Theory of Evolution - Honors Biology 9

mutation

a change in an organisms coding region of DNa leading to a new allele

somatic mutation vs germline mutation

somatic is developed after conception, to cells other than sperm and egg. germline is inherited for the egg and sperm during conception

natural selection and adaptations

when an allele makes an organism able to survive and reproduce in a given environment. adaptations help certain organisms survive and reproduce increasing allele frequency

gene flow

the gain or loss of alleles from a population by the movement of individuals or gametes into or out of an established population

immigration

to join or enter an area

emigration

to exit an area

migration

both enter and exit a population

genetic drift

the population variation decreases due to chance, changing the allele frequency of the gene pool

Founder Effect (Genetic Drift)

a decrease in genetic variation caused by the formation of a new population by a (random) small number of individuals from a larger population

Bottleneck Effect (Genetic Drift)

a change in allele frequencies of a new population caused by a sudden decrease in population size due to a random event - usually a natural disaster (not due to fitness or lack of an adaptation)

Non-Random Mating (Sexual Selection)

the selection of mates other than by chance/convenience. Females choose their mates so males have to compete.

5 conditions of natural selection

1. Must be variation

2. Must be competition

3. Some organisms will survive the competition and some won’t

4. Some organisms will reproduce and some will not (aren’t long enough or nobody chooses to mate with them)

5. Those that survive and reproduce pass on their genes and unique traits to their children and evolve (increasing favorable allele frequency

Stabilizing Selection

when natural selection selects against the extremes and favors the intermediate/average

Directional Selection

natural selection favors one extreme over the other and the average

Diversifying/Disruptive Selection

favors both the extremes

How do we know if evolution is occurring?

If the allele frequency is different than the value expected from the Hardy-Weinberg equation (allele frequency stays the same)

allopatric speciation

when the ancestral population becomes separated by a geographical (physical) ex: Grand Canyon and ground squirrels

sympatric speciation

a species evolves into two different species without a physical barrier ex: mating season doesn’t align

5 characteristics of a population in Hardy-Weinberg Equilibrium

1. No Natural Selection

2. No migration

3. No mutation

4. Random Mating

5. Large Population Size

punctuated equilibrium

a new species undergoes changes quickly from the parent species, then remains largely unchanged for a long time

Gradual Speciation Model (Gradualism)

species diverge gradually over time in small steps with intermediate organisms

why is the significance of reproductive isolation in speciation>

It is critical for the maintain diversity

Prezygotic Barriers

prevent mating/fertilization between species (no zygote is formed)

Postzygotic Barriers

occur after mating and fertilization but present hybrid offspring from being viable or fertile

Temporal Isolation (Sympatric Speciation)

species that breed during different times of day, different seasons, or different years cannot mix gametes

Behavioral Isolation

unique behavior patterns and rituals isolate species and they can no longer identify members of the species or attract males of the same species

Mechanical Isolation

morphological (physical) differences can prevent successful mating (spiral penis can’t fit into a vagina)

5 Pieces of Evidence for Evolution

1. Fossil Record

2. Comparative Anatomy

3. Comparative Embryology

4. Comparative Biochemistry

5. Biogeography/Geographic Distribution

Homologous Structure (Comparative Anatomy)

a trait that was passed on from the common ancestor to all of the organisms from that point on

Analogous Structure

when structures arise independently - usually due to the different species living in similar environments

Vestigial Structure

modern organisms that have organs that serve little or no function ex: eye sockets on a fish with no eyes

comparative biochemsity rule

more similarities in DNA = the more closely related the organisms are

biogeography/Geographic distribution

the distribution of species on Earth provides evidence that informs our understanding of both the evolution of life and the monument of continents across the globe via plate tectonics

macroevolution

large-scale changes ex:the origin of extinction of a species

speciation

the process of Evolution that creates 2 different species

hybrid

the offspring resulting from the cross between parents of different species

microevolution

small-scale changes ex:mutation, gene flow, non-random mating, etc.

covergent evolution

when organisms that are not closely related evolve independently to have similar kinds of traits

divergent evolution

when related species graduallybecome different

coevolution

the evolution of one species in response to new adaptations that appear in another species (as one species changes, it causes another to change) ex: pollinators and plants, predator and prey, parasits and hosts