final test

natural selection

A natural process resulting in the evolution of organisms best adapted to the environment.

random evolution

mutation, genetic drift, and gene flow

directional evolution

occurs when a certain allele has greater fitness than others, resulting in an increase of its frequency

selective pressure

when the environment pushes an individual or population to adapt or evolve

natural selection conditions

variation, heritability, differential reproductive success

Evidence for natural selection

-Fossil record
-Earth's age
-Mechanism for heredity
-Comparative anatomy

artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms

CRISPR

Hardy-Weinberg equilibrium

condition in which a population's allele frequencies for a given trait do not change from generation to generation

Population

A group of individuals that belong to the same species and live in the same area

gene pool

Combined genetic information of all the members of a particular population

allele frequency

Number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene

Allele

Different forms of a gene

p

frequency of dominant allele

q

frequency of recessive allele

p+q=1

allele frequency equation

BB

p^2

Bb

2pq

bb

q2

p^2+2pq+q^2=

1 or 100%

sample problem

Example: 2500 individuals in rabbit population, 900 have white fur
Must know that white is recessive to black
900 out of 2500 are bb q2 = 900/2500 = 0.36
q = 0.6 and p = 0.4 (because p + q = 1)

allele frequencies change due to...

small population size
non-random mating
mutations
migrations
selection

Hardy-Weinberg equilibrium assumptions

1) Large population
2) No mutation
3) No immigration or emigration
4) Random mating
5) No natural selection

Breaking Assumptions

1)genetic drift randomly changes allele frequencies from generation to generation
2)inbreeding increases homozygosity non-random mates favor certain traits
3)mutations add genetic diversity
4)gene flow homogenizes distinct populations
5)selection can fix beneficial alleles, purge deleterious alleles, or maintain an appropriate balance between them

genetic drift

random change in allele frequencies that occurs in small populations

silent mutation

alters a base but does not change the amino acid

nonsense mutation

changes a normal codon into a stop codon

missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

Any violation of the conditions necessary for Hardy-Weinberg equilibrium can result in

changes in allele frequencies

Speciation

Formation of new species

species

A group of similar organisms that can breed and produce fertile offspring.

Speciation concepts

members of populations that are able to interbreed
-may not actually do so, but are capable of doing so
-offspring must be viable and fertile

ability to interbreed is not necessarily based on similar morphology, but has a variety of underlying causes
-relies on reproductive barriers

reproductive barriers

factors that prevent different species from reproducing

pre-zygotic barriers

A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted

post zygotic barriers

reduced hybrid viability, reduced hybrid fertility, hybrid breakdown

habitat isolation

populations live in different habitats and do not meet

temporal isolation

form of reproductive isolation in which two populations reproduce at different times

behavioral isolation

isolation between populations due to differences in courtship or mating behavior

mechanical isolation

Morphological differences prevent fertilization.

gametic isolation

Sperm of one species may not be able to fertilize eggs of another species

reduced hybrid viability

When the genes of different species interact and impair hybrid development.

reduced hybrid fertility

Sterile hybrids due to uneven chromosome number.

hybird breakdown

hybrid offspring are born and fertile, but their offspring are weak and/or infertile

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

allopatric variance

non-overlapping habitats are formed by extrinsic events that split up a population

ex: lake drying up to form smaller lakes

results in isolated populations that diverge if the gene flow stops not all species are affected equally

-not all species are affected equally

allopatric dispersal

when a few members of a species move to a new geographical area

sympatric speciation

The formation of new species in populations that live in the same geographic area

Sympatric sexual selection

habitats overlap, but a population gradually diverges into tow new species

Sympatric habitat differentiation

habitats overlap, but a population gradually diverges into two new species

Autopolyploidy

an individual that has more than two chromosome sets that are all derived from a single species

Polyploidy

condition in which an organism has extra sets of chromosomes

Biomes

A community of living organisms of a single major ecological region.

