AP biology- evolution

Aristotle

• viewed species as fixed and arranged them on a scala naturae

adaptive evolution

• is a continuous process

• Genetic drift and gene flow do not consistently lead to adaptive evolution as they can increase or decrease the match between an organism and its environment

Carolus Linnaeus

• interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose

Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms

Fossils

• helped to lay the groundwork for Darwin’s ideas

• Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata

catastrophism

Georges Cuvier advocated this, speculating that each boundary between strata represents a catastrophe

Charles Lyell

percieve that changes in Earth’s surface can result from slow continuous actions still operating today;

• principle of uniformitarianism states that the mechanisms of change are constant over time

• This view strongly influenced Darwin’s thinking

Lamarck

hypotehsized that species evolve through use and disuse of body parts and The inheritance of aquired characteristics

Charles Darwin

perceived adaptation to the environment and the origin of new species as closely related processes; wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar

• Descent with modification explains life’s unity and diversity

•  Natural selection is a cause of adaptive evolution

Adaptations

Inherited traits that have become popular due to selective advantage

Artificial selection

Darwin noted that humans have modified other species by sleelcting and breeding individuals with desired traits

if some heritable traits are advantageous, these will accumulate in the population, and this will increase the frequency of individuals with adaptations

What process explains the match between organisms and their environment?

evolve; populations evolve over time; natural selection can only increase or decrease heritable traits in a population

Individuals do not____

Natural Seleciton

Increases the adaptation of organisms to their environment over time; If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species

Population

is a localized group of individuals capable of interbreeding and producing fertile offspring

gene pool

consists of all the alleles for all loci in a population

locus

• is fixed if all individuals in a population are homozygous for the same allele

p

percentages of dominant alleles

q

percent of recessive alleles; p + q=1; to find p, it would be 1-q

Hardy-weinberg

• principle describes a population that is not evolving

• If a population does not meet the criteria of the Hardy-Weinberg principle, it can be concluded that the population is evolving

• states that frequencies of alleles and genotypes in a population remain constant from generation to generation

• In a given population where gametes contribute to the next generation randomly, allele frequencies will not change

• Mendelian inheritance preserves genetic variation in a population
  

Hardy-Weinberg equilibrium

• describes the constant frequency of alleles in such a gene pool

• If p and q represent the relative frequencies of the only two possible alleles in a population at a particular locus, then

  • p² + 2pq + q² = 1

where p²and q² represent the frequencies of the homozygous genotypes and 2pq represents the frequency of the heterozygous genotype

No mutaitons

Random Mating

No natural selection

Extremely large populations size

No gene flow

The Hardy-weinberg is based off of these five things:

mutation and sexual production

produces the variation in gene pools that contributes to differences among individuals

• individual phenotype

• Not all phenotypic variation is heritable

• Natural selection can only act on variation with a genetic component

variation in individual genotype leads to variation in________?

Discrete characters

• can be classified on an either-or basis

Quantitative characters

vary along a continuum within a population

cline

Some examples of geographic variation occur as this, which is a graded change in a trait along a geographic axis

relative fitness; Differential success in reproduction

results in certain alleles being passed to the next generation in greater proportions

Genetic Drift

• describes how allele frequencies fluctuate unpredictably from one generation to the next

• Genetic drift tends to reduce genetic variation through losses of alleles

founder effect

• occurs when a few individuals become isolated from a larger population

• Allele frequencies in the small founder population can be different from those in the larger parent population

bottleneck effect

• is a sudden reduction in population size due to a change in the environment 

• The resulting gene pool may no longer be reflective of the original population’s gene pool

• If the population remains small, it may be further affected by genetic drift

Gene flow

consists of the movement of alleles among populations; alleles can be transferred through the movement of fertile individuals or gametes

Gene flow tends to reduce differences between populations over time

Direcitonal selection

favors individuals at one oend of the phenotypic range

disruptive selection

favors individuals at both extremes of the phenotypic range

stabilizing selection

favors intermediate variants and acts against extreme phenotypes

Sexual selection

is natural selection for mating success

sexual dimorphism

marked differences between the sexes in secondary sexual characteristics

intrasexual selection

is competition among individuals of one sex (often males) for mates of the opposite sex

intersexual selection

• often called mate choice, occurs when individuals of one sex (usually females) are choosy in selecting their mates 

• Male showiness due to mate choice can increase a male’s chances of attracting a female, while decreasing his chances of survival

good genes hypothesis

• suggests that if a trait is related to male health, both the male trait and female preference for that trait should be selected for

Heterozygote advantage

occurs when heterozygotes have a higher fitness than do both homozygotes

frequency dependent selection

• the fitness of a phenotype declines if it becomes too common in the population

• Selection can favor whichever phenotype is less common in a population

Neutral variation

is no genetic variation that appears to confer no selective advantage or disadvantage

• For example, 

  • Variation in noncoding regions of DNA

  • Variation in proteins that have little effect on protein function or reproductive fitness

endosymbiosis

• proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells

An endosymbiont is a cell that lives within a host cell

Phylogeny

the evolutionary history of a species or group of related species

systematics

• classifies organisms and determines their evolutionary relationships

• Systematists use fossil, molecular, and genetic data to infer evolutionary relationships

Taxonomy

• is the ordered division and naming of organisms

phylogenic tree

represents a hypothesis about evolutionary relationships

• Each branch point represents the divergence of two species

Sister taxa are groups that share an immediate common ancestor

With this though, systematists need to distinguish whether a similarity is the result of homology or analogy

Convergent evolution

• Occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages

Cladistics

group organisms by common descent

• A clade is a group of species that includes an ancestral species and all its descendants

• Clades can be nested in larger clades, but not all groupings of organisms qualify as clades

Homology

is similarity due to shared ancestry

Analogy

is similarity due to convergent evolution

convergent evolution

(the process where unrelated organisms independently evolve similar traits[analogous] due to adapting to similar environmental pressures or ecological niches)

shared ancestral character

a character that originated in an ancestor of the taxon

shared derived character

• is an evolutionary novelty unique to a particular clade

• A character can be both ancestral and derived, depending on the context

by going from left to right; there should be a dash on the far left that has no animal, but the dash leads to other animals; the break off/ branch shows a different feature gained from an organism

you read a phylogenic tree?

outgroup

• is a species or group of species that is closely related to the ingroup, the various species being studied; the outgroups have little/no inherited traits

• Systematists compare each ingroup species with the outgroup to differentiate between shared derived and shared ancestral characteristics

to reproduce and have fertile offspring

what classifies a species?

vestigial structures

structures that are useless in today’s age; not needed anymore for sruvival

speciation

deals with Allopartic speciations (physical barrier that separated population 1 and 2, which can deter their species and become different) and sympatric (the populations are in the same geographic are, but stop reproducing, which their species can fade or be different)

extinction

causes the permanent loss of a genotype; can happen due to factors of loss of habitat, invasive species, etc.

primordial soup

the fact taht gases back in the day were not inhabitable until said lightning strike made gases more simple and easier for organisms to be inhabited