1. Darwin and Speciation Notes

2. Meet Charles Darwin
Published On the Origin of Species in 1859
Fun fact! Darwin dropped out of medical school after seeing his first cadaver

3. Darwin’s Findings
Darwin observed many species during his voyage on the HMS Beagle
In the Galapagos, Darwin observed the variations of animals and plants from island to island.
This eventually led to his theory of evolution by natural selection

4. Building on Earlier Science
Darwin built his theory off the work of Jean-Baptiste Lamarck
Lamarck wrote that living things change over time
Lamarck thought that organisms passed on their most-used traits to their offspring
Is this true? No!

5. Macroevolution
6/10/2018
What is a Species?
A species is a group of similar individuals capable of interbreeding to produce fertile offspring.
G. Podgorski, Biol. 1010

6. How Many Species Are There?
Macroevolution
6/10/2018
How Many Species Are There?
We don’t know
Estimates range from 4 to 100 million
~2 million species have been described
G. Podgorski, Biol. 1010

7. Macroevolution
6/10/2018
How Do Species Arise?
Speciation- evolutionary process by which reproductively isolated biological populations evolve to become distinct species.
Let’s break that down, shall we?
First things first: Evolution = ?
Change over time!
G. Podgorski, Biol. 1010

8. Macroevolution
6/10/2018
How Do Species Arise?
The key to speciation is reproductive isolation of populations.
Geographic isolation is most common
G. Podgorski, Biol. 1010

9. Process of speciation:
Macroevolution
6/10/2018
Process of speciation:
Parent
species
2 separate species
III. No Longer
Able to interbreed
II. Diverge
and Mutate
I. Barrier
G. Podgorski, Biol. 1010

10. Two Types of Speciation
Macroevolution
6/10/2018
Two Types of Speciation
1. Allopatric speciation: geographic isolation creates a reproductive barrier (an extrinsic mechanism).
G. Podgorski, Biol. 1010

11. Allopatric Speciation Example
Macroevolution
6/10/2018
Allopatric Speciation Example
Harris’ antelope squirrel
White-tailed antelope squirrel
Two species of ground squirrel are thought to have descended from a common ancestral population that was separated by formation of the Grand Canyon.
G. Podgorski, Biol. 1010

12. Two Types of Speciation
Sympatric speciation: reproductive barrier is created by something other than geographic isolation (intrinsic mechanism).

13. Sympatric Speciation Example
Ancestors of apple maggot flies laid their eggs on hawthorns, a plant species native to North America.
When immigrants came from Europe, they brought apple seeds.
Apple maggot flies now had a choice of where to lay their eggs—hawthorns or apples.
Flies hatched on apples only mate with apple-hatched flies, while flies hatched in hawthorns only mate with hawthorn-hatched flies.

14. How Fast Does Speciation Occur?
Macroevolution
6/10/2018
How Fast Does Speciation Occur?
It depends! Speciation relies on many factors
Examples: A slow rate of speciation evidenced by a living horseshoe crab (13 extant species) and a 300 million year-old fossil species.
In contrast, Galapagos finches have diversified into 13 species within the last 100,000 years.
G. Podgorski, Biol. 1010

15. What do we mean by “better?” Better for survival and reproduction
Macroevolution
6/10/2018
Does Evolution Create the Perfect Organism?
No, only better organisms as evolution is constrained by history and buffeted by random events.
What do we mean by “better?”
Better for survival and reproduction
G. Podgorski, Biol. 1010