bio exam 1

evolution

heritable change in characteristics of a population or species between generations

microevolution

changes in single gene in a population over time

macroevolution

formation of new groups of species

species

group of related organisms that share a distinct form, sexually reproducing species interbreed

population

members of the same species likely to encounter each other and will interbreed

empirical thought

relies on an observation to form an idea/hypothesis, a big shift towards empirical thought happened in the 1600s

john ray

the first to carry out a thorough study of the natural world, developed an early classification system used in modern species concept, mid to late 1600s, neither of his ideas proposed evolution

1700s scientists found lifeforms arent

fixed

george buffon

“life forms change over time”

jean baptiste lamark

found that some animals remain the same while others change, believed living things evolved towards human perfection

uniformitarianism hypothesis

slow geological processes lead to substantial change, earth is older than 6k years (against ideas at time)

thomas malthus

economist, said only a fraction of any population survives and reproduces

charles darwin

noticed distinctive traits of island species that allowed them to better exploit their environment

charles darwin accomplishments

formulated theory of evolution mid 1840s, spent years studying barnacles, worked with alfred wallace to publish joint similar papers, published them titled on the origin of species, and was the crews naturalist on the HMS beagle voyage

Descent with modification

evolution based on variation within a given species with heritable traits, genetic basis was not yet known

natural selection

more offspring produced than can survive, competition for limited resources, better traits flourish and reproduce

grants

observed natural selection in finches, focused much work on island daphne major, a moderately isolated undistrurbed habitat and its resident finches

evidence of evolutionary change

fossil record, biogeography, convergent evolution, selective breeding, homologies including anatomical, developmental, and molecular

Fishapod

illuminates steps leading to evolution of tetropods

transitional form

provides link between late and early forms

fossil record spans how long

50 million years

terrestrial tetropod evolved to aquatic animals lacking hind limbs

order: whales→ dolphins→porpoises

biogeography

study of the geological distribution of extinct and modern species

isolated islands and continents have

distinct plant and animal communities

endemic

naturally found only in a particular location

evolution of major animal groups corrolate with

known changes in distribution of landmasses on earth

first mammals arose

225 million years ago when australia was still connected

why does australia have no large terrestrial placental mammals

has marsupials, most of which are exclusive to australia because pangea led australia to be isolated and placental mammals never outcompeted the marsupials

plate tectonics theory

the crust divided into giant, irregularly shaped plates that float on top of the mantle (includes both ocean and land)

continental drift

movements in the mantle that cause the plates to move

boundaries of some plates are hotspots for

geological activity (earthquakeks etc)

earthwuakes signal

plates are scraping past or colliding with each other

continental drift majorly impact evolution by

reshaping the physical features of the planet and altering the environment organisms live in

when was pangea formed

250 million years ago, reduced shoreline, deepened ocean basins, lowered sea levels

convergent evolution

two different species from different lineages show similar characteristics due to similar environments and arent related evolutionarily

selective breeding

programs and procedures designed to modify traits in domesticated species (artificial selection)

homology

descent from a common ancestor, can be anatomical, developmental, molecular

anatomical homology

ex: multiple species sharing phalanges, derived from a common ancestor

vestigal structures

anatomical with no apparent function but resembles ancestors (tailbone)

developmental homology

similarities in embryotic stages, presence of gill ridges in humans suggests evolution from fishy ancestor, human embryos have long bony tails

molecular homology

similarities in cells on a molecular level shows common ancestor, all living species use dna, certain biochemical pathways found in nearly all species

sequences of closely related species tend to be more ___ than distantly related species

similar

homologous genes

two genes derived from the same ancestral gene

orthologs

genes in different species that evolved from a common ancestral gene by speciation, typically retaining the same function, reveals molecular details of evolutionary change

two sequences can be ____ but not ___ because of accumulation of random mutations

similar, identical

gene duplicates

produce gene families

gene families are

two or more paralogs within the genome of a single organism (ex, globin genes, allow for specialized function, expression at different times or in different tissues).

