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AP Biology: Unit 7 Cheat Sheet (DRAFT) by

Natural Selection & Evolution

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Natural Selection Background

2 defini­tions of evolution
1. descent with modifi­cation
2. change in the genetic compos­ition of a population from generation to generation
 
natural selection:
indivi­­duals with certain inherited traits tend to survive and reproduce more than others because of those traits
artificial selection:
breeding to encourage the occurrence of desirable traits
*indiv­­iduals don't evolve, popula­­tions evolve
*natural selection only works on traits that differ in indivi­­duals
*envir­o­n­mental factors change, so favorable traits change

Important People

1. Linnaeus
- made the format of naming species
2. Cuvier
- catast­rop­hism: catast­rophes cause changes in species
3. Hutton
- Earth's geological features due to mechanisms still around today (ex. rock cycle)
4. Lyell
- unifor­mit­ari­anism: same processes occurring today also happened in the past
5. Lamarck
- use and disuse: parts of the body used become more advanced and those not used deteri­orate
- inheri­tance of acquired traits = organisms pass modifi­cations to offspring
6. Darwin
- develo­pment of the theory of natural selection

Darwin's Evidence for Evolution

1. homology
↳ similarity in charac­ter­istics resulting from a shared ancestry
- homologous struct­ures: structures in different species that are similar (struc­tur­ally) because of common ancestry
- vestigial structure: feature of an organism that is a historical remnant of one once used
2. embryology
↳ structures present in embryos can explain the simila­rities in different species
- convergent evolution: similar features in indepe­ndent evolut­ionary lineages
- analogous struct­ures: charac­ter­istics that are similar because of convergent evolution
3. fossils
- indicate structural simila­rities between different species
- document formation of new species
4. biogeo­graphy
↳ study of the past and present geographic distri­bution of species
5. artificial selection

Allele Frequency

3 MECHANISMS THAT CHANGE ALLELE FREQUENCY
1. Natural Selection
↳ improves the match between organism and the enviro­nment
2. Genetic Drift
↳ chance events alter allele freque­ncies
↳ founder effect~ few indivi­duals isolated from the larger population & establish a new population
↳ bottleneck effect~ population is reduced by natural disast­ers­/human actions
3. Gene Flow
↳ transfer of alleles between popula­tions (from migration & mating)
 
genetic variation: differ­ences in indivi­duals compos­ition of their genes/DNA segments (ex. mutations)
↳ in sexual reprod­uction= crossing over; indepe­ndent assort­ment; fertil­ization
geographic variation: differ­ences in the gene pools of geogra­phi­cally separate popula­tions
↳ cline~ graded change in a character along a geographic axis
(^ microe­vol­ution ^)

Hardy-­Wei­nberg

Hardy-­Wei­nberg principle:
freque­ncies of alleles and genotypes remain constant for each generation
↳ Hardy-­Wei­nberg equili­brium predicts the allele freque­ncies in a nonevo­lving population
5 Conditions
1. NO Mutations
2. Random Mating
3. NO Natural Selection
4. Large Population Size
5. No Gene Flow
* if one not present --- genes evolving
(^ microe­vol­ution ^)

Hardy-­Wei­nberg Equations

Selection

relative fitness:
contri­bution an individual makes to the gene pool in relation to their ability to survive in their enviro­nment
3 MODES OF SELECTION
1. Direct­ional selection
favors 1 extrem­e/side
2. Disruptive selection
favors both extrem­es/­sides
3. Stabil­izing selection
favors interm­ediate
Sexual Selection
sexual selection:
indivi­duals with certain charac­ter­istics are more likely to obtain a mate
sexual dimorp­hism:
differ­ences between secondary sex charac­ter­istics of males and females
intras­exual selection:
compet­ition among indivi­duals of 1 sex for mates
inters­exual selection:
1 sex choosy in selecting their mates of the other sex
hetero­zygote advantage:
better reprod­uctive success of hetero­zygotes (preserve variation)
(^ microe­vol­ution ^)

Speciation

adaptive radiation
period in which organisms form many new species whose adapta­tions have them fill different niches
punctuated equili­brium
long periods which a species undergoes little change interr­upted by brief periods of sudden change
reprod­uctive isolation:
biological factors that impede members of 2 species from producing viable, fertile offspring
postzy­gotic barrier:
reprod­uctive barrier that prevents hybrid zygotes from developing
hybrid:
offspring resulting from the mating of 2 different species
prezygotic barrier:
reprod­uctive barrier that hinders the fertil­ization between species
PREZYGOTIC BARRIERS
1. Habitat isolation
different habitats then they never interact
2. Temporal isolation
breed at different times of the day/se­aso­ns/­years
3. Behavioral isolation
courtship rituals differ
4. Mechanical isolation
morpho­logical differ­ences
5. Gamete isolation
sperm can't fertilize egg
POSTZY­GOTIC BARRIERS
1. Reduced hybrid viability
genes of parents impair hybrid develo­pme­nt/­sur­vival
2. Reduced hybrid fertility
hybrid sterile due to chromo­somes from parents
3. Hybrid breakdown
when hybrids mate, offspring are feeble­/st­erile
Species Concepts
a. morpho­logical
by body shape/­str­uctural features
b. ecological
by ecological niche
c. phylog­enetic
smallest group that share a common ancestor
d.* biolog­ical*
by inbreeding of members
↳ limita­tions: designates absence of gene flow & doesn't apply to asexual organisms
Speciation Types
a. allopatric speciation
when a species is geogra­phi­cally isolated from original population
↳ geographic separation → mutations → reprod­uctive isolation → speciation
b. sympatric speciation
when a species is isolated with NO geographic isolation
↳ ex). disruptive selection; polypl­oidy; lateral transfer
c. parapatric speciation
when species interbreed over a geographic continuum
↳ ex). clines- elevation change
(^ macroe­vol­ution ^)
  

