BIOL 221 Midterm

key events 4.6-4 bya

geoformation of earth

key events 4-2.5 bya

earliest life in oceans

key events 2.5-1 bya

prokaryotes dominating

photosynthesis (cyanobacteria)

eukaryote beginnings

key events 1 bya - 541 mya

diversification of eukaryotes

multicellularity

animal origins (sponges, movement, ediacara)

key events 541 - 485 mya

most modern phyla

invertebrates dominant

key events 485 - 419 mya

early fishes

plants/fungi move to land

key events 419-354 mya

land animals and forests develop

key events 354-298 mya

seed plants & amphibians

key events 298-201 mya

permian extinction (wiped out 99% of taxa)

beginning of dinos

origin of mammal ancestry

key events 201 - 66 mya

peak of Dinos and large reptiles (origin of birds)

insect-flower evolution

key events 66 - 2.3 mya

mammals replace dinos

grassland development

key events 2.3 mya

human lineage begins to dominate

radiometric dating

relies on constant decay (half-lives) of unstable radioisotopes

ex. 14C > 14N (more stable)

strata

layers of sedimentary and volcanic rocks

can be used to determine relative dates of fossils

resin-inclusion fossils

entire organism (usually small) preserved in amber, byproduct from plants

perimineralization fossils

shape of organism filled by inorganic material

original is gone, copy remains

impression fossils

impression left in soft bodied organism which then hardens and is preserved

trace fossils

traces animals left behind, not part of the animal itself

ex. footprints

evidence of behaviour, not just presence

why is there bias in the fossil record?

formation of a fossil depends on habitats, size, body composition, abundance, time period, destruction and predation

fossil discovery is also variable and a factor

what can fossils tell us?

behaviour, presence, age, abundance, anatomy, habitat, co-occuring species, lifestyle, food, diseases and development

stromatolites

oldest fossils formed by sedimentation and fossilization of bio film forming bacteria

transition to multicellularity

evolved independently across many origins

typically clonal entities

size of organism increases

specialization increases

emergent (new) properties that single cell organisms weren’t able to perform

ediacara (570-540MYA)

pre-cambrian time of abundant diversity

almost no surviving organisms

numerous impression fossils on ocean floor

cambrium explosion (541-484MYA)

time of development and evolution of nearly all living animals

chordate (538MYA)

organism that as an embryo has a notochord, post-anal tail and gill slits

adaptation lost in species that no longer need them ex. humans

benefits/costs of terrestrial dwelling organisms

develop breathing structures, sunlight, gravity pull, still need to find water source, better visibility, less locomotive resistance, easy access to soil, less thermal conductivity

benefits/costs of aquatic dwelling

no oxygen, less gravity, shielded from UV rays, less temperature extremes, reduced visibility, passive dispersal

costs/benefits of being a small organism

large SA/V ratio (easy gas exchange and excretion)

easier passive dispersal

internal transport via diffusion

shorter growth period

require fewer resources

easier to hide

favourable biomechanics

costs/benefits of being a large organisms

small SA/V ratio (heat/moisture preservation)

can eat smaller things

faster speed

environmental manipulation easier

larger internal reserves relative to enivronmental fluctuations

Cope’s rule

tendency for organism size to increase as lineage progresses

phylogeny

evolutionary history of a lineage/s

visually represented by phylogenetic tree

node

represent common ancestors for all descendent lineages

internal is between two terminal nodes of a clade

monophyletic

CA and all descendants

para-phyletic

ancestor and SOME descendants

polyphyletic

a group of taxa that DO NOT share a CA

synapomorphy

derived character state shared by ancestor and descendants

outgroup

a species that doe not belong to area of interest but is used to infer character states

symplesiomorphy

character state that is shared by ALL

autapomorphy

derived character state in only ONE taxon of a lineage

principle of parsimony

simplest scenario requiring fewest steps is preferred

homology

shared traits inherited from common ancestor

divergent evolution

ex. post-anal tail in humans, dolphins

homoplasy

traits that arise from similar environment/niche

convergent evolution

ex. bird vs bat wings; reptile jawbones and human inner ear bones

polygamy

can’t determine which members are most closely related

usually many grouped together

horizontal gene transfer

lineage receiving genetic information from other lineages

tiktaalik

transitional fossil in tetrapod evolution

why are transitional fossils rare?

