Evolution

Chemical Evolution

• Dust cloud condenses to form molten Earth (4.7 bya)

• Earth cools sufficiently to form crust (3.8 bya)

• a) volcanic eruptions, meteorites allow water vapor to escape inner earth

• b) vapor cools ---> rain ---> dissolved minerals ---> oceans, mud ponds

Miller’s primordial soup

• CO2, N2, H2O, CH4, etc exposed to lightning and UV form organic molecules, including amino acids

Biological Evolution

• 1st prokaryotic cells (bacteria) (3.5 bya)• a) no ozone so lived 10m below

sea surface• 1st photosynthesis: cyanobacteria

(2.3-2.5 bya)• (Gaia hypothesis)• O2 levels increase (2 bya)

Biological Evolution

• O2 at current levels (1.5 bya)

• 1st eukaryotic cells (1.2 bya)

• h) O3 formed and UV levels were low enough for life (plants) on land (400-500 mya)

Natural Selection

1) mutations (alleles) ---> envir cond change

+1) adaptation (adaptive trait: must be

heritable)---> differential reproduction = natural selection

1) environmental cond. change---> adaption, migration, extinction

2) artificial selection ( selective breeding)

Three types of natural selection

1) directional natural selectionlow frequency alleles --> high frequency

(resistance to pesticides)2) stabilizing natural selection

high freq alleles dominate(no envir change)

3) diversifying natural selectionlow freq alleles at either end become favorable (new food supply)

Lamark’s Theory

• How did giraffes get long necks?

Coevolution (pos feedback loop)

• change in one population makes a certain trait more favorable in another species

• (e.g owls and mice: Drought--> loss of food for mice--> mouse pop declines. Certain owls become better hunters, then certain mice survive (faster, better hider). As population of mice decreases, owls must be faster, have better eyesight to survive. (adaptation)

Niche vs habitat

• 1) fundamental niche vs realized niche-niche overlap leads to competition

• 2) generalist vs specialist species(cockroaches vs giant panda, spotted

owl)• 3) convergent evolution

-similar niches lead to similar traits in otherwise unrelated species that are geographically isolated

Fig. 4-7, p. 91

Generalist specieswith a broad niche

Nu

mb

er o

f in

div

idu

als

Resource use

Specialist specieswith a narrow niche

Nicheseparation

Nichebreadth

Region of niche overlap

Plate Tectonics

• 225 mya: Pangaea (N.A. at equator)

• 180 mya: continents separate

• 65 mya: Indian plate seperate

Fig. 4-5, p. 88

135 million years ago

Present65 million years ago

225 million years ago

Speciation

1. Geographic isolation

1. Plate movement (Madagascar)

2. Long migration (Galapagos, Hawaii)

Artic vs Gray

• Adapted to cold through heavier fur,short ears, short legs,short nose. White fur matches snow for camouflage.

• Adapted to heat through lightweight

fur and long ears, legs, and nose, which give off more heat.

Speciation

2. reproductive isolation

a. mutations and natural selection

occur independently in 2 populations

that are geographically isolated

b. eventually 2 pop cannot reproduce

- different breeding times, etc

Fig. 4-10, p. 92

Different environmentalconditions lead to different selective pressures and evolution into two different species.

SouthernPopulation

Northernpopulation

Gray Fox

Arctic Fox

Spreadsnorthward

and southwardand separates

Early foxPopulation

Fig. 4-9, p. 91

Maui Parrotbill

Fruit and seed eatersInsect and nectar eaters

Kuai AkialaoaAmakihi

Crested Honeycreeper

Apapane

Akiapolaau

Unknown finch ancestor

Greater Koa-finch

Kona Grosbeak

Macroevolution

• gradualist model vs punctuated equilibrium hypothesis

Extinction

• Due to changing environmental conditions• Can be caused by

1) plate movement

2) gradual climate change

3) abrupt, catastrophic climate change

Extinction• All species become extinct (4-22 million

years); mammals (2-5 million years)

• Endemic species are vulnerable to extinction (Madagascar)

• Mass extinction vs background extinction

Species Diversity

• Species richness (nunber of species)

• Species Evenness (pop of each species

Theory of Island Biogeography

• Big vs Small

• Close vs far from mainland

• Application to national parks• With road vs roadless

Species Roles

Generalist vs Specialist1. Advantage?

2. Native

3. Nonnative (alien, invasive, exotic)

a) no predators?

b) killer bees

4. Indicator species

Fig. 4-8, pp. 90-91

Piping plover feedson insects and tinycrustaceans on sandy beaches

(Birds not drawn to scale)

Black skimmerseizes small fishat water surface

Flamingofeeds on minuteorganismsin mud

Scaup and otherdiving ducks feed on mollusks, crustaceans,and aquatic vegetation

Brown pelican dives for fish,which it locates from the air

Avocet sweeps bill throughmud and surface water in search of small crustaceans,insects, and seeds

Louisiana heron wades intowater to seize small fish

Oystercatcher feeds onclams, mussels, and other shellfish into which it pries its narrow beak

Dowitcher probes deeplyinto mud in search ofsnails, marine worms,and small crustaceans

Knot (a sandpiper)picks up worms andsmall crustaceans leftby receding tide

Herring gull is atireless scavenger

Ruddy turnstone searches

under shells and pebbles

for small invertebrates

Species Roles

• Keystone species

• Foundation Species

Disappearing Amphibians

Vulnerable because:– No shell on eggs– Permeable skin

Disappearing Amphibians

Human related Causes?– Pesticides on insects– Habitat loss– Pollution– Increase in UV– Climate change– Overharvesting

Disappearing Amphibians

• Downside– Indicator species– Niche: eat insects, place in food chain– Pharmaceutical possibilities