exam2 ecoevo

phylogeny

the evolutionary history of a lineage (populations, genes, or species)

phylogenetic tree

a visual representation of a phylogeny

nodes

represent common ancestors for all descendent lineages

clades

a common ancestor and all its descendants, share derived character states

synapomorphy

derived character state shared by an ancestor and its descendants

outgroup

used to infer approximate ancestral character states

homology

similarity in characteristics due to shared ancestry

homoplasy

character state similarity not due to common descent

convergent evolution

when two species evolve under similar environmental pressures even though they come from different evolutionary paths

evolutionary reversal

reversion back to an ancestral character state

ancestral trait

character state that was present in the common ancestor

derived trait

character state that arose later

monophyletic

includes a single common ancestor and all of its descendants; a clade

paraphyletic

includes a single common ancestor and only some of its descendants

polyphyletic

includes unrelated organisms that do not share an immediate common ancestor, usually grouped together due to convergent evolution or similar features

cladogram

only shows relative ancestry

phylogram

shows branches proportionally to the amount of evolutionary/genetic change

ultrametric

shows branches proportional to geological time

homologous characteristics

have different structure and function but are all derived from the same part of a common ancestor

homoplasious characteristics

have similar structure and function but are not derived from a shared common ancestor

parallelism

when common environmental factors exert similar selective forces on morphological variation in populations in different geographic localities

radiometric dating

relies on half-life decay of radioactive elements to allow scientists to date rocks and materials directly

stratigraphy

provides a sequence of events from which relative dates can be extrapolated

molecular clocks

allow scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates

relationship among extant great apes

chimpanzees and bonobos share 99%, gorillas 98%, and orangutans 97% of their genomes with humans

homo adaptations

crushing/griding foods with robust head, generalist body form, lost tree climbing, legs and feet evolved to walking and running

australopithecus time period

4.25-1.75 mya

homo time period

2.5 mya-present

homo erectus

first to migrate out of africa 1.8 mya, all modern humans are descendants

homo heidelbergensis

second wave to migrate out of africa 600,000 ya, probable common ancestor of all five later homo species

homo sapiens

last human migration out of africa 180,000 ya, sophisticated hunters skilled in making tools

homo floresiensis

satan himself god save me

denisovans

shared a common ancestor with neanderthals, both these and neanderthals interbred with the lineages of living humans

homo naledi

south africa, 1m tall, 200-300,000 ya, anatomy is a mosaic of ancestral and derived from australopithecus and neanderthals, small brain, curved fingers for climbing

mitosis

process of cell division that results in two identical daughter cells, each with the same genetic material as the parent cell

meiosis

type of cell division that reduces the chromosome number by half, produces four genetically unique haploid gametes (sperm and egg cells) for sexual reproduction

genotype

the genetic makeup of an individual

phenotype

an observable, measurable characteristic as the manifestation of the genotype of an organism

gene

a segment of dna that code for particular proteins which in turn affect particular traits

gene pool

consists of alleles from all of the genes of every individual in a population, have high variation in populations that reproduce sexually

quantitative characters

those that vary along a continuum within a population, usually due to polygenic inheritance in which the additive effects of two or more genes influence a single phenotype character, have normal distribution

discrete characters

usually determined by a single locus with different alleles with distinct impacts on the phenotype, low environmental influence

polyphenic trait

single genotype produces multiple phenotypes depending on environment

DNA

double helix polymer, encode protein molecules, universal molecule for heredity

mutation

a change in dna sequence, most occur during dna replication, is random

somatic mutation

mutation that affects the cells in the body of organisms, affect the daughter cells produced by affected cells and affect the phenotype of the individual, are not passed down to offspring

germline mutation

mutation that occurs in reproductive cells like eggs and sperm, gets passed down to offspring

mutation rates too low

cannot adapt to the changes in environment

mutation rates too high

all the good adaptation from the past will be destroyed

mutation rates in asexual organisms

tends to evolve faster, increases genetic variation and likelihood of beneficial traits, but also increases likelihood of harmful traits

recombination

the exchange of genetic material between paired chromosomes during meiosis, generates variation, occurs in sexual organisms

independent assortment

ensures novel combinations of alleles, occurs in sexual organisms

ploidy

the number of copies of unique chromosomes in a cell

haploid: one complete set

diploid: two complete sets

gene flow

any movement of genetic material from one population to another and is an important source of genetic variation

