Exam 3 Ch6

Evolution

Gradual change of species

Genetic variation affect probability individuals survive and reproduce, adaptations that increase likelihood of having offspring will eventually predominate in the population

Mendels pea plants found mutations could arise spontaneously and passed to future generations

Evolution by natural selection

Mechanistic theory by Darwin and Wallace

Observed: reproduction will increase a population rapidly unless factors limit it, individuals of a species are not identical, some variation is inherited, not all offspring survive to reproduce

Genome

Set of complete instructions for making organism, all genes

Chromosomes

Contain DNA, within DNA are genes that encode proteins

Forms of natural selection

Directional- an advantageous mutation spreads in population

Stabilizing- favors reduced variation in a trait

Disruptive- favors development of 2 forms of a trait in different sub populations

Gradualist evolution

Certain anatomical traits transformed gradually giving rise to new species

Punctuated equilibria

Evolution proceeds in non-continuous manner with long stagnant periods interrupted by short periods of rapid transformation leading to new species

Convergent evolution

Results in similar solutions in different species

Homoplasy

Resemblance of characteristics due to convergent evolution

Homology

Similarity based on common ancestry, forelimbs

Analogy

Similar function despite differences in structure and evolution

Genus

Group of species that resemble each other

Species

Group of individuals that can interbreed and produce fertile offspring

Phylogeny

Evolutionary history of a particular group of organisms often represented as a family tree

Taxonomy

Classification of organisms makes use of genetics to reconstruct phylogeny

Nervous system

Animals with bilateral symmetry and centrally located NS has survivor advantages

Triune brain theory

Reptilian brain: oldest, controls vital functions, reliable but tends to be rigid and compulsive, brain stem, cerebellum

Limbic brain: emerged in the first mammals, record memories, responsible for emotions, value judgements, hippocampus, amygdala, hypothalamus

Neocortex: importance in primates with 2 hemispheres, human language, abstract thought, imagination, and consciousness, flexible, almost infinite learning abilities, led to human cultures

Encephalization factor

Measure of brain size relative to body size, the vertical distance from regression line

Brain structure sizes

Medulla becomes proportionally smaller relative to brain size

Cerebellum retains its relative size

Cortex becomes proportionately larger

Ecological niches

Animals evolved specific behaviors and neural mechanisms that allow them to exploit specific sets of environmental opportunities

Cortex

Thin layer of neurons that covers surface of each cerebral hemisphere, cortex divided into three parts from evolution

Archicortex: developed in association with olfactory system, corresponds to dentate gyrus and hippocampus in mammals, and does not have 6 layers of neocortex

Paleocortex: also associated with olfactory system not striated into layers corresponds to piriform cortex and parahippocampal gyrus

Neocortex: largest portion of cortex in primates, stratified into 6 layers

Hominin

Brains enlarged rapidly in recent evolution

Australopithecines- hominids that made and used tools but had relatively small brains

Hypotheses

Social brain hypothesis - larger brain needed to maintain social relationships between individuals

Language hypothesis- larger brains needed for language

Posture hypothesis- larger brain a result of erect posture

Large brain costs

Long gestation time and difficulty birthing

Brain growth for years, requiring prolonged dependence on parents

High metabolic cost

Complex genes vulnerable to mutation