Phylogeny

phylogeny
evolut­ionary history of a specie­s/group of organisms
phylog­enetic tree
branching diagram repres­enting the evolut­ionary history of organisms
taxonomy
naming and classi­fying forms of life
taxon
taxonomic unit at any given level of classi­fic­ation
cladistics
organisms are placed into groups called clades based on common descent
clade
groups of species that includes an ancestral species & ALL its descents
monoph­yletic group
a common ancestor & ALL its descen­dents
paraph­yletic group
a common ancestor & SOME of its descen­dants
polyph­yletic group
derived from 2+ different ancestors
outgroup
group that is least closely related to the other oganisms
ancestral character
character shared by members of a certain clade originated in an ancestor not a member of the clade
derived character
character that is new/unique to a certain clade

Phylog­enetic Tree vs. Cladogram

* represent hypotheses

Binomial Nomenc­lature

- made by:
Linnaeus
- two parts:
genus & species
- rules:
first word capita­lized, second lowercase
 
all italic­ize­d/u­nde­rlined
8 LEVELS OF CLASSI­FIC­ATION
(Dear King Philip Came Over For Good Soup)
Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

Kingdoms & Domains

* protista kingdom not really considered (closely related to the other eukarya kingdoms)
* evidence of common ancestry of all eukaryotes = membra­ne-­bound organe­lles, linear chromo­somes, & introns

Prokar­yotes Inform­ation

(bacteria, archaea, & protists)
capsul­e/slime layer
protects against dehydr­ati­on/­shield against immune system
fimbriae
hair like appendages used to attach to host
pilli
appendages that pull 2 cells together
nucleoid
region in a prokar­yotic cell where DNA is located
positive chemotaxis
movement TOWARDS nutrie­nts­/oxygen
negative chemotaxis
movement AWAY from a toxic substance
endospore
can survive in harsh/­ins­uff­icient enviro­nments (dormant but viable)
POPULATION GROWTH
- in ideal lab conditions =
20 minutes
- typical human intestines =
12-24 hours
4 Limita­tions
1. exhaust nutrient supply
2. poison themselves with metabolic wastes
3. compet­ition from other microo­rga­nisms
4. consumed by other organisms

Bacterial DNA Transfer Types

transf­orm­ation: assimi­lation of external DNA
transd­uction: viruses carry bacterial DNA from one cell to another
conjug­ation: direct transfer of DNA

Endosy­mbiosis

Mitoch­ondria~
- first eukaryotes acquired mitoch­ondria by engulfing an aerobic prokaryote
↳ evidence: DNA data & found in all eukaryotes
Plasids~
- eukaryotes acquired photos­ynt­hetic bacterium that evolved into plastids
↳ evidence: plastid and photos­ynt­hetic bacterium genes closely resemble
secondary endosy­mbiosis
process in which a eukaryotic cell engulfed a photos­ynt­hetic eukaryotic cell

Early Earth

- Miller & Urey experi­ment:
demons­trated how the atmosphere could sponta­neously produce organic molecules
↳ other possible source of organic molecules: volcanoes or deep-sea vents
protocell
abiotic precursor of a living cell that had an internal chemistry different from its surrou­ndings
↳ created sponta­neously when lipids are added to water
*RNA World
life on Earth began with an RNA molecule that could copy itself
↳ ribozymes~ enzyme that makes copies of RNA
EVENTS
1. earth formation
2. stroma­tol­ite­s/o­ldest cells (unice­llular)
3. photos­ynt­hetic bacteria (releases O
2
)
4. aerobic respir­ation
5. eukaryotic organisms
6. sexual reprod­uction
7. multic­ell­ula­r/t­err­estrial algae
* more O
2
in atmosphere helps ozone protect against radiation
Cambrian explosion
brief time in history when there was an explosion of land & water diversity
↳ claws & defensive adaptation become present
mass extinction causes...
volcanic eruptions; astero­ids­/co­mets; human actions

Fossils

FOSSIL­IZATION
RATES
HIGH
LOW
- existed a long time
- existed a short time
- abunda­nt/­wid­espread
- not abundant
- hard shells­/sk­eleton
- soft/no shell/ no skeleton
- sedime­ntary rock
- not in sediments
radiom­etric dating
method to determine absolute age based on half-life
- isotope used:
carbon 14 (becomes nitrogen 14)