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39 Cards in this Set

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What did Darwin mean by "descent with modification".
Animals change from ancestors to something more different but are still the same.
Evolution
Change of frequency of alleles in a population
Lamarck theory
Traits could be acquired during lifetime depending how often it is used. Traits that were used would be passed on.
What is natural variation?
Differences among individuals of a species. -Can be found in all species
What is artificial selection?
Nature provieded variation among different organisms, and humans selected the variations that were found useful.
What is fitness?
An individual's ability to survive and reproduce in its environment.
Adaptation
Any inherited characteristic that increases an organism's chance of survival.
Survival of the fittest
Individuals w/ low fitness die or leave few offspring. Individuals with high fitness- survive and reproduce.
Natural selection
Traits being selected by nature that contribute to an organism's fitness in its environment.
What happens over time in natural selection?
Natural selection results in changes in the inherited characteristics of a pop. The changes increase a species' fitness in environment.
Descent with modification
Each living species descended, with changes, from other species over time.
Common descent
All species-living and extinct- came from common ancestors.
"Tree of life"
Links all living things on Earth
Evidence for the process of evolution can be found in where?
Fossil record, where living organisms are placed geographically, homologous structures of living organisms, and similarities in early development.
How can two species that look different from each other be more closely related than two other secies that look similar to each other?
Species living on different continents had different ancestors. But they lived under similar ecological conditions and faced with similar pressures of natural selection, different species ended up evolving some features in common.
Homologous Structures
Differ greatly in form and function, but made from the same basic bones.
-different form and function, but made from same basic bones.
Vestigial organs
Like the human appendix. Structures hardly used and reduced in size.
Descent with modification
Each living species descended, with changes, from other species over time.
Common descent
All species-living and extinct- came from common ancestors.
"Tree of life"
Links all living things on Earth
Evidence for the process of evolution can be found in where?
Fossil record, where living organisms are placed geographically, homologous structures of living organisms, and similarities in early development.
How can two species that look different from each other be more closely related than two other secies that look similar to each other?
Species living on different continents had different ancestors. But they lived under similar ecological conditions and faced with similar pressures of natural selection, different species ended up evolving some features in common.
What are the two main sources of genetic variation?
-Mutations
-Genetic shuffling (from sex. reproduction)
What does the number of phenotypes of made for a given trait depend on?
It depends on how many genes control the trait.
Single-gene trait
Trait tat is controlled by a single gene that has two alleles. (widows peak)
Polygenic traits
Traits that are controlled by two or more genes. (height)
Natural selection on single-gene traits can lead to what?
Leads to changes in allele frequencies, then to evolution.
Natural selection can affect the distributions of phenotypes in three ways.
Directional, stabilizing, disruptive selection
What is genetic drift?
Random change in allele frequency
What is genetic equilibrium?
Situation where allele frequencies remain constant
What 5 conditions are needed to maintain genetic equilibrium?
-Random mating
-population must be large
-no movement into or out of population
-no mutation
-no natural selection
Reproductive isolation
When members of two populations cannot interbreed and produce offspring
behavioral isolation
Is one of three reproductive isolations. Two populations are able to interbreed but choose not to because of differences in mating rituals.
Geographic Isolation
Two populations are unable to interbreed due to a natural barrier. Rivers, mountains, bodies of water
Temporal Isolation
Two populations reproduce at different times. E.g; 3 similar species of orchid releases pollen only on a single day. They release pollen on different days, so they cannot pollinate one another.
How is reproductive isolation related to the formation of new species?
When gene pools get to be very different because of reproductive isolation eventually two populations will not interbreed with each other. The two gene pools remain isolated from each other- even when living together in the same place. The two populations are now two species.
Allele frequencies can change by
Natural Selection and Genetic Drift
Natural selection acts on
Single-gene traits and polygenic traits
Polygenic traits can be affected by
Directional selection, Stabilizing direction, and disruptive selection