They can influence death rates of their prey, influence the rates of population growth Can be a source of negative feedback They have the potential to regulate prey populations around an equilibrium
Why do population cycles occur?
They occur because the population growth of the predator influence the population growth rate of the prey and vice versa Lynx are specialist predators on hares
What are the interactive effects that affect the population of hare?
The forces of predation by lynx and competition for food Determined by the grass plot experiment
What happens when prey change their behavior in response to the presence of a predator?
All vital rates can change
What vital rates can predators changes?
All of them BIDE
What is an example of how predators force their prey to emigrate?
Sunfish run away (emigration) from patches with bass and forage at the edges of ponds & lakes
What is an example of how predators make their preys' birth rates decline?
Because sunfish are hiding from bass, they are more concerned with surviving than with fitness
How do predators influence species diversity in communities?
Because the sea star Pisaster is a predator of muscles, it keeps the population of muscles down and allows biodiversity. However, removing Pisaster allows muscles to multiply and outcompete most other species so biodiversity declines
What is herbivory?
It is usually non-lethal, predation on plants. Many different kinds of organisms attack plants from herbivores to diseases. Herbivores rarely kill while diseases often do.
How do herbivores influence plant populations and community structure?
Deer, for example, reduce plant abundance thus changing the community composition (identity of remaining species)
What are the three hypotheses to explain why the world is green?
Herbivore populations are regulated below carrying capacity by predators Plants are not good sources of nutrients and can't support high herbivore populations Plants are well-defended against herbivores and respond to attack by increasing their defenses
What are constitutive defenses?
Defenses that are present at all times, whether herbivores are feeding on the plant or not
What are induced defenses?
Defenses that are activated when a predator is in the area
What is an example that proves animal prey can have induced defenses?
Some crabs feed on mussels, yet mussel shells grow thicker when mussels detect the presence of crabs in the environment
What are some of the known evolved constitutive defenses it animals?
Camouflage, schooling, weaponry
What is Mullerian mimicry?
An insect species is poisonous, so any insect that is also poisonous is assumed to be a general poisonous appearance for an insect. Everyone leaves the look-a-like, who is poisonous anyways, alone
What is Batesian mimicry?
When insects that are non-toxic appear to look like toxic species, they benefit because no one wants to be poisoned
What is the evolutionary arms race?
Prey become even better defended while predators become ever better at overcoming those defenses. "Anything you can do I can do better"
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