1. 40 Population Ecology and the Distribution of Organisms40
Population Ecology and the Distribution of Organisms
Questions prepared by
Fleur Ferro, Community College of Denver
Eric Ribbens, Western Illinois University
John Zarnetske, Hoosick Falls Central School

2. it’s warmer near the equator.
One reason that deserts tend to be found at 20N and S latitude is that
deserts are dry.
it’s warmer near the equator.
global wind and pressure patterns affect where rain falls.
desert soils are different from tropical rain forest soils.
mountains change rainfall patterns.
Answer: C

3. it’s warmer near the equator.
One reason that deserts tend to be found at 20N and S latitude is that
deserts are dry.
it’s warmer near the equator.
global wind and pressure patterns affect where rain falls.
desert soils are different from tropical rain forest soils.
mountains change rainfall patterns. 3

4. From this graph, we can conclude that
each biome has distinct temperature and mean annual precipitation.
precipitation and temperature determine biomes.
precipitation determines temperature.
tundra and tropical forest are climatically different.
biomes determine precipitation.
Answer: B
Figure 40.8 4

5. From this graph, we can conclude that
each biome has distinct temperature and mean annual precipitation.
precipitation and temperature determine biomes.
precipitation determines temperature.
tundra and tropical forest are climatically different.
biomes determine precipitation. 5

6. Describe the seasonal turnover in deep temperate lakes in terms of the physical properties of water. Discuss the importance of this seasonal turnover to the organisms in a lake ecosystem.
Answer: Seasonal turnover is centered on water’s density change due to temperature. Water is most dense in its liquid state and when it is 4C. This means that when heated by the sun in the summer, water warms near the surface and a distinct thermocline forms, which separates the warmer, less dense water from the cooler, more dense water. In the fall as ambient temperatures cool, the surface water becomes cooler (4C), sinks, and pushes water that has been at the bottom all summer to rise. As winter temperatures continue to fall, the surface will turn into the solid form of water, which is less dense than liquid water, so it floats on the surface of liquid water that ranges from below freezing to 4C. In the spring, as temperatures rise, the ice melts, mixes with the surface waters, and heats to 4C, causing it to sink and forcing a spring upwelling of water that has been on the bottom all winter.
The importance of the biannual overturns is to exchange oxygen and nutrients between the zones of the lake seasonally. Specifically, dissolved oxygen that accumulates in the surface layers in the spring needs to sink to the bottom to replenish the low oxygen levels of the organisms living there throughout the year. Likewise, in the fall, nutrients that tend to accumulate at the bottom and be used up by organisms at the surface during the summer are replenished during the fall overturn. 6

7. In which marine zone would you find the majority of plankton?
benthic zone
pelagic zone
intertidal zone
abyssal zone
Answer: B
The pelagic zone is the open ocean, where the majority of plankton are found. 7

8. In which marine zone would you find the majority of plankton?
benthic zone
pelagic zone
intertidal zone
abyssal zone 8

9. Which of the following is not an abiotic factor organisms could come into contact with?
salinity
temperature
sunlight
bacteria
oxygen
Answer: D
Bacteria are living organisms, which would make them biotic, not abiotic. 9

10. Which of the following is not an abiotic factor organisms could come into contact with?
salinity
temperature
sunlight
bacteria
oxygen 10

11. Population ecologists are primarily interested in
understanding how biotic and abiotic factors influence the density, distribution, size, and age structure of populations.
the overall vitality of a population of organisms.
how humans affect the size of wild populations of organisms.
studying interactions among populations of organisms that inhabit the same area.
how populations evolve as natural selection acts on heritable variations among individuals and changes in gene frequency.
Answer: A 11

12. Population ecologists are primarily interested in
understanding how biotic and abiotic factors influence the density, distribution, size, and age structure of populations.
the overall vitality of a population of organisms.
how humans affect the size of wild populations of organisms.
studying interactions among populations of organisms that inhabit the same area.
how populations evolve as natural selection acts on heritable variations among individuals and changes in gene frequency. 12

