unit one: evolution

describe how scientists developed the present-day theory of evolution

• studying how organisms interact with their environment

• how populations change over time

• ecological pressures promote natural selection and genetic diversity

define adaptation

• a heritable trait that aids an organism’s survival and reproduction in its present environment

explain convergent evolution

• similar traits that evolve independently in species that do not share a common ancestor.

define divergent evolution

• species that evolve in different ways from a common point.

describe homologous structures

• anatomy in different species that share a common origin and bone structure, even if they have different functions

describe vestigial structures

• anatomical parts that lost their original function over the course of evolution

discuss misconceptions about the theory of evolution

• individuals can evolve. individuals do NOT evolve, populations evolve

• organisms evolve “on purpose”. natural selection is RANDOM and acts on variation among individuals in the population

• all evolution is due to natural selection. evolution can occur through 5 evolutionary forces: random genetic drift, non-random mating, mutation, migration, and natural selection

define species

• species: ability to interbreed in nature and produce viable and fertile offspring

describe scientists identify species as different

• a group of organisms whose members possess similar anatomical characteristics and have the ability to interbreed.

describe genetic variables that lead to speciation

• identical populations must diverge

• reproductive isolation must evolve to maintain differences

define prezygotic isolating mechanisms

• prevent the formation of zygotes (no hybrids)

identify prezygotic reproductive barriers

• geographic isolation: species occur in different areas

• ecological isolation: utilizing different portions of the same environment

• behavioral isolation: courtship rituals

• temporal isolation: varying breeding seasons

• mechanical isolation: reproductive structural difference

• gametic barrier: biological block that stops sperm and eggs from fusing

define postzygotic isolating mechanisms

• reproduction has occurred, prevents proper functioning of zygotes after they form (reproduced hybrid fitness)

identify postzygotic reproductive barriers

• hybrid sterility

• abnormal sexual organ development

• chromosome alterations

explain allopatric and sympatric speciation

• allopatric: speciation in populations that are spatially separated (things found in different environments) MOST COMMON

• sympatric: speciation that occurs in the same environment

defines types of polyploidy

• autopolyploidy: occurring in the same species

• allopolyploidy: occurring between two species

describe adaptive radiation

• process producing a cluster of species, occupying similar habitats, all evolving from a recent ancestor

describe pathways of species evolution in hybrid zones

• reinforcement: selection will act on traits that reinforce mating with individuals who do not have alleles that reduce the fitness of offspring

• fusion: reproductive barriers weaken until species become one

• stability: fit hybrids continue to be produced

explain the two major theories on rates of speciation

• punctuated equilibrium: evolution proceeds in spurts, with long periods of little movement in between

• gradualism: slow rate of gradual change