bio 1108 exam 1 (herrick)

what are two factors that contribute to phenotype?

genotype and environment

species

individuals that are able to exchange genetic material

gene pool

all alleles present in individuals of that species

populations

interbreeding groups of organisms of the same species living in the same geographical area

what are two main sources that lead to genetic variation?

mutation and recombination

what can somatic mutations lead to?

cancer, disease and even death to an INDIVIDUAL

what can germ line mutations lead to?

mutations that are passed down to offspring

recombination; name two ways it can occur

new alleles may be generated through crossing over and independent assortment

allele frequency

rate of occurrences of alleles in a population

gene locus

the location of a certain gene/allele

allele

a form of a gene; one copy of a gene

example: A, a

how is genetic variation measured?

through the allele frequency equation

what is the allele frequency equation?

AF=(# of copies of an allele)/(total # of alleles in population)

evolution

change in allele frequency or genotype frequency over time

how is evolution measured?

examinable physical traits, gel electrophoresis, DNA sequences;

most importantly: the hardy-weinberg equilibrium

what does the hardy-weinberg equilibrium model describe?

the situation in which evolution does NOT occur

a population in the HW equilibrium meets what requirements?

1. closed population (no migration or gene flow)

2. no mutations

3. large population (no genetic drift)

4. random mating (no sexual selection)

5. no natural selection

what is the HW equation?

p^2 + 2pq + q^2

natural selection occurs when...

...individuals with certain traits reproduce more offspring than do individuals without those traits

stabilizing selection

against the extremes

directional selection

against one extreme

disruptive selection

against the mean

STRONG and QUICK

artificial selection

selection by breeder rather than competition

positive selection

selection that increases the frequency of a FAVORABLE allele

negative selection

selection that decreases the frequency of a deleterious allele

balancing selection

refers to when two allele are maintained in the population

ex: malaria and the heterozygote advantage (heterozygote's fitness is higher than either homozygotes resulting in selection that ensures both alleles to remain in the population)

sexual selection

promotes traits that increase an individuals access to reproductive opportunities

migration

movement of individuals from one population to another

gene flow

movement of alleles from one population to another; increases genetic variation

genetic drift has a large effect on what type of populations?

small

genetic drift: bottleneck

a sharp reduction in the size of the population due to environmental events (earthquakes, floods, etc)

founder event

a few individuals leave the population and start a new population

molecular evolution

change in DNA or amino acid sequences over time

molecular clock

the correlation between the time two species have been evolutionarily separated and the amount of genetic divergence between them

phylogenetic tree

a reasoned hypothesis of the evolutionary relationship among organisms

node

point of common ancestry; can be rotated

speciation

the process which physically, psychologically or ecologically isolated populations diverge from one another to the point where they can no longer produce fertile offspring

classification hierarchy

domain, kingdom, phylum, class order, family, genus, species

phylogenetics

the study of evolutionary relationships among organisms which aim to discover the pattern of evolutionary relatedness among groups of species

sister groups

groups that are closely relative to each than either of them is to any group

1. share a common ancestor

2. are each others closest relatives

monophyletic

all members share a single common ancestor not shared with any other group of species

paraphyletic

includes a common ancestor and some, but not al of its descendants

polyphyletic

does not include the common ancestor

character

anatomical, physiological or molecular features that make up an organism

character states

several observable conditions (absent or present)

-character states can be similar due to either homology or analogy

homology

similarity resulted from shared common ancestry of the two groups, retained over time

analogy

similarity resulted from convergent evolution, independently evolved in the two groups as an adaptation to similar environments

synapomorphies

shared derived characters shared by some but not all

-helps define groups and sister groups

cladistics

phylogenetic reconstruction on the basis of synapomorphies

almost synonymous to phylogeny except phylogenies give you a sense of time from when organisms branched of (or when speciation occured)

parsimony

choosing the simpler of the two or more hypothesis to account for a given set of observations

-assumes that evolutionary change is rare

what are four ways fossils are beneficial for phylogenies

1. provide a selective record of past life

2. geological data indicates age and environment of fossils

3. contains unique combinations of characters

4. indicative of past rare mass extinctions that altered evolution

trace fossil

tracks and trails as animals move about

molecular fossils

preserved biomolecules

two examples of unusual conditions that preserved fossils

1. Burgess Shale

2. Messel Shale

isotopes

variants of an element that differ in the number or neutrons

radiometric dating

determining the age of an organisms through radioactive decay of carbon-14

the history of life must be reconstructed from evolution's two great patterns. what are they?

