BIO 181 Exam 2

Nucleotides are composed of

- Deoxyribose (sugar backbone) and nucleic acids (bases)

Nucleic Acid bases

- A

- T

- C

- G

DNA

- a molecule (can be different amounts)

Gene

- segment of DNA that codes for a protein

- one gene = one protein

- = a trait

Chromosome

- one whole strand of DNA

How do genes impact structure and function

- Genes (DNA) code for proteins (=traits)

- each chromosomes has 100s - 1000s of genes

Amino Acid

- each codon (set of three bases)

- 4 bases of DNA

- 20 of them

20,000 proteins in humans

- used at different times (in development or due to environmental/phycological triggers)

- used alone or with others in different combinations

Gene -> protein

- copied in nucleus (into RNA 0

- transported to ribosome

- reads copy and builds protein

mutation

- change in DNA sequence

- from external influences (radiation, chemicals) or from replication errors

substitution (type of mutation)

- exchange one base

deletion or insertion (type of mutation)

- remove or add 1+ base

- frame shift

allele

- different combinations of nucleotides within a gene segment

- different forms of a trait

what can a mutation do?

- nothing

- small change

- large change

sexual recombination

- genes shuffle during gametogenesis

- genes combine during fertilization

- meiosis is random

- fertilization is random

Evolution

- variation + selection

- changes over time (generations)

- exponential, not linear

heritability

- traits pass down to offspring

selection

- cause by environment, mates, humans, and random events

over-reproduction

- too many offspring produced to survive

Variation: Step 1

- mutations and recombination

- mutations can create new traits

- mutations are random (non purposeful)

- traits may be helpful or harmful

Variation: Step 2

- Selection by selective pressures

- some traits harm or kill the organism

- some traits reduce energy needed to survive or reproduce

- some traits result in more offspring than others

Selective pressure

lowers diversity

microevolution

- change in traits over time within a species (still interbreed)

macroevolution

- change in traits over time above the species level (no interbreeding)

Genetic Variation Impacts

- external traits (coloration, size, forms)

- physiological traits (functions such as transports, immunity, metabolic pathways, senses, behaviors)

- growth and development (sequence, regulation, transitions)

Gene flow

- spreads mutation within a species

- movement of genes among populations

- = migration

Variation builds up

- inherit DNA (changes build up over time)

- build up of changes in proteins

- Build up diversity = up range/niches = more populations = higher chance of divergence (NEW SPECIES)

speciation

- higher chance of divergence

Using genes to see evolution

- use DNA sequences

- use protein sequences

duplicate gene

- mutations can occur without hurting organism

molecular clock

- for DNA segments without selective pressure (pseudogenes), mutations occur at a relatively constant rate

Hemoglobin

- protein divergence

- transports oxygen and carbon dioxide

modern synthesis

- Malthusian competition

- Variation

- mutation

- natural selection

- genetic variation

- mendelian inheritance

Malthusian competition

geometric population growth, limited resources

Variation

breeds, races, subspecies

mutation

small changes in individual characteristics

natural selection

survival of the fittest

genetic variation

alleles of individual genes, combing to give continuous variation

mendelian inheritance

2 copies of each gene, 1 from each parent

type of selective pressures

- by environment (natural)

- by humans (artificial)

- by mates (sexual)

- by random events (genetic drift)

natural selection

- successful traits due to survival, energy use, and reproduction

- acts on all traits over entire lifetime

- predictable (selects which traits are successful)

- =/ evolution

3 steps to natural selection

- 1. limited resources + overproduction = struggle for survival

- 2. variation of traits (gene) = some survive better

- 3. traits of inherited = over time, successful traits become more prevalent

artificial selection

- successful traits due to desirability to another species (humans)

- acts on few traits during growth and reproduction

- generally decreases survival via natural selection

sexual selection

- successful traits due to attractiveness to mate

- acts on sexual characteristics during courtship

- generally decreases survival via natural selection

genetic drift

- random selection, especially in small populations

- two tops: bottleneck effect, founder effect

bottleneck effect

- catastrophe decreases population to few

- surviving traits due to luck

founder effect

- new population form with few individuals

- traits due to luck

Trait shifts (selection)

