Food Chains Begin With Photosynthesis

Program Overview


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In this episode, a single algae cell is rescued and its green secrets revealed through experiments performed on board the Cyclops. The ship’s naturalist discovers that, given light, the green cell generates oxygen (something the crew is in dire need of at the time) along with several kinds of food molecules. Swim­ming outside, the micronauts see vast numbers of green photosynthetic cells. Larger cells show up and start gorging on the algae, creating a food chain that ultimately sustains the fish, birds, amphibians and mammals living in and around the pond.

ABOUT FOOD CHAINS AND THE PROCESS OF PHOTOSYNTHESIS

Photosynthesis is the process of converting light energy into chemical energy useful to living things. It occurs in green plants, green algae, yellow and red algae, and in certain kinds of bacteria.

Chloroplasts are filled with stacks of discs covered with chlorophyll molecules that absorb blue and red wavelengths of light, reflecting away the green.


Lyra, has a horseshoe-shaped chloroplast.)

In plant leaves, and in algae, the cells contian many particles often shaped like green jelly beans, but in the cell captured by Lyra, the green particle was bent around the cell nucleus like a horseshoe. These particles are called chloroplasts, because they contain chlorophyll molecules. Chlorophyll molecules absorb light energy in the blue and red regions of the spectrum and reflect away green - which explains why plants appear green.

In ponds, algae cells are used as food by all sorts of small animals and protists. In this episode of Eye of the Cyclops the crew witnesses an attack by Paramecia and other ciliated protists on a swarm of small green cells. The abundant green cells create an un­usual feeding opportunity for Paramecium which usually subsists on a bacteria diet. The paramecia, in turn, become food for small pond animals such as baby fish, mosquito larva, water worms, and colonies of filter-feeding animals known as the bryozoan colony seen at the end of the episode. Dead organisms and waste materials fall to the pond bottom where they are digested by bacteria. Bacteria are eaten by protozoans. The protozoans are eaten by small water animals and so on.

At each step in the food chain, only part of the energy contained in the organism being eaten is stored in the cells and tissues of the eater. A rough rule is that only about 10% of the energy moves from one food chain step to the next. Using the 10% rule try creating an Òenergy pyramidÓ if the top consumer is a Great Blue Heron that weighs ten pounds. The food chain steps, working backward from the Heron would beÑHeron eats fish, fish eats mosquito larva, mosquito larva eats Paramecium, Paramecium eats single cell green alga. Calculate how many pounds of algae are represented by that 10 pound Heron.

Food chain terminology:

producer:
an organism that manufactures biological molecules from raw materials using light energy (photosynthesis), or energy stored in inorganic molecules (chemosynthesis).
first level consumer:
An organism that eats the producer. In this case Paramecium was acting as a first level consumer when it engulfed the green photosynthetic cells.
second level consumer:
An organism that feeds on first level consumers, and so on.

Building the pyramids ...

At each step in the food chain, only part of the energy contained in the organism being eaten is stored in the cells and tissues of the eater. A rough rule is that only about 10% of the energy moves from one food chain step to the next. Using the 10% rule try creating an energy pyramid if the top consumer is a Great Blue Heron that weighs ten pounds.

The food chain steps, working backward from the heron would be: heron eats fish, fish eats mosquito larva, mosquito larva eats Paramecium, Paramecium eats single cell green alga. Calculate how many pounds of algae are represented by that 10 pound heron.

Student Research

Looking for green jelly beans with a microscope

This is your chance to observe the particle on which almost all life depends on the chloroplast.

Try examining subjects you think might contain chloroplasts. The best ones will be very thin so that light can pass through the subject.

Some suggestions: tiny moss leaves placed in a drop of water and pressed flat with a coverglass; a leaf of elodea, a common aquarium plant; any bright green algae scraped from a damp wall or found in a pond or stream.

Can Earth support more rice eaters, or hamburger eaters?

Using the 10:1 conversion ration, estimate how many pounds of cattle food a growing 100 pound person who eats nothing but hamburgers represents.

Let’s go live on the moon:

This is a sit down research problem requiring no field work or laboratory experiment. Working with what you have learned from this video program create what you consider would be the most efficient life support system for a self sufficient colony of humans on the moon. Consider the type of food needed to support the colony, what you would do with waste materials, where would oxygen needed for life be ob­tained, and any related questions that come to mind. Tip: ecologists often use diagrams with arrows assigned to products, to depict such close systems.

Vocabulary

Habitat:
the place where an organism lives.
Unicellular algae:
single celled photosynthetic organisms.
Protist:
general name for unicellular life.
Enzymes:
protein molecules that catalyze reactions cuch as the digestion of large organic molecules, breaking them down into their molecular building blocks.
Phagocytosis:
the engulfment of food particles (other organisms) by cells.
Food Vacuoles:
membrane bubbles within cells where digestion occurs.
Chloropast:
the green organelles found in plant cells and green algae. Chloroplasts carry out the process of photosynthesis.
Photosynthesis:
the fundamental energy transforming process on which almost all living things depend. The process of converting light energy into the chemical bond eneergy contained in food molecules.
Ecosystem:
all of the organisms that interact with each other living in a particular environment. Examples: pond ecosystem, a stream ecosystem, a forest ecosystem.
Food Chains:
description of who eats whom.
Producer:
an organism that gets energy from light or from inorganic molecules.
Consumer:
an organism that obtains energy by eating other organisms.
Decomposers:
organisms such as bacteria and fungi that break down organic molecules in the environment.
Ecological pyramid:
a graphic presentation that shows the relationship of producer organisms to consumer organisms. These graphs show at a glance the amounts of energy transferred theough a food chain.
Adaptation:
a structure, behavior, or physiological process that fits the organism to its niche. A structure that has survival value.

Photosynthesis Gallery Challenge

Chloroplasts in plants are spheres or bean shaped (seen in the moss leaf cells). Chloroplasts in algae take on different shapes. All have the same internal structure seen in the electron micrograph.
Which photo shows a first level consumer?

 
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