half hour to fall from a height of 6 feet down to the ground. And, of course, the air isn’t perfectly still,” says Marr. “So it can easily be blown around during that time and stay in the air for longer or shorter.”
What’s more, coughs and sneezes create turbulent clouds of gas that can propel respiratory particles forward.
“For symptomatic, violent exhalations including sneezes and coughs, then the droplets can definitely reach much further than the 1 to 2 meter [3 to 6 feet] cutoff,” says Lydia Bourouiba, an infectious disease transmission researcher at MIT, referring to the distance typically cited as safe for avoiding droplet-carried diseases.
In fact, studies show that “given various combinations of an individual patient’s physiology and environmental conditions, such as humidity and temperature, the gas cloud and its payload of pathogen-bearing droplets of all sizes can travel 23 to 27 feet,” she wrote in a recent article published online by the Journal of the American Medical Association.
…. Some of the strongest evidence that an airborne route of transmission might be possible for this virus comes from a report published last month by the New England Journal of Medicine that described mechanically generating aerosols carrying the SARS-CoV-2 virus in the laboratory. It found that the virus in these little aerosols remained viable and infectious throughout the duration of the experiment, which lasted 3 hours.
WHO mentioned this study in its recent review of possible modes of transmission and noted that “this is a high-powered machine that does not reflect normal human cough conditions … this was an experimentally induced aerosol-generating procedure.”
It may have been artificial, says Marr, but “the conditions they used in that laboratory study are actually less favorable for survival compared to the real world. So it’s more likely that the virus can survive under real world conditions.”
Scientists Probe How Coronavirus Might Travel Through The Air
Reference: Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19
Lydia Bourouiba, JAMA insights, March 26, 2020. doi:10.1001/jama.2020.4756
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Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1
March 17, 2020 , DOI: 10.1056/NEJMc2004973
A novel human coronavirus that is now named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (formerly called HCoV-19) emerged in Wuhan, China, in late 2019 and is now causing a pandemic. We analyzed the aerosol and surface stability of SARS-CoV-2 and compared it with SARS-CoV-1, the most closely related human coronavirus.
… We found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested. This indicates that differences in the epidemiologic characteristics of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic.
Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed).
These findings echo those with SARS-CoV-1, in which these forms of transmission were associated with nosocomial spread and super-spreading events, and they provide information for pandemic mitigation efforts.
Neeltje van Doremalen, Ph.D., Trenton Bushmaker, B.Sc.
National Institute of Allergy and Infectious Diseases, Hamilton, MT
Dylan H. Morris, M.Phil., Princeton University, Princeton, NJ, Myndi G. Holbrook, B.Sc.
National Institute of Allergy and Infectious Diseases, Hamilton, MT
Amandine Gamble, Ph.D.
University of California, Los Angeles, Los Angeles, CA
Brandi N. Williamson, M.P.H.
National Institute of Allergy and Infectious Diseases, Hamilton, MT
Azaibi Tamin, Ph.D., Jennifer L. Harcourt, Ph.D.
Natalie J. Thornburg, Ph.D., Susan I. Gerber, M.D.
Centers for Disease Control and Prevention, Atlanta, GA
James O. Lloyd-Smith, Ph.D.
University of California, Los Angeles, Los Angeles, CA, Bethesda, MD
Emmie de Wit, Ph.D., Vincent J. Munster, Ph.D.
National Institute of Allergy and Infectious Diseases, Hamilton, MT
Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1
#NEJM
How to deal with a viral pandemic
What is a pandemic?
A pandemic is an epidemic occurring on a scale which crosses international boundaries, usually affecting a large number of people.
Pandemics can also occur in important agricultural organisms (livestock, crop plants, fish, tree species) or in other organisms.
from The Continuum of Pandemic Phases, CDC
The World Health Organization (WHO) has a classification – starts with the virus mostly infecting animals, with a few cases where animals infect people, then moves through the stage where the virus begins to spread directly between people, and ends with a pandemic when infections from the new virus have spread worldwide.
A disease is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer is responsible for many deaths but is not a pandemic because the disease is not infectious or contagious.
(Intro adapted from Wikipedia article, Pandemic)
Viruses spread exponentially
How does the likelihood of death from any common cause compare to the likelihood of death from something that spreads exponentially? The important difference is that for any other cause of death, that cause is (a) usually not transmissible, and (b) the rate of death stays (more or less) the same over time.
But for deaths caused by a virus the situation is different – (c) it is transmissible from one person to another, and (d) the number of people infected grows exponentially over time.
Animation: Global Deaths Due to Various Causes and COVID-19
Methodology and sources for the animation
How would we respond to a pandemic?
What happens if a pandemic hits? Jon Evans, Techcrunch, 2/23/2020
Don’t get all disaster-movie here. Some people seem to have the notion that a pandemic will mean shutting down borders, building walls, canceling all air travel and quarantining entire nations indefinitely. That is incorrect.
Containment attempts can slow down an outbreak and buy time to prepare, but if a pandemic hits, by definition, containment has failed… [so] the focus will switch from containment to mitigation: slowing down how fast the virus spreads through a population in which it has taken root.
Mitigation can occur via individual measures, such as frequent hand washing, and collective measures, such as “social distancing” — cancellations of mass events, closures, adopting remote work and remote education wherever possible, and so forth.
The slower the pandemic moves, the smoother the demands on health-care systems will be; the less risk those systems will have of becoming overloaded; the more they can learn about how best to treat the virus; and the greater the number of people who may ultimately benefit from a vaccine, if one is developed.
Observed cases vs non-observed cases
How should we respond to a pandemic?
Past Time to Tell the Public: “It Will Probably Go Pandemic, and We Should All Prepare Now” by Jody Lanard and Peter M. Sandman
1. Tell friends and family to try to get ahead on their medical prescriptions if they can, in case of very predictable supply chain disruptions, and so they won’t have to go out to the pharmacy at a time when there may be long lines of sick people. This helps them in a practical sense, but it also makes them visualize – often for the first time – how a pandemic may impact them in their everyday lives, even if they don’t actually catch COVID-19….
