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Evolution –THINGS YOU NEED TO KNOW
Natural selection -acts on phenotypes not individuals. Evolution acts on populations not individuals.
Adaptations
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Are caused by variations in a population (alleles)
Genes are passed to the next generation
Allow speciation to occur when the gene flow is isolated
Lead to change in a species
Allow species to survive natural selection and reproduce
Individual organisms do not change on their own genes in order to adapt. (camouflage is a
adaptation that increases survivability)
Are heritable structures that allow an organism to survive.
Differential Reproductive Success – allows animals to survive, live into adulthood and reproduce.
Homologous structures
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Example Bird wing and a bat wing.
structures that have different mature forms in different organisms but develop from the same
embryonic tissues
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Homologies are similarities in anatomical structure
Analogous Structure
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Structures that do not have a common evolutionary origin but are similar in function, (develop
from different embryonic tissue).
Structurally different pattern of development.
Example -Bird wing and an insect wing.
Vestigial Organs -organs that serve no useful purpose for the organism; these suggest that sometime in
the past they were useful. Pelvic bones in whales, leg bones in snakes.
Natural Selection
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process by which individuals that are better suited to their environment survive and reproduce
most successfully; also called survival of the fittest. Acts on the phenotype of a species.
Common Descent
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Principle that all living things were derived from common ancestors. The more DNA an
organism has with another organism causing them to have similar amino acids sequence this is
evidence they have common ancestors. Even though they may look unrelated. The more DNA
sequences species have in common the closer they are related.
Disruptive selection - natural selection that favors individuals with either extreme of a trait; tends to
eliminate intermediate phenotypes. Disruptively selected for extreme.) Black rabbits White rabbits but
no gray rabbits in a population.
Directional selection- natural selection in which individuals at one end of the phenotypic range survive
or reproduce more successfully than do other individuals.
Stabilizing selection -natural selection in which intermediate phenotypes survive or reproduce more
successfully than do extreme phenotypes. Organisms become adapted and can increase genetic
diversity throughout a population.
All fetuses
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have pharyngeal
gill slits,
bony tail,
if it was a mammal fetus it would also have a fine coat of fur
Convergent evolution –Organism that has similar functional structures, but come from very different
species.
Geographical Isolation is a barrier for populations it determines the ability of the population to move
freely from place to place. The finches on the different islands developed different beaks would be an
example of Geographical Isolation. Isolates gene flow
Gene Flow is the movement of genes or alleles from one population to another. The number of alleles
or allele frequency in a population is what would determine if a mutation would become and
adaptation.
Behavioral Isolation- Species mating rituals are different. Examples -mating calls, mating signals, mating
dances.