14.3.3 Nature vs. Nurture: Is There a Genetic Basis for Behaviors?

Question 1

Nature vs. Nurture: Is There a Genetic Basis for Behaviors?

Answer 1

• From the gene’s perspective, behaviors produce successful organisms.
• The selfish gene concept provides a framework for understanding genetically based behaviors.
• Experiments on lovebirds and honeybees show that certain behaviors have a genetic basis and are inherited in a Mendelian fashion.

Question 2

Richard Dawkins

Answer 2

• first conceptualized the selfish gene in 1976. According to the concept, a gene will produce an organism that is successful so that in turn, the gene is
  successful. In turn, the gene will be replicated in subsequent generations. The selfish gene concept provides a framework for understanding the genetic basis of behaviors.
• Social behavior, based in part on genetic factors, can enhance individual survivorship in penguins. The selfish genes of the penguin favor this successful behavior.

Question 3

note

Answer 3

• Experiments and observations of nest building behavior in different species of lovebirds provide insight into the genetic basis of behavior.
• The Fischer’s lovebird acquires nest building material by tearing long strips of paper and carrying them back to the nest. The peach-faced lovebird tears short strips that it weaves into its feathers.
• A hybrid of the two species tears medium length strips for the nest. It attempts to tuck the strip into its tail but doesn’t let go, pulling the strip back out and sometimes dropping it. Eventually the bird learns to keep the strip in its beak.
• Another example of the genetic component of behaviors involves honeybees.
• Honeybees are sometimes predisposed to a particular bacterial infection. When a larva is infected, adults uncap the cell and remove it. This so-called hygienic strain exhibits the “uncap-and-drag” behavior. Unhygienic strains ignore the infected larva.
• The experimenters hypothesized that separate genes controlled uncapping and dragging.

Question 4

note 2

Answer 4

• Previous experiments had shown that each of the uncapping and dragging behaviors was dominant, whereas the absence of these behaviors was recessive. The experimenters then established pure breeding lines of hygienic and unhygienic bees and crossed the two strains. The resulting F1 offspring displayed both hygienic behaviors of uncapping and dragging. The F1 offspring were then backcrossed with the unhygienic strain to determine their genotype.
• Because the unhygienic strain’s genotype was known, it was possible to make predictions about the ratio of F2 offspring for a given F1 genotype. Based on the phenotypic outcome, it was determined that the F1 genotype matched the expected genotype.
• The results confirmed that the behaviors were inherited in a Mendelian fashion and thus were genetically based.

Question 5

_________ developed the selfish gene theory in 1976.

Answer 5

• Richard Dawkins

Question 6

Hygienic bees that uncap honeycombs containing diseased larvae and drag the larvae out of the honeycomb were crossed with non-hygienic bees that leave diseased larvae in the honeycomb. The resulting bees exhibited various behaviors including the hygienic behavior, the non-hygienic behavior, uncapping the honeycomb but leaving the larvae in it and only dragging larvae out of the honeycomb if it was uncapped for them. What is the point of this experiment?

Answer 6

• There are genes that control the behavior of honeybees and these genes can be adaptive

Question 7

When a Fischer’s Lovebird, which tears long strips of paper for its nest, is crossed with a Peach-Faced Lovebird, which tears short pieces of paper for its nest, what is the behavior of the hybrids?

Answer 7

• All of the hybrids tear medium length strips.

Question 8

In a testcross, a __________ organism is crossed with an organism whose genotype is unknown. The ratio of the offsprings’ __________ determines the unknown __________.

Answer 8

• homozygous recessive; phenotype; genotype

Question 9

Richard Dawkins extended his idea of the selfish gene in a book called The Extended Phenotype. In this book he suggested that genes can go beyond influencing behaviors of organisms, they can actually influence the environment. Which of the following might be an example of the extended phenotype?

Answer 9

• A beaver builds a dam that blocks a river and provides protection from predators for its offspring.

Question 10

True or false?

The selfish gene concept provides a framework for understanding the genetic basis of behaviors.

Answer 10

• true