BILD 3 Final UCSD

descent with modification

over time traits that have a reproductive advantage become more popular within a population

divergence

different forms or structures of related species evolving differently to adapt to various environments

limits on population growth

predation

starvation

emigration

habitat loss

pathogens/parasites

fire/flood/drought

natural selection

variation in a heritable characteristic that affects survival or reproduction

principle of succession

living organisms are similar to fossils in their regions because they descended from those same ancestors with modification

Darwin's inferences

1. All species are related to a common ancestor

2. Evolutionary modification happens when organisms find themselves in new environments and adapt to those new environments via natural selection

3. The diversity on Earth has to do with how old the planet is

adaptive radiation

diversification of species from common ancestor to fill wide range of ecological niches

artificial selection

selecting for traits that are useful for humans

Alfred Russel Wallace

Collected beetles

4 years in amazon

Noticed that isolation + time = divergence

microevolution

Short time scales

Change in the genetic composition of a population across generations

macroevolution

change in composition of species over time

microevolution + millions of years = macroevolution

fossilization

usually found in sedimentary rocks

stratigraphy

younger fossils on top, older on bottom

Tiktaalik roseae

scaly fossil fish

Found in Canadian arctic

transitional between fish and tetrapods

probably a relative of the ancestor of modern tetrapods

Archaeopteryx

transitional form between dinosaurs and birds from late Jurassic

Extinction

Wiping out of a species

Controversy of extinction ended with discovery of Irish elk

vestigial structures

Functionless structure in one species that has an important function in another, related species

homology

similarity due to inheriting a trait from a common ancestor

developmental homology

inherited similarities during development, despite differences in adults

molecular homology

similarities among organisms as the molecular level

genetic code

in nearly all organisms, the same codons specify the same amino acid

phenotype

characteristic of an organism as a result of genes and the environment

genotype

genetic composition of an organism

phenotype determination

determined by:

Genes, the environment, or both

harmful mutation

impedes the function of a beneficial gene

negative/purifying selection

weeds harmful mutation out of population when they appear, conserves useful traits

evolution by natural selection happens when:

there is VARIATION in a HERITABLE characteristic that affects SURVIVAL or REPRODUCTION

directional selection

an extreme phenotype is the most fit

stabilizing selection

an intermediate phenotype is the most fit

disruptive selection

two extreme phenotypes are more fit than there intermediate counterparts

effects of directional selection

the population mean changes

variation decreases

effects of stabilizing selection

population mean does not change

variation decreases

effects of disruptive selection

population mean does not change

variation increases

locus (plural loci)

location of each gene on a chromosome

allele frequency formula

frequency of allele D = p

frequency of allele d = q

p + q = 1

Hardy-Weinberg Equilibrium

Means that a population is NOT evolving

If observed = expected : No evolution

-No natural selection

-No new mutation

-No genetic drift

-Random mating

calculating observed genotype frequencies

-# LL in population/# individuals

-#Ll in population/# individuals

-#ll in population/# individuals

calculating observed allele frequencies

-Freq L/# alleles in population

-Freq l/# alleles in population

calculating PREDICTED genotype frequencies

-frequency LL = p^2

-frequency ll = q^2

-frequency Ll = 2pq

processes that violate HWE

-mutation

-natural selection

-non-random mating

-gene flow

-genetic drift

gene flow

transfer of alleles in/out of a population as a result of movement of individuals or their gametes

genetic drift

change in genetic composition of a population caused by chance events

fixation

-effect of genetic drift

-all members of the population have the same allele of a particular gene

genetic bottleneck

a sudden change that drastically and randomly reduces the population size, leads to a change in allele frequencies

founder effect

a small number of individuals start a new population and the gene frequencies of the new populations are different from the source of the population by chance

neutral theory of evolution

in all populations, drift governs what happens to neutral alleles

diploidy

harmful recessive alleles "hide out" in heterozygotes, shielded from selection

sexual selection

selection for greater reproduction, sometimes at the expense of survival

can result in sexual dimorphism

sexual dimorphism

visible differences between the sexes

ancestral homologies

shared because this clade and earlier ancestors have it

derived homologies

unique to only one clade

also referred to as synapomorphies

outgroup

a taxon that shares many traits with the clade being studied, but not the synapomorphy that defines the clade

parsimony

asserts that the tree with the fewest evolutionary changes is most likely to be correct

why are phylogenies useful/important?