depurination

when a purine base is lost from a nucleotide through hydrolysis even though the sugar phosphate backbone in unaltered, can cause mutations during the next round of replication

environmental mutation

dna interacts with the environment and sometimes that interaction can be detrimental to genetic information
UV light from the sun causing skin cancer

chemical mutation

oxidizing agents (free radicals) can chemically modify nucleotides in ways that alter their base-pairing capacities
carcinogens from smoking causing lung cancer

point mutation

a single base changes from one nucleotide to another

insertion

a segment of dna is inserted into the middle of an existing sequence

deletion

a segment of dna may be deleted accidentally

inversion

a segment of dna is flipped around and inserted back

duplication

a segment of dna is copied a second time

frameshift

a deletion of insertion in a dna sequence that shifts the way the sequence is read

chromosome fusion

two chromosomes are joined together as one

genome duplication

entire genome is duplicated, leading to increased ploidy

genetic polymorphism

the presence of two or more variant forms of a specific dna sequence, contributes to phenotypic variation

phenotypic plasticity

changes in phenotype produced by a single genotype in different environments

populaion

a group of interacting and potentially interbreeding individuals of the same species

genetic locus

location of a specific gene or sequence of dna on a chromosome

hardy-weinberg equailibrium

states that the genetic variation in a population will remain constant from on generation to the next in the absence of disturbing factors
p²+2pq+q²=1

p+q=1

hardy-weinberg assumptions

population is infinitely large, genotypes do not confer differences in fitness, there is no mutation, mating is random, there is no migration

genetic drift

mechanism of evolution that results from random sampling error and results in the alteration of allele frequencies over time, stronger impact on smaller populations, reduces genetic variation, creates genetic distance between populations

bottleneck

results in a nonrepresentative set of alleles for subsequent populations, even after the population size rebounds, reduces genetic variation, rare alleles are more likely to be lost

founder effect

a type of bottleneck resulting from a small number of individuals colonizing a new, isolated habitat. leads to speciation

fitness

the survival and reproductive success of an individual with a particular phenotype, includes survival to reproductive age, mating success, and the capacity to produce viable offspring

relative fitness (w)

contribution of individuals with one genotype compared with the average contribution of all individuals in the population

pleiotropy

mutation in a single gene affects more than one phenotypic trait

antagonistic pleiotropy

beneficial effects for one trait but detrimental effects for other traits

negative selection

alleles that lower fitness

positive selection

alleles that increase fitness

negative freuqncy-dependent selection

common phenotypes are selected against, and rare phenotypes are favored

heterozygote advantage

heterozygosity confers greater fitness than homozygotes

inbreeding coefficient (F)

the probability that two alleles at any locus of an individual are identical by descent, results in reduced fitness

no subdivision

no barriers between populations

intermediate subdivision

some barriers between populations

extreme subdivision

populations are completely cut off from each other

morphological species concept (MSC)

members of a morphological species are similar to each other and morphologically distinct from other groups, useful for fossils, limited by convergent evolution and cryptic species

cryptic species

organisms that look almost identical morphologically but belong to separate, genetically distinct evolutionary lineages

biological species concept (BSC)

species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups, limited by asexual reproduction

phylogenetic species concept (PSC)

a species is a monophyletic group that is diagnosably different from other such groups, limited by where to draw the line and the potential for species to come back together

general lineage concept (GLC)

species are metapopulations that have enough gene flow to maintain the same evolutionary lineage

metapopulations

group of spatially separated populations of the same species that interact at some level

geographic isolating barriers (allopatry)

extrinsic properties of landscape that prevent gene flow, natural or manmade

reproductive isolating barriers

features of organisms that prevent interbreeding, premating or prezygotic and postmating or postzygotic

premating barrier

timing of reproduction, specific courtship rituals, pollinator isolation

copulatory behaviroal isolation

postmating, prezygotic barrier. mating between species results in damage to female reproductive tract, different species male’s copulatory courtship results in eggs not fertilized by deposited sperm

gametic incompatibility

postmating, prezygotic. sperm or pollen from one species fails to penetrate and fertilize the egg of another species

postzygotic barriers

hybrids are produced but have low fitness including: hybrid inviability, hybrid sterility, ecological inviability, and behavioral sterility

allopatric speciation

geographic separation, reproductive isolation, then genetic divergence. islands provide opportunity for it

reinforcement

natural selection favors prezygotic isolation mechanisms that prevent the formation of hybrids with reduced fitness, increases prezygotic reproductive isolation