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Darwin's main ideas can be traced back to...


Aristotle and early Judeo-Christian culture believed...

that species were fixed and designed by a creator, but there were exceptions

Charles Darwin observed here:

Galapagos Islands

Two main features of Darwin's theory of evolution:

1. diverse forms of life have arisen by descent with modification
2. natural selection

Darwin observed that organisms:

- vary in many characteristics that can be inherited
- produce more offspring than the environment can support

Evolution by Natural Selection:

1. Individuals don't evolve, populations evolve from generation to generation
2. Natural selection can amplify or diminish certain heritable traits
3. Evolution is not goal-directed


groups of individuals of the same species living in a defined area


a group of populations whose individuals can interbreed and produce fertile offspring

Artificial Selection

humans change a species over time

Examples of Natural Selection:

camouflage; development of pesticide resistance

Key Points About Natural Selection:

1. more of an editing process than a creative mechanism
2. contingent on time and place
3. significant evolutionary change can occur in a short amount of time

Evidence Supporting Evolution:

fossils, the fossil record, intermediate forms, birds, comparative anatomy, evolutionary trees

Fossil Record

an ordered array in which fossils appear within layers of sedimentary rock

Intermediate Forms

the missing links

Birds are...

living dinosaurs

Homologous Structures

features that often have different structures but are structurally similar because of common ancestry

Comparative Embryology

as developing embryos, many vertebrates have common structures


the geographic distribution of species suggest that organisms evolve from common ancestors

Molecular Biology

comparisons of DNA and amino acid sequences between different organisms reveal evolutionary relationships


the ultimate source of genetic variation that serves as raw material for evolution

Sexual Recombination

causes genetic variation that makes adaptation possible


if two or more morphs in a population are present in noticeable numbers

Natural Selection

occurs when individuals with certain traits are more likely to survive and reproduce compared to individuals with other traits

Genetic Drift

the change in the gene pool of a population due to a chance event

Gene Flow

the transfer of alleles from one population to another, as a result of movement of individuals or their gametes

Endangered species often have...

reduced variation

Natural selection can alter variation in a population in three ways..

1. stabilizing selection
2. directional selection
3. disruptive selection

Sexual Selection

differential reproductive success owing to variation in the ability to obtain mates

Sexual Dimorphism

males and females of many species are physically different; result of competition for mating partners

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