2. We also recommend that people might want to slowly (so no one will accuse them of panic-buying) start to stock up on enough non-perishable food to last their households through several weeks of social distancing at home during an intense wave of transmission in their community. This too seems to get through emotionally, as well as being useful logistically.
3. Three other recommendations that we feel have gone over well with our friends and acquaintances: Suggesting practical organizational things they and their organizations can do to get ready, such as cross-training to mitigate absenteeism. Suggesting that people make plans for childcare when they are sick, or when their child is sick.
4. Right now, today, start practicing not touching your face when you are out and about! You probably won’t be able to do it perfectly, but you can greatly reduce the frequency of potential self-inoculation. …
How should we respond to a pandemic?
Develop vaccines
Josh Michaud, Associate Director Global Health at Kaiser Family Foundation, John Hopkins School of Advanced International Studies, writes:
CDC guidance urges flexibility in implementing mitigation measures, and continual re-assessment of their effectiveness as new information comes in. A “targeted, layered” approach that addresses current circumstances is the best practice.
The ultimate goal of such measures is to reduce the intensity of an outbreak, flattening out the epidemic curve and therefore reducing strain on the health system, and on social economic well-being (see this graphic representation).
With community transmission of #COVID19 in multiple countries it appears that containment of the virus in China will not happen (this outcome was not unexpected). Emphasis in many places could turn from containment to “mitigation”. What does mitigation mean?
First, to be clear: it’s not either/or, because containment efforts and mitigation efforts encompass a spectrum of activities, are complementary and can occur at the same time.
Still, we can contrast their goals: containment is meant to halt transmission, while mitigation is meant to reduce negative impacts of transmission.
For the U.S., CDC has long had recommendations for how communities can use mitigation to address pandemic influenza. A revision to this guidance came in 2017, incorporating lessons learned from the 2009 H1N1 influenza pandemic.
“Community Mitigation Guidelines to Prevent Pandemic Influenza — United States, 2017”
https://www.cdc.gov/mmwr/volumes/66/rr/rr6601a1.htm?s_cid=rr6601a1_w
Not all guidance from pandemic influenza is applicable to #COVID19 because the epidemiology and circumstances differ, but countries face similar challenges with both.
For example, both are highly transmissible, and in both cases we have no specific countermeasures available at first (e.g. vaccines). Containment is difficult if not impossible in both cases.
The 2009 H1N1 pandemic is often remembered as being “mild”, but there was a quite a significant health impact: an estimated 43-89 million people in the US were infected and 12,000 people died between Apr2009-Apr2010.
CDC talks about mitigation in three buckets: 1) individuals behaviors (hand hygiene, staying at home, avoiding ill people); 2) “social distancing” (closing schools and public gatherings, and 3) environmental mitigation (surface cleaning efforts). Let’s focus in 1 and 2.
Encouraging better individual hygiene behaviors is cornerstone of mitigation. Good hand hygiene (wash those hands!), and voluntary home isolation when ill (and even home quarantine when potentially exposed) are recommended.
Many studies show the effectiveness of hand hygiene; one study on H1N1 from Egypt highlighted by CDC showed 47% fewer cases of influenza occurred after twice-daily hand washing and health hygiene instruction was provided in elementary schools.
Studies of the US public during H1N1 found that people actually did change their hygiene behaviors: in one survey 59% of Americans reported washing hands more frequently and 25% said they avoided public places like sporting events, malls, and public transportation.
CDC guidelines also support social distancing in some cases, including school closures, canceling public gatherings, and workplace closures/telework.
During H1N1, CDC recommended communities with confirmed cases consider closing child care facilities and schools. From Aug–Dec 2009, communities in 46 states implemented 812 dismissals (in a single school or all schools in a district), affecting 1,947 schools.
This number of schools represented 0.7% and 3.3% of all urban and rural schools, respectively, in the U.S. Evidence from TX indicated school closures there reduced acute respiratory illness in households with school-age children by 45%–72%.
Interestingly, surveys of parents whose children were affected by school closures found strong support for, and belief in the effectiveness of these measures: 90% of parents agreed with dismissal decisions, and 85% believed dismissals reduced transmission.
Even so, closing schools was disruptive, and a systematic review of US school closures during H1N1 was not able to determine whether the benefits outweighed the cost in this “mild” epidemic, though they did recommend such measures during a “severe” pandemic.
CDC guidelines also note there are practical obstacles to asking people to stay home from school and work: in 2009 a major difficulty was that many people did not have access to paid leave, and therefore had a hard time following guidance.
Another challenge for mitigation in the U.S. is that while CDC can offer recommendations and guidance, implementation of these policies mostly occurs at local district, county, & state levels. This can lead to a patchwork of different mitigation approaches across locations.
A recent publication looked at US local health department decision-making around social distancing during outbreaks, and concluded resources available and actions implemented are inconsistent and unpredictable across the country. https://journals-sagepub-com.proxy1.library.jhu.edu/doi/pdf/10.1177/0033354918819755
CDC guidance urges flexibility in implementing mitigation measures, and continual re-assessment of their effectiveness as new information comes in. A “targeted, layered” approach that addresses current circumstances is the best practice.
The ultimate goal of such measures is to reduce the intensity of an outbreak, flattening out the epidemic curve and therefore reducing strain on the health system, and on social economic well-being (see this graphic representation).
Reliable sources of information
CDC: Centers for Disease Control – Coronavirus Disease 2019 (COVID-19)
Massachusetts Department of Public Health
US FDA Food and Drug Administration Coronavirus Disease 2019
Coronavirus disease: Myth busters – WHO World Health Organization
The Math and Biology of Beauty: Averages and Symmetry
It is popular to believe that aesthetic judgements of physical attractiveness – beauty – are arbitrary. Many people believe popular ideas about attractiveness are mostly social constructs. However science shows that this idea is incorrect.
