The Single Cell versus Colonial Algae

Transcription

1 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-

2 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.

3 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.

4 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.

5 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?

6 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?

7 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?

8 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?

9 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?