rapid speciation (punctuated equilibrium) and morphological change

punctuated equilibrium

periods of stasis punctuated by periods of rapid change

adaptive radiation

rapid diversification from CA

population genetics

study of distribution and frequencies of alleles in populations

how and why they change

hardy-weinberg equilibrium

no evo change

predict genotypes

population infinitely large

no natural selection

no mutation

mating is random

no genetic drift

genetic drift

random changes in genetic composition of a population across generations due to random chance events

more likely to happen in smaller populations

pleiotropy

a single gene affecting the expression of more than one phenotypic trait

antagonistic pleiotropy

a mutation with beneficial effects for one trait but detrimental for others

negative selection

decrease in frequency of an allele

evolutionary fitness

the survival and reproductive success of an individual with a particular phenotype

need to survive to repro age, successfully mate, produce offspring

relative fitness

individual fitness compared to average fitness of a population

ex. you can have an overall evolutionary fitness of 1, but if you produce the same amount of offspring as all the other dolphins, then you are just average at being a dolphin

average excess fitness

difference between relative contribution of individuals with one genotype and average fitness of the population as a whole

positive selection

alleles that increase in fitness

additive allele

expresses double the phenotypic effect

most likely to reach fixation in a populations

negative frequency dependent selection

rare genotypes have higher fitness than common

balancing selection

favours more than one allele

inbreeding coefficient

probability two alleles will be the same due to common descent

F

epistasis

effects of an allele at one locus are modified by alleles at another

heterozygote advantage

selection that favours heterozygote individuals

inbreeding depression

reduction in the average fitness of inbred individuals relative to that of outbred individuals

landscape genetics

field of research that combines population genetics, landscape ecology and spatial statistics

population structure

the occurrence of populations that are subdivided by geography, behaviour, or other influences that prevent individuals from mixing completely

genetic distance

a measure of how different populations are from each other genetically

gene flow

movement or migration of alleles between populations

allele

an alternative form of a DNA sequence at a particular gene locus

genetic polymorphism

the occurrence of two or more discrete phenotypes in a population

polyphenism

a trait for which multiple, discrete phenotypes can arise from a single genotype

quantitative trait

measurable phenotype that varies among individuals over a given range to produce a continuous distribution of a phenotype

broad sense heritability

the proportion of total phenotypic variance of a trait that is attributable to genetic variance where genetic variance is represented in its entirety as a single value

broad sense heritability formula (H^2)

Vg/Vp

narrow sense heritability

proportion of total phenotypic variance of trait attributable to the additive effects of alleles

directional selection

favours individuals on one end of distribution

stabilizing selection

favours average phenotypes

disruptive selection

favours tails of distribution

selection differential (S)

a measure of the strength of phenotypic variation

quantitative trait locus

a stretch of DNA that is correlated with variation in a phenotypic trait

quantitative trait locus analysis

1. genetically different parents
2. cross to mix genetic material
3. look for association between local genotype and phenotype

explains

inversion

a segment of DNA is flipped around and inserted backward into its original position

physical linkage

when two or more loci are adjacent on the same chromosome

genome-wide association mapping (GWA)

involves scanning through the genomes of many different individuals with a focal trait of interest to search for markers associated with the expression of the trait

single-nucleotide polymorphism

a genomic variant at a single base position in the DNA, a one letter locus in a genome

reaction norm

pattern of phenotypic expression of a single genotype across a range of environments

supergene

a group of functionally related genes that are so close they segregate as a single unit

linkage disequilibrium

when the occurrence of an allele at one loci is associated with the presence/absence of an allele at another locus

used in GWAS, QTL analysis and consumer genetic testing

broken over time by recombination

causes of linkage disequilibrium

recent mutation

low recombination

selection

linkage equilibrium

when the occurrence of an allele at one locus is independent of the presence/absence of an allele at another locus

loci on different chromosomes are typically in linkage equilibrium

gene tree

branched genealogical lineage of homologous alleles that traces evolution back to ancestral allele

do not always match species trees

coalescence

mathematical model aiming to trace alleles of a gene back to single ancestor

homologous alleles merging in common anscestor

ortholog

one of at least two homologous genes separated by speciation event

paralog

homologous gene that arises from duplication event

come together to form gene family

introgression

movement of alleles from one species or population to another

incomplete lineage sorting

genetic polymorphism persists through several speciation events

pattern of retention is the reason gene tree differs from lineage tree

maximum parsimony

statistical method for reconstruction phylogenies that minimizes the total number of steps required to fit data into tree

purifying selection

form of stabilizing selection

removal of deleterious alleles in a population

bootstrapping

statistical method

assigns measures of accuracy (strength) to sample estimates of existence of particular node in phylogenetic tree

uses resampling WITH replacement