05 Genetics and Evolution

How do biology and natural selection shape our lives?

WHAT ARE THE GENETIC MECHANISMS OF TRAIT INHERITANCE?

• Made up of DNA, chromosomes inside cell nuclei contain all the genetic information needed to make an organism.
• Human cells contain 23 pairs of chromosomes, including an XX or XY pair that determines whether an individual is male or female.
• Egg and sperm cells contain half the genetic information of other cells. They combine during fertilization, passing on parents’ genetic information in a new permutation.

IN WHAT WAY DO GENES AND ENVIRONMENT INTERACT TO MAKE US WHO WE ARE?

• Some traits, such as eye colour, depend entirely on genetics. Others, such as height and weight, can be influenced by the environment.
• While genetics might predispose an individual to a certain trait, how that trait is expressed can depend on environmental factors.
• An environment may be external or chemical.

HOW HAS THE IDEA OF EVOLUTION BY NATURAL SELECTION INFLUENCED THE STUDY OF HUMAN BEHAVIOUR?

• According to the theory of natural selection, organisms with features that best adapted to their environment are more likely to survive and reproduce.
• Some genes are dominant or recessive, affecting the likelihood that a particular trait will be passed on.
• Research in behaviour genetics, molecular genetics, and evolutionary psychology has developed from the idea of natural selection.

WHAT ARE THE TYPICAL MATING PATTERNS OF DIFFERENT SPECIES?

• Mating patterns depend on gender differences in parental investment.
• There are four types of mating patterns: polygyny, polyandry, monogamy, and polygynandry.