ortholog genes are related by

vertical descent from a common ancestor, encode proteins with the same function in different species

paralogs

homologous genes that have evolved by duplication and code for a protein with similar but not identical functions

horizontal gene transfer

exchange of gene material among different species (common)

where does horizontal gene transfer take place

prokaryotic to eukaryotic, vice versa, between prokaryotes, between eukaryotes, and is widespread among bacteria

evolution also occurs at the ____ level

genomic

evolution at the genomic level

involves changes in chromosome structure and number (humans have one large chromosome while apes have it divided into separate chromosomes)

chromosome 3 between humans and orangutans are very similar but orangutans have a large _____ of the chromosome which may have established orangutans as a new species

inversion

population genetics

studies genes in populations and genotypes, aims to understand extent of genetic variation, why how, and what changes happen
also helps understand how genetic variation is related to phenotypic variation

population

group of individuals of the same species that share environment and can interbreed

discrete populations

population that occupies wide geographical range is divided into smaller populations

changes in population size and location =

changes in genetic composition

genes are usually _________

polyphormic

polyphormic genes are

two or more variations for a given character, due to two or more alleles that influence phenotype

polyphormic gene definition short

2 or more alleles

monophormic gene

predominantly single allele

single nucleotide polymorphisms (SNPs)

smallest type of genetic change in a gene, most common type of change, responsible for 99% of variation in human gene sequence

large healthy populations exhibit high level of genetic _____

diversity

what are analysis of SNPs important for

personalized medicine

allele frequency equation

number of copies of a specific allele in a poopulation / total number of all alleles for that gene in the population

genotype frequency equation

number of individuals with a particular genotype in the population / total number of individuals in population

hardy weinburg equation

p²+2pq+q²=1

p²

genotype frequency of C^dominantC^dominant homozygotes

q²

genotype frequency of C^recessiveC^recessive homozygotes

2pq

2 times the genotype frequency of C^rC^d heterozygotes

hardy weinburg equillibrium

predicts that allele and genotype frequencies will remain the same provided a population is not evolving through generations

what standards must a population be in to fit the hardy weinburg equllibrium?

population must not be affected by evolitionary mechanisms that change allele and genotype frequencies including:

no mutations must occur

no natural selection

population is too large for alleles to change due to random sampling error

no migration occurs between different population

random mating

does hardy weinburg equllibrium ever happen

no, but its still useful for approximating some genes

microevolution

changes in a populations gene pool generation to generation

why does microevolution occur

a new genetric variation is introduced: mutations, duplications, horizontal transfer

is microevolution a major factor in allele frequencies

no (microevol)

what evolutionary mechanisms alter the prevalence of an allele of genotype

natural selection, non random mating (increases potential for widespread genetic change)

natural selection

process in which beneficial traits that are heritable become more common in successive generations, over time resulting in adaptations that promote survival and reproduction in a particular environment

fitness

relative likliness the genotype will contribute to the next generation

reproductive success

likelihood of an individual contributing fertile offspring to the next generation, attributed to two categories of traits

2 categories of traits for reproductive success

1) traits directly associated with reproduction, 2) characteristics that make organisms more likely to survive to reproductive age

modern description of natural selection

within a population, allelic variation arises from random mutations that cause different dna sequences, some alleles encode proteins that enhance survival or reproductive capability compared to other members of the population (these individuals are more likely to survive and reproduce for their alleles to be added to next gen gene pool)

over many generations, allele frequencies may significantly alter _____ of a population

characteristics

mean fitness of a population

average reproductive success of a population

as individuals with higher fitness values become more prevalent,

natural selection increases the mean fitness of the population

sexual selection

directed at traits of sexually reproducing species that make it more likely for individuals to find or choose a mate or engage in successful mating, in many species affects male population more than female

sexual dimorphism

significant different between the morphologies of the two sexes within a species

directional selection

individuals at one extreme of a phenotypic range have greater reproductive success in a particular environment

initiators of directional selection

new alleles of higher fitness are introduced with prolonged environment change

stabilizing selection

favors the survival of indiciduals with intermediate phenotypes, extreme values of a trait are selected against: ex, too big or too small of a litter decreases survivability and productivity, so an intermediate is selected for

diversifying selection

favors the survival of two or more different genotypes that produce different phenotypes, likely to occur in populations that occupy heterogenous environments. members of the populations can freely interbreed

balancing selection

maintaints genetic diversity

balanced polymorphism:

two or more alleles are kept in balance, and therefore are maintained ina population over the course of many generations.

intrasexual selection

males directly compete for mating opportunities or territories, between members of same sex, horns and such in males as a result

intersexual selection

members of one sex, usually females, choose their mates from individuals of the other sex based on desirable characteristics, often results in showy characteristics for males

cryptic female choice

genetic tract/egg selects against genetically related sperm to inhibit inbreeding

what does sexual selection explain

traits that decrease survival but increase reproductive success ex colored fish

results of sexual selection

in places where preadators are few, there are more colorful males and opposite for high amounts of predators, relative abundance of brightly and dully colored males depends on the balance between sexual selection

cichlidae have over ____ species

3000