Chapter 1. An Introduction to Animal Behavior

natural selection

the process that occurs when individuals differ in their hereditary traits and the differences are correlated with differences in reproductive success

evolutionary change

the process that occurs when groups differ in their collective attributes and these differences affect the survival chances of the group

self-sacrificing behavior

a type of natural selection that favors the reproductive success of an organism’s relatives, even at a cost to the organism’s own fitness

• acts on traits used to compete for mates with others of the same sex, or to attract members of the opposite sex in order to mate with them

evolutionary change is inevitable if…

1. variation (population members differ in a characteristic)

2. differential reproductive success (individuals with particular characteristics have more offspring than others)

3. heredity (parents can pass characteristics to offspring)

trait

• a character or feature of an organism

• any measurable aspect of an individual’s body or behavior that arises form an interaction of the individual’s genes with its environment

fitness

how successful an individual is at passing on its heritable traits to the next generation

• depends on survival and reproduction

adaptations

traits associated with successful survival and reproduction, and upon which natural selection acts

genes

regions of DNA that encode traits

alleles

a form of a gene; code for distinctive variants of the same trait

phenotype

an aspect of an individual that arises from an interaction of the individual’s genes with its environment

genotype

the genetic constitution of an individual

• specific alleles of one gene or the individual’s complete set of genes

descent with modification

the foundational idea of evolution that individuals pass varied genetic traits to their offspring, and differences in reproductive success among individuals in a population cause a population or species to evolve over time

fitness costs

the negative effect of a trait on an individual’s reproductive/genetic success

fitness benefits

the positive effect of a trait on an individual’s reproductive/genetic success

infanticide hypothesis

infanticide is a reproduction-enhancing tactic practiced by males

ultimate causes

an evolutionary, historical reason for why a behavior is the way it is

• historical

• adaptive evolutionary

proximate causes

an immediate, underlying reason for why a behavior is the way it is based on the operation of internal mechanisms possessed by an individual

• developmental

• physiological

Tinbergen’s four questions

a scheme developed by Nikolaas Tinbergen to address the proximate and ultimate causes of a behavior

development proximate level

how genetic-developmental mechanisms influence the assembly of an animal and its internal components

mechanism proximate level

how neuronal-hormonal mechanisms that develop in an animal during its lifetime control what an animal can do behaviorally

evolutionary history ultimate level

the evolutionary history of a behavioral trait is affected by descent with modification from ancestral species

adaptive function ultimate level

the adaptive value of a behavioral trait as affected by the process of evolution by natural selection

parsimony

(Occam’s razor)

simpler explanations are more likely to be correct than complex ones

divergent evolution

• the evolution by natural selection of differences between closely related species that live in different environments (subject to different selection pressures)

• acquisition over time of similar characteristics in 2+ unrelated species

convergent evolution

• independent acquisition over time of similar characteristics in 2+ unrelated species

• evolution of differences between closely related species living in different environments (subject to different selection pressures)