Chapter 4

Question 1

Weather

Answer 1

the variation in temperature and precipitation over periods of hours or days.

Question 2

Climate

Answer 2

the typical atmospheric conditions that occur through the year, measured over many years.

Question 3

Large-scale spatial variation

Answer 3

caused by factors such as climate, land topography, and soil type

Question 4

small scale variation

Answer 4

generated by factors such as plant structure and animal behavior.

Question 5

Phenotypic trade-off

Answer 5

a situation in which a given phenotype experiences higher fitness in one environment, whereas other phenotypes experience higher fitness in other environments.

Question 6

Phenotypic plasticity

Answer 6

the ability of a single genotype to produce multiple phenotypes.

Question 7

Acclimation

Answer 7

which is an environmentally induced change in an individual’s physiology, can also be relatively rapid.

Question 8

Hermaphrodites

Answer 8

individuals that produce both male and female gametes; individuals are able to fertilize their eggs with their own sperm (i.e., they are self-compatible).

Question 9

Inbreeding depression

Answer 9

the decrease in fitness caused by matings between close relatives due to offspring inheriting deleterious alleles from both the eggs and the sperm.

Because of this cost, some species wait until self-fertilization becomes the last chance for reproduction.

Question 10

Dormancy

Answer 10

a condition in which organisms dramatically reduce their metabolic processes.

Question 11

Diapause

Answer 11

involves a partial or complete physiological shutdown in response to unfavorable conditions; common in insects.

Example:
Insects facing drought conditions enter diapause by dehydrating themselves. Some form an impermeable outer layer to prevent further dessication.

Question 12

Hibernation

Answer 12

individuals reduce the energetic costs of being active by lowering heart rate and decreasing body temperatures; common in mammals.

Example:
During winter, chipmunks slow breathing and heart rates and reduce body temperature to close to 0C.

Question 13

Torpor

Answer 13

a brief period of dormancy in which individuals reduce activity and body temperature; common in birds and mammals.

Example:
The West Indian hummingbird loses much of the heat it generates to cold temperatures. To save energy, the bird enters torpor when it is resting at night.

Question 14

Aestivation

Answer 14

the shutting down of metabolic processes during the summer in response to hot or dry conditions. Well-known examples include snails, desert tortoises, and crocodiles.

Question 15

Foraging decisions

Answer 15

Foraging is a plastic behavior because different feeding strategies represent different behavioral phenotypes.

Since resources vary in space and time, no single foraging strategy can maximize an animal’s fitness.

Animals must determine where to forage, how long to feed in a certain patch of habitat, and which types of food to eat.

Question 16

Central place foraging

Answer 16

foraging behavior in which acquired food is brought to a central place (e.g., a nest with young birds).

As an individual forages farther from the central place, it finds greater amounts of resources, but this increases energy costs and the amount of food the individual must bring back.

As an individual feeds and collects prey, it becomes increasingly difficult to hold or consume the next prey item (i.e., there are diminishing benefits over time).

Question 17

What do foraging decisions depend on?

Answer 17

the time needed to travel round-trip to site with resources (i.e., traveling time) and the time spent obtaining food at a site (i.e., searching time).

At sites farther away, birds should spend more time searching for food and bring back more food to offset the extra travel time.

Question 18

Risk-sensitive foraging

Answer 18

foraging behavior that is influence by the presence of predators.

Example:
Creek chub feed on tubifex worms, but locations with worms also contain more predators.

Research has found that past a certain threshold of resource abundance, creek chub will risk feeding in an area with predators.

Below that threshold, creek chub avoid areas with predators.

Question 19

Handling time

Answer 19

the amount of time that a predator takes to consume a captured prey.

The energy benefit of a resource item divided by the handling time is the amount of energy gained per unit time.

A predator should always eat the prey species that provides the highest amount of energy gained per unit time.

If the highest energy prey is rare, the animal should include less profitable items in its diet.

Question 20

Diet mixing

Answer 20

Some foragers consume a varied diet because one type of food might not provide all of the necessary nutrients.

Examples:
Humans combine food items to consume all essential amino acids.

Nymphs of the American grasshopper grow faster when provided a mixed diet of plants, even though each of the plants is relatively low quality.