Evolution - created from Mind Map

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Evidence

Speciation

Mechanisms

The cumulation of changes in the heritable characteristics of a population

Fossil Records

Selective Breeding

Structures

Patterns of Variation

Sequence of changing fossils from layers of rock strata

Carbon dating (radioisotopes)

Phylogenic tree can be made

(-) Gaps in records

e.g. Equus

fossils only form in environments that prevent decay

Breed differentiation has occurred in domesticated animals

(-) Human rather than natural selection

Evolution in short time-period

e.g. Dogs

Homologous Structures (Divergent Evolution)

Analogous Structures (Convergent Evolution)

Similar structure, different function

Often formed similarly in embryo

e.g. Pentadactyl limb

Rudimentary/vestigial organs

same bones in similar positions "unity of type" - Darwin

“Adaptive radiation”

different purposes

i.e. radius and ulna attached to humerus

swimming, running, digging, jumping

e.g. human appendix, snake hip bones

Similar function, different origin

e.g. fish and whale tails

Continuous variation

Discrete variation

therefore, causes divergence

across geographical range

e.g. human skin colour

e.g. industrial melanism

Divergence in the gene pool of a population

Models

Causes

Polyploidy

can be confirmed if two diverged populations are merged and do not interbreed

Phyletic Gradualism

Punctuated Equilibrium

e.g. Galapagos finches

many intermediate forms between species

long periods of relative stability (stasis) and then periods of rapid evolution

explains gaps in fossil records

incited by sudden environmental changes

Mass speciation event - natural disaster causes extinction and new species can erupt to take advantage of resources

Gradualism: Darwin observes Adaptive radiation

Punctuated Eq.: Peter and Rosemary Grant observed drought

in drought, bigger beaks survived

Directional natural selection

Change in allele frequencies in populations

Reproductive Isolation

Gene pools contain all the genes and the different alleles of a population

Theoretical: Hardy-Weinberg Equilibrium formula

Actual: ALFreD database

Genetic equilibrium - when all members of a population have an equal chance of contributing to the future gene pool i.e. same chance of reproduction

Heritability is the proportion of variation that is due to genes

Sympatric

Allopatric

Temporal

Behavioral

e.g. flowering at different time

e.g. mating displays change

Geographical

i.e. no interaction with other populations

esp. Endemic species

Causes

Organism that has more than two sets of homologous chromosomes

Effects

e.g. Red viscacha has 102 chromosomes, 4n=112 then shed some

Autopolyploidy

Allopolyploidy

single species, problem in meiosis

hybrid

diploid and haploid gamete fuse

organism not sterile since there will always be a chromosome to pair with if it mates with another polyploid or self-pollinates

Instant speciation when only polyploids can reproduce together

evolution for angiosperms that clone themselves

desirable crops can self-pollinate

e.g. Allium

Natural Selection

Genetic Drift

Genetic Flow

Selective Pressures

Patterns of Natural Selection

i.e. competition

Causes

Effects

Stabilizing selection

Directional selection

Disruptive selection

mean of the normal curve is preferred

e.g.. birth size of humans, # of eggs hatched

shift to one extreme due to a selective pressure or environmental resistance

e.g.peppered moths, beak sizes, antibiotic resistance

mutations occur that make the bacteria resistant to antibiotics

exchanging of plasmids

the mean is undesirable

tends to drive speciation most because offspring occupy divergent niches

e.g. Red crossbill, small or large fish

variation within a species

populations produce more offspring than an environment can support

Mutations

meiosis (independent assortment, crossing over)

sexual reproduction and random fertilization

plasmid transfer

environmental resistance

survival of the fittest

adaptation to make an individual more suited to its environment

Only animals that reproduce pass on their genes to offspring

Natural selection increases the frequencies of beneficial alleles

Organisms that reproduce more often evolve faster

occupies a niche

"progressive change"

i.e. geographical separation

i.e. migration of populations

i.e. extenuating factors