-provide an efficient structure for organizing biodiversity

-allow us to develop a conception of the totality of evolutionary history

-can help us answer specific questions of how evolutionary changes arose

speciation

divergence of a lineage to create new species

biological species concept

a species is a group whose members have the potential to interbreed in nature and produce fertile, viable offspring

prezygotic barriers

no zygote formed, often no mating takes place at all

postzygotic barriers

mating occurs but offspring is not viable or fertile

problems with biological species concept

-mating or lack of mating is hard to observe

-cannot be applied to fossils

-cannot be applied to asexual populations like bacteria

morphological species concept

-traits are defined by morphological traits alone

-used by paleontologists to define fossils

ecological species concept

species defined by the ecological niches they occupy

allopatric speciation

reproductive isolation occurs because populations are geographically separated either by vicariance or dispersal

vicariance

divergence of two populations due to a physical barrier

dispersal

divergence of a small population away from a large, ancestral population

sympatric speciation

speciation in geographically overlapping populations

polyploidy

organisms is >2 copies of chromosomes

caused by failure of cell division

radiometric dating

uses radioactive isotopes, decay spontaneously at a constant rate

evolutionary milestones during the Precambrian

-origin of life

-increase in atmospheric oxygen

-eukaryotes appear

-multicellularity arises

eukaryotes

internal, membrane-bound structures: nucleus, mitochondria, chloroplast

endosymbiosis theory

mitochondria and chloroplasts were formerly small prokaryotes living in larger host cells

phyletic gradualism

new species arise by gradual change

punctuated equilibrium

rapid changes during speciation, then long periods of stasis

paleozoic era

starts with cambrian explosion, ends with major mass extinction

Cambrian explosion

first appearance of the extent of many phyla

invention of predation

ordovician period important events

diverse marine invertebrates

early vertebrates started to diversify

possible start of colonization of land by plants

silurian period important events

terrestrial, vascular plants

devonian period important events

first terrestrial anthropods

first tetrapods

carboniferous period

abundance of giant tree ferns and horsetails

amniotic egg

permian extinction

the biggest mass extinction

may have been caused by Siberian traps volcanoes , triggered cycles of extreme heating and cooling

Mesozoic era

Drifting apart of Pangea

"Age of Dinosaurs"

K-T mass extinction

massive asteroid, similar damage to several million modern nuclear weapons

background extinction

extinctions that happen at a normal rate, 10-100 species per year

mass extinction

high period of species go extinct i a short time due to some major event

evolutionary development (evo/devo)

study of how evolution has shaped the developmental process to generate different bodies

history of evo-devo

morphological similarity

transcription factor

a protein that turns other genes on or off

homeotic genes

"you are here" genes

transcription factors that specify body part identity

they tell other genes where to be expressed during development

homeobox "hox" genes

a very conserved sequence of 180 nucleotides common to all animals and shared by yeast and plants.

"you are at this position along the anterior/posterior axis"

ardipithecus ramidus ("Ardi")

partrially bipedal

evolution of early human necks

australopithecus aferensis (Lucy and Salem)

feet planted on the ground, not for climbing

ape-like upper bodies, human-like lower bodies

homo habilis

Eastern and Southern Africa

Larger brains

Stone tools

homo erectus

originated in Africa

migrated out of Africa

similar bodies to modern humans

extremely tall with long legs

fire and hand axes

homo heidelbergensis

Europe, China, and Africa

European likely ancestors to neanderthals, while Africans likely gave rise to homo sapiens

homo neanderthalis

Europe to southwestern and central Asia

homo floriensis

dwarf species

island in indonesia

speciescape

size is proportional to described species in each taxon

3 domains of life

archaea, bacteria, eukarya

dinoflagellates

cells reinforced with cellulose plates, twin flagella

diatoms

cell walls composed of silica

freshwater and marine major component of plankton in lakes and ocean

green algae (archaeplastida)

marine, freshwater, and terrestrial

mostly multicellular

paraphyletic (should include land plants)