define the term species
a group of organisms with similar characteristics that can interbreed to produce fertile off spring
define the term speciation
a process whereby one gene pool gives rise to more than one gene pool
name the two types of speciation
- allopatric
- sympatric
describe allopatric speciation
- allopatric means different counties
- when two populations become geographically isolated by a physical barrier so they cannot interbreed
what happens for allopatric speciation to occur?
- organisms are separated by a physical barrier
- they cannot interbreed
- genetic differences increase though selection due to environmental conditions
- eventually they become uable to interbreed to produce fertile offspring b
give examples of physical barriers that can mean species are geographically isolated
- rive
- sea
- mountain
describe the stages leading to allopatric speciation
- no interbreeding between populations
- mutation occur that could be advantageous
- different environmental conditions so different selection pressures
- advantageous features are more likely to reproduce, increasing allele frequencies
describe sympatric speciation
sympatric means same country
-when populations are productively isolated from each other
why could reproductive isolation occur?
- seasonal/temporal isolation
- mechanical isolation
- behavioural isolation
what is the main reason for sympatric speciation?
random mutations
describe seasonal/temporal isolation
members of the two populations reproduce at different time of year
describe mechanical isolation
anatomical differences may prevent mating occurring for example it may be physically impossible for the penis to enter the vagina
describe behavioural isolation
member of two populations have different courtship patterns
define the term natural selection
selection pressures change thew allele frequencies over time