1. the similarity in observable traits and molecular sequences of living organisms

2. direct historical archive of the fossil record

why is it difficult to define the word "species"?

as an evolutionary unit, species must be, by definition, fluid and capable of changing, giving rise to new species through evolution- it is difficult to define because IT IS DYNAMIC

the biological species concept (BSC)

Ernst Mayr (1904-2005)

"species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups"

-most widely used and accepted definition

morphospecies concept

holds that members of the same species must also look alike (size, shape, coloration); extended to DNA

limitations of BSC and morphospecies concept

1. difficult to apply in the real world

2. cannot be applied to asexual or extinct organisms

3. does not account for genetic exchange in ring species

4. does not account for hybridization of plants

ring species

populations that are reproductively but not genetically isolated

ecological niche

complete description of the role the species play in its environment; habitat requirements

-it is impossible for two species to coexist in the same location if niches are too similar; competition can drive one to extinction

ecological species concept

idea that there is a one to one correspondence between a species and its niche

phylogenetic species concept

idea that members of the same species share a common ancestor (and common fate)

reproductive isolation

the inability of species to breed successfully with related species due to geographical, behavioral, physiological or genetic barrier differences

pre-zygotic reproductive isolation

barriers before fertilization; prevent fertilization

-behavioral, gametic, mechanical, temporal, geographic/ecological

post-zygotic reproductive isolation

barriers after fertilization; failure to produce fertile offspring

-genetic incompatibility, sterile offspring (mule)

how does speciation occur?

it is a by product of the genetic divergence of separated populations; mutations will appear until the point of speciation

partially reproducitively isolated

populations that have genetically diverged but not enough for full reproductive isolation; not yet a separate species but offspring may be hybrid and have reduced fertility or viability

allopatric

(populations) that are geographically separated from each other

allopatric speciation

speciation due to geographical separation

subspecies

allopatric populations that have yet to evolve into even partial reproductive isolation but have accumulated a few population specific traits

how do populations become allopatric? (two reasons)

1. dispersal

2. vicariance

dispersal

some individuals colonize a distant place far from the the main source population

vicariance

geographical barriers arises within a single population separating it into two or more populations

peripatric speciation

when the new population (isolated island population) is outside the species normal range (mainland population)

adaptive radiation

unusual rapid evolutionary diversification which natural selection accelerates the rate of speciation and adaptation

what usually follows peripatric speciation?

adaptive radiation

what usually causes adaptive radiation usually stemming from peripatric speciation?***

a combination of emptiness (availability of ecological opportunity) and potential for allopatric speciation

co-speciation

when organisms speciate in response to each other

sympatric speciation

organisms who are not geographically separated undergo speciation

-usually the result of disruptive selection

-must be strong in order to counteract the homogenizing effect of gene flow!!!!******

can speciation occur with or without natural selection?

yes

(see instantaneous speciation)

instantaneous speciation

sympatric; can occur in a single generation caused by hybridization between two species in which offspring are reproductively isolated from both parents

-usually does not occur in humans

plant polyploidy

multiple chromosome sets in plants

-another type of instantaneous speciation

-similar to hybridization

does natural selection always lead to speciation?

no; in allopatry, drift can drive change which sus non adaptive

evidence that human lineage branched off the great apes

1. comparative anatomy (physical features)

2. molecular analysis (DNA)

3. fossil record

who is our closest living relative?

bonobos and chimpanzees; DNA differ ny only 1%

hominin

human/chimpanzee common ancestor

what feature did ardi (Ardipithecus ramidus) have that was revolutionary?

ardi was capable of moving upright

which was the first hominin that was discovered to be fully bipedal?

Lucy; Australopithecus afarensis

which hominin first left Africa?

homo ergaster

how do Homo neanderthalensis differ from Homo sapiens?

they had thicker bones and bigger skulls

what are the trends of human evolution?

bipedalism, increase in cranium size, disappearance of brow ridges and need for strong jaw muscles, upright stance

african origin: the multi regional hypothesis

-homo ergaster roots

-migrated out of Africa 2MYA

-separated migrations from dif populations

-modern humans evolved parallel out of the different populations

(not well supported)

african origin: the out-of-africa hypothesis

-more recent move out of Africa

-200,000 YA rather than 2MYA

-modern humans evolved from Homo ergaster (H. heidelbergensis) while still in Africa

-then split into different populations as they continued to migrate and separate

mitochondrial DNA (mtDNA)

small circle of DNA found in mitochondria; inherited from mother (no opportunity for genetic recombination)

what are the four distinct features of the human species?

1. bipedalism

2. neoteny

3. large brains

4. FOXP2 GENE

neoteny

retention of juvenile features in the adult animal

FOXP2 gene

encodes transcription factors that play a role in development, proper language and speech