Bio 2 exanm 2 please ehlp me

Directional Selection

selection that favors an extreme phenotype

• the average changes

• pouplation moves towards extreme

Stabilizing Seelection

selection acts against extremes, middle favoured

• avg the same

• tradeoff that variation decreases

• stabilizing does not mean 50%

Disruptive selection

selection acts against the average, middle ones

• population can be splitting into 2 groups

• increased variation

• average does not stay the same

fixation

being ‘fixed’ - reach 100% frequency in a population with other alleles being eliminated

allelels to be beneficial will move towards → fixation

alleles to be strong deleterious → loss

Synamorphy

trait unique to group,, character shared due to being inherited form common ancestor

Homoplasy

(convergent evolution) character shared due to evolving multiple times

Why is smaller the population the stronger the effect of a drift

for even slightly deleterious alleles can increase in frequency due to drift in small populations

transposable elements

mobile parts of genome, can move around copying themselves

genetic drift

changes in allele frequencies due to chance, ex. flipping coin 10 times should be hypothetically speaking 5 times tails 5 times head, genetic drift is the sample bias/error of deviation from this expected

what does genetic drift do

reduces genetic variation when leads to fixation or loss of alleles

what events cause genetic drift

founder events and BN

founder events

occur when relatively small # of individuals disperse to a new havitat, found or estalish completely new populatioin

BN

occurs when a species undergoes large and rapid decrease in pop size due to disease epidemic catastrophic sotmr or other change

gene flow

causes allele frequencies to change when individuals and/or alleles move from 1 population to join another → makes allele for homoegenos similar n 2 diff pop;s

Hardy Weinberg Equilbrium

no new mutations, so large that no new genetic drift occurs, random mating, no selection (same fitness), no gene flow

Morphological Species Concept

species as group that possess unique anatomical features

• only approach that can be used to identify species in the fossil record

downside of morphological species cocnept

many species can not be distinguished by unique anatomical features

biological species concept

if species is evolving independently of every other species, it means that no gene flow is occuring

• lack of gene flow is the defining principle of the biological species concept, giving that specieis are identified by reproductive isolation

• a group of organisms that can interbreed with each other, and produce viable fertile offspring, and are reproductively isolated from other groups

downside of biological species concept

• only relevant to eukaryotes that undergo s reproduction - a relatively tiny subset of organisms on tree of life, can’t be used for fossil species

• if 2 populations are not in physical contact and thus don’t have the opportunity to do so, its difficult to know wheterh they are considered different species by the biological species concept

• can NOT be used for fossils

phylogenetic species concept

• researchers can use DNA sequencies or other data to estimate where a population falls on tree of life

downside of phylogenetic species concept

lead to oversplitting (basically when dividing poulations into more species that actually exist based on small or unimportant differences)

Null Model

• Hardy Weinberg is a null model

• telling us what genotype frequencies should look like for any particular set of allele frequencies if there’s no evolution

• if no evolution, then can detect as change in genotype frequency from what null model predicts

Pre-mating, pre-zygotic reproductive barrier in biological species concept

can not mate together

post-mating, pre-zygotic reproductive barrier in biological species concept

can mate, can not form viable zygotes

post-mating, post-zygotic reproductive barrier in biological species concept

can mate, form zygotes, allele flow stops when nce offspring adults

geography of speciation - allopatric

“different country” - seperation of population in diff species due to a geographic barrier forming

geography of speciation - sympatric

“same country”, non-geographic isolation

parts of a phylogenetic tree (root)

ancestor of all other species or groups included in the tree

branch

each horizontal line, represents specific species when it changes through time

node

occurs when branch splits into 2 or more descendant groups during a speciation event

tips

ends of tree, with name of taxon represented at each tip, taxon represents any named group

assumptions for hardy weinberg principle

no migration

no mutation

no selection

no drif

no evolution

random mating

small populations wont work - affected by genetic drift

adaptive radiation

fast diversification of a single lineage into a large number of species, each with adaptions that allow them to exploit difference resources and habitats

2 reasonings for adaptive radtiona

1. Ecological opportunity - niche- a range of resurces that a species can use and the range of environmental conditions it tolerates

2. Morphological innovation - allows individuals to exploit resources in a new way

deep time

unamingiably immense sweep of the time since earth formed

Relative dating

researchers use observations about how rocks form to make conclusions about whether a rock formation is older or younger relative to other

• younger rock layers form on top of older rock layers

• rock formations horizontal when first

• if older rocks develop cracks, that got feidl by lava or rock forming sediments the crack filling or intruding rocks were younger than the layers aorund them

absolute dating

scientists use data from radioactive isotopes trapped inside rocks to assign a chronological age to rocks

mass extinction

atleast 60% of species alive @ time go extinct within period of 1 million years

background extinction rate

the normal , long-term average at which species go extinct over time, outside of mass extinction rates

• each radioative isotope decays with a chracteristic half life time - the time it takes half the element to decay

