14.4.1 Competitive Behaviors and Survivability

Question 1

Competitive Behaviors and Survivability

Answer 1

• In the short term, the cost/benefit ratio measures the immediate success of a behavior. Costs include energy expenditure or—more severely—the loss of life. Benefits include increased energy intake or survivorship of the organism.
• A behavior with a high cost/benefit ratio decreases the organism’s fitness and will not be selected for. A behavior with a small cost/benefit ratio causes an increase in an organism’s fitness and will be selected for.

Question 2

note

Answer 2

• There are cost/benefit ratios associated with every behavior that determines an organism’s evolutionary success.
• If the cost of a behavior is too high, death can result.
• The cost/benefit ratios of two different foraging strategies in fish are shown in the chart on the left. Acquiring large prey is beneficial in terms of nutrient gain, but it requires more energy expenditure for capture. Smaller prey are less costly to catch, but provide fewer calories.

Question 3

agonistic behaviors

Answer 3

• When members of the same species vie for limited resources (such as food or a mate), intraspecific competition may take the form of agonistic behaviors.
• These aggressive behaviors usually do not program the individual to fight to the death. The individual postures, instead, thus preserving the individual’s life. In rare instances, mate availability is severely limited, and males will fight to the death for the opportunity to mate. Such a situation occurs in some species of ground squirrels.

Question 4

note 2

Answer 4

• Certain bird songs are actually territorial messages to warn other male birds of the same species.
• Genetically based behaviors may determine when birds migrate. Bird 1 on the left migrates north in March. The early migration leaves him vulnerable to harsh winter conditions and insufficient food supply. Bird 2 leaves later and has more stored fat for the migration. Bird 2 may be successful in capturing territory from weaker birds.

Question 5

Which of the following would not be considered a cost to an organism?

Answer 5

• increased reproduction

Question 6

Which of the following is not an example of intraspecific competition?

Answer 6

• Mountain chickadees defend small territories against migrating eastern deciduous chickadees.

Question 7

______________ competition is competition among members of the same species.

Answer 7

• Intraspecific

Question 8

True or false?
Dominance hierarchies exist in groups of antisocial organisms in order to establish which members in the group will get food and mate.

Answer 8

• false

Question 9

If the cost of a behavior is greater than the benefit,

Answer 9

• it will probably not persist very long in a population

Question 10

Why would a male ground squirrel have a gene for fighting another male ground squirrel to the death?

Answer 10

• Female ground squirrels only have a few hours a year when they are fertile so the males must fight for the opportunity to mate.

Question 11

Optimal foraging theory

Answer 11

• is the concept that natural selection will favor animals that choose foraging strategies that maximize benefits while reducing costs.

Question 12

A bluegill in a low prey density environment will eat ____________ in order to obtain ____________ at the cost of passing up potentially larger prey.

A bluegill in a high prey density environment will eat ____________ in order to obtain ____________ at the cost of expending extra energy.

Answer 12

• the first available prey;
• guaranteed nutrients;
• the largest prey;
• the most nutrients