51. Community Ecology

Under which of the following circumstances would interspecific competition be most obvious?

The niche of an animal is __________.

When goats were introduced to an island off the California coast, the goats inhabited the same areas and ate the same plants as the native deer. The deer population dwindled and finally disappeared. This is an example of __________.

Flounder is a type of fish that looks like the seafloor. This is an example of __________.

The flower fly resembles a honeybee, but the flower fly has no stinger. This is an example of what natural phenomenon?

The poison-arrow frogs Dendrobates of tropical America are all brightly colored and have very similar patterns. Although each species is distasteful to predators and all possess toxic skin secretions, some of the species live quite separately from the others. The adaptive relationship among these species is best termed __________.

Certain species of acacia trees in Central and South America have hollow thorns that house stinging ants, which attack anything that touches the tree. The ants feed on nutrients produced by the acacias. This is an example of __________.

What is the key difference between a dominant species and a keystone species?

A species of malaria-carrying mosquito lives in a forest in which two species of monkeys, A and B, coexist. Species A is immune to malaria, but species B is not. The malaria-carrying mosquito is the chief food for a particular kind of bird in the forest. If all these birds were suddenly eliminated by hunters, which of the following would be an immediately observable consequence?

Fill in the blanks in the table below summarizing the interspecific interactions in a community.

What is niche differentiation? a. the evolution of traits that reduce niche overlap and competition b. interactions that allow species to occupy their fundamental niche c. the degree to which the niches of two species overlap d. the claim that species with the same niche cannot coexist

Compare and contrast the species interactions of mutualism, predation, and competition.

The principle of competitive exclusion states that a. two species cannot coexist in the same habitat. b. competition between two species always causes extinction or emigration of one species. c. two species that have exactly the same niche cannot coexist in a community. d. two species will stop reproducing until one species leaves the habitat.

The relationship between corals and the photosynthetic protists they harbor is an example of a. commensalism. b. competition. c. consumption. d. mutualism

What is true about inducible defenses? Select True or False for each statement. T/F They are always present; thus, an individual is always able to defend itself. T/F They make it impossible for a consumer to launch surprise attacks. T/F They result from a coevolutionary arms race. T/F They make efficient use of resources, because they are produced only when needed.

To ensure adequate nitrogen for a crop, a farmer would want to decrease _________ by soil bacteria. a. nitrification b. denitrification c. nitrogen fixation d. a and c

Cite an example to explain why species interactions are conditional and dynamic.

Evaluate this statement: Species want to increase their fitness by helping friendly species and hurting enemy species.

Explain how seed dispersal by animals is an example of mutualism in some cases.

Which of the following is an example of a mutualistic relationship? a. moles catching and eating earthworms from the moles' underground tunnels; b. cattails and reed canary grass growing together in wetland soils; c. cleaner fish removing and eating parasites from the teeth of sharks; d. Colorado potato beetles consuming potato plant leaves; e. more than one of the above

In some circumstances, the use of probiotics, which stimulate the rapid growth of bacteria that are mutualistic or commensal with humans, can eliminate the need to use antibiotics, which can wipe out helpful bacteria along with harmful bacteria. The use of probiotics is an example of which process? a. succession b. competitive exclusion c. parasitism d. niche differentiation

How do animals help flowering plants reproduce? How do the animals benefit?

Lyme disease is caused by infections of the bacterium Borrelia burgdorferi (stained blue in inset, among red blood cells) which is transferred to humans via blood-sucking bites from the tick, Ixodes scapularis. Lyme disease can cause flu-like symptoms in the short term and more serious illnesses in the long term, if not treated. Why is Lyme disease on the rise in eastern North America? In relation to humans, B. burgdorferi is a/an ____________ and the tick is a/an _____________. a. endoparasite/ectoparasite b. endoparasite/host c. parasitoid/host d. parasite/predator

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants, but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind. What nutritional impact do the ants have on fanged pitcher plants? Do the pitcher plants derive any nutritional benefit from this relationship? Based only on the information provided here, make a prediction on the effect of diving ants on overall pitcher plant growth.

