speciation

species

species

a group of organisms that normally interbreed in nature to produce fertile offspring

speciation

the formation of a new species due to reproductive isolation

population

members of a group that live in the same geographical area

gene pool

the total number of alleles in a population

reproductive isolating methods

any factor that prevents members of the same species from breeding together. acts as a barrier to gene flow between populations

prezygotic

before fertilisation

postzygotic

after fertilisation

geographical isolation

physical barriers

temporal isolation

breeding behaviour occurs at different, non-overlapping times

behavioural isolation

differences in behaviour, often related to mating/courtship rituals

mechanical isolation

morphological differences in the external reproductive organs of species

gametic isolation

gametes are incompatible

hybrid inviability

not viable so will die during development

hybrid sterility

hybrid reaches maturity but is infertile

hybrid breakdown

hybrid reaches maturity and can breed, but subsequent generations have reduced reproductive capacity

mutation

permanent change in the base sequence of DNA

inbreeding depression

gametes decrease in fertility over generations

allopatric speciation

due to geographical separation due to different natural selection pressures, and then RIMS

sympatric speciation

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

chromosome mutations

randomly occurring changes during meiosis where chromosomes fail to separate correctly

non-disjunction

chromosomes are incorrectly attached to spindle fibres when lined up at the equator

polyploidy

more than 2 sets of chromosomes

aneuploidy

if fertilisation occurs with a haploid gamete, the zygote will have more or less chromosomes than normal body cells

somatic doubling

number of chromosomes double. can occur during mitosis or induced using chemical agents

hybrid virgour

when the hybrid is superior to both parents

autopolyploidy

polyploidy due to same species from non-disjunction or somatic doubling

allopolyploidy

chromosomes from two different species. hybrid will be infertile

evolution

changes in heritable traits of a population over time

coevolution

two or more species reciprocally affect each other’s evolution. one species acts as a selection pressure for the other

convergent evolution

two or more unrelated species evolve similar features or characteristics due to experiencing similar selection pressures

analogous structures

structures with very different evolutionary origins but are similar in terms of appearance and function

adaptive radiation

rapid evolution of a large number of species from an ancestral group

what does adaptive radiation do

evolution of a new structure or behaviour enabling exploitation of different aspects of a habitat

homologous structures

features that are similar in feature but different in function. same evolutionary ancestor

deme

subset of a population that has limited gene flow with members of the larger population

cline

a gradual change in the phenotypes and genotypes of a species across a geographical gradient

genetic analysis

compare DNA sequences, mutation rate/molecular clock