Download Speciation Notes

Speciation Notes
Biological Species Concept
Two organisms belong to the same species IF:
1) They can mate
2) And produce living and fertile offspring
When it comes to species, appearance
isn’t everything!
The Western meadowlark (left) and the Eastern
meadowlark (right)appear to be identical, and
their ranges overlap, but their distinct songs
prevent interbreeding. They are considered to be
different species.
Arrowhead Plants
Arrowhead plants look
different, but can
interbreed so they are of
the same species.
Grows in Water
Grows on Land
Key Idea: BSC depends on
reproductive isolation.
Problem: How do we classify organisms we cannot
observe carrying out sexual reproduction?
Additional Ways to Define Species
It can be difficult to group all organisms based
on their ability to reproduce, so scientists also
consider morphology (physical
characteristics) , ecological role, and genetic
history.
Remember the concept of a “species” is made
up by humans to organize life. Organisms
don’t always neatly fall into our categories.
• Key Idea: New species evolve when populations
become reproductively isolated from each other.
• Reproductive Isolation- Barriers to reproduction
that prevent organisms from mating or producing
living and fertile offspring.