Attractiveness is agreed upon by most people, across cultures and history, because it is defined by evolution by natural selection. What we experience as physical attraction is our brain’s innate ability to ascertain a potential mate’s health, mental fitness, and ability to reproduce (create healthy offspring.)
Attractiveness, from this scientific point of view, turns out be a person’s desire to seek an average mate: Note we are using a mathematical, scientific definition of the word “average.”
“Averageness” describes the physical beauty that results from averaging the facial features of people of the same gender and approximately the same age.
Scientific studies use photographic overlays of human faces, in which images are morphed together.
The term “average” here is a mathematical definition = arithmetic mean, = the sum of a collection of numbers divided by the count of numbers in the collection.
It turns out that an averaged face is not unremarkable, but is, in fact, quite good looking.
Image from Koinophilia and human facial attractiveness, Aishwariya Iyengar et al. Koinophilia and human facial attractiveness, April 2015, Volume 20, Issue 4, pp 311–319
Nor is averageness typical in the sense of common or frequently occurring in the population, though it appears familiar, and is typical in the sense that it is a good example of a face that is representative of the category of faces.
The evolutionary explanation for averageness is koinophilia: animals seek mates with average features, because extreme or uncommon features indicate disadvantageous mutations.
Discerning mutations by just looking
Most humans have a good innate ability to discern whether a person has chromosomal damage just by looking at facial features. The shape of a person’s face is defined by instructions from our genes.
Thus if one has certain chromosomal mutations then other people pick up on that subconsciously.
There are characteristic changes in facial features created by Williams syndrome, Smith-Magenis syndrome, Fragile X syndrome, Jacobsen syndrome, trisomy 21 (classic mental retardation,) etc.
If one takes measurements, one can mathematically discern the existence of these chromosomal changes with a smartphone app (available only to doctors.)
Detecting genetic disorders with 3d face scans
Apps
FaceResearch.org – Make Your Own Average
Gender and faces
The human face is sexually dimorphic, with the average male face differing from the average female face in the size and shape of, and distance between, the jaws, lips, eyes, nose and cheekbones.
Even within sex, there are considerable variations in these dimensions, leading to individuals appearing more or less feminine or masculine than the prototypical gendered face. While the origin of this variability remains unclear, there has been significant interest in the influence of the most abundant androgen, testosterone, in the development of face structure.
Genetic sex is determined at conception, but gonadal hormones play a vital role in the differentiation of male and female phenotypes throughout human development.
Prenatal testosterone exposure is related to sexually dimorphic facial morphology in adulthood
Andrew J. O. Whitehouse et al. Proceedings of the Royal Society B Biological Sciences 10/7/2015
Prenatal testosterone may have a powerful masculinizing effect on postnatal physical characteristics. However, no study has directly tested this hypothesis. Here, we report a 20-year follow-up study that measured testosterone concentrations from the umbilical cord blood of 97 male and 86 female newborns, and procured three-dimensional facial images on these participants in adulthood (range: 21–24 years).
Twenty-three Euclidean and geodesic distances were measured from the facial images and an algorithm identified a set of six distances that most effectively distinguished adult males from females.
From these distances, a ‘gender score’ was calculated for each face, indicating the degree of masculinity or femininity. Higher cord testosterone levels were associated with masculinized facial features when males and females were analysed together (n = 183; r = −0.59), as well as when males (n = 86; r = −0.55) and females (n = 97; r = −0.48) were examined separately (p-values < 0.001).
The relationships remained significant and substantial after adjusting for potentially confounding variables. Adult circulating testosterone concentrations were available for males but showed no statistically significant relationship with gendered facial morphology (n = 85, r = 0.01, p = 0.93).
This study provides the first direct evidence of a link between prenatal testosterone exposure and human facial structure.
https://doi.org/10.1098/rspb.2015.1351
Scientific papers
Note (1) Grammer, K.; Thornhill, R. (October 1994). “Human (Homo sapiens) facial attractiveness and sexual selection: the role of symmetry and averageness”. Journal of Comparative Psychology. 108 (3): 233–42. doi:10.1037/0735-7036.108.3.233. PMID 7924253. Retrieved 4 May 2019.
Rhodes, Gillian; Zebrowitz, Leslie A. (2002). Facial Attractiveness: Evolutionary, Cognitive, and Social Perspectives. Ablex. ISBN 978-1-56750-636-5.
Jones, B. C., Little, A. C., Tiddeman, B. P., Burt, D. M., & Perrett, D. I. (2001). Facial symmetry and judgements of apparent health Support for a “‘ good genes ’” explanation of the attractiveness – symmetry relationship, 22, 417–429.
Alison Pearce Stevens writes “Research shows that people with more symmetrical faces don’t just look nice. They also tend to be healthier than asymmetrical people. Genes provide the instructions for how a cell is to perform. All people have the same number of genes. But people with more average faces tend to have a greater diversity in the genes they are born with. And that, research has shown, can lead to a stronger immune system and better health.” What makes a pretty face? Science News for Students
Papers
Iglesias-Julios M, Munoz-Reyes JA, Pita M et al. Facial Features: What Women Perceive as Attractive and What Men Consider Attractive. PLoS ONE. 2015.
Farmer H, McKay R, Tsakiris M. Trust in Me: Trustworthy Others Are Seen as More Physically Similar to the Self. Psychological Science. 2013.
Coetzee V, Keckp S, Kivleniece I et al. Facial attractiveness is related to women’s cortisol and body fat, but not with immune responsiveness. Biology Letters. 2013.
Clarifying codon wheel usage
A student is told to use a “codon wheel” to help with protein translation. What codons go with which resulting amino acid? Here I saw students come to different conclusions because many infographics were not distinctly labeled.
Some students thought that every codon wheel lets us input 3 DNA nucleotides.
