1) How could you experimentally test whether herds of African antelope affect th
ID: 216712 • Letter: 1
Question
1) How could you experimentally test whether herds of African antelope affect the abundance of plants on which they graze? (Ch. 14)
2) Explain why an herbivore that consumes many different species of plant might be less successful at regulating the abundance of a well-documented plant species compared to an herbivore that specializes on eating a single species of plant. (Ch. 14)
3) In the classic experiment of C. F. Huffaker with mites and oranges, what mechanisms allowed the predator and prey populations to persist? (Ch. 14)
4) Which factors determine the duration of population cycles and which determine the magnitude of change in population sizes? (Ch. 14)
5) According to the Lotka-Volterra model of predator-prey interactions, why do predator and prey populations cycle? (Ch. 14)
6) How do search image formation and prey switching behavior lead to a type III functional response in predators? (Ch. 14)
7) Compare and contrast a predator’s numerical response and functional response.
(Ch. 14)
8) Explain the causes of an evolutionary arms race between consumers and the species that they consume. (Ch. 14)
Explanation / Answer
Ans 1. We could do an experiment placing African antelopes occupy an area full of grass andmigrating them to other grass covered areas to allow the grass to recover its growth again. Thenwe could compare these results and seeing whether herds of African antelopes affect theabundance of plants on which they graze.
Ans 2. flexible herbivore will avoid the well-defended species in preference for easier food.
Ans 3. increased dispersal of prey.
Carl Huffaker conducted experiments, through this he was able to establish populationsof sex spotted mites on trays of orange that sometimes were used as a form of habitat and orfood. He found out that without predator’s prey populations increased vs with predators whereeverything became extinct. Extinction of both populations took far longer if the oranges weremore further spread out, ultimately making it longer for predators to find the prey.
Ans 4. the mortality rate of the predator and the prey capture rate.
Ans 5. the Lotka-Volterra model is its reliance on unrealistic assumptions. For example, prey populations are limited by food resources and not just by predation, and no predator can consume infinite quantities of prey. Examples of cyclical relationships between predator and prey populations have been demonstrated in the laboratory or observed in nature, but in general these are better fit by models incorporating terms that represent carrying capacity (the maximum population size that a given environment can support) for the prey population, realistic functional responses (how a predator's consumption rate changes as prey densities change) for the predator population, and complexity in the environment.
Ans 6. search image-When a new prey species appears in the area its risk of becoming selected as food by a predator is low. The predator has not yet acquired a search image --- way to recognize that species as food item. Once the predator has captured an individual it may identify the species as desirable prey. It then has an easier time locating others of the same kind. In time the number of this particular prey species becomes so reduced the predator stopped recognizing it and it can create a cycle like the type III functionality curve where at low prey density consumption is low up until a point where it increases rapidly.
Prey Switching-Attack efficiency and search image formation contribute to pattern of prey switching, where a species will favor one prey over another at different levels of abundance.
Type 3- Mechanisms:
search image formation
switching between prey types
switching between different habitats
Note: S-shaped functional responses are typically found in generalist predators (predators that attack more than one type of prey)
Ans 7.
Functional Response
A functional response is the intake rate of a consumer as a function of food density (the amount of food available in a given ecotope). It is associated with the numerical response, which is the reproduction rate of a consumer as a function of food density.
It include a predator spends its time on 2 kinds of activities:
Numerical Response
Numerical response means that predators become more abundant as prey density increases. However, the term "numerical response" is rather confusing because it may result from 2 different mechanisms:
Reproduction rate of predators naturally depends on their predation rate. The more prey consumed, the more energy the predator can allocate for reproduction. Mortality rate also reduces with increased prey consumption.
Ans 8.
Evolutionary arms races
consumer-resource>prey continually evolves better defenses and predators continually evolve better offenses.
Example-Macaw, ants/parasites (red abdomen makes them look like berries so they are eaten by birds), butterfly/plants (plants evolve spots that look like eggs), Darwin's orchid: nectar at bottom of foot long tube for moth.
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