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 Grows on Land Grows in Water Arrowhead plants look different, but can interbreed so they are of the same species.

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.