Others thought that it let us input 3 mRNAs.
While others thought that it let us input the 3 anticodons on the tRNA molecule.
In other words, many students failed at step 1 because the main idea was not labeled clearly.
In this example (click link) we see mRNA codon wheel. If we input mRNA sequence then it tells us the amino acid that will be the eventual output from the translation process.
Why mention this? Because there are also tRNA codon wheels, and even DNA codon wheels! Each of these wheels can be fine – but only when we know for certain which one we are using.
Let’s follow an example through, step by step.
For the following image, the original DNA sequence must be:
TAC GCC TCT
The corresponding mRNA sequence is
AUG CGG AGA
The anticodon sequence for the tRNAs is
UAC GCC UCU
The amino acids carried by these tRNAS would be
Met Ala Ser
This image from ATDBio Ltd., Transcription Translation and Replication
Autism Shares Brain Signature with Schizophrenia and Bipolar Disorder
What is autism? Autism is a complex developmental condition that involves persistent challenges in social interaction, speech and nonverbal communication, and restricted/repetitive behaviors.
The effects of ASD and the severity of symptoms are different in each person.
What causes autism? Read Causes of autism
Autism Shares Brain Signature with Schizophrenia and Bipolar Disorder
By Nicholette Zeliadt, Spectrum, Scientific American, February 8, 2018
Gene expression patterns in the brains of people with autism are similar to those of people who have schizophrenia or bipolar disorder, according to a large study of postmortem brain tissue.
All three conditions show an activation of genes in star-shaped brain cells called astrocytes, and suppression of genes that function at synapses, the junctions between neurons. The autism brains also show a unique increase in the expression of genes specific to immune cells called microglia.
“This study demonstrates for the first time that [gene expression] can be used to robustly define cross-disorder phenotypes that are shared and distinct,” says lead investigator Daniel Geschwind, professor of neurology, psychiatry and human genetics at the University of California, Los Angeles. “And these phenotypes are related to the molecular and cellular pathways that likely have gone awry.”
People who have one of these conditions may have features in common, such as language problems, irritability and aggression. They also share certain genetic variants that raise the risk of the conditions.
The new work shows that the overlap among risk variants is related to the commonality in their gene expression patterns. This hints that the variants raise risk in part by turning on or off certain sets of genes in the brain.
“We’re seeing all these studies coming out finding links between genetic variants and psychiatric [conditions], but how do we go from genetic risk to mechanisms?” says Emma Meaburn, senior lecturer of psychological sciences at Birkbeck University of London, who was not involved in the study. “This paper begins to fill that gap.”
Networks of genes derived from certain ‘modules’ (neuron, top right, and astrocyte, bottom left) are altered in autism, schizophrenia and bipolar disorder.
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Autism may share inherited variants with other psychiatric conditions
By Nicholetter Zeliadt, Spectrum News, 1/13/2020
Some of the inherited variants implicated in autism also increase the odds of other conditions, including schizophrenia, bipolar disorder, depression and attention deficit hyperactivity disorder (ADHD), according to a new study1.
The results come from an international effort called the Psychiatric Genomics Consortium, which involves more than 800 scientists. “These disorders, which we think of as very clinically different, might be related at the level of their genetic basis,” says lead investigator Jordan Smoller, associate chief for research in psychiatry at Massachusetts General Hospital in Boston.
Smoller and his colleagues analyzed data from 727,126 people, about one-third of whom have one or more of eight psychiatric conditions. The team focused on so-called common variants — single-letter changes to DNA that appear in 1 percent or more of the population.
The team linked 146 variants to least one condition, and most of them to multiple conditions. Variants in the latter group tend to affect genes that are highly expressed throughout life, starting during the second trimester of fetal development, and may be key to brain development.
“More and more, the picture that’s emerging is that there are multiple [variants] associated with, let’s say, a psychiatric vulnerability that is not specific to one disorder,” says Tinca Polderman, assistant professor of complex trait genetics at Vrije Universiteit Amsterdam in the Netherlands, who was not involved in the work. “Whether it develops into autism or [something else] may have to do with other factors.”
Reference – Genomic Relationships, Novel Loci, and Pleiotropic Mechanisms across Eight Psychiatric Disorders, There are 606 authors, collectively referred to as the Cross-Disorder Group of the Psychiatric Genomics Consortium. Cell. 2019 Dec 12; 179(7):1469-1482.e11. doi: 10.1016/j.cell.2019.11.020.
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The Same Genes May Underlie Different Psychiatric Disorders:
A distinct set of genes may underlie several psychiatric conditions.
By Mark Fischetti, Scientific American, July 1, 2018
People who have autism, schizophrenia and bipolar disorder may have different challenges, but the ailments might arise from a common set of genes.
Researchers compared genetic analyses of 700 human brains from deceased individuals who had one of those three disorders, major depression or alcoholism (columns) with brains of individuals who had none of the conditions. They examined 13 groups of genes thought to function together (rows).
The scientists found that five groups had a pattern of overactivity or underactivity across at least three of the five conditions (blue and gray panels). Bipolar disorder, for example, was more similar to schizophrenia than to major depression even though clinicians may link bipolar disorder and depression, based on their symptoms.
These insights could possibly reveal new treatments, says neurogeneticist Daniel Geschwind of the University of California, Los Angeles, one of the investigators. He adds that one path to that result, which has not yet been tested, could be to “put the different groups of genes in lab dishes and see which drugs reverse any overexpression or underexpression of the genes.”
Graphic by Martin Krzywinski; Source: “Shared Molecular Neuropathology across Major Psychiatric Disorders Parallels Polygenic Overlap,” by Michael J. Gandal et al., in Science. Vol. 359; February 9, 2018
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Networks of genes altered in autism brains, study says
Virginia Hughes, 5/25/2011, Spectrum News
Networks of genes altered in autism brains, study says
Autism is known for its diversity in symptoms and in the genes that might cause it. “[But] there is a remarkable consistency in the molecular changes that are occurring in the brain,” notes lead investigator Daniel Geschwind, distinguished professor of neurology, psychiatry and human genetics at the University of California, Los Angeles.
