1. Biological Species Concept
“Species are groups of interbreeding natural populations that are reproductively isolated from other such groups”
reproductive isolation: genetic differences preventing successful interbreeding
- Ernst Mayr, 1940

2. Species on Earth # species on Earth today: ~3-50 million
# of species that ever lived: ~ million
It has been estimated that ~99% of all species that have ever lived are extinct

3. Speciation Speciation How? Classes of reproductive isolation
the process by which one species splits into two or more species
How?
Subgroups of the species become reproductively isolated
Classes of reproductive isolation
Prezygotic: prevents zygote formation
Postzygotic: prevents survival or reproduction of offspring

4. Classes of speciation Allopatric Parapatric Sympatric
geographic separation
Parapatric
divergence across a continous habitat
Sympatric
No separation

5. “Female Fickleness May Split a Species”
NY females prefer males with bright yellow bibs
WI females prefer males with large black masks
When mixed, preferences stayed the same
Source: Matt Kaplan, ScienceNOW Daily News, 11/30/2007

7. Transitional fossils
Fossils of organisms with morphological features intermediate between those of an ancestral species and its descendants ?

8. Fish to tetropods Tiktaalik
Discovered in 2004 on Ellesmere Island, Canada.
million years ago

9. Dinosaurs to Birds
150 Million years ago
Archaeopteryx

10. Land mammals to sea mammals
Source: evolution.berkeley.edu

11. Fossil DNA
ancient DNA
Remnants in a present-day genome of previously functional DNA that “eroded” due to an accumulation of mutations
…CAATGACGTTAGCATGAG…
…GAATGGCGTAAGCCTGAG…
present-day DNA

12. Human chromosome 2: A fusion
Remnants of old centromere
Remnants of old telomeres
Chimp chromosomes 2q and 2p