U6 C1 Flashcards
Evolution
The process of biological change in populations over time that
makes descendants genetically different from their ancestors
Microevolution
- Small scale evolution affecting a single population`\
Macroevolution
- Large scale evolution affecting a species across populations
- Natural selection
Mechanism of evolution where organisms with the “best” traits
are favored and thus live longer and reproduce more, causing
changes in the population over time so that the fittest survive
Fitness
A measure of how well an organism can survive in its
environment
- Adaptation
A feature that allows an organism to better survive in its
environment
*Gene pool =
- The combined alleles of all individuals in a population
*Genetic drift
- Mechanism of evolution that occurs when random change
in the allele frequency happens in the population`
*Gene flow =
- Mechanism of evolution caused by the movement of genes
into or out of a population
*Sexual selection
- Mechanism of evolution that favors traits that potentially
decrease survival, but increase likelihood of reproduction
*Genetic equilibrium
When there are no changes in the allele frequencies in a
population over time, and thus evolution is not occurring
Explain the principles of natural selection. Write a real
world example of evolution and how each principle was
met.
*Overproduction of offspring, Variation, Adaptation, Descent with modification,
There is an overproduction of offspring that leads to more
organisms than resources, and thus creates competition.
* Within any population there will be variation.
* Some innate variations will allow organisms to better survive
than others (adaptations).
* Over time, those traits should become more common because
organisms with those traits will live longer and reproduce more,
creating descendants with modifications from their
ancestors.
Explain how diversity within a species has resulted
in an increase in fitness (survival of the fittest).
The more diverse a species is the less likely the entire
species can be eliminated by a sudden event.
- This is why sexual reproducers tend to be better at surviving in
regularly changing environments than asexual reproducers,
whose only source of variation is random mutation.
List the different factors that contribute to genetic
variation and explain which is considered to be the
“ultimate” source.
- Random mutations
- Ultimate source because the others don’t affect asexual
reproducers - Genetic recombination during meiosis
- Migration/gene flow
Explain what is meant by the phrase, “Individuals don’t
evolve, populations do.”
- Natural selection acts on traits that are heritable, not traits that
are acquired in a lifetime. - It is impossible for an individual to change their allele
frequencies. - Thus only populations can evolve because only within
populations do allele frequencies change over time.
3 mechanisms of microevolution
Genetic drift
Gene flow
Sexual selection (non-random mating)
Genetic drift
random change in a population that often
decreases variation
Gene flow
the movement of genes into or out of a
population, affecting the variation within the population
Sexual selection (non-random mating)
= favoring traits that
increase reproduction over survival
Give an example of how genetic drift would have a
bigger impact on a smaller population than a larger
one.
- If a hurricane comes and flooding occurs and wipes out half of
a population of 1,000 insects, there are still 500 remaining and
most likely a decent amount of innate variation within them. - But if that same flooding occurs in a population of 100 insects
and only 50 survive, most likely a lot of variation was eliminated
and if those 50 only reproduce with each other, the traits that
exist in their alleles will be favored and the others will die out of
the population.
List the 5 conditions that must be met for evolution
to not occur.
- No mutations
- No natural selection
- LARGE population
- No migration
- Random mating
