Ecology: Predation and Herbivory Part 1

Intraspecific interaction

interactions between individuals of the same species

interspecific interactions

interactions between individuals of different species

mutualism

when both species benefit

competition

both species are negatively affected by competing for resources

commensalism

one benefits while the other is unaffected

amensalism

one is harmed while the other is unaffected

consumer resource

consumer benefits while resource is harmed

consumer species

feed on other species

what are the 3 types of consumer species?

predators, parasites, and parasitoids

whats the difference between parasites and parasitoids?

parasites consume living tissue of their hosts while parasitoids consume living tissue eventually killing their host

resource species

fed upon by other species

what are the two types of resource species?

prey and host

are population sizes regulated by what organisms eat or by what eats them?

both because many species are middle links in food chains

bottom up control

availability of resources limits population growth

top down control

predators limit population sizes by eating them

Explain the graph. What trends does it show about how food availability and predation affect population abundance?

The green curve represents plants, which are the resource. More food supports a larger rabbit population, increasing rabbit carrying capacity. The red curve represents coyotes, which are the predators. The predators reduce the rabbit population.

In the graph example, the coyotes limited prey populations. The rabbits, which are herbivores, limited what?

producer populations

Biological control

reducing “pest” populations by intentional introduction of their consumer

Colonists of Australia introduced cane toads to control native beetles that attacked sugar cane crops. Why were 2 reasons why this was a failed example of biological control?

The cane toads were being fed upon by other predators in Australia. The toxins cane toads released were killing off many native Australian predators. Additionally, beetle larvae lived underground and fed on plant roots, so toads couldn’t reach them anyway.

What are trophic cascades?

the effects of predators spread downward through a food chain alternating between positive and negative effects at each level

Explain how this image represents a trophic cascade.

When foxes increase, they eat more rabbits. The decrease of rabbits means less grazing on plants. Less grazing allows more plants to grow. So, the foxes and plants experiences positive effects while the rabbits experience a negative effect.

what are the 5 different types of defenses?

behavoiral, crypsis, structural, chemical, and mimicry

behavoiral defense

actions that help organisms avoid predators

Give an example of a behavioral defense involving copepods.

Copepods migrate to deeper water every day to avoid fish predators

Crypsis defense (camoflauge)

blending into the environment to avoid detection

Give an example of crypsis involving common potoo (bird).

Common potoo sits still and stretches its body to look like a broken tree branch

Structural defense

physical features that discourage predators or herbivores

Give an example of a structural defense involving plants.

thorns on plants protect them from herbivores

Chemical defense

chemicals that deter or harms predators and herbivores

Give an example of a chemical defense involving beetles.

Bombardier beetles spray hot liquid when threatened

Mimicry defense

resembling another organism to avoid being eaten

Give an example of mimicry defense involving a wasp.

a harmless hoverfly mimics the look of a wasp deterring predators since wasps are known to sting

convergent evolution

different species independently evolve similar adaptations since they face similar environmental pressures

what is consumer counter evolution?

occurs when consumers evolve adaptations to overcome the defenses of the organisms they eat

Milkweed contains toxic compounds that interfere with the sodium pottasium pump that can disrupt heart function. Most animals can’t eat milkweed because of these toxins. What did scientist find when comparing the sodium pump of species that eat milkweed vs. species that don’t?

they discovered that milkweed eating species independently evolved changes to the pump’s protein structure making the toxins ineffective