The study turned up several unexpected findings. For example, the frontal lobe and temporal lobe in healthy controls show significant differences in gene expression, reflecting their distinct cell types and functions. But in the autism brains, “those differences are essentially wiped out,” Geschwind says. Many of these genes are first turned on during embryonic development, he says, suggesting that the abnormal trajectory of autism brains begins early.
“This has never been reported before — it’s definitely an original contribution and an advance,” notes John Allman, professor of neurobiology at the California Institute of Technology, who was not involved in the study.
Lichens and mosses
What are lichens and mosses? Many people speak about them together, as if they are related. But this turns out not to be correct – they are entirely different forms of life.
I. Lichen
A colony of two organisms living together as a single unit.
One is a fungus, and the other is something that performs photosynthesis
Either green algae or a photosynthetic bacterium, cyanobacteria.
from Miller and Levine Biology, Chap 21, MaCaw
Two organisms living together in a close relationship is called symbiosis.
How do these two different species help each other?
The green algae or cyanobacteria carry out photosynthesis. This provides the fungus with food.
The fungus provides the green algae or cyanobacteria with water and minerals.
The fungal hyphae protect the delicate green cells from bright sunlight.
Lichens can grow in places where few other organisms can survive.
Even on rocks in desert and on mountaintops.
Lichens are often the first organisms to enter barren environments. They gradually break down the rocks on which they grow. In this way lichens help in the early stages of soil formation.
Lichens are very sensitive to air pollution. They are among the first organisms affected when air quality gets worse
Some colonies of lichens have existed for 9,000 years.
II. Moss
A very simple type of plant.
This image by Bob Blaylock, Wikipedia, CC BY-SA 4.0
Image: A patch of moss showing both gametophytes (the low, leaf-like forms) and sporophytes (the tall, stalk-like forms)
Mosses are small flowerless plants.
They form dense green clumps or mats, often in damp or shady locations.
The individual plants are usually composed of simple leaves that are generally only one cell thick.
These are attached to a stem that may be branched or unbranched and has only a limited role in conducting water and nutrients.
Role of mosses in the ecosystem
Mosses are extremely important for ecological succession.
They stabilize the soil surface, reducing erosion, reducing evaporation of water, making more available for succeeding plants.
Mosses are not an important source of food for vertebrate herbivores.
Peat mosses are the dominant plants of extensive northern wetland areas, and are largely responsible for the development of bogs.
Most species of mosses are not of any direct economic importance, and none are a food source for humans.
Peat mosses are economically the most important mosses. Peat mosses are an important source of fuel in some countries. Peat is abundant in northern regions and represents a vast reservoir of potential energy. In northern Europe, peat has historically been dried, and in some cases compressed into briquettes for use in fireplaces and stoves. In Ireland, peat is still extensively used for cooking.
In recent years, mosses have become important in monitoring the health of ecosystems, especially in relation to atmospheric contamination. Because bryophytes lack roots, many of their nutritional requirements are met by nutrients deposited from the atmosphere. Thus, they are sensitive indicators of atmospheric pollutants. Changes in the distributions of mosses (and lichens) are therefore an early-warning signal of serious effects of atmospheric pollution.
pH diets, health, and homeostasis
Students need to be aware of pseudoscience diets. Some of these claim that by eating more acidic or basic foods you can change your body’s pH level, and thus treat disease.
Not only is this entire idea incorrect, if a person does change their pH beyond even a tiny bit then they will almost immediately die. Changing one’s body pH is almost impossible, but when it happens it is fatal,
What are acids and bases? Acids are bases are complimentary types of chemicals. Acids perform one kind of chemical reaction; bases perform the opposite action. Learn more here about acids and bases.
Here’s the critical point: When it comes to living, what matters is whether acids and bases are working in a safe balance. Cells only work correctly in a very narrow range of conditions.
Too much or too little of any molecule, and they begin to malfunction or die. Homeostasis is the body’s way of keeping chemicals in a safe, dynamic balance.
Alkaline Diet, SkepDic
Alkaline Diet, RationalWiki
pH Mythology: Separating pHacts from pHiction
Alkaline Water Surges Despite Lack of Evidence
Alkaline food, McGill University
Chemistry lesson for The Food Babe… and everyone else #19: Alkaline Diets Do Not Cure Disease, McGill University
MCAS Classification
MCAS Classification questions
32. The table below shows the classifications of three different sea lions.
a. Identify which two of the sea lions are most closely related.
b. Justify your answer to part (a).
c. Describe and explain two types of evidence scientists would have used to determine the proper classifications of these three sea lions.
____________________
____________________
2016.
5. A scientist concludes that two organisms belong to the same species within the
class Mammalia. Which of the following observations most likely led the scientist
to conclude that the organisms are the same species?
A. The organisms move in the same way.
B. The organisms live in the same habitat.
C. The organisms are nocturnal and carnivorous.
D. The organisms mate and produce fertile offspring.
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24. The brush mouse and the northwestern deermouse are both classified in the
genus Peromyscus. Which of the following conclusions can be made from this information?
A. The two types of mice live in the same habitat.
B. The two types of mice have the same fur color.
C. The two types of mice are closely related to each other.
D. The two types of mice can successfully interbreed with each other.
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32. The table below gives the common names, scientific names, and known geographic locations of several wild cats.
a. Using their common names, identify all the wild cats listed in the table that belong to the same genus.
b. Identify and explain one type of evidence scientists could have used to classify these wild cats.
The three kinds of tigers listed in the table are all classified as one species.
c. Based on the information in the table, identify which kind of tiger has the greatest chance of becoming a separate species. Explain your answer.
d. Describe how scientists could determine if one of the kinds of tigers becomes a separate species.
