Biology 102 Chapter 13 & 14 - Species, Evolutionary Trees,
& Taxonomic Classification
What is a Species?
A species is a group of individuals group that:
● descend from a common ancestral population.
● Can successfully breed with each other, but not with individuals of other species.
● Maintain phenotypic and genotypic cohesion. (they look similar and have the same
genes)
Species
How do we know if two organisms belong to the same species?
Biological species concept: a group of natural populations capable of interbreeding and
producing fertile offspring but cannot breed with such other groups.
Problems with the BSC
● Doesn’t work with asexual organisms
● Doesn't work with fossils
The origins of species
Species come from preexisting species
Populations can also split into 2 new species via speciation.
Speciation
If gene flow stops between two populations for long enough, new species arise
Reproductive isolation.
Reproductive isolation
1
& Taxonomic Classification
What is a Species?
A species is a group of individuals group that:
● descend from a common ancestral population.
● Can successfully breed with each other, but not with individuals of other species.
● Maintain phenotypic and genotypic cohesion. (they look similar and have the same
genes)
Species
How do we know if two organisms belong to the same species?
Biological species concept: a group of natural populations capable of interbreeding and
producing fertile offspring but cannot breed with such other groups.
Problems with the BSC
● Doesn’t work with asexual organisms
● Doesn't work with fossils
The origins of species
Species come from preexisting species
Populations can also split into 2 new species via speciation.
Speciation
If gene flow stops between two populations for long enough, new species arise
Reproductive isolation.
Reproductive isolation
1
