Module 08: Behavior Unit 2: Individuals and Populations

Objectives Define terms. Describe the relationship between evolution and behavior. Discuss sexual selection, its basis, and mechanisms. Recognize and discuss different mating systems. Describe social systems and their components

Evolution Behavior is part of a organism’s phenotype. At least partially controlled by genetics. Subject to natural selection. Can be as adaptive as morphology or physiology. All behaviors have a fitness cost and a fitness benefit. Ultimate and proximate causes of behaviors might differ.

Fundamental mechanisms Stimulus-response Highly stereotyped – Invariant Courtship displays Communication Any action that alters the probability of a behavior of an another individual. Visual, auditory, olfactory, and tactile signals. Discrete or graded response.

Selection and Sex Females bear greater direct (anatomical, physiological, and energetic) costs of reproduction. To a point a female’s fitness cannot be increased by producing more young. Female fitness depends on the quality of the offspring that she produces. Males have less cost and are less limited in the number of offspring that they can produce. Access to breeding females becomes the critical limiting factor. Sexual dimorphism – Color, morphology, and size Bateman’s principle – greater variation in the reproductive output of males than females.

Selection and Sex Sexual Selection Form of natural selection Traits that enhance the ability of one sex (usually males) to compete for or attract mates are favored. Two forms Female choice Male-male competition

Sexual and Natural Selection Interaction between sexual selection and natural selection Balance hypothesis Natural selection optimizes the costs and benefits of exaggerated traits. Truth in advertising Exaggerated traits advertise the genetic quality of the potential mate Mates can then select the highest quality mate and increase their own fitness.

Mating Systems The relationships between males and females during reproduction. Number of mates with which an individual copulates. Relative contribution of males and females to parental care. How long the female-male relationship lasts.

Mating Systems Monogamy Polyandry Polygyny Serial monogamy Female defense polygyny Leks

Plant Mating Systems Outcrossing – mating among different individuals Autogamy – self-fertilization Apomixis – asexual reproduction

Plant Mating Systems Long-distance dispersal and colonizing abilities favors autogamy. Ability to rapidly exploit local resources or ephemeral favorable conditions favors apomixis.

Habitat Resources Physical and biological characteristics Home range Territoriality Habitat selection

Social System Group size and composition Degree of cooperation Solitary Cost and benefits of living in groups? Degree of cooperation Cooperative hunting Altruistic behavior Inclusive fitness Mating System