Evolution

theories of evolution

catastrophism: catastrophe wiped out a population

gradualism: effect slow but continuous progress

uniformitarianism: processes today have not evolved over history

Lamarck

So close award

first theory of evolution - inheritance of acquired characteristics, two forces

1. a force based on alchemy drove organisms up the ladder

2. another environmental force

   idea that species could change/transmutate

Darwin

no animal “higher” than other

all animals descended from common ancestor

organisms adapted to their environment, branched out from development through natural selection

work on the voyage of HMS Beagle - Galapagos notable

natural (& sexual) selection

favorable traits helped individuals survive and they pass that trait to their offspring

can cause two populations of same species to change drastically if they lived in different environments

sexual: changes in populations due to reproductive preferences

support for evolution/the common ancestor

natural and sexual selection, comparative anatomy and adaptations, comparative genomics, fossils, biogeography, speciation

comparative anatomy and adaptations

analogous features: different lineages but similar niches (ex: wings)

homologous features: same lineages but different niches (same structure, different function)

vestigial organs - organs that no longer function, may become smaller (ex: appendix)

adaptation as process vs. trait

process: organisms change over time to become more fit to their environment

trait: specific trait an organism has developed over time to survive in ecological niche

comparative genomics

all organisms have a genetic code

high degree of similarity in DNA in different species (sequence of ribosomes)

some genes (Hox) have same or similar functions across species, like embryonic development

phylogenetic trees

fossils

fossil records show development of complex organisms over millions of years

mass extinction of events (asteroid, volcano, methane from oceans)

radiometric dating - how much radioactive element a fossil has

stratigraphy - relative dating of fossil based on rock layer

geologic time

eons and eras of earth’s history

Paleozoic: cambrian explosion

mesozoic first vertebrate land animals + dinosaurs

Cenozoic: K-T event (asteroid, ¾ of plant and animal species)

first hominis by end of Cenozoic era

supercontinents

pangea: small super continents formed large land mass - broke up to gondwana and laurasia

post gondwana are Americas, Australia, India, Africa, Antaractica

India collided back with Asia

biogeography

how species have been distributed around the world

fossils, continental movement, and plate tectonics

species range - region on Earth that a particular species inhabits is called its range

dispersal - migration organisms and how biogeographical barriers influence their distribution

population genetics

use population statistics to figure out how common certain alleles are and how often there are population changes

Hardy Weinberg equilibirum

1. large population

2. no migration/gene flow

3. no mutations

4. random mating

5. no natural selection

if all are met, population is NOT evolving.

Hardy Weinberg formulas

p = dominant allele frequency

q = recessive allele frequency

p² = homozygous dominant genotype frequency

q² = homozygous recessive genotype frequency

2pq = heterozygous genotype frequency

p+q = 1 AND p²+q²+2pq = 1

fitness

ability to find a mate, raise viable and fertile offspring, compete with other members for food (interspecific and intraspecific), find food, find resting sites, survive weather, consume food

dependent on environment

populations with high population fitness usually have high genetic density

genetic drift (smaller population)

random changes in allele frequency

lowers variation and population fitness

founder effect: higher frequency of allele than the general population

bottleneck effect: after a disaster or large population shrinking event, population left behind will have different p&q than original

nonrandom mating (inbreeding)

mating between similar individuals

lowers variation and fitness - higher incidence of lethal alleles

speeds up genetic drift in smaller population

increase in homozygous, decrease in heterozygous

mutation

random change in DNA

increase variation and can be beneficial if it helps adaptation

new mutations enter the population gene pool, if rate increases in species p & q will change radically

increase from exposure to mutagenic chemicals/radiation

gene flow (migration)

population gets individual from another

increases variation and could increase fitness

introduces new phenotypes, populations become more similar

natural selection (negative selection)

selects against a phentoype

lowers variation, can increase fitness but maybe less able to adapt

natural selection (balancing selection)

support both phenotypes - heterozygote advantage

increase variation and fitness, help adaptation

types of selection

directional: one phenotype favored by the environment, new average phenotype, environment changing

stabilizing: intermediate phenotype favored, environment unchanging

disruptive: extreme phenotypes have advantage, eliminate mean, leads to directional or speciation

antibiotic resistance

bacteria evolve to become resistance to antibiotics due to overuse/misuse of them

sexual selection

intersexual: one member choose mates of the other sex

intrasexual: members of same sex competes with each other for mates (agnostic behavior)

sexual dimorphism: development of secondary sexual characteristics that distinguish males from females

convergent evolution

when a trait or characteristic evolves more than one time

similar function, different structure (analogous)

structure not present in common ancestor

divergent

features from ancestor’s body strucutre

homologous structures and vestigial organs

coevolution

two species in same environment can affect each other’s evolution

mutualism→flowering plants (develop flowers to attract pollinators)

competing to “out do” each other - evolutionary arms race

with parasite, the host may evolve defenses while the parasite evolves ways to overcome those defenses

bond parasitism - cuckoo bird lays eggs in another species’ nest

speciation

two populations of one initial species change enough, no longer can reproduce together

artificial speciation in labs

observe speciation in wild populations

allopatric and sympatric

biological species

population or group of populations whose members have the potential to interbreed in nature and produce fertile viable offspring

reproductive barriers

prezygotic: habitat, temporal, behavioral, mechanical, gametic

postzygotic: reduced hybrid viability, reduced hybrid fertility, hybrid breakdown

punctuated equilibrium

theory that species remain unchanged for long periods of time, speciation happens in short bursts

fossil record supports punctuated equilibrium - lot of speciation after a catastrophe

allopatric speciation

geographical isolating event

when populations meet again, will not be able to reproduce car natural selection took place

peripatric speciation

when allopatric speciation happens in very small isolated population

artificial speciaiton

selective breeding and isolation of populations by farmers of scientists

parapatric speciation

partial speciation by a geographical barrier but individuals of each population can still come in contact with each other

heterozygotes disadvantage because of environmental conditions

sympatric speciation

two geographical barrier

pre and postzygotic mechanisms