  • after 1 half life, half of element has decayed

  • after 2 half. lifes, half of what remains has decayed as well

  • after 3 half lives half of what is left over is decayed as well

archaea synamorphy

cell membrane dominanted phospholipids that have several unique strucutral features

arache shared characterisits with bacteria

lack of nucleus, unicellular, single circular chromsome

archaea shared characterists with eukarya

i. archaeal dna wraps around histone proteins to form chromsomse, but bacteria doesent have histones

ii. protein syntehsis starts w/ unmodified version of amino acid methanane, while bacteria use modified verison of methione

iii. molecules and machien function in formation processing much more similar in arachehaand eukarya compared to bacteria

bacteria synamorphy

cells walls that feature strucutre carbhohydratd peptidlycan which is made of sugars

eukarya synamorphy

chromsomes found inside double-membraned envelope, forming nucleus

i. meisosi

ii. nucleus

iii. mitochondrion

difference between prokaryotes and eukaryotes other than nucleus

prokaryotes very freely exchange DNA

family of antibiotics called B lactamase including penciclin cdaphalorpins and carbopene

inhbitibt peptiglydogn syntehsis

genetic bottleneck

large rapid decrease in indidivdual popualtion size offucrs within an exisiting poulation

• caused by a catastrophic event (e.g disease, storm, hunting) killing off most indiiduals and leaving only a random few to survive

malaria treatment

public health interventions (mosquito nets), vaccines long out of reach, may be in progress

resistance to artemisin

mutations in the Kelch 13 gene can cause sloer clearance of malaria parasite from body upon artemisisn treatment

• frequency of Kelch 13 would increase over time to allow for the malaria to spread/survive better

mutation types inside - substitution

one nucleotide changed into antoher

• Silent (synonymous) - amino acid changed

  • Nonsynomous substituion (missense, nonsence) - amino acid code changed

    • typically decrease fitness because they have a deleterious effect - more liekly to break and enzyme ( deleterious mutations i protein coding regions more common)

outside of protein coding

• some mutations have a functional effect- promoter regions, splicing

• mutations unlikely to hit important element when genome is so vast

Sequence convservation

implications - if mutations are very rare, the rate of evolution is a funtion of the fraction of mutatins that are neutral (f_0)

• human genome is not necessarily due to natural selection but rather random variations within the genotype

• think of the plane model, where the bullet holes are on plane are the important factors, but where they are not so as to know where to protect (essential to survivial of the plane)

genomic organization

introns do not code for anything, so mutations can occur and there will be no effect on the function

• Exception - the introns responsible for splicing, but those are a small amount

• Most of our dna is a bunch of repeated sequences in our genomes

  • Alu element - 10% of our DNA that is the exact same sequence over and over again

problem with single locus

speciation cannot easily happen at just one locus, since it might not be compatabile with the other locus

epistatsis

when the effect of one gene depends on the prescence of another

• e.g a and b evolved independnetly and have never been tested together, when they meet as a hydribe they are inocmpativle, sterile, die

• the resulting is that though both populations evolved naturally and stayed at good fitness in their respective enrionments, they are now 2 different species because they can now no longer produce healthy offspring

hardy weinberg equilbirum

null hypothesis, assumes that the alleles and genotypes frequencies are remaining constant, and no eovlution occuring

• if evolution is occuring, can detect change for genotype frequency

monophyletic

a group of organisms descended from a common ancestor and and one thats not shared with any othe group

paraphyleitc

grouping that includes a common ancestor and some but not all of its descendans

what eolved first RNA or DNA

rna ebolbed before dna and proteins, stored genetic information in the cells

DNA is what’s changing and is driving evolution, what we can read about a organism and build phylogentic tress upon

likely first beause it can store inofmration similarly to DNA, can catalyze reactions like proteins

maximum parsimony

finding the tree that minimizes the number of evolutionary events

outgroup

to root the tree, and organism we know is equally distant from all other species - helps figure out what ancestor looks like to see in what order traits evolved

bacteria start translation with

modified methione (AUG)

eurkarya synamoprhies what

1. Mitochondria - organelles w ith double membrane around them

2. nucleus - specifical compartment for DNA with double membrane

3. meisois - linear dna unlike archeae

domestication syndrome

set of traits that evolved together consistently during domestication

neutral theory of molecular evolution

since neutral mutation has no effect on fitness, natural selection doesen’t rlly act on it, and it is randomly , the rate of evolution depends on the fraction of neutral mutations (f_0),

• if more mutations are neutral, the more mutations survive

RATE OF EVOLUTION = MUTATION RATE * FRACTION OF NEUTRAL MUTATIONS

end-Permian extinction

a large spike of atmospheric CO2 from volcanic erruptions led to intense global warming and environemntal distaster cause by anoxia and acidification

oxygen revolution (2400 MYA)

when plants were able to do photosyntehsis either animals evolved or hid , wiped out the rest since oxygen was toxic for organisms

third one (tc)

astrroid, crated ash clouds, organisms couldn’t photosyntehsize

Archaeplastids

have chlorplasts ‘plastids’ from ancient bacteria

• red and green algae, and land plants

metamonads

4 flagella, include giardia , in symbiosis with bacteria, are symbiotic with termites to allow cellulose digestion

• amoeba like , living in water

• include species that paratisize humans and ohter mamamals ad cause dirahea

• include groups that live in the guts of termites and harbor the bacteria that break down cellulose, enabling termites to eat wood

amoebozoids

crawl around due to cytoskeeltons, sister group to opisthokonths

Opisthokonths

• Fungi (closely related to humans)

  • cell walls

  • critical for ecosystem renwal

• Animals

  • all multicellular organisms

  • nerve muscle cells (not al)

SAR

organisms we dont know what to do with