Question 1

Anthropologists have long wondered what happened to the inhabitants of Easter Island.It is clear that part of the island was arable.Which of the following likely occurred after the island was depopulated?

Accepted Answer

After the island was depopulated, the vegetation and natural ecosystem were disturbed, and plants and animals could establish themselves in the area creating secondary succession.

Question 2

Which of the following is an example of a trophic cascade?

Accepted Answer

A trophic cascade is a series of indirect effects that occur when a change in one trophic level (such as a predator) impacts multiple other levels of the ecological food web. In this case, the mountain lion preying upon deer would result in a decrease in the deer population, which would then lead to an increase in the abundance of the grass species, as the remaining deer would eat less of it. This is an example of a trophic cascade because the predator's impact on one level of the food web (the deer) ended up cascading down to affect the abundance of a completely different organism (the grass).

Question 3

Which of the following choices explains a dominance-controlled community?

Accepted Answer

A dominance-controlled community is characterized by the dominance of one or a few species over other species in the community. In this case, species are not competitively equivalent, meaning that some are better adapted to their environment and outcompete others, resulting in a lower species richness.

Question 4

You have studied a population of birds over a three year period.You want to learn how this population experiences mortality at each phase of the life cycle.What analysis could you use to do this?

Accepted Answer

A k-value analysis, also known as a survivorship analysis, would be the most appropriate analysis to study mortality at each phase of the life cycle. This analysis can determine the probability of individuals surviving to different ages or stages in their life, allowing for a better understanding of mortality patterns throughout the life cycle of the studied population. Meta-analysis, structure analysis, and SNP analysis are not relevant to this specific question.

Question 5

You have researched outbreaks of West Nile virus.You see a pattern whereby the numbers of incidences of outbreaks increases ten days after a period of precipitation in which daily temperature is below 20 degrees Celsius,soil moisture is between 50% to 65%,and relative humidity is above 60% over a continuous period of 5 days.What can you conclude from these data?

Accepted Answer

The observed pattern shows a correlation between certain environmental factors and an increase in West Nile virus outbreaks. However, correlation does not necessarily prove causation. Therefore, it is not appropriate to conclude that these environmental factors are the sole cause of the increase in West Nile virus outbreaks.

Question 6

Which of the following terms is used to define a collection of subpopulations that can go extinct and appear again through recolonization?

Accepted Answer

A metapopulation is a group of spatially separated subpopulations that are connected by occasional movements of individuals between them. These subpopulations may go extinct locally but can be recolonized by individuals moving from other subpopulations within the metapopulation.

Question 7

You want to understand if many amphibians respond to chemical stimuli from predators in the same way.What is one approach you could take to test this without actually having to conduct experiments on hundreds of aquatic prey?

Accepted Answer

Conducting a meta-analysis of the primary literature would allow for a comprehensive review of studies that have already been conducted on chemical stimuli responses in amphibians. This can provide valuable insights into patterns and variations in responses across different species without having to conduct experiments on hundreds of aquatic prey.

Question 8

Which stage of community succession occurs when the most efficient competitors outcompete other species?

Accepted Answer

The stage described in which the most efficient competitors outcompete other species is the climax stage of community succession. At this stage, the community has reached stability and equilibrium, where the dominant species have established and are able to maintain their position.

Question 9

You review successional data,which show a subset of plants colonizing a gap in the following order: Common chickweed (annual)-> salvias (herbaceous perennial shrub)-> toyon (woody perennial shrub).Using these data,does it appear that plants are following a typical sequence of dominant vegetation? If so,which species might follow?

Accepted Answer

The successional order seen in the data follows a typical sequence of dominant vegetation, with annual plants being replaced by herbaceous perennial shrubs, which are then replaced by woody perennial shrubs. The next species in the sequence would likely be a late succession plant, which is often a woody tree or a dominant shrub that can shade out the current species. Therefore, choice B is the best answer.

Question 10

Which choice accurately defines species richness?

Accepted Answer

Species richness refers to the total number of different species present in a community, without considering the abundance of each species.

Question 11

Which of the following defines a trophic cascade?

