Question 1

An area is undergoing secondary succession.Early in the process, facilitating species such as nitrogen fixers and decomposers predominate.Later in succession, there are more inhibiting species, such as competitors.What is a major reason that facilitating species outnumber inhibiting species early in succession?

Accepted Answer

Facilitating species such as nitrogen fixers and decomposers prepare the environment for later species to come by transforming the physical and chemical components of the ecosystem. Early settlers must facilitate each other to survive in the initial stages of succession, as the environment lacks the necessary resources for growth and development. As the environment becomes more suitable for growth, competitors, which inhibit the growth of other species or consume shared resources, begin to outnumber facilitating species.

Question 2

A single pitcher plant containing a group of interacting species and an entire forest, also filled with interacting species, both can be defined as _______.

Accepted Answer

The answer of A single pitcher plant containing a group...

Question 3

A new herbivore species is introduced into a community and appears to be well adapted to the environmental conditions.However, it fails to compete well with existing herbivores and, after several years of low reproductive success, it dies out.This species was excluded through the process of _______.

Accepted Answer

The answer of A new herbivore species is introduced into...

Question 4

The plants that grow best on recently formed moraines at Glacier Bay are those that

Accepted Answer

Recently formed moraines have poor soil quality and limited nutrients, including nitrogen. Plants that are able to form mutualistic relationships with nitrogen-fixing bacteria are more likely to thrive in such conditions. These bacteria are able to convert atmospheric nitrogen into a form that the plant can use for growth, giving the plant a competitive advantage over others that cannot access this vital nutrient.

Question 5

The aspect of community structure that measures both the number of species in a community and how evenly they are apportioned is the _______ of the community.

Accepted Answer

The answer of The aspect of community structure that measures...

Question 6

The Hawaiian Islands were formed by volcanic activity, and the original lava and soil substrate was deficient in nutrients, particularly nitrogen.This suggests that many of the earliest plants to become established on the islands were probably

Accepted Answer

Nitrogen fixers are able to take nitrogen from the air and convert it into a form that can be used by plants. This would have been advantageous for early plant colonization on the nutrient-deficient Hawaiian Islands.

Question 7

Area A has 50 species.One species is very dominant, making up 90 percent of the total biomass, while the others are very rare.Area B has only 20 species, but they are distributed so that all are present in relatively equal numbers.Compared with area B, area A has a very high level of _______.

Accepted Answer

The answer of Area A has 50 species.One species is...

Question 8

The first limitation regarding which species can become members of a community is that they must be present in the regional _______ and be able to disperse into the new community.

Accepted Answer

The answer of The first limitation regarding which species can...

Question 9

Species cultivated for aquaculture can be set up so the byproducts or wastes of one crop (such as finfish or shrimp) are converted into fertilizer, food, and energy for the other crops, such as filter feeders (mussels) and algae.This process uses food, energy, and nutrients more efficiently by recycling them.This example shows the use of which practice to increase stability and productivity of the aquaculture system?

Accepted Answer

This is an example of polyculture, where multiple species are cultivated together in a system that utilizes their byproducts and waste to increase efficiency and productivity.

Question 10

In 1963, an oceanic volcanic eruption off the southern coast of Iceland formed the island of Surtsey.If the Surtsey volcano erupted again and a new layer of lava completely covered the island, would the resulting succession be considered primary or secondary succession?

Accepted Answer

If a new layer of lava completely covered the island, it would create a new, bare surface with no existing life, and thus primary succession would occur again.

Question 11

An ecologist constructs a diagram to describe the structure of a city park community.The diagram includes the trophic levels connecting park organisms.It also includes information on which pollinators pollinate various plants and on major competitors in the community.This diagram could best be described as a(n) _______.

Accepted Answer

The answer of An ecologist constructs a diagram to describe...

Question 12

Tilman's experiments showed that increasing species richness enhanced the stability of plant production in the plots because

Accepted Answer

Tilman's experiments demonstrated that different species have varying performances under different environmental conditions, such as drought or wet years, which contributes to overall stability in plant production as species richness increases.

Question 13

A woodland was felled, stripped of its existing vegetation, and left to undergo secondary succession.Which factor in this situation is different from primary succession and ensures that secondary succession occurs more rapidly than primary succession does?

Accepted Answer

The presence of seeds and roots remaining in the soil after the initial disturbance in secondary succession allows for faster regeneration of vegetation compared to primary succession, where there is no existing seed bank or root system. In primary succession, it may take many years for vegetation to establish from wind-dispersed seeds. Additionally, animals and other factors may be slower to arrive and establish in primary succession.

Question 14

Refer to the graph, which is from Tilman's study on species diversity and community function in grassland ecosystems.It shows the change in efficiency of nitrogen use correlated with number of species in a community.  Based on the graph, one can conclude that as species richness increases,

Accepted Answer

The graph shows that as the number of species in the community increases, the efficiency of nitrogen use also increases, meaning that more nitrogen is being taken up by the plants. At the same time, the nitrogen content in the soil decreases, indicating that the plants are taking up more nitrogen from the soil. Therefore, option B is the best choice.

Question 15

Peas, beans, clover, and peanuts are all legumes, which are nitrogen-fixing plants.Ecologically, these plants can all be placed in the same _______.

Accepted Answer

The answer of Peas, beans, clover, and peanuts are all...

Question 16

A person studying a region's diversity at various levels, from genetic to species to community, is studying the region's _______.

Accepted Answer

The answer of A person studying a region's diversity at...

Question 17

Refer to the figure.  The process illustrated in the figure is known as

Accepted Answer

The answer of Refer to the figure.  The process...

Question 18

The presence of soil fauna increases the likelihood that many plants will be established during succession.This is an example of

Accepted Answer

Facilitation refers to the process in which one species benefits another by making it easier for it to establish or survive, and in this case, the presence of soil fauna is making it easier for many plants to establish during succession.

Question 19

In a desert food web, cacti are eaten by flies.Flies are eaten by scorpions, which are eaten by roadrunners.In this food web, the primary consumers are the _______.

Accepted Answer

The answer of In a desert food web, cacti are...

Question 20

After the 1980 eruption of Mount St.Helens, populations of small mammals and other organisms recovered much more quickly in the zones of secondary succession than in the Pumice Plain, where primary succession occurred.This more rapid recovery was aided by all of the following factors except

Accepted Answer

Areas devoid of life, as described in choice D, would not aid in the rapid recovery of ecosystems following a disturbance like a volcanic eruption. In contrast, existing life, soil, nutrients, and structures like burrows contribute to quicker recovery by providing the necessary resources and habitats for new growth and colonization. Choice D, referring to a "blank canvas," actually describes conditions more typical of primary succession, which is a slower process starting from scratch, rather than aiding recovery in zones of secondary succession where some life and soil structure remain.

Quiz 56: Communities