Unit 7 - Natural Selection

Evolution of a species, via natural selection, involves a change in the species genetic makeup over time.

Charles Darwin

Charles Darwin

english naturalist, researched the Glapagos Islands and how birds like finches diversified and gave rise to new species

theory of natural selection through evolution

Evolution

change in genetic makeup of a population over time; descent with modification

Natural Selection

individuals that have certain traits tend to survive and reproduce at higher rates than other individuals because of those traits

Fitness

ability to survive and reproduce measured by reproductive success

“Traits are Heritable”

characteristics can be passed from parents to offspring

Adaptations

inherited characteristics of organisms that enhance their survival and reproduction

“More offspring are produced than can survive”

leads to competition for limited resources which results in differential survival (favorable traits lead to survival and will accumulate in the population)

Artificial Selection

selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits

Population

a group of individual of the same species that live in the same area and interbreed to produce fertile offspring

Gene Pool

a population’s genetic makeup and consists of all copies of every type of allele

Microevolution

small scale genetic changes in a population; change in allele frequencies within a single species or population

Mutations

a change in the DNA sequence of an organism, virus, or extrachromosomal DNA and can result in genetic variation

Genetic Drift

chance events that cause a change in allele frequency from one generation to the next and can lead to a loss of genetic variation

Butterfly Effect

when a large population is drastically reduced by a non-selective disaster

Founder Effect

when fewer individuals become isolated from a large population and establish a new small population with a gene poll that differs from the large population and loses genetic diversity

Gene Flow

transfer of alleles into or out of a population due to fertile individuals or gametes

Relative Fitness

number of surviving offspring that an individual produces compared to the number left by others in the population and measures reproductive success

Directional Selection

Natural Selection towards 1 extreme phenotype

Stabilizing Selection

Natural Selection towards the mean and against the extreme phenotypes

Distriptive Selection

Natural Selection against the mean; both phenotypes extremes have the highest relative fitness

Sexual Selection

type of natural selection that explains why many species have unique/showy traits

Hardy Weinburg Equilibrium

a model used to assess whether natural selection or other factors are causing evolution at a particular locus

p + q = 1

frequency of the dominant allele in a gene population plus frequency of the recessive allele in a population

p² + 2pq + q² = 1

percentage of the homozygous dominant individuals + twice the percentage of the heterozygous individuals + percentage of the homozygous recessive individuals

Fossil Records

remains or traces of past organisms gives a visual of evolutionary change over time and geographical data from where the organism is found

Comparative Morphology

analysis of the structures of living and extinct organisms

Homology

characteristics in related species that have similarities

Embryonic Homology

many species have similar embryonic development

Vestigial Structures

structures that are condensed even through they no longer have a use

ex. human tailbone and appendix

Molecular Homology

many species share similar DNA and amino acid sequences

Homologous Structures

characteristics that are similar in two species because they share a common ancestor

ex. arm bones of many species

Analogous Structures

Structures that are similar but have separate evolutionary origins

ex. wings in birds vs. bats

Biogeography

distribution of animals and plants geographically

ex. species on oceanic islands resemble mainland species but species on the same continent are similar and distinct from species on other continents

Phylogeny

hypothesis of evolutionary history

Systematics

classification of organisms and determining their evolutionary relationship

Taxonomy

naming and classifying species

Phylogenetic Trees

DIagrams that represent the evolutionary history of a group of organisms and show the amount of change over time measured by fossils

Cladograms

show the branching linkage of common ancestors of all species represented by a node

sister taxa are two classes from the same node

basal taxon is a lineage evolved from the root and is unbranched

Synapomorphy

a derived character shared by Claude members

Derived Characteristics

similarily inherited from the most recent common ancestor of an entire group

Ancestral Characteristics

similarily that rose prior to the common ancestor

Monophyletic Group

includes the most recent common ancestor of the group and all of its decendants

Paraphyletic Group

includes that most recent common ancestors of the group, but not all its descendants

Polyphyletic Group

does not include the most recent common ancestor of all members of the group

Speciation

a formation of a new species (a group able to interbreed and produce viable, fertile offspring) results in diversity of life forms

Allopatric Speciation

physical bamer divides population or a small population is sperated from main population and prevents gene flow often caused by natural disasters

Sympatric Speciation

new species evolves while still inhabiting the same geographic region as the ancestral species usually due to the exploitation of a new niche

Prezygotic Barriers

prevent mating or hinder fertilization; five types

Habitat Isolation

species live in different areas or they occupy different habitats within the same area

Temporal Isolation

species breed at different times of the day, year, or season

Behavior Isolation

unique behavioral patterns and rituals seperate species

Mechanical Isolation

reproductive anatomy of one species does not fit with the anatomy of another species

Gametic Isolation

preoteins on the surface of gametes do not allow for the egg and sperm to fuse

Postzygotic Barriers

prevent a hybrid zyogote from developing into a variable, fertile adult

Reduced Hybrid Viability

the genes of different parent species many interact in ways that impair the hybrid’s development or survival

Reduced Hybrid Fertility

a hybrid can develop into a healthy adult, but it is sterile usually results due to differences in number of chromosomes between parents

Hybrid Breakdown

the hybrid of the first generation may be fertile, but when they mate with a parent species or one another, their offspring will be sterile

Macroevolution

large evolutionary pattens

Stasis

no change over long periods of time

Punctuated Equilibrium

when evolution occurs rapidly after a long period of stasis

Gradualism

when evolution occurs slowly over hundreds, thousands, or millions of years

Divergent Evolution

groups with the same common ancestors evolve and accumulate differences resulting in the formation of a new species

Adaptive Radiation

If a new habitat ot niche becomes available, then a new species can diversify rapidly

Convergent Evolution

two different species develop similar traits despite having different ancestors; similar adaptations that have evolved in distantly related organisms due to similar environments

Extinction

termination of a species