General Ecology Exam 3

Exploitative interactions differ from competitive interactions as exploitative interactions:

are beneficial to the fitness of one of the interactants, yet harmful to the other.

Parasitism generally is distinguished from predation in that parasitism:

does not involve the killing of the host by the parasite.

To examine predator-prey dynamics, Georgii Gause conducted an experiment in which he introduced individuals of a predatory, single-celled eukaryote, Didinium nasutum, two days after the introduction of individuals of a prey species, Paramecium caudatum. The results of this experiment are provided in the figure below:

The results of this experiment are best explained by which of the following identified outcomes of predator-prey dynamics? *will have an image*

Prey extinction with consequential predator extinction

The following figure depicts the zero-growth isoclines for a prey population (dashed line) and a predator population (solid line), with five points (labeled A to E) representing different values of N_predators and N_prey. *will have an image*

From this model, which of the following points would represent values for N_predators and N_prey that would result in abundance declines in both populations?

Part A

The following figure depicts the zero-growth isoclines for a prey population (dashed line) and a predator population (solid line), with five points (labeled A to E) representing different values of N_predators and N_prey. *will have an image*

From this model, which of the following points would represent values for N_predators and N_prey that would result in an increase in predator population abundance, but a decrease in the prey population abundance?

Point B

The modification of the Lotka-Volterra model for the growth rate of a prey population from ___ to ___ (see image) primarily involves adding factors that consider the impacts of:

density-dependent change in prey growth rates.

The following figure depicts the Lotka-Volterra zero-growth isoclines for an exploiter (predator, solid line) and a prey (dotted line) population that considers density-dependence in the growth rate of the prey population:

From this figure, determine the equilibrium density of the prey population.

600 individuals

The following figure depicts the Lotka-Volterra zero-growth isoclines for an exploiter (predator, solid line) and a prey (dotted line) population that considers density-dependence in the growth rate of the prey population:

From this figure, determine the equilibrium density of the exploiter/predator population.

200 individuals

Type ______ functional responses consider slow rates of exploiter/predator consumption when prey densities are low, faster rates of exploiter/predator consumption as prey densities increase, and finally, steady rates of exploiter/predation consumption once high prey densities

III

The phenomenon whereby individual fitness in a population declines with population density is referred as:

an Allee effect.

Insect exploiters that lay their eggs and/or larvae in their host, whereby the larvae consume the host, are referred to as:

parasitoids.

The evolution of the harmless milk snake to have a similar morphology/appearance to that of the venomous false coral snake is an example of:

Batesian mimicry

The Red Queen hypothesis proposes that:

prey should continually evolve to maintain fitness under changing environmental pressures.

Read the following description of a relationship between two species and choose the type of relationship it is.

The bullhorn acacia tree produces thorns that acacia ants can use for shelter. The bullhorn acacia will fare poorly without the acacia ants because the ants prevent other organisms from eating the acacia. Acacia ants can form relationships with up to four different species of acacia trees, which means that acacia ants do not need the bullhorn acacia specifically to survive but can survive on other species of acacia.

Obligate-faculative mutualism

Read the following description of a relationship between two species and choose the type of relationship it is.

European honeybees will pollinate many different species of plants in the rose family. Several other generalist pollinators and some specialist pollinators can also pollinate these plants.

Facultative-facultative mutualism.

Mutualism offers many different benefits to a species. Which of the following are mutualism benefits?

All these answers are correct.

Coyotes and badgers will hunt burrowing animals together. When their prey runs down a burrow, the badger and coyote take up different positions. Coyotes will go and cover an escape hole close to the burrow the animal is using in case they attempt to escape. All the while, the badger will dig up the main burrow to get the prey item. The prey may be eaten by either animal depending on if it stays where the badger is digging or if it tries to escape where the coyote is waiting. Both species benefit from this hunting mutualism as both can get access to prey.

In the above description of mutualism, which of the following mutualism benefits do the plants receive?

Acquisition of energy and nutrients

There are certain species of tarantula that allow frogs to enter their burrow and reside within. These frogs protect the tarantula’s egg sacs from egg predators by eating them. The tarantula in return will offer the frogs a place to live and can prevent frog predators from entering the burrow.

In the above description of mutualism, which of the following mutualism benefits do the frogs receive?

Protection and defense.

For the Lotka-Volterra variations of the logistic growth model to work for mutualisms, we must change the schematic model for the competition from _____ to better represent a mutualistic interaction.

