Evolution Pt. 3

Species

pop at time and space where individuals can successfully reproduce with fertile viable offspring

cryptic species

2 species misidentified as 1 because of similar morphologies however they cannot interbreed

Biological Species Concept (Mayr)

group of actually or potentially interbreeding populations, which are reproductively isolated from other such groups

Problems with Biological species concept

asexually reproductive species, extinct species, ambiguous situations in nature

Phylogenetic species concept

Species are the smallest possible group descending from a common ancestor and recognizable by unique, derived traits

General Species Lineage

species are metapopulations that exchanges genes frequently enough to comprise the same gene pool

agreed upon aspects of a species

allele flow between populations, evolutionary force effects all populations, evolve as a lineage

benefits of biological species concept

focused on how species formed (barriers to gene flow)

Barriers to gene flow

Prezygotic barriers, postzygotic barriers

Prezygotic barriers

hinders mating or fertilization

Pre mating prezygotic barriers

ecological isolation (timing, habitat), behavioral isolation (mating rituals), mechanical isolation (anatomical)

Post mating prezygotic barriers

gametic isolation (sperm survivorship in females, molecules on egg coatings)

copopulatory behavioral isolation

unique mating rituals required for successful reproduction

Post-zygotic barriers (ie. hybrid has been formed)

intrinsic factors (hybrid fitness is low regardless of enviro) and extrinsic factors

intrinsic barriers

viability and fertility is low, and hybrid breakdown where 1rst generation is fertile and viable but the second generation is not

extrinsic factors

ecological invariability and behavioral sterility

behavioral sterility

hybrids produce normal gametes but cannot obtain mates

ecological inevitability

hybrids have lower viability because they cannot find an appropriate ecological niche (polar-brown bear hybrids)

reinforcement

increase in reproductive isolation between populations through selection against hybrids

Why will lions and tigers breed?

lack of reinforcement

models of speciation

allopatric speciation and sympatric speciation

allopatric speciation

geographical barrier initially blocks gene flow, isolating a population (mountain ranges, glacier movement, formation of land Bridges, emergence of unfavorable habitat)

kinds of allopatric speciation

vicariance and peripatric

natural selection, genetic drift, and sexual selection drive allopatric speciation through

cause evolution of prezygotic barriers and reproductive isolation

sympatric speciation

reproductive isolation without geographic isolation through disruptive selection

disruptive selection

when individuals mate no randomly with those more similar to themselves

hybrid zones

areas where hybrids exist

Allopolyploid

derivative of diploid of species between 2 species (instant speciation)

Parapatric Speciation

isolation by distance and ecological adaptation

horizontal gene transfer

complicates classification of microbes

stable ecotype model

species arise from adaption to a particular niche distinct from other niches of other species

sympatric

when species overlap in range

magic traits

traits that confer local divergent local adaptions and act as a reproductive barriers

Speciation examples

crickets in Hawaii (with high rates of speciation), Polar Bears from Brown Bears (allopatric speciation),

speciation through hybridation

when hybrids only mate between themselves and become a new species as a result

macroevolution

origination, evolution, and extinction over an extended period of time

biogeography

study of distribution of species over space and time

vicarence

vicariance: divergence of 2 large populations

peripatric

divergence of a small population from a large ancestral population

Biogeography of marsipuals

distributed in Australia > South America > North America (Asia to North America, North America back to Asia + to South America, Antartica to Australia, and then extinction, with recent dispersal to North America from South America)

Population size formula

N + B + I - D - E

Formula for Diversity where D(t+1) is diversity

D(t) + O - E (current diversity + origination - extinction)

turnover

disappearance of some species and replacement by others

standing diversity

number of taxonomical units present at a given time in a particular area (increases when origination rate is high and extinction rate is low)

symbols that represent extinction and origination rate

alpha-origination, omega-extinction

punctuated equilibra

periods of stasis punctuated by rapid change

gradualism

slow, gradual morphological changes over time

tempo of evolution

gradualism and punctuated equilibrium

adaptive radiation

recognized by phylogenies (lots of splits)

when origination is greater than extinction

lackk of competition and key innovation

biodiversity decreases when

extinction rate increases and origination rate decreases

Nautiloid decline

only 5 remaining species with 2400 fossils

mass extinction

statistically significant departure from background extinction rates resulting in a substantial loss of taxonomic diversity

