Evolution Concepts 1-4

Evolution

Evolution

the process of biological change in populations over time that make descendants genetically different from their ancestors

microevolution

evolution over a small scale affecting a SINGLE population

macroevolution

evolution over a large scale, affecting multiple species across populations

natural selection

organisms with the “best” suited traits have a higher chance of survival and reproduce more, causing changes in a population over time

fitness

a meausure of how many of your offspring survive to reproduce

overproduction of offspring

principle of natural selection- lots of offspring and limited resources cause competition for those resources

variation

principle of natural selection- differences in physical traits of organism- can be caused by random mutations, crossing over, sexual reproduction, and migration (gene flow)

adaptation

principle of natural selection- beneficial traits (adaptations) become more common over time, since fitter organisms will reproduce more- (this changes the gene pool)

descent with modificaition

principle of natural selection- natural selection leads to new phenotypes better suited to their environment (change in gene frequency over time)- individuals don’t evolve, populations do!

directional selection

increases the expression of an extreme version of a trait in a population (ex: increased height over time)

disruptive selection

favors two extremes that splits the population in 2 groups- (ex: only white and black bugs can camouflage, so grey bugs die)

stabilizing selection

favors the mean of the population-eliminates extreme expressions of a trait when the average expression leads to higher fitness.

allele frequency

the number of times an allele appears in a population

gene pool

the combined alleles of all individuals in a population

P=?

dominant allele, p+q=1

Q=?

recessive allele, p+q=1

mutations: mechanisms of microevolution

any change in genetic sequence, changes allele frequency and increases genetic variation

natural selection: mechanisms of microevolution

organisms more fit for their environment will survive and reproduce more (beneficial traits become more common)

genetic drift: mechanisms of microevolution

random change in the frequency of alleles in a population over time- LOSS of genetic variation- changes are more apparent in small populations

gene flow: mechanisms of microevolution

movement of genes into/out of a population- occurs during migration and INCREASES genetic variation

sexual selection (non-random mating): mechanisms of microevolution

The selection of traits that aren’t necessarily good for survival fitness, but without them, you can’t pass on your genes at all because you can’t reproduce- (ex: male peacock feathers attract mates but also attract predators)

Genetic equilibrium (HWE)

when there are NO changes in the allele frequencies in a population over time.

conditions for HWE

1.Population is large.

2.Must be random mating.

3.No migration.

4.No mutations.

5.No natural selection.

if any of these conditions aren’t met- the population is evolving

HWE explanation

p^2 + 2pq + q^2 = 1, p^2 = genotypic frequency of homozygous dominant individuals (RR) 2pq = genotypic frequency of heterozygous individuals (Rr) q^2 = genotypic frequency of homozygous recessive individuals (rr)

strategies to find HWE

If you are trying to figure out if a population is in HWE and you aren’t sure: First use the actual numbers to calculate genotype and allele frequencies. Refer back to Practice #2 earlier in notes. Once you have p and q, use p^2 + 2pq + q^2 = 1 to find genotype frequencies if the population were in HWE. If these genotype frequencies don’t match up with the actual frequencies initially calculated, then the population is not in HWE and is evolving! If they do, the population is in HWE.

speciation

forming of a new species by evolution from a pre-existing species- some sort of isolation must occur and the 2 groups must become too different to reproduce

species

a group of organisms that can successfully interbreed and produce viable, fertile offspring.

extinction

elimination of a species

gradual extinction

occurs at a slow rate.

Mass extinction

occurs when a catastrophic event changes the environment suddenly.

gradualism

slow, constant changes over time

Punctuated Equilibrium

Bursts of change followed by periods of stability.

Divergent Evolution

A number of different species arise from one common ancestor- new environments caused differences to involve in populations

adaptive radiation

a type of divergent evolution happening over a short period of time

Convergent Evolution

unrelated species evolve similar characteristics because they live in similar environments (ex bat wings/birds)

Coevolution

Occurs when two populations of organisms form a specialized relationship and thus change in response to each other.

paleontology

study of prehistoric life using fossil records

morphology

the study of the form of living things

biogeography

study of the geographic distribution of plants and animals.

embryology

study of embryo development

biochemistry

study of chemical processes in living things

fossils

preserved remains of organisms (bones, footprints, feces)

transitional fossils

link ancestral species to their descendants (ex: archaeopteryx served as a transitional fossil between birds & dinosaurs)

homologous structures

similar structures that suggest evidence of common ancestry (Similar structure, but different function, due to being used in different environments.)- result of divergent evolution

vestigial structures

structures with little or no function to an organism (can be leftover from an ancestor) ex- ostrich wings, goosebumps, wisdom teeth, appendix- result of divergent evolution

Analogous structures

similar structures that evolved independently in different organisms due to serving similar purposes- Different structurally but same functionally, due to living in similar environments.- result of convergent evolution

Endemic species

species that exist only in one geographic region. (ex galapagos tortoises)

evidence in embryology

similar embryo in the early stages of vertebrae suggest a common ancestor

evidence in biochemistry

Analyzing DNA and proteins from different species allows us to compare similarities to predict common ancestry. Closely related species would have similar DNA sequences.

Pseudogenes

evidence for divergent evolution, nonfunctional genes (think of them as vestigal structures in your DNA)

Evidence from Direct Observation

Microevolution that has been directly observed due to occurring in populations with short life cycles that reproduce quickly. Examples: Peppered moths, Mosquitos resistant to pesticides like DDT, MRSA = a type of antibiotic-resistant bacteria

taxonomy

field of biology that classifies organisms

3 domains of life

eubacteria, archaebacteria, eukarya

eubacteria

prokaryotes- true bacteria, like pathogens

archaebacteria

prokaryotes in extreme environments

eukarya

eukaryotes

binomial nomenclature

2-name naming system, Genus species

phylogeny

evolutionary history of a species

Endosymbiotic theory

suggests that over time, coevolution of the two prokaryotes occurred and eventually led to speciation and the 1st eukaryotes.

what phylogeny does

phylogeny works to piece together evolutionary history of relatedness based on shared inherited characteristics.

Phylogenetic tree:

a diagram used to predict evolutionary relationships

Maximum parsimony:

use the simplest explanation for creating the tree.

taxa

groups in phylogenetic trees that represent evolutionary relationships