Biology Unit 4 AOS 2

species

a grouping of organisms that can interbreed and produce viable and fertile offspring

Allele frequency

a measure of how common particular alleles of a gene are in the population

population

a group of individuals of one species interacting in a particular area

gene pool

the complete set of allele carried by all the individuals of a population

larger/more diverse gene pool

greater range of alleles > greater genetic diversity

smaller/less diverse gene pools

lower range of alleles > low genetic diversity

mutations

random permanent changes in the DNA base sequence of an organism which may result in the formation of new allele

changes in allele frequency

1) initial gene pool 2) natural selection occurs 3) migration occurs

point mutations

a change in a single DNA nucleotides

Block mutations

changes to a larger segment of a chromosome

silent point mutation

does not change amino acid sequence

missence point mutation

different amino acid coded for

nonsense point mutation

early STOP codon coded for

duplication block mutation

segments of chromosomes become duplicated

inversion block mutation

segments of chromosomes are flipped

deletion block mutation

segments of chromosomes are last

translocation block mutation

segments are exchanged between non homologus chromosomes

polyploidy

more than 2 sets of chromosomes

fitness of mutations

its value to the survival and reproductive success of the organism

silent fitness mutation

no consequential effect on the phenotype

lethal fitness mutation

embryos are non-viable

harmful fitness mutation

lower and individual fitness

beneficial fitness mutation

increase fitness gives an advantage

gene flow

the movement of individuals and their alleles between populations of the same species

genetic drift

a change in allele frequencies in a population due to random events

founder effect

a small no. of individuals migrate away from the original population

natural selection

environmental selection pressures that impact the ability of individuals to survive and reproduce

selective breeding

involves breeding individuals with the most desirable phenotypes

Principles of natural selection

1) Variation in phenotypes exist in populations 2) There is a struggle for survival in the environment , acts as selective pressures 3) Individuals with suitable phenotypes will survive at a higher rate (selective advantage) 4)organisms that are selected for will reproduce in greater numbers over time this increases frequency of allele

speciation

the process of populations genetically diverging until they become different species

Allopatric speciation

when species become geographically isolated

Sympatric speciation

when populations living in the same location form new species

Allopatric speciation stage 1

Populations form = separate populations form, gene flow occurs

Allopatric speciation stage 2

geographical isolation = physical barriers isolate populations, gene flow is prevented

Allopatric speciation stage 3

differences accumulate = different selection pressures act on the population on favour with traits suited to the environment

Allopatric speciation stage 4

reproductive isolation = over time, differences between the populations accumulate

extinction

when all members of a species dies out

mass extinction

an abrupt increase in extinction rates affecting huge no. of species

fossils

the persevered remains or imprint in a rock of an organism

transitional fossils

fossil which are immediate between ancestral species and a descent species

phylogenetics

the study of evolutionary relationships between species

homologus structure (divergent evolution)

structures found in different species which may look and function very differently from one another but could be derived from a common ancestor

analogus structure (convergent evolution)

structures that serve the same function in different organisms but have evolved independently

vestigial structure

structures found in some organisms which serve no function