BIO - Speciation

Evolution

Founder population

a small subset of a population breaks away from the main area and colonises a new area

Gene flow

movement of alleles between populations

Allopatric Speciation

occurs when populations of the same species become geographically isolated

Divergent Evolution

species sharing a common ancestry becomes more distinct due to differential selection pressures

Species

individuals that can breed and produce fertile offspring

Adaptive Radiation

multiple species evolving from a single ancestor species

Selection Pressure

environmental factors that influence the likely success of an individual

Convergent Evolution

Two unrelated species develop similar traits because they live in similar

Natural Selection

individuals most favourable phenotypes to the environment will survive and reproduce, and will pass these favourable alleles on to their offspring

Analogous Structure

features of different species that are similar in function but not in structure

Mutation

random permanent change in the DNA base sequence

Gene pool

all the alleles contained within a population

Genetic drift

random change in allele frequency in populations

Niche

role of the organism within the environment

Coevolution

Over time, two unrelated species develop specific adaptations to enable their existence in the presence of the other organism

Stabilising Selection

favours the average over the extremes

Directional Selection

favours one extreme over the average and the other extreme

Disruptive Selection

favours both extremes over the average

How does divergent evolution occur

isolation of a population from the main gene pool with geographical then reproductive barriers, resulting in new species

Biogeography

study of geographic distribution of species

Endemic Species

species found only in specific geographic locations

Plate tectonics

continetal drift, explains why similar species are found on different continents

Homolgous structure

physical features found in different organisms that share an ancestor

Vestigal Organs

Degenerate structures that no longer perform the same function as in other organisms

Polypeptide Similarity

Analysis of protein sequences to determine similarities and differences

How does Polypeptide Similarity work

High similarity in polypeptides indicates evolutionary relatedness, supporting the idea of common ancestry and evolutionary divergence

DNA Hybridisation

DNA from different species is mixed to see how well it pairs

How does using DNA Hybridisation work

degree of hybridisation indicates genetic similarity. Greater hybridisation indicates closer revolutionary relationships, supporting the idea of common ancestry

What is DNA Fingerprinting

identifying individuals by analysing specific patterns in their DNA. Comparing unique DNA patterns from different organisms

How does DNA fingerprinting work

genetic similarities and differences among species can reveal evolutionary relationships and common ancestry

Speciation

process by which new species are formed

When does speciation occur

Occurs when gene flow has ceased between populations where it previously existed

How is speciation brought about

brought about by the development of reproductive isolating mechanisms the integrity of the gene pool

What do RIMS do

prevent breeding between speices/barriers to gene flow

When do pre-zyogtic isolating mechanisms occur

before fertilisation to prevent successful breeding

List the 4 Pre-Zygotic RIMs

Temporal, Behavioural, Structural, Gamete Mortality

Explain Temporal RIMs

• may breed at different seasons

• may be nocturnal or diurnal

Explain Behavioural RIMs

• species may have specific calls, rituals, that enable them to recognise potential mates

Explain Structural RIMs

• compatible reproductive organs

Gamete Mortality

• if sperm and egg fail to unite, fertilisation will be unsuccessful

When do Post-Zygotic RIMs act

act after fertilisation to prevent successful reproduction

Explain Hybrid Inviability

fertilised egg may fail to develop properly

Explain hybrid sterility

hybrid of 2 species may be sterile

Explain hybrid breakdown

the first generation may be fertile but subsequent generations are infertile or non-viable

Stages of species formation

different types of isolating mechanisms operate and different amounts of gene flow take place as two populations diverge to form new species

Polyploidy

condition in which a cell or organism has three or more times the haploid chromosome number

When ploidy occurs in same species and who does this

autopolyploidy - plants

When ploidy happens across different species

allopolyploidy

Explain autopolyploidy as instant speciation

autopolyploidy is a form of instant speciation because the formation of the new tetraploid individual is genetically isolated from both parent species as the gametes may be incompatible

Polyploidy as RIMs

offpsring have different chromosome numbers than their parents so are unale to breed with the parent species due to not having homologous pairs

When does polyploidy occur

when chromosomes fail to correctly seperate during mitosis or meiosis (Non-disjunction)

Polyploidy as a source of variation

polyploids are often larger than their parent species (cuz they contain extra genetic material)

Advantages of hybrids

increase in heterozygosity reduces the frequency of expressed recessive mutations

What is heterozyogsity

heterozygous for a gene

How does polyploidy occur in same species

chromosomes fail to seperate during meiosis

cells fail to divide after chromatids have seperated

What happens if a diploid gamete fuses with a haploid gamete

a triploid is formed, triploids are generally unstable and sterile

What happens if two diploid gamete fuses

tetraploid forms, can be fertile

Result of allopolyploidy

hybrid produced, contains chromosomes from each parent. however can be infertile

How can Mitotic non-disjunction in sterile hybrid can produce homologous chromosomes

all gametes may end up in one cell

What does polyploidy result in

can result in gene redundancy and provides opportunity to diversify gene function

What is Allopatric Speciation

populations become geographically seperated, each being subjected to different natural selection pressures, establishing RIMs

Sympatric Speciation

a population forms a new species within the same area as the parent species

What is a parapatric speciation

speciating populations are only partially seperated geographically, so some individuals on each side are able to meet across a common boundary during the speciation process

4 Steps to Allopatric Speciation

moving into new environments, geographical isolation, formation of a sub-species, reproductive isolation

Steps to Sympatric Speciation

Change in habitat preference (for the insect), establishing reproductive isolation

What does phyletic gradualism state

evolutionary processes proceed slowly but continously and eventually the accumulation of changes result in speciation occuring

Adding on to phyletic gradualism

over a long time period, this gradual change would produce for us to see gradualism, we would see a gradual change in morphology due to selection pressures remaining constant, as even though mutations occur, no major change in form is selected for

What does punctuated equilibrium state

there are long periods of very little evolutionary change (stasis) interrupted by short bursts of rapid speciation. These rapid changes may be triggered by sudden changes in the environment.

Adding on to punctuated equilibrium

long periods of the same form being selected for (stasis) and interrupting this, we suddenly see, in the fossil record, new forms/species that would have resulted from diverse selection pressures selecting rapidly for a change in form. Thus, mutations that offered a different trait are selected for

Define fossil record

total collection of discovered fossils that document the history and evolution of life on Earth

What is genetic equilibrium

theoretical state where allele or genotype frequencies in a population’s gene pool remain constant from generation to generation