13. buffalo grazing on a prairie. bluegills swimming in a northern lake.
Dispersion patterns tend to be highly dependent on the spatial scale of the observer. For example, football players lined up on the scrimmage line are clumped at the scale of 100 yards but uniformly dispersed at the scale of a meter. An example of animals that are likely to be clumped at a large scale but uniformly distributed at a small scale is
buffalo grazing on a prairie.
bluegills swimming in a northern lake.
ant nests in an abandoned field.
red-winged blackbirds in a cattail marsh.
all of the above.
Answer: E 13

14. buffalo grazing on a prairie. bluegills swimming in a northern lake.
Dispersion patterns tend to be highly dependent on the spatial scale of the observer. For example, football players lined up on the scrimmage line are clumped at the scale of 100 yards but uniformly dispersed at the scale of a meter. An example of animals that are likely to be clumped at a large scale but uniformly distributed at a small scale is
buffalo grazing on a prairie.
bluegills swimming in a northern lake.
ant nests in an abandoned field.
red-winged blackbirds in a cattail marsh.
all of the above. 14

15. shift from Type I to Type II or III. shift from Type II to Type I.
Imagine that a species of fish used to be a broadcast spawner (producing many eggs that then get no subsequent parental care) but has evolved to be a mouth brooder (holding the eggs in the parent’s mouth until they hatch and then caring for the young for a while). We would expect the survivorship curve of this species to
shift from Type I to Type II or III.
shift from Type II to Type I.
shift from Type III to Type I or II.
shift from Type II to Type III.
vary unpredictably.
Answer: C 15

16. shift from Type I to Type II or III. shift from Type II to Type I.
Imagine that a species of fish used to be a broadcast spawner (producing many eggs that then get no subsequent parental care) but has evolved to be a mouth brooder (holding the eggs in the parent’s mouth until they hatch and then caring for the young for a while). We would expect the survivorship curve of this species to
shift from Type I to Type II or III.
shift from Type II to Type I.
shift from Type III to Type I or II.
shift from Type II to Type III.
vary unpredictably. 16

17. none of the elephants died.
The exponential growth model describes the increase in population size of a population that is not constrained by resources or space. The graph shows the elephant population in Kruger National Park, which appears to have been reproducing exponentially from 1900 to From this graph, you can tell that
none of the elephants died.
a female elephant living around 1960 was more likely to have a baby than a female elephant living around 1920.
the elephants adapted to the new park conditions around 1955.
the vegetation the elephants eat could supports more than 5,000 elephants.
the more elephants there are, the more tourists will visit the park.
Answer: D 17

18. none of the elephants died.
The exponential growth model describes the increase in population size of a population that is not constrained by resources or space. The graph shows the elephant population in Kruger National Park, which appears to have been reproducing exponentially from 1900 to From this graph, you can tell that
none of the elephants died.
a female elephant living around 1960 was more likely to have a baby than a female elephant living around 1920.
the elephants adapted to the new park conditions around 1955.
the vegetation the elephants eat could supports more than 5,000 elephants.
the more elephants there are, the more tourists will visit the park. 18

19. You do a study on elephants and find that there are eight elephants per acre. This is a measurement of
density.
dispersal.
demographics.
survivorship.
Answer: A
Density is defined as a certain amount per unit of area. 19

20. You do a study on elephants and find that there are eight elephants per acre. This is a measurement of
density.
dispersal.
demographics.
survivorship. 20

21. A population of deer grows from 100 to 200 to 600, and when it gets to 600, it levels off. This population must have reached
exponential growth.
carrying capacity.
logistic growth.
Answer: B
Carrying capacity is reached when the environment can no longer sustain a population of a certain size, which usually causes the population amount to level off. 21

22. A population of deer grows from 100 to 200 to 600, and when it gets to 600, it levels off. This population must have reached
exponential growth.
carrying capacity.
logistic growth. 22