Accepted Answer

A trophic cascade is a process whereby predators reduce abundances of their prey, and as a result, abundances of the prey's own resources increase. This can then have cascading effects on lower trophic levels, leading to changes in community structure and ecosystem functioning. Choice A is incorrect because trophic cascades do not necessarily require abiotic disturbances. Choice B is incorrect because trophic cascades do not involve primary succession. Choice C is incorrect because it describes the opposite of what actually happens in a trophic cascade.

Question 12

An island is newly formed by a volcanic eruption.You want to follow what happens with plant communities on the island.What type of succession is this?

Accepted Answer

This is an example of primary succession because the island was formed from a non-living environment (volcanic eruption) and there were no pre-existing plant communities on the island. As such, the pioneer species, such as lichens and mosses, will colonize the barren island and gradually make way for other plant species to establish. The succession process will continue until a stable, self-sustaining plant community is achieved.

Question 13

Food webs appear to be most controlled by what process?

Accepted Answer

Top-down control, also known as trophic cascade, suggests that the highest trophic level (usually predators) controls the structure and dynamics of lower trophic levels in a food web. This means that changes in predator populations can have significant effects all the way down to the base of the food web, leading to a chain of indirect effects. Research has shown that top-down control is a crucial process for maintaining ecosystem stability and biodiversity.

Question 14

Which of the following is the correct sequence of dominant vegetation in a community undergoing succession?

Accepted Answer

Succession typically starts with pioneer species such as annual weeds, followed by herbaceous perennials, shrubs, early successional trees, and finally late successional trees as the climax community. This sequence reflects the increasing complexity and stability of the ecosystem over time.

Question 15

Who challenged the ideas of Hairston et al.and what did they contend?

Accepted Answer

Murdoch challenged the ideas of Hairston et al. and contended that the world is green because herbivores are limited by the defenses plants have evolved.

Question 16

In what type of community are species approximately equivalent in their ability to invade gaps and hold those gaps against other species during their lifetime?

Accepted Answer

In founder-controlled communities, species are approximately equivalent in their ability to invade gaps and maintain those gaps against other species throughout their lifetime.

Question 17

Assume a community undergoing succession approaches its climax stage.Which of the following predictions is most likely?

Accepted Answer

In ecological succession, species diversity typically increases during the early stages due to colonization. However, as the community reaches the climax stage, competition for resources can lead to a decrease in species numbers.

Question 18

According to Hairston et al.,why is the world green?

Accepted Answer

Hairston et al. proposed that the world is green because predators limit the number of herbivores, allowing plants to flourish. This is known as the "top-down" control hypothesis, where predators control the population of herbivores, thus reducing the pressure on plants and allowing them to dominate landscapes.

Question 19

In 1944,a researcher observes 710 ithomiine butterflies in a lek in a Central American rainforest.In 1945,1946,and 1947,the same researcher observed 722,711,744,and 702 individuals in a lek at the same location.In 2012,a different researcher revisited the same location and observed 694 ithomiine butterflies in the lek.What can you say about the stability of these ithomiine butterflies?

Accepted Answer

Without further information or analysis, it is difficult to determine the stability of the ithomiine butterfly population. The population has shown some fluctuation over time, with peaks and valleys in different years. However, it is not clear if these changes are significant or within the normal range of variation for this population. Additionally, there is no information about other environmental factors that could be affecting the population, such as habitat loss, climate change, or predation. Therefore, it is not possible to make a definitive statement about the stability of these ithomiine butterflies based on the information provided.

Question 20

Approximately 20 years ago,a large fire burned through part of a national park.You are shown data that describe the species identified and enumerated over this 20 year period.These data show that some species colonized the land relatively fast.Those same species,however,are not present in the last 5 years of the data.Other species appear to maintain abundances throughout the 20 years.How would you characterize this process?

Accepted Answer

The described process is that of community succession, where different species colonize and occupy an area over time, with some species persisting and others being replaced by new ones. This is distinct from primary succession, which occurs in entirely new, barren areas, and typically takes longer periods of time. The other options are not applicable to the described scenario, as there is no indication of founder effects or metapopulation dynamics in the data.

Quiz 9: From Populations to Communities