Background extinction

normal rate of extinction for a taxon or biota

mass extinctions

5 + Anthroprocene

Types of species interactions

mutualism, parasitism/predation, commensalism, amensalism, competition

Coevolution

reciprocal evolutionary change between ecologically intimate species, driven by natural selection (requires: heritable variation in traits relevant to interactions + reciprocal selection)

did we coevolve with dogs

no, we domesticated dogs; dogs did not reciprocally select traits in us

which species interactions can lead to coevolvution

mutualism, parasitism, and predation/herbivory

Geographic mosaic theory of coevolution

variance in type of selection, strength of selection, and response to selection

coevolutionary antagonisms

(pred prey…) negative frequency dependence: common host becomes rare, rare parasites are selected, repeated

coevolutionary alternation

when multiple species interact (one species is antagonistic with multiple species)

coevolutionary arms race

antagonistic players get caught in escalation of ever-increasing ability (defense mechanisms in prey → evolutionary response to counter defense in predator)

antagonist pleiotrophy

more common in prey

TTX in newts

less TTX increase offspring amount but decreased survival, too much TTX decreases fitness, increases survival

snakes tradeoff

no TTX resistance: fast and unable to eat toxic newts, excess TTX resistance: slow but able to eat toxic newts

hot spots in terms of coevolutionary arms race

areas where species have matched abilities

cold spots with coevultionary arms race

areas where species have mismatched abilities (favorable for predators)

deaccelerating arms race

virulence in australian rabbits

mutualism

new alleles that enhance mutualistic interactions are favored by selection and spread (positive frequency dependence)

diverse network of mutualism

Mullerian mimicrisy (species look similar, signally harmful effects), Bayesian mimicry (cheating where one is not actually harmful)

key features of primates

5 digit hands and feet with flat nails, opposable thumbs/big toes, acute vision (depth perception), large complex brain, prolong pre and post natal development

defining features of apes

shoulder structure that allows full shoulder rotation and no tail

human features

extremely large brains relative to body size, bipedalism (walking on two legs upright), long thumbs that enable precision grip, long life span + development, complex tool making and use

major differences in hominins

burdens of bipedalism

neck pain, broken hip, rotary cuff injuries, shin splints, etc.

tradeoffs (cost benefit) for bipedalism

benefit: free up hands, more energy efficient, and greater vision costs: lower back problems and mechanical issues

tradeoffs between bipedalism and large brains

wide pelvis prefered for birth, narrow pelvis for efficient walking → carrying of fetus for as long as possible but deliver before head is too big (reason for high baby head size to narrow cervix size)

humans originate from

africa

Non Africans have

lower diversity (high linkage disequilibrium) with about 2% neanderthal ancestory (east Asians have 20% more than Europeans)

asian waves of migration

had at least 2 early waves (ancestors of Australians and other ancestors of East Asians)

when were people present in oceania

47,000-55,000 ya

americans (indigenous) arose

early, with current indigenous pops more related than other pops (complex)

Neandrethal dna (benefits and risks)

boost immune system, correlated with worse COVID-19 response

reasons for human susceptibility to disease

pathogens evolve faster, limits of natural selection (environmental, historical constraints, tradeoffs, etc.), disease can actually be adaptation

health issues from mismatch

diabetes, skeletal/posture, obesity, etc.

hypothesis on obesity

thrifty genotype, phenotype, or epigenotype (Genotype: genome makes most of calories, Phenotype: senses poor calorie environment in mother and adjusts own metabolism, epigenetic: mother senses and adjusts childs metabolism)

Cancer

most arise sequentially from division as cells cannot recombine

hypothesis for mutation rate existing for cancer

1. zero mutation rate is bad for adaptation, we have evolved the optimal mutation rate

2. selection favors 0, but constraints mean we cant get there

is cancer a trade off

yes, occurs in places with a faster division rate (epithelial tissue)

why do humans age

window of reproductive success that is correlated with the lowest risk of accidental death

pathogens

evolve quickly

virulence selection pressures

transmission (opposite) and replication rate (directly corelated)

cholera

virulent but low transmittance

behavior

internally stimulated response to an external stimulus, which is a phenotype

variation in morphology and behavior

linked to supergene, sometimes cryptic

selection on behavior results in

changes in morphology due to promiscuous genes and pleiotrophy

why would organisms share traits

evolutionary history or similar selection pressures

differences between behavior and morphology

behavior changes more quickly, doesn’t fossilize, and relies on complex mechanisms