unit 3: speciation

define speciation

the process when one species splits into two or more species after

what are reproductive barriers? name also the 2 kinds

biological features of an organism that prevents individuals of different species from interbreeding

the two kinds are prezygotic barriers and postzygotic barriers

define prezygotic barriers?

prevents different species from mating or fertilizing

define postzygotic barriers

barriers that occur after the hybrid zygote forms

what are the 4 kinds of prezygotic barriers?

1. habitat = unlikely to reproduce based on different habitats

2. temporal = breed at different times/seasons

3. behavioural = populations are isolated from each other due to signals being sent is wrong for the species

• example: birds doing different dances, therefore, female birds are looking for different dances

4. mechanical = physical incompatibility of reproductive parts between species

what are the 4 kinds of postzygotic barriers?

1. gametic incompatibility = when the DNA clashes, incompatibility, chromosomes cannot properly “mix & match”

2. reduced hybrid viability = ended in stillbirth, post birth has many health issues and dies, miscarriage

3. reduced hybrid fertility = hybrids unable to reproduce (example: a mule)

4. hybrid breakdown = hybrids breed and the next generation after them are not fertile. generations after become less and less fertile

what is allopatric speciation?

when a population is divided and isolated geographically and then develops subpopulations

how does speciation happen?

when reproductive barriers are established

• different food sources

• different pollinators

• different predators

what is sympatric speciation?

when a new species arises in the same geographic area as its parent species

what are hybrid zones

these are regions where different species meet and mate, resulting in the production of a hybrid offspring

• it starts out as many populations of a species and then one population (due to some sort of barrier—allopatric or sympatric) evolves and becomes its own species. then new and original meet up in hybrid and make hybrids

what is punctuated equilibria?

this is when a species divides very abruptly → probably caused by a sudden change of environment

• compared to a gradual pattern, we see that the species changes pretty evenly over time, nothing sudden or too long

what is the average speed of speciation?

6.5 million years