Lesson 3 – Interactions in Ecosystems

Ecological Niche An ecological niche is the function a species serves in its ecosystem, including where it lives, what it eats, what eats it, and how it behaves Consider a black bear: They eat plant parts (nuts and berries), insects, other small animals Few predators other than humans Biting insects and parasites feed on them Hibernate in winter

Types of Consumers What each species eats has an important impact on an ecosystem Consumers fit into the following types based on what they eat and how they behave Herbivore – eats only plants or other producers Carnivore – eats only other consumers Omnivore – eats both producers and consumers Scavenger and decomposer – feed on the remains of other, dead or decaying, organisms

Food Chains Food chains show the feeding relationships among species in an ecosystem Food chains illustrate what each species uses for food Seeds of a pine tree (producer) are eaten by a red squirrel (herbivore) Red squirrel is eaten by a weasel (carnivore) Weasel is eaten by a goshawk (carnivore)

Food Chains Carnivores linked in a food chain have a predator-prey relationship The animal being eaten is the prey (the fish), the animal eating is the predator (the osprey)

Energy in the Food Chain Chemical energy stored in pine seeds is passed to the red squirrel Some energy passes to the weasel, and some of that to the goshawk Food chains show how energy passes through an ecosystem

Energy in the Food Chain The arrows show the direction of energy flow (always point at the organism that is eating)

Feeding Levels The trophic level describes the position of an organism in a food chain The first trophic level contains producers The second contains herbivores or primary consumers The third contains carnivores or secondary consumers The fourth contains carnivores and are called tertiary consumers

Feeding Levels

Feeding Levels Organisms use energy to live and release thermal energy Typically, only about 10 % of the energy taken in by organisms is passed on to the organism that consumes it

Food Webs Food chains show simple feeding relationships A more complete model can be seen in a food web Food webs show a series of interconnecting food chains A consumer that feeds on many species is less affected if one of those populations decreases or becomes scarce A newly introduced species can disrupt a food chain

Food Webs

Food Webs The rusty crayfish invades this ecosystem and competes with native species for the same food