____________________
33. The table below shows taxonomic information for the gray wolf and four other species.
Based on this information, which of the following lists the species in order from most closely related to least closely related to the gray wolf ?
A. 1, 2, 3, 4
B. 1, 2, 4, 3
C. 2, 1, 3, 4
D. 2, 1, 4, 3
31. All organisms classified in kingdom Animalia must also be classified as
which of the following?
A. Archaea
B. Eubacteria
C. Eukaryota
D. Protista
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45. A student researching bears found the chart below in a textbook. The chart shows the
classifications of several types of bears.
Which of the following conclusions is best supported by the data given in this chart?
A. Modern bears evolved from species that are now extinct.
B. The short-faced bear was the ancestor of the Asiatic black bear.
C. Present day bear species are more closely related than their ancestors were.
D. Natural selection favored the brown bear over the American black bear. .
MCAS Plants
MCAS Plant questions from the Biology MCAS
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31. A plant species growing along a coast produces seeds with fluffy hair-like
fibers on one end. A seed from one of the plants is shown below:
Some of these seeds were dispersed by the wind to islands off the coast, where new plants grew. Within 10 years, the seeds of the island plants were different
from the seeds of the mainland plants. Compared to the mainland seeds, the
island seeds were heavier and had shorter hair-like fibers. Which of the following statements best explains why heavier seeds with shorter fibers were favored in the island environment?
A. These seeds carried more genes than the mainland seeds did.
B. These seeds were less likely to be blown off the island by wind.
C. The island plants needed to prevent animals from eating the seeds.
D. The island plants used more energy to produce heavy seeds than to grow.
____________________
33. Students investigated the effect of acid rain on photosynthesis. Several plants
were given water with a pH of 4 each day for two months. The results showed
that the plants had a reduced rate of photosynthesis.
How did the acidic water most likely reduce the plants’ rate of photosynthesis?
A. by storing excess oxygen produced by the plants
B. by changing the effectiveness of enzymes in the plants
C. by causing root hairs to grow on the roots of the plants
D. by increasing the amount of carbon dioxide taken in by the plants
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34. Waxes form a waterproof coating over the stems and leaves of many terrestrial plants. The waxes are composed of fatty acids linked to long-chain alcohols. Based on this information, waxes are which type of organic molecule?
A. lipids . B. nucleotides . C. polysaccharides . D. proteins
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37. Maltose is a carbohydrate molecule that provides energy to plants early in their
life cycle. Which elements are most common in a molecule of maltose?
A. carbon and hydrogen
B. copper and nitrogen
C. iron and phosphorus
D. magnesium and sulfur
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Algae, and the scientific method
The rate of photosynthesis in organisms depends in part on the wavelength of visible light. In the late 1800s, Thomas Engelmann demonstrated the relationship between the wavelength of light and the rate of photosynthesis. His experiment is described below.
• Engelmann used a prism to produce a visible light spectrum of violet, blue, green, yellow, orange, and red light.
• He shined the light spectrum onto cells of the algae Spirogyra.
• Once the light was shining on the Spirogyra cells, Engelmann added aerobic bacteria to the system. Aerobic bacteria need oxygen to live and grow.
• After adding the bacteria, Engelmann observed the regions of the light spectrum where the bacteria concentrated around the Spirogyra cells.
The setup and results of Engelmann’s experiment are represented by the diagram below:
Mark your answers to multiple-choice questions 8 through 11 in the spaces provided in your Student Answer Booklet. Do not write your answers in this test booklet, but you may work out solutions to multiple-choice questions in the test booklet.
8. Why are the greatest numbers of aerobic bacteria found at the 400–500 nm and 600–700 nm wavelengths of light?
A. Photosynthesis rates are highest there, producing large amounts of water.
B. Photosynthesis rates are highest there, producing large amounts of oxygen.
C. Photosynthesis rates are lowest there, producing small amounts of glucose.
D. Photosynthesis rates are lowest there, producing small amounts of carbon dioxide.
9. What is the role of visible light when Spirogyra cells perform photosynthesis?
A. It provides the energy for the photosynthesis reaction.
B. It concentrates the photosynthesis products for export.
C. It activates the DNA that directs the photosynthesis reaction.
D. It transports photosynthesis reactants across the cell membrane.
10. What is exchanged between the Spirogyra and the bacteria in
Engelmann’s experiment?
A. DNA and RNA
B. starch granules and spores
C. chlorophyll and cytoplasm
D. oxygen and carbon dioxide
11. A scientist used Engelmann’s data to predict how the concentrations of different substances in and around Spirogyra cells will change when the cells are exposed to different wavelengths of light. A graph for one substance is shown below.
What is represented on the y-axis?
A. chlorophyll concentration . B. hydrogen concentration
C. oxygen concentration . D. water concentration
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3. All corn plants contain the ZmLA1 gene. Some corn plants contain a certain mutation in the ZmLA1 gene. The graph below shows the amount of ZmLA1 RNA produced in plants with the normal gene and in plants with the mutated gene.
Based on the graph, what most likely happens in corn plant cells as a direct result of the mutated gene?
A. DNA replication increases.
B. Lipid production decreases.
C. Glucose synthesis increases.
D. Protein production decreases.
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4. The growth of plants in many ecosystems is limited by the supply of
nitrogen. Which of the following groups of organisms plays the largest role in
moving nitrogen between the atmosphere and plants?
A. bacteria . B. earthworms . C. insects . D. protists
____________________
7. Lithops are multicellular organisms found in sandy soil in deserts. They
have large, central vacuoles in their cells that store water. Which of the following best classifies lithops?
A. They are bacteria because they store water.
B. They are animals because they are multicellular.
C. They are fungi because they are found in sandy soil.
D. They are plants because they have large, central vacuoles.
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14. There are many fungus species that live inside plant tissues. What determines
whether the relationship between a fungus and a plant is commensalism,
mutualism, or parasitism?
