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Plant life

Learning goals

Characteristics of animals
* What makes plant cells different from our cells
* What molecules plants need, produce

Characteristics

Plants are eukaryotes. Great…. what does that mean?

On the left is a plant cell, on the right is an animal cell. They look different, but they have some basic similarities:

Eukaryotes are any cells have an organized nucleus, and organelles (each organelle has their own distinct job)

Fungus cells are also eukaryotic.

Levin 8e/Wiley fig 8-37 w174

How are plant cells similar to, or different, from animal cells?

Plant cells have both a membrane (lipid bilayer)  and a cell wall (cellulose.)

The membrane is made up of fats; it is flexible.

The cell wall is still and provides structure and strength.

Animal cells only have the cell membrane.

Plant cell has a wall adapaproject

Plant cell has a wall adapaproject

Plant cells have one huge vacuole (storage organelle.)

Animal cells have many tiny vacuoles.

Plant cells have chloroplasts.

This is where photosynthesis occurs.

Animal cells never have chloroplasts.

Plants are autotrophs

Organisms that make their own food are called autotrophs. Sometimes they are called producers. (both mean the same thing.)

Plants don’t eat food – they produce their own food molecules.

(Although of course they do need CO2 gas, water, and energy from the sun.)

Some plants are parasites

Parasites are heterotrophs – this means that they need to get food from other sources. As surprising as this may sound, a few plants are parasites on other plants,

This is cactus mistletoe (Tristerix aphylla), from Chile.  This is a bright red parasitic plant. It can only live on a cactus.

Echinopsis chiloensis and Tristerix aphylla

Pic by Scott Zona. Echinopsis chiloensis + Tristerix aphylla. At Parque Nacional La Campana, Chile.

What plants need, what they produce

They need:

Energy from visible electromagnetic radiation (“sunlight”)

CO2 (carbon dioxide gas)

H2O (water)

Trace amount of minerals, absorbed through the plant’s roots.

What they produce:

Sugars (organic molecules)

Complex carbohydrates (made from the sugars)

O2 (oxygen gas molecules)

How does this work? Photosynthesis

Let’s follow the diagram: Energy enters from sunlight.

We see an organelle with little green stacks absorbing the sunlight. That’s the chloroplast. What comes out of it?

Chemistry Photosynthesis

We see organic molecules – sugars! – come out of the chloroplast. Also O2 (oxygen gas) comes out of it.

Where do they go? They enter another organelle, the mitochondria – the powerhouse of the cell!

This produces ATP, a chemical that stores energy. Everything else in the cell that uses energy? That would use these ATP molecules.

 

Here’s an animation of how this works, as a formula:

photosynthesis vs cellular respiration

from the Amoeba sisters

Family tree of plants

Like all other forms of life on Earth, plants developed over time.

They developed through a processevolution by natural selection.

In this graph, the bottom is the very distance past. As you move up the chart you move close towards the modern era. At the top level of the chart is life on earth today.

Plant cladogram larger

Green algae

What about green algae – are they plants? We’ll have a separate lesson on that: Algae.

Vasculature

All animals, including people have a system of blood vessels, arteries, veins.  We call this system “vasculature.” Do plants have anything like this?

vasculature circulatory veins arteries

Plants don’t have blood, but some plants have vasculature as well!

Many plants have a system of vessels through which water, sugars, and minerals will flow.  You can see these tubes in this celery stalk.

celery vasculature

You can see plant vasculature in this leaf.

leaf vasculature

 

The simplest plants, however, do not have vasculature. Consider bryophytes: These are small, simple, green land dwelling plants. A few of them are aquatic.

Examples: Hornworts, Liverworts, and Mosses.

bryophytes

These are the largest group of land plants – 25,000 different species found throughout the world.

Most are found in areas which are humid and damp with a cold to moderately warm climate. They can withstand being frozen in snow without damage.

Bryophytes have no internal means for transporting water or nutrients.

They are often said to have leaves – but these are not equivalent to the leaves of vascular plants.

Bryophytes are mostly one cell thick.

They don’t have any roots, but do have filaments which anchor them down.

They don’t produce flowers, and therefore never produce seeds.

They reproduce by spore production.

 

Apps & animations

Flash animation showing water & nutrient transport through vascular plants

Phloem loading. Biology (Flash)

Sciencenetlinks.com. icell-app

Seed plants

Seed plants create soils, forests, and food.

Seed-producing plants are probably the most familiar plants to most people, unlike mosses, liverworts, horsetails, and most other seedless plants which are overlooked because of their size or inconspicuous appearance.

Conifers are seed plants; they include pines, firs, yew, redwood, and many other large trees.

Other major group of seed-plants are the flowering plants, including plants whose flowers are showy, but also many plants with reduced flowers – such as the oaks, grasses, and palms.

Seeded plants are either angiosperms or gymnosperms

Classification

{ http://www.easypacelearning.com/science/plants/plants/1332-plant-classifications-of-flowering-and-non-flowering-plants }

plants3

{ https://imanshomeschool.wordpress.com/2013/05/01/plant-classification-chart/ }

plant-poster

Plant reproduction

http://www.shmoop.com/plant-biology/plant-reproduction.html

http://www.biology4kids.com/files/plants_main.html

Learning Standards

Massachusetts Science and Technology/Engineering Curriculum Framework

Life Science (Biology), Grades 6–8.
Classify organisms into the currently recognized kingdoms according to characteristics that they share. Be familiar with organisms from each kingdom.

Biology, High School
5.2 Describe species as reproductively distinct groups of organisms. Recognize that species are further classified into a hierarchical taxonomic system (kingdom, phylum, class, order, family, genus, species) based on morphological, behavioral, and molecular similarities.

Benchmarks for Science Literacy, American Association for the Advancement of Science

Students should begin to extend their attention from external anatomy to internal structures and functions. Patterns of development may be brought in to further illustrate similarities and differences among organisms. Also, they should move from their invented classification systems to those used in modern biology… A classification system is a framework created by scientists for describing the vast diversity of organisms, indicating the degree of relatedness between organisms, and framing research questions.

SAT Biology Subject Area Test

Evolution and diversity: Origin of life, evidence of evolution, patterns of evolution, natural selection, speciation, classification and diversity of organisms.

Teaching About Evolution and the Nature of Science, National Academy Press (1998)

Biological classifications are based on how organisms are related. Organisms are classified into a hierarchy of groups and subgroups based on similarities which reflect their evolutionary relationships. Species is the most fundamental unit of classification.

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