Chapter 2

• The general intellectual climate of our culture is known as zeitgeist
• The tendency to think about behavior in terms of dichotomies is illustrated by questions like:

  • Is it physiological, or is it psychological?
  • Is it inherited, or is it learned?
• During the Renaissance period (1400-1700), scholars started to study things directly by observing them, leading to the birth of modern science
• Descartes advocated a philosophy that separated the universe into physical matter and the human mind, known as Cartesian dualism
• Early North American experimental psychologists were committed to the nurture side of the nature-nurture issue
• European ethology focused on instinctive behaviors and the role of nature in behavioral development
• The physiological-or-psychological and nature-or-nurture debates are flawed ways of thinking about the biology of behavior
• All behavior is the product of interactions among genetic endowment, experience, and perception of the current situation
• Charles Darwin's theory of evolution, published in 1859, described how species evolve through natural selection
• Natural selection leads to the evolution of species better adapted to surviving and reproducing in their environment
• Social dominance in many species establishes a stable hierarchy through combative encounters, impacting copulation and offspring production
• Courtship displays in many species precede copulation and promote the evolution of new species through reproductive isolation
• Complex multicellular water-dwelling organisms first appeared on earth about 800 million years ago
• Chordates evolved 250 million years later - animals with dorsal nerve cords
• The first chordates with spinal bones (vertebrae) evolved about 25 million years later
• Vertebrates are chordates that possess vertebrae
• There are seven classes of vertebrates: three classes of fishes, plus amphibians, reptiles, birds, and mammals
• Amphibians evolved from bony fishes about 410 million years ago
• Fins and gills of bony fishes transformed into legs and lungs in amphibians
• Amphibians have a larval form that must live in water, only adult amphibians can survive on land
• Reptiles evolved from a branch of amphibians about 315 million years ago
• Reptiles were the first vertebrates to lay shell-covered eggs and be covered by dry scales
• Mammals evolved from small reptiles about 225 million years ago
• Mammals stopped laying eggs and started nurturing their young internally
• Humans belong to the order primates, with about 16 groups of primates
• Apes include gibbons, orangutans, gorillas, and chimpanzees
• Chimpanzees are the closest living relatives of humans, sharing about 99% of genes
• Hominins include primates of the same group as humans, with six sub-groups including Australopithecus and Homo
• Homo is composed of at least eight species, with Homo sapiens being the only existing one
• The human brain has increased in size during evolution, with most of the increase in the cerebrum
• The human brain evolved from the brains of our closest primate relatives
• Gregor Mendel's research on pea plants informed us about the mechanisms of inheritance
• Mendel studied dichotomous traits and true-breeding lines in his experiments
• Mendel proposed that there are two kinds of inherited factors for each dichotomous trait, called genes
• Mendel proposed that each organism possesses two genes for each trait, known as alleles
• Mendel's experiment challenged the idea that offspring inherit the traits of their parents
• Phenotype refers to an organism's observable traits, while genotype is the traits passed on through genetic material
• Mendel proposed that each organism possesses two genes for each of its dichotomous traits
• Alleles are the two genes that control the same trait
• Organisms with two identical alleles are homozygous, while those with different alleles are heterozygous