A. where the fungus is located in the plant
B. how long the fungus survives in the plant
C. whether the fungus reproduces in the plant with spores, seeds, or runners
D. whether the effect of the fungus on the plant is neutral, positive, or negative
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37. Plants in floodplains often get covered by water during floods. Some
plants survive the floods because they can continue photosynthesis
underwater. However, the plants’ rates of photosynthesis are much lower
underwater than above water.
Which of the following helps to explain why the rates of photosynthesis are
lower underwater than above water?
A. There is too much oxygen in the water.
B. There is no carbon dioxide in the water.
C. The chloroplasts do not function underwater.
D. The available light is less intense underwater.
____________________
17. Carbon fixation is an important part of the carbon cycle. Carbon fixation is the conversion of carbon dioxide into organic compounds such as glucose. Which of the following organisms cannot fix carbon?
A. grass
B. green algae
C. mushrooms
D. oak trees
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3. A botanist studied two groups of rice plants to determine how they are related. Both groups of plants have similar shapes, but one group has longer stalks. When the botanist cross-pollinated plants from one group with plants from the other group, the seeds produced did not sprout or grow.
Which of the following conclusions is best supported by this information?
A. The two groups are the same species because the plants have similar shapes.
B. The two groups are different species because they have differently sized stalks.
C. The two groups are different species because the seeds produced cannot sprout or grow.
D. The two groups are the same species because the plants were cross-pollinated and produced seeds
____________________
20. A partial food web is shown below. Which organisms in the food web are both primary and secondary consumers?
A. bluegills
B. cattails
C. coyotes
D. snakes
____________________
28. A student looks at a cell under a microscope. Which of the following
observations would indicate that the cell is from a plant rather than an animal?
A. a nucleus located inside of the cell
B. numerous cilia on the outside of the cell
C. chloroplasts in the cytoplasm of the cell
D. a thin membrane around the edge of the cell
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30. Prolonged periods of drought in an area cause decreases in plant population
sizes. Which of the following statements describes how the decreases in plant
population sizes then affect other populations in the area?
A. Omnivore population sizes increase, and herbivore population sizes increase.
B. Omnivore population sizes decrease, and carnivore population sizes increase.
C. Herbivore population sizes increase, and carnivore population sizes decrease.
D. Herbivore population sizes decrease, and carnivore population sizes decrease.
Could there be a shadow biosphere?
Could there be a shadow biosphere here on Earth?
I. Life on Earth, but not as we know it?
This section excerpted from Life on Earth… but not as we know it,
Robin McKie, The Guardian (UK), 4/13/2013
These researchers believe life may exist in more than one form on Earth: standard life – like ours – and “weird life”, as they term the conjectured inhabitants of the shadow biosphere.
All the micro-organisms that we have detected on Earth to date have had a biology like our own: proteins made up of a maximum of 20 amino acids and a DNA genetic code made out of only four chemical bases: adenine, cytosine, guanine and thymine,” says Cleland.
“Yet there are up to 100 amino acids in nature and at least a dozen bases. These could easily have combined in the remote past to create lifeforms with a very different biochemistry to our own. More to the point, some may still exist in corners of the planet.”
Science’s failure to date to spot this weird life may seem puzzling. The natural history of our planet has been scrupulously studied and analysed by scientists, so how could a whole new type of life, albeit a microbial one, have been missed?
Cleland has an answer. The methods we use to detect micro-organisms today are based entirely on our own biochemistry and are therefore incapable of spotting shadow microbes, she argues. A sample of weird microbial life would simply not trigger responses to biochemists’ probes and would end up being thrown out with the rubbish.
That is why unexplained phenomena like desert varnish are important, she says, because they might provide us with clues about the shadow biosphere. We may have failed to detect the source of desert varnish for the simple reason that it is the handiwork of weird microbes which generate energy by oxidising minerals, leaving deposits behind them.
The idea of the shadow biosphere is also controversial and is challenged by several other scientists.
Biological Dark Matter
This section is originally from ‘Dark Matter’ in Biology, Ian Dunn, Biopolyverse, 3/21/2011.
That website no longer exists, so we present this here as a resource for our students.
… All current examples of ‘biological dark matter’ cited in the literature are, in essence, uncharacterized manifestations of known types of entities. Consider the issue of ‘dark’ products of complex genomes, in the form of numerous transcribed RNAs with unknown functions. However exotic the biological roles of certain non-coding RNAs, the general chemical nature of any RNA molecule is very familiar …
A strict analogical extension of cosmic to biological dark matter would then be the discovery of a biological effect that cannot be accounted for by ‘ordinary’ biological mediators or processes. And just as dark matter in the universe is a recent finding, such a hypothetical biological effect might itself be long unrecognized, rendering the agency involved truly obscured.
… there are levels and levels of ‘darkness’ in any area of investigation, not least of which is biology. In other words, a hierarchy of novelty / unfamiliarity / strangeness can be readily constructed when we consider new biological discoveries, and speculate upon their ‘outer limits’...
Some discoveries may provide interesting precedents for processes or structures hitherto unreported, but without causing too many eyebrows to be raised.
This image from Illuminating the dark matter in metabolomics, Ricardo da Silva, PNAS. http://www.pnas.org/content/112/41/12549
Still other findings may indeed cause considerable supra-ocular hair elevation, yet fall short of seriously challenging key biological principles.
With these considerations in mind, it is not difficult to categorize the experimental input of new biological information as a spectrum of sorts:
‘Dark Matter’ in Biology http://biopolyverse.com/2011/03/21/dark-matter-in-biology/
Extremely hypothetical dark life from actual, cosmological dark matter
This section excerpted from Could Dark Matter Spawn ‘Shadow Life’?
By Ian O’Neill, 2/7/2018, HowStuffWorks
The vast majority of mass in our universe is invisible, and for a while, physicists have been trying really hard to understand what this elusive “stuff” is.
