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Week 9 questions
Terms in this set (17)
A change in the rate of consumption at one trophic level that results in a series of changes in species abundance or composition at lower trophic levels.
Describe what 'top-down' control of a community means, and how this differs from 'bottom up' control.
top-down control - occurs when abundance of a population is limited by predators
bottom-up control - occurs when abundance of population is limited by nutrient supply/food availability
Give three reasons why trophic cascades might NOT exert strong control over plant community composition or biomass. What type of communities are more likely to exhibit strong trophic control?
Herbivores have a very strong top-down control over plants.
Are small or large herbivores more selective in their choices of food items and why?
Small herbivores because they have less room for bulk detox. Large herbivores can deal with infections more easily.
What is the difference between Qualitative and Quantitative defenses of plants?
quantitative defense - tannins, thorns, spines, fuzz
qualitative defense - cardiac glycosides, caffeine, opium, THC
Herbivores can overcome some kinds of plant defenses by eating large quantities of their food. Are herbivores engaging in this kind of behavior more likely to be eating quantitatively or qualitatively defended plants?
-avoid/tolerate plant spines
-evolved digestive enzymes
-larvae in insect chews slowly on plant where resin canals (toxins) are located so it doesn't squirt
How are prey and predator population dynamics different in the case of specialist v. generalist predators? Describe how prey tactics to defend against generalist v. specialist predators might differ.
Generalist predators have a wider variety of diet so they do not focus on one species of prey while specialists are very limited in what they can eat. Specialists have more of an effect on population dynamics.
How are parasitism and predation similar and different, in terms of evolutionary constraints to both actors (predator/ parasite v. prey/ host)?
Benefits of parasitism: Easy living, do not need to work as hard to get what you need, host does everything essentially.
Challenges of parasitism: if your host dies, so do you. Finding a host is difficult, the host has defenses against you, you have little mobility.
Benefits of predation: Way more evolved to deal with predator over parasites, strong selective pressure.
Define "complex life cycle" in parasites, and describe how these life cycles overcome the unique challenges associated with being a parasite.
They have increasing effectivness of spreading. It is the easiest way to get to where you want to be for a parasite.
2. Round worms
3. Tape worms
Why is Toxoplasmosis' effect on behavior different in humans v. mice?
How does Rp change during the course of an epidemic, and which variable drives this change? How does vaccination change this phenomenon?
Goes up and down, a vaccination causes it to stay down.
The ability to spread quickly or slowly. If you want to kill your host, you spread quickly. If you want to keep your host alive, you will spread at a slower rate (STD).
What is the general formula for Rp? Draw a figure that shows how Rp changes during an epidemic.
Rp= next reproduction of parasite
Rp= (how long the infected individual is infected) x (Average number of susceptibles encountered) x (possibility of transmission)
Graph: Rp: curved downwards & infected curves up then back down
if Rp = 2, what will happen if a diseased individual is introduced to a population of healthy
animals? What will happen if Rp is 0.1?
Rp:1 (infection is dying) (not an epidemic)
For common childhood diseases (for which we commonly vaccinate), is Rp higher in European countries or the U.S., before an epidemic occurs? How might vaccination policies change virulence v. transmission rate in the U.S. v. European countries?
Less vaccinations in Europe means there is an increase in susceptibility.
Explain the virulence and transmission probability tradeoff, as well as what "resource" results in this tradeoff.
High virulence is offset by high transmission probability. High virulence means low length of infection.
Describe how the transmission dynamics of sexually transmitted diseases are different than diseases transmitted via other methods, especially why the few number of individuals with a high number of contacts play an important role in disease transmission.
STD's have different transmission rates. It is the rate at which you are exposed to STD's, the more you sleep around the higher chance you have at getting one.
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