Download Interactions in Ecosystems

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
insects, other small
– Few predators other than humans
– Biting insects and parasites feed
them
– Hibernate in winter
animals
berries),
on
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