Assumed to be some kind of particle, there are hopes that the Large Hadron Collider might produce a dark matter particle or that a space telescope might detect the obvious gamma-ray telltale signature of dark matter particles colliding. But so far, hints have been few and far between; a problem that’s forcing theoretical physicists to think up new ideas.
In a mind-bending 2017 op-ed for Nautilus, famed theoretical physicist Lisa Randall delved into one of the more extreme possibilities for dark matter. Rather than thinking of dark matter as one type of particle, might dark matter be composed of an entire family of particles that create dark stars, dark galaxies, dark planets and, perhaps, dark life?
This dark universe’s chemistry might be as rich and varied as our “ordinary chemistry.”
…Astrophysicists have hypothesized in the past that “dark stars” — stars made of dark matter — may have existed in our primordial universe and may persist to this day. If this is the case, Randall argues, perhaps “dark planets” may have formed, too.
She then takes this idea a step further: If there’s a family of dark matter particles, governed by forces only accessible in the dark sector, might this realm also have complex chemistry? If so, might there be life? If there is “shadow life” living out its days parallel to our universe, you can forget any hopes of detecting it, however.
Does Dark Matter Harbor Life?
Excerpted from Does Dark Matter Harbor Life? An invisible civilization could be living right under your nose. By Lisa Randall
… The Standard Model contains six types of quarks, three types of charged leptons (including the electron), three species of neutrinos, all the particles responsible for forces, as well as the newly discovered Higgs boson. What if the world of dark matter—if not equally rich—is reasonably wealthy too?…
If we were creatures made of dark matter, we would be very wrong to assume that the particles in our ordinary matter sector were all of the same type. Perhaps we ordinary matter people are making a similar mistake.
Given the complexity of the Standard Model of particle physics, which describes the most basic components of matter we know of, it seems very odd to assume that all of dark matter is composed of only one type of particle. Why not suppose instead that some fraction of the dark matter experiences its own forces?
In that case, just as ordinary matter consists of different types of particles and these fundamental building blocks interact through different combinations of charges, dark matter would also have different building blocks—and at least one of those distinct new particle types would experience non-gravitational interactions….
Ordinary matter’s many components have different interactions and contribute to the world in different ways. So too might dark matter have different particles with different behaviors that might influence the universe’s structure in a measurable fashion.
When first studying partially interacting dark matter, I was astonished to find that practically no one had considered the potential fallacy—and hubris—of assuming that only ordinary matter exhibits a diversity of particle types and interactions….
… Perhaps nuclear-type forces act on dark particles in addition to the electromagnetic-type one. In this even richer scenario, dark stars could form that undergo nuclear burning to create structures that behave even more similarly to ordinary matter than the dark matter I have so far described. In that case, the dark disk could be populated by dark stars surrounded by dark planets made up of dark atoms. Double-disk dark matter might then have all of the same complexity of ordinary matter.
- Lisa Randall is the Frank B. Baird, Jr., Professor of Science at Harvard University, where she studies theoretical particle physics and cosmology.
Tags
#shadowbiosphere #shadowlife #darklife #exobiology
Further reading
Hypothetical types of biochemistry, Wikipedia
Purple Earth Hypothesis, Wikipedia
‘Dark Matter’ in Biology
http://biopolyverse.com/2011/03/21/dark-matter-in-biology/
Paradigms and Biological ‘Dark Matter’
http://biopolyverse.com/2011/03/28/paradigms-and-biological-%E2%80%98dark-matter%E2%80%99/
‘Dark Matter’ in Biology: Great Expectations and Biological Limits
http://biopolyverse.com/2011/04/05/%E2%80%98dark-matter%E2%80%99-in-biology-great-expectations-and-biological-limits/
A Dark Shadow Biosphere with Unorthodox Orthogonality?
http://biopolyverse.com/2011/04/12/a-dark-shadow-biosphere-with-unorthodox-orthogonality/
A Dark Shadow Biosphere with Unorthodox Orthogonality?
Does ‘Dark’ Biology Have Its CHARMs?
http://biopolyverse.com/2011/05/03/does-%E2%80%98dark%E2%80%99-biology-have-its-charms/
Learning Standards
Next Generation Science Standards: Science & Engineering Practices
● Ask questions that arise from careful observation of phenomena, or unexpected results, to clarify and/or seek additional information.
● Ask questions that arise from examining models or a theory, to clarify and/or seek additional information and relationships.
● Ask questions to determine relationships, including quantitative relationships, between independent and dependent variables.
● Ask questions to clarify and refine a model, an explanation, or an engineering problem.
● Evaluate a question to determine if it is testable and relevant.
● Ask questions that can be investigated within the scope of the school laboratory, research facilities, or field (e.g., outdoor environment) with available resources and, when appropriate, frame a hypothesis based on a model or theory.
● Ask and/or evaluate questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of the design
MA 2016 Science and technology
Appendix I Science and Engineering Practices Progression Matrix
Science and engineering practices include the skills necessary to engage in scientific inquiry and engineering design. It is necessary to teach these so students develop an understanding and facility with the practices in appropriate contexts. The Framework for K-12 Science Education (NRC, 2012) identifies eight essential science and engineering practices:
1. Asking questions (for science) and defining problems (for engineering).
2. Developing and using models.
3. Planning and carrying out investigations.
4. Analyzing and interpreting data.
5. Using mathematics and computational thinking.
6. Constructing explanations (for science) and designing solutions (for engineering).
7. Engaging in argument from evidence.
8. Obtaining, evaluating, and communicating information.
Scientific inquiry and engineering design are dynamic and complex processes. Each requires engaging in a range of science and engineering practices to analyze and understand the natural and designed world. They are not defined by a linear, step-by-step approach. While students may learn and engage in distinct practices through their education, they should have periodic opportunities at each grade level to experience the holistic and dynamic processes represented below and described in the subsequent two pages… http://www.doe.mass.edu/frameworks/scitech/2016-04.pdf
KaiserScience 