1. Evolution and Speciation

2. Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primate Family: Hominidae Genus: Homo Species: sapiens Varieties and Breeds Classification System

3. What is a species? Its not as straightforward a question as most believe. Evolution creates new species, but … These are members of different species - eastern (left) and western (right) meadowlark. Defining Species

4. What is a Species? There is only one extant (existing) human species.

5. What is a Species? And these are all members of a single species.

6. Determining What Is and What Isn’t a Distinct Species Can Be Difficult Northern spotted owl (left) and barred owl (right).

7. What is a Species? Lets start with the most widely accepted definition: 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 a problem.

8. Hybrid Infertility Horse X Donkey = Mule Cannot Reproduce and produce Fertile offspring.

9. So a better definition of a species might be: A group of individuals capable of interbreeding to produce offspring that are fertile and these offspring, in turn, can produce offspring that are fertile.

11. Another problem with the Biological Species Concept For asexually-reproducing organisms, like these bacteria, what constitutes a species?

12. 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 10-15 million being a more commonly considered upper estimate).

13. Two Patterns of Speciation One species completely replacing another One species evolving from another with both then existing at same time

14. How Do New Species Arise? The key to speciation is reproductive isolation of populations **It is reproduction that makes more organisms…so mess with reproductive success and you mess with population!.

15. What does it mean to have reproductive isolation? It means that for whatever reason, one or more organisms are prevented from being able to reproduce with others in the population of that species. 1. Organism itself changes because of random mutation(s) 2.Environment changes, causing separation of population into two or more subgroups of the original population.

16. Intrinsic Reproductive Isolating Mechanisms Something changes about the organisms in the population that interferes with reproductive success but is not caused by geographic isolation! Maybe something about mating ritual Maybe something about sperm or egg Maybe something about time of year they mate Etc.

17. Extrinsic Reproductive Isolating Mechanisms Something happens to the ENVIRONMENT of the organism which interferes with reproductive success.

18. Reproductive Isolation May Occur With or Without Geographic Isolation Allopatric speciation occurs when geographic isolation creates a situation where reproduction can’t occur (an extrinsic mechanism). Sympatric speciation occurs when reproduction is not inhibited by geographic isolation but something about the individual organisms of the population changes and interferes with reproductive capability. (an intrinsic mechanism)

19. Allopatric Speciation: A change in the environment Two species of ground squirrel are believed to have descended from a common ancestral population that was separated by formation of the Grand Canyon. Harris’ antelope squirrel White-tailed antelope squirrel

20. Intrinsic Reproductive Isolating Mechanisms Are Always Required for Speciation…Even when allopatric speciation has already occurred. Intrinsic mechanisms involve changes to the 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. Harris’ antelope squirrel White-tailed antelope squirrel

21. Intrinsic Isolating Mechanisms (different habits within an overlapping range)

22. Courtship rituals, are critical for mating within a species, but ineffective for attracting members of other species. Intrinsic Isolating Mechanisms Continued:

23. Mating RitualBlue-footed Booby Mating Ritual Fiddler Crab Male Waving

24. Intrinsic Isolating Mechanisms Continued

25. Salamander Evolution Subspecies evolving At different Locations in California… ALL ARE SAME SPECIES

26. Speciation Occurs at Widely Differing Rates A slow rate of speciation is seen with a living horseshoe crab which has diversified into 13 species within the last 300 million years. A rapid rate of speciation is seen in Galapagos finches which have diversified into 13 species within the last 100,000 years.

28. What else, other than isolating Mechanisms, can contribute to the formation of new species?

29. Sometimes simply CHANCE EVENTS can contribute to speciation! Genetic Drift any change in the allelic frequency in a population that is due chance events (floods, insects getting sprayed with insecticides, earthquakes, fires, etc) Allelic frequency: a measure of how common an allele is in a population Especially true in small populations because the chance of losing an allele completely becomes greater!

30. Type of Genetic Drift Founder Effect: when a small population colonizes a new habitat (separate from the rest of that population) and interbreeds. Alleles that were once fairly uncommon in a population now may be more common because this subset of the population is so small. Amish population: Dwarfism, Polydactyly

31. Migration may contribute to speciation as well! Transports genes to different gene pools if they mate while they are migrating. b/c their genes are isolated from their original population and the alleles enter a different gene pool.

32. Speciation Rates Generalists (eat many different foods, well-adapted to many different habitats) like the horseshoe crab, tend to remain as stable species. Specialists (eat more specific foods and only adapted to live in certain habitat), like the Galapagos finch, tend to be unstable as a species and More likely to change! Speciation also becomes rapid when, new niches become available to the organisms, as seen with Galapagos islands.

33. Formation of New Species- Gradualism or Punctuated Equilibrium? Punctuated Equilibrium Gradualism

34. Does Evolution Create the Perfect Organism? No, only organisms which are better suited to survive and reproduce in that environment at that time!

35. Scenario Groups:

36. Species Come and Go Best estimates from the fossil record indicate that greater than 99% of species that have existed are now extinct. A typical “lifetime” for a species is about 1 million years.

37. Mass Extinctions Are a Fact of Life

38. Gary Larson The Cretaceous/Tertiary Mass Extinction 65.5 mya Asteroid Impact Theory 85% of all species died

39. Are We Now Causing a Mass Extinction?

40. Are humans causing the 6 th mass extinction? Humans and Extinction Mass Extinction Current Mass Extinction