Lesson 6 Speciation Flashcards
Species
The biological definition for the word
species is:
A population that is
reproductively compatible. Members
of the population can interbreed and
produce viable, fertile offspring.
Speciation
The formation of a new species.
The Olinguito was
discovered in 2013.
The first new
mammal species
found in 30 years.
Reproductive
Isolation
The inability to produce viable offspring
with members of a different species due
to some form of biological barrier.
For a species to remain distinct it must
become and remain reproductively
isolated
Biological Barriers
1. Behavioural Isolation
Species specific behaviours
that prevent interbreeding
among closely related
species.
Ex. Bird song, mating rituals,
pheromones etc.
Biological Barriers
2. Habitat Isolation
Species may live in different
habitats and rarely encounter
each other.
Biological Barriers
3. Temporal Isolation
Species may share the same habitat but mate at
different times or seasons
Biological Barriers
4. Mechanical Isolation
Species are anatomically incompatible.
Biological Barriers
5. Gametic Isolation
Gametes are incompatible. Gametes can not fuse or
recognize each other.
Male gametes can not survive in the reproductive tract
of the female.
Biological Barriers
6. Hybrid Inviability
Hybrid embryos between the two species die before birth or fail to develop.
Biological Barriers
7. Hybrid Sterility
Hybrids between the two species are unable to produce gametes (meiotic failure) and as a result are sterile.
Ex. Mules – hybrid of horse and donkey
Biological Barriers
8. Hybrid Breakdown
The first generation of hybrids
between two species is fertile and
viable but the second generation
degenerates.
Allopatric Speciation
Speciation that occurs as a result of a population becoming geographically isolated from the parent
population.
Process of Allopatric Speciation
Geographic isolation can occur due to the formation of physical barriers such as mountains, canyons, rising sea levels, glaciers etc.
The physical barriers prevent gene flow between the two populations.
The different populations are subjected to different selection pressures causing allele frequencies of genes to change.
The two populations accumulate sustained genetic differences so that they become reproductively isolated
and are unable to interbreed.
Sympatric Speciation
Speciation occurring as a result of the
restriction of gene flow between members of a population due to
ecological isolation (Niche Differentiation) or polyploidy.
Process of Sympatric Speciation
Some members of a population may be better adapted to a slightly different habitat in an ecosystem and begin to specialize in that habitat
Different selective pressures in the two habitats leads to genetic changes in the organisms.
The two populations become reproductively isolated. Alteration in behaviour, chromosomal mutations, non – random mating, altered gene flow are all factors leading to sympatric speciation.