- directional

- diversifying

- stabilizing

survival of the fittest

- fittest = best fit

- not strongest, biggest, fastest, smartest, etc

- best fit changes with different environments

adaptation

- surviving trait

- not purposeful traits for an environment

How do traits mix

- mix within species (gene flow)

- do not mis between species

allopatric (type of speciation)

- Separated by barrier

- geographic isolation

sympatric (Type of speciation)

- separated while sharing same range

- behavioral isolation

parapatric (types of speciation)

- separated due to distance in a large range

Clade (evolutionary trees)

Clade

- a group of organisms with 1 ancestor and all descendants of that ancestor

4 billion years ago

- first life + prokaryotes

- fossil prokaryotes - stromatolites

- first land masses

3 billion years ago

- early photosynthesis = first O2

oxygen catastrophe

- Mass extinction due to photosynthesis waste product oxygen by bacteria

- 2.5 billion years ago

2.5 billion years ago

- success: eukaryotes (speciation)

1 billion years ago

- earliest multicellular organisms

- proto-plants, animals, fungi

500 million years ago

- Cambrian explosion

Cambrian explosion

- A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history;

500 million years ago

- colonization of land

- plants (mosses), then arthropods (450 mya)

400 million years ago

- colonization of land by vertebrates

- due to high competition in water

- tiktaalik (375 mya)

300 million years ago

- first reptiles and conifers

250 million years ago

- Permian extinction

- great dying

Permian extinction (great dying)

- 96% all marine species

70% terrestrial vertebrates

many million year recovery

6 C warming average

extinctions create open ____

niches

250 million years ago

- early dinos

65 million years ago

- Late dinos

- Cretaceous extinction event

Cretaceous Extinction

- the extinction of more than half of all species on the planet, including the dinosaurs

- birds survive

- birds and mammals expand into open niches

Lilliput effect

- reduction of size of animals during an extinction event

50 million years ago

- miniscule picture

- animals similar to today

study of geology

- from coal mines

- industrial revolution (1750)

geologists noticed ...

- 1. different layers of earth with different fossils

- 2. deeper fossils were simpler

- 3. some species were no longer found (extinction)

how fossils are made

- 1. life form dies in/by water

- 2. covered by silt

- 3. if undisturbed, buried beneath additional layers

most likely to fossilize

- hard structure

- numerous organisms - higher chance that one will fossilize

- aquatic environments w/ fine mud deposits

- low decomposition rates

- no erosion

what can you learn from a fossil

- shape and movement

- function and form

- color and texture

- behaviors (food, fighting, care of young, etc)

- species interaction

- community and structure

- palynology and paleoecology

fossil dating

- rock layers (relative dating)

- radiometric dating

biogeography (fossils)

- 1. more similar individuals closer; less similar individuals further apart

- 2. when separated by natural barriers, species diverge

Biogeography of Islands and Speciation

- Near islands = higher immigration

- large islands = higher immigration

- same latitude = higher immigration

evolutionary developmental biology (evo-devo)

- uses development of structures (embryology) to determine evolutionary origins

Divergent evolution

- most recent ancestry : same

- selective pressures : different

Convergent Evolution

- most recent ancestry : different

- selective pressures : same

divergent evolution -> homologous traits

- same ancestral trait in different environment = trait develops different function/appearance

convergent evolution -> analogous traits

- different ancestral trait in similar environment -> trait develops similar function/appearance

Vestigial organs

- organ that serves no useful function in an organism

- ie. wings in flightless birds, whale hips

- in humans: wisdom teeth, body hair, ear muscles

human evolution: 10000 ya

- agriculture, immune system, lactase and amylase

human evolution: 5000ya

- reduction of brain size

human evolution: 4000ya

- malaria and sickle cell anemia

human evolution: 1000 ya

- Sama-Bajau spleen size and deep-diving

Human evolution: 100s ya

- later menopause

how long have modern humans existed in a 24 hour clock?

-~ 4 seconds

primate groups

- prosimians (lemurs)

- new world monkeys (in Americas)

- old world monkeys (in Africa/Asia)

- apes (chips, gorillas, orangutans, and humans)

Human evolution

- humans did not 'descend from monkeys'

- we share a common primate ancestor

Hominid

- great ape (including human) ancestors

Hominin

- Human ancestors

- over 6,000 individuals

65 million years ago

- survival of small mammals through Cretaceous extinction

50 million years ago

- one population of insectivores

- primates