1. Unit A: Interactions and Ecosystems Topic 4: How Organisms Interact

2. Review Biotic factors – living organisms in an ecosystem; or material that came from living organisms. Biotic factors – living organisms in an ecosystem; or material that came from living organisms. Abiotic factors – Non-living things in an ecosystem. Abiotic factors – Non-living things in an ecosystem. Remember that biotic and abiotic factors interact with each other. They affect each other. Remember that biotic and abiotic factors interact with each other. They affect each other. Soil is a combination of biotic (worms, bugs) and abiotic (dirt, rocks, clay). Soil is a combination of biotic (worms, bugs) and abiotic (dirt, rocks, clay).

3. The Niche The area and role that an organism fills. The area and role that an organism fills. An organism can fill more than one niche in the same ecosystem. An organism can fill more than one niche in the same ecosystem. Eg. A venus flytrap is a producer because it is a plant, however it is also a consumer/carnivore because it ‘eats’ bugs. Eg. A venus flytrap is a producer because it is a plant, however it is also a consumer/carnivore because it ‘eats’ bugs. Also an organisms can have different niches by moving through different ecosystems. Also an organisms can have different niches by moving through different ecosystems.

4. Producers Producers – Green plants that produce their own food through photosynthesis. Most living things in an ecosystem are producers. Producers – Green plants that produce their own food through photosynthesis. Most living things in an ecosystem are producers. Photosynthesis – the process where plants take in solar energy and change it into sugar that they use for food. Photosynthesis – the process where plants take in solar energy and change it into sugar that they use for food.

5. Consumers Any organism that has to eat other organisms to get the energy it needs. Any organism that has to eat other organisms to get the energy it needs. There are five main kinds of consumers: herbivores (eat only plants), carnivores (eat only animals), omnivores (eat both plants and animals), scavengers (only eat dead organisms), and decomposers (absorb nutrients from dead organisms.) There are five main kinds of consumers: herbivores (eat only plants), carnivores (eat only animals), omnivores (eat both plants and animals), scavengers (only eat dead organisms), and decomposers (absorb nutrients from dead organisms.) The difference between scavengers and decomposers is that scavengers eat dead material, and decomposers absorb the nutrients from the material. The difference between scavengers and decomposers is that scavengers eat dead material, and decomposers absorb the nutrients from the material.

6. Food Chains A model of how energy moves through an ecosystem. A model of how energy moves through an ecosystem. Energy starts at the sun, goes through plants through photosynthesis, then through herbivores, and so on until it is partly recycled by decomposers. Energy starts at the sun, goes through plants through photosynthesis, then through herbivores, and so on until it is partly recycled by decomposers. A food web is more realistic than a food chain because it shows the complex connections between species in an ecosystem. The downside is that it is more complex than a food chain. A food web is more realistic than a food chain because it shows the complex connections between species in an ecosystem. The downside is that it is more complex than a food chain.

7. Where does the Energy Go? Anytime food is eaten, about 90% of the energy in the food is used up or lost. Anytime food is eaten, about 90% of the energy in the food is used up or lost. Energy is used to keep the organism alive by helping it breath, keep it warm, pump blood etc. Energy is used to keep the organism alive by helping it breath, keep it warm, pump blood etc. Only a small part of the original energy is absorbed by the decomposers at the end of the ecosystem. Only a small part of the original energy is absorbed by the decomposers at the end of the ecosystem.

8. Pyramid of Numbers and Biomass Because so much energy is lost each time an organism eats another organism, a big group of producers can only support a smaller population of herbivores, which can support an even smaller number of omnivores, and so on. Because so much energy is lost each time an organism eats another organism, a big group of producers can only support a smaller population of herbivores, which can support an even smaller number of omnivores, and so on. In an ecosystem you might have millions of plants, hundreds of caribou, and maybe 30-40 wolves in a wolf pack. In an ecosystem you might have millions of plants, hundreds of caribou, and maybe 30-40 wolves in a wolf pack.

9. Biomass represents the total mass of each level of organism. represents the total mass of each level of organism. Just like with numbers of organisms, the most mass in an ecosystem should be at the producer level, followed by herbivores and so on. Just like with numbers of organisms, the most mass in an ecosystem should be at the producer level, followed by herbivores and so on.

10. Sample Food Pyramids