Deck 37: Populations

Question 1

How does a habitat differ from a niche? Describe your own habitat and niche.

Answer 1

A habitat is a physical place where members of a population typically live.  A niche is all the resources a species exploits for its survival, growth, and reproduction.  My habitat is my home and the other physical locations where I spend time; my niche includes the habitat plus the food I eat, the water and air I breathe, the other resources I exploit, and the job I do.

Question 2

As the human population in the United States has increased, we have reduced or eliminated the populations of top predators such as wolves and coyotes. How might this history relate to the recent explosion of deer populations? Using the ecological principles you have learned in this chapter and chapter 36, what are some possible ways to reduce deer populations? What are the pros and cons of each approach?

Answer 2

Without the top predators, death rates in deer populations declined, leading to an increase in population size.  To reduce the population you could increase death rates by controlled hunting, or you could decrease birth rates with birth control or sterilization measures.  Hunting puts humans in the role of top predator and this re-establishes a balance. Unlike wolves, however, humans do not cull the sick and old deer. Instead, they attempt to remove the prime specimens, which could alter the gene pool of the population.  Sterilization or birth control methods are awkward, time-consuming and expensive.

Question 3

What is the competitive exclusion principle?

Answer 3

The competitive exclusion principle states that two species cannot coexist indefinitely in the exact same niche:  sooner or later, the one with the greater reproductive rate will replace the other.

Question 4

Describe the steps of the water, carbon, nitrogen, and phosphorus cycles.

Question 5

Distinguish between primary and secondary succession.

Question 6

Pigs and chickens in commercial farms may eat food made from herrings, anchovies, and other fish. What are some possible consequences to marine food webs?

Question 7

List three examples of symbiotic relationships.

Question 8

Describe how a terrestrial ecosystem can interact with a faraway aquatic ecosystem.

Question 9

How can two species share the same habitat without one driving the other to extinction?

Question 10

In the United States alone, tens of millions of domesticated cats consume hundreds of millions of songbirds. Use the Internet to learn more about songbird diets, then predict how predation by cats might affect the rest of the food web.

Question 11

Describe some adaptations that protect against herbivory and predation.

Question 12

Describe the relationship between panic grass, the fungus, and the virus.

Question 13

List some additional components of your abiotic environment.

Question 14

Some farmers and ranchers kill the prairie dogs on their land. Use the Internet to research the ecology of prairie dogs and some of the techniques used to control prairie dog populations. How does each technique affect the prairie ecosystem?

Question 15

How are keystone species important in communities?

Question 16

The fungus-virus partnership helped young grass plants survive at very high temperatures. What would be the benefits of inoculating all of our food crop plants with the fungus-virus team? What else would you need to know before recommending that strategy? Can you think of any possible drawbacks?

Question 17

Describe and give examples of three types of symbiotic relationships.

Question 18

Use the second law of thermodynamics and a pyramid of energy to explain why most food chains have four or fewer levels.

Question 19

Define coevolution and describe an example.

Question 20

Where do primary, secondary, and tertiary consumers fit into this concept map?

Question 21

. Some forms of mercury biomagnify in aquatic food chains. High concentrations of mercury in fish are prompting health advisories that warn pregnant women not to eat tuna and some other fish species. From this information, do you think tuna is an herbivore or a carnivore? Explain your reasoning. What properties do you predict that mercury shares with DDT and other pollutants that biomagnify as they ascend food chains?

Question 22

What is succession?

Question 23

In one type of mimicry, a harmless species such as a jumping spider physically resembles a noxious species such as an aggressive type of ant. Explain why this type of mimicry can exist only if the spiders are less abundant than the ants.

Question 24

. How do organisms return water, carbon, nitrogen, and phosphorus to the abiotic environment?

Question 25

Distinguish between primary and secondary succession.

Question 26

What is a keystone species? How do researchers design experiments that help them identify keystone species?

Question 27

Use the carbon cycle to trace a hypothetical path of a carbon atom from Abraham Lincoln's body into your own.

Question 28

What processes and events contribute to primary and secondary succession?

Question 29

How is natural selection apparent in ecological succession?

Question 30

Suppose your friend says "I hate germs! I wish we could kill all the bacteria in the world!" What would happen to your friend if she didn't harbor bacteria in her own body? What would happen to nutrient cycles without bacteria?

Question 31

. How do disturbances prevent true climax communities from developing?

Question 32

Why are true climax communities rare?

Question 33

Several sites on the Internet offer water- or carbon-footprint calculators. Choose one and compute your footprints. What are the assumptions that go into these calculations? What strategies could you use to reduce either footprint?

Question 34

Identify the trophic levels of a food chain.

Question 35

After fires destroyed much of Yellowstone National Park in 1988, forest managers suggested humans could help the areas recover by feeding deer, bringing in plants, and planting trees. What are some advantages and disadvantages of intervening in recovery from a disaster?

Question 36

Use the Internet to look up the components of a so-called "low-carbon" diet. How does each element of a low-carbon diet help reduce CO2 emissions into the atmosphere?

Question 37

What sources of energy sustain ecosystems?

Question 38

When Mount St. Helens erupted in 1980, areas nearest the volcano were totally devastated. Farther away from the blast site, however, the disturbance was milder. Predict how the rate of forest succession would change with distance from the volcano, and explain your prediction.

Question 39

Review the structures of organic molecules in chapter 2. How do the molecules in living cells create interconnections between the carbon, nitrogen, and phosphorus cycles?

Question 40

What roles do primary producers and decomposers play in ecosystems?

Question 41

Can you think of an example of an organism that is both a producer and a consumer?

Question 42

Distinguish among communities, ecosystems, and populations.

Question 43

How efficient is energy transfer between trophic levels in food webs?

Question 44

Where do mutualism, commensalism, and parasitism fit into this concept map?

Question 45

Identify a consumer in an ecosystem not mentioned in the text.

Question 46

Name some abiotic and biotic components of your environment.

Question 47

Draw an energy pyramid for an ecosystem with three levels of consumers.

Question 48

How does a community differ from an ecosystem?

Question 49

Krill are tiny, shrimplike plankton that are abundant in Antarctic waters. Some people have suggested that we "farm'' the krill in Antarctic waters and use it to feed people who are starving. Predict the effects of krill farming on the Antarctic ecosystem.

Question 50

Distinguish between habitat and niche.

Question 51

Explain how biomagnification disproportionately affects organisms at the top of a food chain.

Question 52

How are decomposers and autotrophs essential to ecosystem function?

Question 53

In a long-term study of a tropical rain forest in Puerto Rico, researchers studied the aftermath of hurricanes Hugo and Georges. Tree debris supported the growth of detritivores. Beetles and flies ate the detritivores. Propose a food chain and trace how the booming insect populations might eventually benefit top predators such as birds and snakes in the forest. What do you predict happened to fruit- and-nectar-eating animals immediately after the storm?

Question 54

How do ecologists measure species diversity in a community?

Question 55

What features do biogeochemical cycles share?