An Introduction to Ecology and the Biosphere

You suspect that deer are restricting the distribution of a tree species by preferentially eating the seedlings of the tree. How might you test this hypothesis?

Commercial fisheries target older, larger cod fish, causing cod that reproduce at a younger age and smaller size to be favored by natural selection. Younger, smaller cod have fewer offspring than do older, larger cod. Predict how evolution in response to fishing would affect the ability of a cod population to recover from overfishing. What other reciprocal eco-evolutionary effects might occur? (See Concept 23.3.)

MAKE CONNECTIONS Hawaiian silverswords underwent remarkable adaptive radiation after their ancestor reached Hawaii, while the islands were still young (see Figure 25.22). Would you expect the cattle egret to undergo similar adaptive radiation in the Americas (see Figure 52.18)? Explain.

Which of the following areas of study focuses on the exchange of energy, organisms, and materials between ecosystems?

(A) organismal ecology

(B) landscape ecology

(C) ecosystem ecology

(D) community ecology

Which of the following is characteristic of most terrestrial biomes?

(A) a distribution predicted almost entirely by rock and soil patterns

(B) clear boundaries between adjacent biomes

(C) vegetation demonstrating vertical layering

(D) cold winter months

The oceans affect the biosphere in all of the following ways except (A) producing a substantial amount of the biosphere’s oxygen. (B) removing carbon dioxide from the atmosphere. (C) moderating the climate of terrestrial biomes. (D) regulating the pH of freshwater biomes and terrestrial groundwater.

Which statement about dispersal is false?

(A) Dispersal is a common component of the life cycles of plants and animals.

(B) Colonization of devastated areas after floods or volcanic depends on dispersal.

(C) Dispersal occurs only on an evolutionary time scale.

(D) The ability to disperse can expand the geographic distribution of a species.

When climbing a mountain, we can observe transitions in biological communities that are analogous to the changes

(A) in biomes at different latitudes.

(B) in different depths in the ocean.

(C) in a community through different seasons.

(D) in an ecosystem as it evolves over time.

Suppose that the number of bird species is determined mainly by the number of vertical strata found in the environment. If so, in which of the following biomes would you find the greatest number of bird species?

(A) tropical rain forest

(B) savanna

(C) desert

(D) temperate broadleaf forest

If the direction of Earth’s rotation reversed, the most predictable effect would be

(A) a big change in the length of the year.

(B) winds blowing from west to east along the equator.

(C) a loss of seasonal variation at high latitudes.

(D) the elimination of ocean currents.

After examining Figure 52.19, you decide to study feeding relationships among sea otters, sea urchins, and kelp. You know that sea otters prey on sea urchins and that urchins eat kelp. At four coastal sites, you measure kelp abundance. Then you spend one day at each site and mark whether otters are present or absent every 5 minutes during the day. Graph kelp abundance (on the y-axis) versus otter density (on the x-axis), using the data below. Then formulate a hypothesis to explain any pattern you observe.

Discuss how the distribution of a species can be affected both by its evolutionary history and by ecological factors. Could ongoing evolutionary change also affect its distribution? Explain.

Jens Clausen and colleagues, at the Carnegie Institution of Washington, studied how the size of yarrow plants (Achillea lanulosa) growing on the slopes of the Sierra Nevada varied with elevation. They found that plants from low elevations were generally taller than plants from high elevations, as shown in the diagram. Clausen and colleagues proposed two hypotheses to explain this variation within a species: (1) There are genetic differences between populations of plants found at different elevations. (2) The species has developmental flexibility and can assume tall or short growth forms, depending on local abiotic factors. If you had seeds from yarrow plants found at low and high elevations, how would you test these hypotheses?

Global warming is occurring rapidly in arctic marine and terrestrial ecosystems. The reflective white snow and ice cover are melting quickly and extensively, uncovering darker-colored ocean water, plants, and rocks. In a short essay (100–150 words), explain how this process might exemplify a positive feedback loop.

If you were to hike up Mount Kilimanjaro in Tanzania, you would pass through several habitats, including savanna at the base, forest on the slopes, and alpine tundra near the top. Explain how such diverse habitats can be found at one location near the equator.