Lyme disease is caused by infections of the bacterium Borrelia burgdorferi (stained blue in inset, among red blood cells) which is transferred to humans via blood-sucking bites from the tick, Ixodes scapularis. Lyme disease can cause flu-like symptoms in the short term and more serious illnesses in the long term, if not treated. Why is Lyme disease on the rise in eastern North America? Newly hatched ticks do not harbor B. burgdorferi. Rather, they pick it up from certain hosts that are reservoirs of the bacterium. When a larval tick crawls onto a host, it may get groomed off and killed by the host, or it may feed successfully, in which case it may or may not then become infected with B. burgdorferi. Felicia Keesing and others measured the rate of tick feeding and infection on different hosts. What percentage of ticks on mice were infected with B. burgdorferi? What percentage of ticks on opossums were groomed off and killed?

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants, but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind. What nutritional impact do the ants have on fanged pitcher plants? Do the pitcher plants derive any nutritional benefit from this relationship? Researchers tested the hypothesis that the relationship between diving ants and pitcher plants is mutualistic (i.e., both species derive a nutritional benefit). To do so, they compared leaf surface area (as a measure of overall growth) in two sets of pitcher plants: plants with diving ants and plants without. The results are shown in the graph. The P values indicate whether there is a significant relationship between the size of the host plants and the surface area of the host plants' leaves. Based on this graph, what conclusions can be drawn about the impact of diving ants on overall plant growth?

Truffles (the fungi, not the chocolates) are the reproductive bodies of ascomycetes that form mycorrhizae with certain tree species. They are highly prized by gourmets for the delicious scent they add to food. Because truffles grow underground, they are difficult to find—human noses are not sensitive enough to locate them. Many animals, however, are excellent truffle hunters and eagerly consume the fungi. Why would these fungi produce a scent that attracts fungus-eating animals?

Lyme disease is caused by infections of the bacterium Borrelia burgdorferi (stained blue in inset, among red blood cells) which is transferred to humans via blood-sucking bites from the tick, Ixodes scapularis. Lyme disease can cause flu-like symptoms in the short term and more serious illnesses in the long term, if not treated. Why is Lyme disease on the rise in eastern North America? Deer are hosts of ticks but are not reservoirs of B. burgdorferi—their immune systems detect and kill the bacterium. But a tick with a prior bacterial infection can consume a blood meal from a deer and then bite and infect a human. The fitness effects of a deer on B. burgdorferi can be summarized as: a. + because the deer supplies the bacterium with food. b. − because the deer kills the bacteria in its blood. c. + because the deer feeds and disperses the tick that can then infect a human with the bacterium. d. − or + depending on whether the deer is the tick's last host.

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants, but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind. What nutritional impact do the ants have on fanged pitcher plants? Do the pitcher plants derive any nutritional benefit from this relationship? Based on the background information presented here, does the relationship between diving ants and pitcher plants appear to be mutualistic? Explain.

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants, but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind. What nutritional impact do the ants have on fanged pitcher plants? Do the pitcher plants derive any nutritional benefit from this relationship? Explain why carnivorous and parasitic plants are most common in nutrient-poor habitats.

SCIENTIFIC THINKING As you learned in symbiotic relationships with mycorrhizal fungi are found in almost all present-day plant lineages. Mosses are a major exception—most mosses lack mycorrhizal associations. Assuming that mycorrhizae were a key factor in the colonization of land by plants, propose an explanation for the absence of mycorrhizae in present-day moss lineages.

A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods. The researchers observed a strong correlation between the number of arthropod species and the number of plant species in the San Lorenzo forest. Pose an evolutionary hypothesis to explain this correlation.

The carnivorous plant Nepenthes bicalcarata ('fanged pitcher plant') has a unique relationship with a species of ant—Camponotus schmitzi ('diving ant'). The diving ants are not digested by the pitcher plants, but instead live on the plants and consume nectar. Diving ants also dive into the digestive juices in the pitcher, swim to the bottom, and capture and consume trapped insects, leaving uneaten body parts and ant feces behind. What nutritional impact do the ants have on fanged pitcher plants? Do the pitcher plants derive any nutritional benefit from this relationship?