Question 1

Succession that begins on bare rock after glaciers have passed, or on newly formed volcanic islands, is

Accepted Answer

Primary succession occurs in lifeless areas where there is no soil, such as on bare rock exposed by a retreating glacier or on new volcanic islands. This type of succession begins with the establishment of pioneer species that can colonize the new area and eventually lead to the development of a more complex ecosystem.

Question 2

What ecological process causes a lake to change into a marsh over a long period of time?

Accepted Answer

Succession is the ecological process where a body of water like a lake gradually fills with sediment and organic matter, eventually transforming into a marsh or terrestrial ecosystem over time.

Question 3

Invasive species outcompete native species because they lack predators and have high reproductive rates.

Accepted Answer

Invasive species often lack natural predators in new environments, which allows their populations to grow rapidly. Their high reproductive rates further enable them to outcompete native species for resources.

Question 4

In a stable ecosystem, the number of predators is greater than the number of prey.

Accepted Answer

In a stable ecosystem, the number of prey typically exceeds the number of predators. This balance ensures that predators have enough food to sustain their population without overexploiting the prey population, allowing both populations to coexist sustainably.

Question 5

After a forested area such as a national forest is clear-cut, what type of succession occurs?

Accepted Answer

After a forested area is clear-cut, secondary succession occurs. This is because the soil and some life (like seeds and roots) often remain, allowing the area to regenerate over time, unlike primary succession which starts from bare rock or barren landscapes.

Question 6

Some toxic animals are brightly colored, as a means of warning others of their danger.

Accepted Answer

Bright colors in toxic animals serve as a warning signal to potential predators, indicating that they are poisonous or venomous and should be avoided. This phenomenon is known as aposematism.

Question 7

Birds follow a herd of water buffalo to catch insects that are disturbed as the large herbivores walk through the grass. When large predators are near, the birds fly into the air and make warning calls. Who are the birds warning?

Accepted Answer

The birds are warning the water buffalo so they can avoid attack by alerting them to the presence of predators.

Question 8

In most environments, two or more organisms occupy identical niches.

Accepted Answer

In most environments, the competitive exclusion principle suggests that two species competing for the exact same resources cannot stably coexist. One species will often outcompete the other, leading to different species occupying different niches to reduce competition.

Question 9

Intraspecific competition limits population size.

Accepted Answer

Intraspecific competition, which occurs when individuals of the same species compete for the same resources (such as food, water, and territory), can limit population size by reducing the availability of resources needed for survival and reproduction.

Question 10

The biotic portion of an ecosystem includes the plants, animals, and water.

Accepted Answer

The biotic portion of an ecosystem includes the living components such as plants and animals, but not abiotic components like water, which are part of the ecosystem's non-living or physical environment.

Question 11

When a community like the tallgrass prairie is maintained by recurring disturbances such as periodic fires set by Native Americans or by lightning, a _________community exists.

Accepted Answer

Subclimax communities, like the tallgrass prairie, are maintained by recurring disturbances (e.g., periodic fires). These disturbances prevent the community from reaching a climax state, which would be a more stable, mature ecosystem without such disturbances.

Question 12

Woodpeckers and squirrels both nest in tree cavities. This is an example of interspecific competition.

Accepted Answer

Interspecific competition occurs when different species compete for the same resource, in this case, tree cavities for nesting.

Question 13

A storm strips an island in Lake Superior down to bare rock. The first organisms to recolonize the island are most likely

Accepted Answer

Lichens are among the first organisms to colonize bare rock after a disturbance, such as a storm. They are well adapted to harsh conditions and can break down rock, contributing to soil formation for other plants to eventually grow.

Question 14

Why is the African elephant considered a keystone species?

Accepted Answer

Elephants are considered keystone species because their activities, such as feeding, walking, and other behaviors, significantly shape their ecosystems. Their removal would lead to major changes in the ecological structure, affecting biodiversity and the environment in ways that are detrimental to many other species.

Question 15

A certain species of animal represents just 3% of the biomass in its ecosystem. We might classify this as a keystone species if its removal

Accepted Answer

Keystone species have a disproportionately large effect on their environment relative to their abundance. The significant decline in plant community diversity (40%) upon the removal of this species indicates its crucial role in maintaining ecosystem structure, thus classifying it as a keystone species.

Question 16

A species that plays a major role in determining the structure of its ecological community is

Accepted Answer

A keystone species is crucial in maintaining the structure and integrity of an ecological community, affecting many other organisms in the environment and helping to determine the types and numbers of various other species in the community. Their role is not necessarily tied to their abundance, size, or being a predator.

Question 17

In mutualistic interactions, one species is harmed and one benefits.

Accepted Answer

In mutualistic interactions, both species involved benefit from the relationship.

Question 18

In a process called coevolution, two species exert natural selection pressures on each other.

Accepted Answer

Coevolution refers to the process where two or more species reciprocally affect each other's evolution through the selective pressures they exert on one another. This can lead to adaptations in each species that may benefit or counteract the other's adaptations.

Question 19

The next time you need to mow the grass, you can excuse yourself, saying that by mowing you are helping to maintain a man-made

Accepted Answer

The answer of The next time you need to mow...

Question 20

The first community that forms on bare rock often has organisms such as

Accepted Answer

Lichens and mosses are pioneer species that can colonize bare rock, initiating the process of ecological succession by breaking down the rock into soil where other organisms can later grow.

Quiz 28: Community Interactions