Ecology

The study of how living things interact with each other and their environment

organismal ecology

behavioral, physiological, and morphological ways individuals interact with environment

population ecology

factors that affect population size & composition

community ecology

interactions between species
ecosystem ecology- energy flow between living and nonliving elements

landscape ecology

study of multiple linked ecosystems

global ecology

study of the biosphere- sum of all the planet's ecosystem

How are biomes determined?

climate

terrestrial biomes

classified by temperature and annual precipitation
biomes determine

-fauna
-flora
-microbes
-fungi

biomes are dynamic
- respond to natural events

tropical forests

-found closer to equator
-tropic rain forest- high amounts of annual rainfall
-tropical dry forest- seasonal precipitation
-intense competition for light
-more animal diversity than in any other terrestrial biome

deserts

-temp varies seasonally and daily
-precipitation is low but varies
-vegetation is sparse
-nocturnal animals
-adaptations to survive water loss

savanna

-equatorial and subequatorial regions
-warm year round
-low rain
-grassland and trees
-supports large herbivorous mammals
-insects such as termites
-fire is important in maintaining savanna biomes

chaparrals

-high plant and animal diversity
-organisms have adaptations to both fire and drought

temperate grasslands

-seasonal variation in temp
-deep fertile soils

-ideal for grain architecture
-most grassland
-deep fertile soils

coniferous forests

-largest terrestrial biome on earth
-home to birds and mammals
-target for logging

-old growth forests disappear

temperate broadleaf forests

-lots of precipitation
-removed for cities
-trees become dormant through winter
-mammals hibernate and birds migrate

tundra

covers large areas of the arctic
-also found on high mountain tops at all latitudes

permanently frozen layer (permafrost) prevents root growth

migratory birds and mammals, though some large mammals stay year-round

aquatic biomes

aquatic biomes are set by the presence of salt vs. fresh water

photic zone

upper layer, receives enough light for photosynthesis

benthic zone

bottom layer of sand & sediment

abyssal zone

deep regions of open, water 2-6km deep

Wetland Biome

-include marshes, bogs, & swamps
-saturated or periodically flooded
-one of the most productive biomes
ex: home to diverse communities
-many microorganisms producing & decomposing
exs:water and soil have low dissolved O2
high capacity to filter dissolved nutrients and pollutants

streams & rivers

-bodies of water that move in one direction
-headwaters- cold, turbulent
ex:
-carry little sediment, mineral, nutrients
-water picks up nutrients and oxygen as it travels downstream
-nutrient content will be determined by terrain and vegitation

further from headwater- water movement slows, more nutrients picked up, path of travel becomes broad

estuaries

-transition between river and sea
-varies in salinity
ex: daily fluctuations from tides
-support many fish and invertebrate species
-crucial feeding areas for many species of birds

intertidal zones

-marine biome sometimes is submerged and exposed
-upper intertidal zone exposed to air longer
ex: greater variation in salinity and temperature
-many organisms live only at a particular level of the intertidal zone
ex: optimized for water, salinity, and temperature ranges

oceanic pelagic biome

- open blue water
- covers 70% of earth surface
- high oxygen levels, low nutrients level

coral reef

-found in the photic zone of stable tropic marine environments
-temp between 18-30c
-reef formed by calcium carbonate skeletons of coral animals
-vertebrates and invertebrates
-reduction in reefs due to coral collection, overfishing, global warming

marine benthic zone

-sea floor; receives no sunlight
-organisms must adapt to continuous cold and extremely high pressure
-unique communities arise around hydrothermal vents

Biogeography

study of past and present distribution of individuals species

biotic factors

living organisms in the environment

abiotic factors

nonliving physical or chemical factors

biotic factors

food availability
predator herbivores for plants
pollinators
parasites/pathogens

abiotic factors

temperature
sunlight
rainfall
temperature
nutrients
soil conditions predation, parastisim, & competition (biotic) non-favorable environmental conditions (abiotic)

sunlight is key for distribution

provides energy that drives nearly all ecosystems

actual range

- area where a species currently lives

potential range

area where a species could live, even though it does not

negative interactions

predation, parasitism, & competition (biotic)
non-favorable environmental conditions (abiotic)

positive interactions

presence of food (biotic) & water (abiotic)
symbiotic species (biotic)
favorable conditions (abiotic)
-ability to camouflage
-correct temperature for physical traits

population

A group of individuals that belong to the same species and live in the same area

population characteristics- density

density results from processes that add or remove individuals

add birth migration
remove death emigration (having to leave)

population characteristics- dispersal

dispersion may be due to habitat preferences, social interaction, or other factors

population characteristics- demographics

demography- study of vital stats in a population

population growth

in an idealized population (with no immigration/ emigration):

ΔN/Δt= B-D

n

change in population size

t

time interval

b

births

d

deaths

per capita birth rate

number of offspring produced per unit time by an avg member of the population

per capita death rate

number of expected deaths per unit time in a population

per capita rate of increase

r=b-d
r>0= pop growth
r