(-,-) to (+,+)

The iterative prisoner’s dilemma strategy that explained the evolution of mutualism between two partners was the _____ strategy, as it allowed mutualism to succeed through niceness and forgiveness.

tit-for-tat

In the figure below, there are two graphs of an economic trade model of mutualism for trees and mycorrhizal fungi. We see that it makes sense that trees and fungi can acquire ____ from the environment in similar amounts, but the tree is able to acquire _____ much easier from the environment than the mycorrhizal fungi.

phosphorus; carbon

Read the following passage and choose the term that would describe giant kelp.

Giant kelp is one of many species of kelp that is found along the shores or California. This species can grow very large and is used as a habitat by many species of marine invertebrates and fishes. Giant kelp occupies a large portion of nearshore habitat, and it relies on sea otters and sunflower stars to eat the sea urchins that regularly can decimate large areas of giant kelp.

Foundation species

Which term describes how certain invasive species can facilitate the establishment of other invasive species, or can increase the impact that they can have on an environment?

Invasional meltdown

When considering the prisoner’s dilemma for mutualism, we should see that cheating in mutualistic interactions should be more common. Which of the following examples shows cheating occurring in a mutualistic interaction?

Hummingbirds are known to be great pollinators of many different flowering plants. At times, they can also pierce flowers at their base to ingest nectar from the flower and do not get coated in pollen, limiting pollination.

A reason that the mutualism model based on the competition model cannot represent all mutualisms is that only one type of mutualism benefit works within the model. Which of the four mutualism benefits is best represented in the mutualism model based on the competition model?

Acquisition of energy and nutrients

Energy that is ingested by a consumer that is not passed as fecal waste, nor used for the consumer’s own respiration will be:

stored within tissues and reproduction structures.

Within food chains and food webs, herbivores:

are also considered to be primary consumers.

As a rule, most species can convert approximately _____ of the calories they consume into biomass.

10%-20%

The following figure depicts the Lake Tahoe food chain, where boxes represent a taxonomic group occupying each trophic level within the chain, and arrows indicate the movement of matter and energy through trophic interactions.

Which of the following statements is best supported by the figure?

The cutthroat trout represents the apex predator within the food chain.

The following figure depicts the Lake Tahoe food chain, where boxes represent a taxonomic group occupying each trophic level within the chain, and arrows indicate the movement of matter and energy through trophic interactions.

Which of the following scenarios correctly demonstrates top-down control within this food chain?

An increase in the cutthroat trout population will lead to a subsequent increase in the zooplankton community.

The following figure depicts the Lake Tahoe food chain, where boxes represent a taxonomic group occupying each trophic level within the chain, and arrows indicate the movement of matter and energy through trophic interactions.

Based on this food chain’s structure, it is most plausible that adding more tui chub to Lake Tahoe would ultimately result in a(n):

increase in the biomass of the algae community.

Which of the following accurately represents an ecological energy pyramid for the following groups of organisms within an ecosystem?

a from the image

This is an image you need to use to answer Q34.

Which organisms in the food web in Q33 would be considered an omnivore? LIST at least 2 and in 1-2 sentences explain what makes them omnivores.

Taxa within a food web that have an arrow that originates from them, and that points back (loops back) to them, are considered to be ____.

The energy introduced into the headwaters of forested lotic systems mainly comes from the decomposition of ____ sources, such as the leaves and branches that fall into them.

exogenous

Kelp populations are protected from overgrazing by populations of sea urchins, through the predation of sea urchins by sea otters via the following trophic pathway.

With the combined overhunting of sea otter populations and the depredation of sea otters by large mammals such as orcas, kelp populations in many marine communities were driven to extinction. The ability of sea otters to help maintain kelp populations could be best described as:

predator-mediated coexistence.

Name one species known as an ecosystem engineer, and in 2-3 sentences explain what makes that species an ecosystem engineer.

In 2-3 sentences, explain what keystone is, and provided an example.

1. In class, we watched “The Return of Manatees”.

   a. What were the 2 things that caused the drastic drop in eelgrass and the loss of manatees in Crystal River?

   b. How did they “fix” Crystal River?

In class, we watched “The Queen of the Trees”. Give examples and explain each example for the following mutualistic relationships:

a. Obligate-obligate mutualistic relationship:

b. Obligate-facultative mutualistic relationship:

c. Facultative-facultative mutualistic relationship: