1. Macroevolution and Speciation
4/26/2017
Macroevolution and Speciation
Evolution creates (and destroys) new species, but …
What is a species?
Its not as straightforward a question as most believe.
These are members of different species - eastern (left) and western (right) meadowlark.
G. Podgorski, Biol. 1010

2. Thursday, September 19, 2013 Get the handouts from the front
Get an iPad if needed
You will have 5 minutes to review your document before presenting
You will present for no more than 5 minutes
Talk about speciation after presentations
Vocab Quiz tomorrow
BONUS DUE TOMORROW

3. Thursday, September 19, 2013 Pick up handouts
Get with your groups to discuss presentation
You’ll have 5 minutes to look over rubric and fix anything
Presentations will be 5 minutes each—MAX
Speciation talk afterward
Vocab quiz 3 tomorrow—time for questions after

4. What is a Species? There is only one extant (existing) human species.
Macroevolution
What is a Species?
4/26/2017
There is only one extant (existing) human species.
G. Podgorski, Biol. 1010

5. What is a Species? And these are all members of a single species.
Macroevolution
What is a Species?
4/26/2017
And these are all members of a single species.
G. Podgorski, Biol. 1010

6. Macroevolution
Determining What Is and What Isn’t a Distinct Species Can Have Economic Consequences
4/26/2017
Northern spotted owl (left) and barred owl (right).
G. Podgorski, Biol. 1010

7. Macroevolution
4/26/2017
What is a Species?
The definition we’ll use is this: A species is a group of individuals capable of interbreeding to produce fertile offspring.
This is the biological species concept. Like all attempts to define a species, it has many problems.
G. Podgorski, Biol. 1010

8. One Problem in the Biological Species Concept
Macroevolution
4/26/2017
One Problem in the Biological Species Concept
For asexually-reproducing organisms, like these bacteria, what constitutes a species?
G. Podgorski, Biol. 1010

9. …and another problem with the Biological Species Concept…
Macroevolution
4/26/2017
…and another problem with the Biological Species Concept…
Where do you draw the line between different ‘species’?
G. Podgorski, Biol. 1010

11. What is a population?
Members of a species that live in the same geographical area and interbreed

12. How Many Species Are There?
Macroevolution
4/26/2017
How Many Species Are There?
We don’t know.
About 2 million species have been described.
Estimates of existing species number range from 4 million to 100 million (with million being a more commonly considered upper estimate).
G. Podgorski, Biol. 1010

13. How did this diversity of life come to be?
Macroevolution
4/26/2017
How did this diversity of life come to be?
Species = basic unit
Continuous lineage - information
passed through genes
Speciation - rise of new species
G. Podgorski, Biol. 1010

14. Two Patterns of Speciation
Macroevolution
4/26/2017
Two Patterns of Speciation
Branching evolution can be Adaptive radiation if many species come from one common ancestor
G. Podgorski, Biol. 1010

16. Macroevolution
4/26/2017
How Do Species Arise?
The key to speciation is reproductive isolation of populations.
There are extrinsic and intrinsic reproductive isolating mechanisms.
Geographic isolation is the primary extrinsic reproductive isolating mechanism.
G. Podgorski, Biol. 1010

17. Process of speciation:
Macroevolution
4/26/2017
Process of speciation:
Parent
species
2 separate species
III. Don’t interbreed
II. Diverge
I. Barrier
G. Podgorski, Biol. 1010

18. Reproductive Isolation May Occur With or Without Geographic Isolation
Macroevolution
4/26/2017
Reproductive Isolation May Occur With or Without Geographic Isolation
Allopatric speciation occurs when geographic isolation creates a reproductive barrier (an extrinsic mechanism).
Sympatric speciation occurs when a reproductive barrier is created by something other than geographic isolation (intrinsic mechanisms).
G. Podgorski, Biol. 1010

19. Allopatric Speciation
Macroevolution
4/26/2017
Allopatric Speciation
Harris’ antelope squirrel
White-tailed antelope squirrel
Two species of ground squirrel are postulated to have descended from a common ancestral population that was separated by formation of the Grand Canyon.
G. Podgorski, Biol. 1010

20. Macroevolution
4/26/2017
Intrinsic Reproductive Isolating Mechanisms Are Always Required for Speciation
Harris’ antelope squirrel
White-tailed antelope squirrel
Intrinsic mechanisms involve changes to organisms that prevent interbreeding.
In allopatric speciation, intrinsic mechanisms come into play once populations are physically separated.
In sympatric speciation, intrinsic mechanisms are the only ones involved.
G. Podgorski, Biol. 1010

21. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Macroevolution
4/26/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
(different habits within an overlapping range)
G. Podgorski, Biol. 1010

22. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Macroevolution
4/26/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species.
G. Podgorski, Biol. 1010

23. Behavioral Isolation Mechanisms
Macroevolution
4/26/2017
Behavioral Isolation Mechanisms
Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species.
G. Podgorski, Biol. 1010

24. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Macroevolution
4/26/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
G. Podgorski, Biol. 1010

25. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Macroevolution
4/26/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
G. Podgorski, Biol. 1010

26. Hybrid Infertility Was the Impetus for Cloning a Mule
Macroevolution
4/26/2017
Hybrid Infertility Was the Impetus for Cloning a Mule
G. Podgorski, Biol. 1010

27. Speciation Occurs at Widely Differing Rates
Macroevolution
4/26/2017
Speciation Occurs at Widely Differing Rates
A slow rate of speciation evidenced by a living horseshoe crab (13 extant species) and a 300 million year-old fossil species
A rapid rate of speciation evidenced by Galapagos finches which have diversified into 13 species within the last 100,000 years.
G. Podgorski, Biol. 1010

28. Macroevolution
4/26/2017
Speciation Rates
Generalists, like the horseshoe crab, tend to remain as stable species.
Specialists, like the Galapagos finch, tend to be unstable as species.
Speciation also becomes rapid when, as occurred with Galapagos finches, new niches become available.
G. Podgorski, Biol. 1010

29. Speciation Dynamics - Gradualism or Punctuated Equilibrium?
Macroevolution
4/26/2017
Speciation Dynamics - Gradualism or Punctuated Equilibrium?
Punctuated equilibrium appears to be a more accurate view of speciation dynamics.
G. Podgorski, Biol. 1010

30. Does Evolution Create the Perfect Organism?
Macroevolution
4/26/2017
Does Evolution Create the Perfect Organism?
No, only better organisms as evolution is constrained by history and buffeted by random events.
Essentially, every organism on earth is in significant part a sum of accidents.
G. Podgorski, Biol. 1010

31. Macroevolution
4/26/2017
G. Podgorski, Biol. 1010

32. Macroevolution
4/26/2017
Species Come and Go
Best estimates from the fossil record indicate that greater than 99% of species that have exited are now extinct.
A typical “lifetime” for a species is about 1 million years.
G. Podgorski, Biol. 1010

33. Mass Extinctions Are a Fact of Life
Macroevolution
4/26/2017
Mass Extinctions Are a Fact of Life
90% of all species that have ever existed are now extinct …
G. Podgorski, Biol. 1010

34. Macroevolution
4/26/2017
Gary Larson
G. Podgorski, Biol. 1010