Ecosystems
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The components of an ecosystem can be divided into two large groups: things that are biotic and things that are abiotic. The biotic parts are living or once living organisms or things derived from a living organism. Biotic parts include plants, animals, fungi, bacteria, and protists. The abiotic parts are nonliving things. Abiotic components include water, air, inorganic soil layers, rocks, temperature, sunlight, and other parts of the ecosystem that lack cell structure and the characteristics of living organisms. |
What biotic components can you identify in the picture? Abiotic? If you said that the rotting log was biotic, you are correct. Even though the tree is dead and decomposing now, it was once living. Look at the way light and shadow play on the plants. You should have been able to identify sunlight as an abiotic factor and infer temperature and air as well.
Eight Signs of Life
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Living organisms have cell structure and .... |
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-Reproduce |
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-Respire |
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-Respond to stimuli |
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-Secrete useful chemicals |
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-Excrete waste |
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-Obtain nutrients (e.g., photosynthesis, ingestion, digestion) |
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-Move in a purposeful way |
Niches and Habitats
The place where an organisms lives is called its habitat. A habitat can be a large as a forest or a small as the gut of a termite. What an organism does in its habitat including its role in the food web is called its niche. There are many words used to describe niches and relationships within an ecosystem.
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Relationship |
Benefit/Harm |
Example |
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Commensalism |
One organism benefits, the other has no benefit or harm |
A robin nests in a tree A barnacle catches a ride on a horseshoe crab |
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Mutualism |
Both organisms receive a benefit from the relationship |
A bee pollinating a flower Fungi and algae combine to form a lichen |
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Parasitism |
One organism benefits while causing harm to the other |
A tapeworm lives off the gut of a human A tick lives off the blood of a deer |
Roles in the Food Web
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Producer |
Makes food for themselves and others (photosynthesis) |
Plants and plant-like organisms, some bacteria |
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Consumer |
Takes in food |
Animals, Fungi, Animal-like and Fungi-like organisms, some bacteria |
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Herbivore |
Consumes plants |
Rabbits, deer |
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Omnivore |
Consumes both plants and meat |
Mice, humans |
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Carnivore |
Consumes meat |
Lions, osprey |
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Scavenger |
Consumes dead organic matter |
Earthworm, sowbug |
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Decomposer |
Breaks down dead organic matter |
Bacteria and fungi |
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Role: |
Predator |
Prey |
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Definition: |
The organism that hunts for and kills its food |
The organism that is hunted and eaten |
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Example: |
Osprey |
Fish |
An Energy Pyramid
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Top Consumer |
Top Carnivore |
Hawk |
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Tertiary Consumer |
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Carnivore |
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Snake |
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Secondary Consumer |
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Omnivore |
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Mouse |
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Primary Consumer |
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Herbivore |
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Insect |
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Producer |
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Plant |
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The energy pyramid shows the flow of energy in an ecosystem. Producers receive energy from the sun and use it to convert carbon dioxide and water into food for themselves and others. Herbivores are animals that eat only plants. They are called primary consumers because they are the first organisms to receive energy from the producers. Omnivores consume both plants and animals and in this pyramid, the omnivore is the secondary consumer. A carnivore is a meat eater. In this case, the carnivore is a snake and is the third consumer or tertiary consumer. Finally, the carnivore or consumer who is not eaten by anything else is called the top consumer. About 10% of an organism's food energy passes on to the consumer at each level. Almost 90% of the food energy is lost to heat and other transformations associated with consumption.
Eventually all organisms in an ecosystem die. Energy is then released through decomposition by fungi and bacteria or through consumption by scavengers. The difference between a scavenger and a decomposer is how they obtain nutrients. Scavengers move to find their food and eat it. Decomposers are deposited on the dead organic matter and break it down externally before absorbing the nutrients.
