Download The Single Cell versus Colonial Algae

The Single Cell versus Colonial Algae
Before plants were made up of many cells, or multi-cellular, they were singlecelled organisms similar to algae that lived in the water.
Algae evolved from single-celled organisms (made up of one cell) to colonial
(made up of many individual cells living together) to multi-cellular (many
specialized cells working together in one organism).
Time
Single celled
Colonies
Multi-cellular
Benefit:
By having many cells working together, some cells can become specialized in
carrying out certain functions like the organs in your body.
Algae cells are also protected from predators, and eventually they evolved to be
more than a colony-
Photosynthesis
Plants make their own food, or sugar, through the process of photosynthesis.
They use the sun’s energy, carbon dioxide, and water.
Photosynthesis, the process of making sugar by plants, happens in cell organelles
called chloroplasts.
Chloroplasts have their own DNA, or genetic information, that is very similar to
that of cyanobacteria.
It is likely that a plant cell captured a cyanobacteria and started to use it to create
sugar for itself. This symbiosis ultimately evolved into chloroplasts in plant cells.
Vascular System in Plants
Plants need to carry water and nutrients from their roots to the rest of their
bodies.
The xylem is the system that carries water and nutrients.
Plants make sugar in their leaves, but need to give that energy to the rest of
their bodies.
The phloem carries sugars from the leaves to the rest of the plant.
Vascular Water Flow
At this station, you will track the path of the water through celery, a vascular
plant. Yesterday, I soaked celery stalks in red-colored water. Now, you will
carefully look at these celery stalks, make sketches, and answer the questions
that follow.
Name: _________________
Period:__________
SC.7.L.15.2 Explore the scientific theory of evolution by recognizing and explaining ways in which genetic
variation and environmental factors contribute to evolution by natural selection and diversity of
organisms.
SC.7.L.15.3 Explore the scientific theory of evolution by relating how the inability of a species to adapt
within a changing environment may contribute to the extinction of that species
MULTICELLULARITY
Hypothesis: What do you think is the advantage of being multi-cellular?
If an organism is able to have many cells in its body rather than one, then it
_____________________________________________________________.
Directions: Observe the algae under the microscope and draw what you see below. Then read
the station description and answer the questions below.
Description:
Multi-cellular animals can use different cells to become different organs. What type of organs
do you think plants were able to develop after evolving from single-celled into multi-cellular
organisms?
What do you think the benefit is of having a colony over being a single cell? Are some cells
protected?
How does this alga compare to the picture of large algae like that on the station information
sheet?
Name: _________________
Period:__________
PHOTOSYNTHESIS
Photosynthesis is the process used by plants and other organisms to convert the light energy
captured from the sun into chemical energy that can be used to fuel the organism's activities.
Hypothesis: What do you think is the advantage of photosynthesis?
If plants can carry out their own photosynthesis, then they have the advantage of
_____________________________________________________________.
Directions: Observe the organisms under the microscope and draw what you see below. Then
read the station description and answer the questions below.
Cyanobacteria:
Elodea Leaf: Label the chloroplasts
Decribe what you see under the microscopes. How are the organisms similar? How are they
different?
Why are chloroplasts important for plants?
Name: _________________
Period:__________
THE VASCULAR SYSTEM
Hypothesis: What do you think is the advantage of having a vascular system in plants?
If a plant has a system that carries water and nutrients to the rest of its body, then it has the
advantage of _____________________________________________________________.
Directions: Observe the microscope slide and draw what you see below. Label the xylem and
phloem Then read the station description and answer the questions below.
If the vascular system in humans is the arteries and veins in humans, how do you think this is
similar to the vascular system in plants?
The vascular system is very tough and runs down the center of a plant stem. What advantage
do you think this provided for plants moving from water to land? What kind of FORCES are
there on land that you don’t feel in the water?
Name: _________________
Period:__________
VASCULAR WATER FLOW
Directions: Examine a piece of celery in front of you. Draw a sketch of the celery below. Then
answer the questions that follow.
Description:
Questions:
1. Does the colored water appear to be distributed to all parts of the stalk evenly or is it
concentrated in certain areas? Why do you think that is?
2. What tissue is made red by the transport of colored water through the plant?
Name: _________________
Period:__________
WRAP-UP QUESTIONS
1. What environmental factors caused plants to evolve into what we see today?
2. What plant adaptations make it possible for plants to survive on land?
3. Define the theory of evolution. How does natural selection play a part in evolution?
4. Seeds are one of the final evolutionary steps in plant evolution. They help plants
reproduce. How are seeds dispersed? Why is this easier than reproducing in the water?
What adaptations do seeds have to help them become dispersed?