Exam 23: Ecological Communities

Competition is an unavoidable consequence when two species whose ________ overlaps live in the same community.

Cowbirds lay their eggs in the nests of smaller birds.The fast-developing cowbird chicks hatch first,and push the other baby chicks out of the nest as they hatch.Which interaction best describes cowbird behavior?

Interactions among organisms are always mutually beneficial.

Milkweed is a mildly toxic plant unless it has been grazed,in which case the toxin concentration greatly increases;this change,stimulated by an attack from herbivores,is an example of a(n)________ response.

The inhabitants of an aquarium,despite its small size,could be considered a community.

Communities change with respect to several timescales;an example of long-term change would be the

As the following figure illustrates,communities vary tremendously in size from as large as an entire forest to the digestive system of a single deer. How do biologists recognize communities?

The following figure illustrates how,although pines first established themselves as the dominant tree in the Lake Michigan sand dune community,black oaks ultimately became the dominant species. What best explains the gradual reduction of the pine?

The interactions among organisms that reside in the same community or ecosystem are unlikely to have much effect on the physical aspects of those systems.

The general process by which species in a community are replaced over time is called ________.

Mistletoe is clearly a parasitic organism,living off the resources of the trees it infects.However,the leaves it drops contain nutrients that nourish the many insects on the forest floor.What interaction describes this later relationship?

In comparing Communities A and B below,the major difference between them is that they differ in

Can a human being be considered an ecological community?

In which of the following situations would secondary rather than primary succession be most likely to occur?

Parasites,and the disease they cause,represent a distinctive type of exploitation because

In the centers of their ranges,two species of hummingbirds have very similar tongue lengths,but where the ranges overlap,one species has a shorter tongue and the other a longer tongue.This would most likely be an example of

The relationship between house pets and people would be best described as

Desertification,the transformation of dry grassland to a desert shrubland,can be natural or human caused;when humans are involved,the process is almost always associated with ________.

When different species of birds compete to use an abandoned woodpecker cavity,the successful competitor directly prevents the use of that resource by all others.This is an example of ________ competition.

Pisaster ochraceus,the common Pacific Northwest sea star,is contending with an apparently new disease termed sea star wasting syndrome,which threatens this species with possible extinction.What community changes can be expected if the sea star population is reduced to low levels or disappears entirely?