1. Mom, Dad… There’s something you need to know… I’m a MAMMAL!
Macroevolution :
How do species arise?
How do we go from species A to Species B?
Mom, Dad…
There’s something you need to know…
I’m a MAMMAL!

2. Tip! Use a simple flow chart to organize your information….
Speciation
Barriers!
Geographic
Pre-zygotic
Post-zygotic
Allopatric
Sympatric
Types A-F
Ex. Hybrids

3. What IS a Species? “Biological species concept”
population whose members can interbreed & produce viable, fertile offspring
reproductively compatible
Distinct species: songs & behaviors are different enough to prevent interbreeding
Humans re so diverse but considered one species, whereas these Meadowlarks look so similar but are considered different species.
Meadowlarks Similar body & colorations, but are distinct biological species because their songs & other behaviors are different enough to prevent interbreeding
Eastern Meadowlark

4. What is the first step to speciation?
END Gene flow between groups!
(reproductive isolation )

5. Once gene flow ends.. Populations can:
Diverge genetically via mutation
Be subject to natural selection pressures
Experience genetic drift

6. 1. Obviously…different types of geographic isolation can occur…
2 different types of isolation can be…
allopatric
geographic separation between groups
sympatric
Group still live in same area

7. There are many other ways to keep groups apart including Reproductive isolating mechanisms
Such mechanisms
Arise as populations move apart (diverge)
They are Heritable aspects of body form
They can be functions of body parts Or Behaviors (that prevent interbreeding among species)

8. There are two types of reproductive isoolating mechanisms
Pre-zygotic isolating mechanisms (prevents successful mating/pollination)
Post-zygotic isolating mechanisms (inability of new individuals to mate successfully)

9. 2. PRE- zygotic (reproduction)
Obstacles to mating or to fertilization if mating occurs
temporal isolation
ecological isolation
geographic isolation
gametic isolation
mechanical isolation
behavioral isolation

10. A. Geographic isolation
Ammospermophilus spp
Most common mode of speciation
physical barrier arises and ends gene flow
We call this: allopatric speciation
(“other country”)
Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel

11. B. Ecological isolation
Species occur in same region, but occupy different habitats (microenvironments) so rarely encounter each other
They are…reproductively isolated
2 species of garter snake, Thamnophis, occur in same area, but one lives in water & other is terrestrial

12. Ex. lions & tigers could hybridize, but they live in different habitats: lions in grasslands tigers in rainforest

13. C. Temporal isolation: timing of reproduction differs
Species that breed during different times of day, different seasons, or different years cannot mix gametes
Another form of reproductive isolation
WE call this: sympatric speciation : new species form within home range of an existing species and in the absence of a physical barrier!
Means: “same country”
Eastern spotted skunk (L) & western spotted skunk (R) overlap in range but eastern mates in late winter & western mates in late summer

14. D. Behavioral isolation
Unique behavioral patterns & rituals isolate species
identifies members of species
attract mates of same species (females of different species are not impressed!)
courtship rituals, mating calls
reproductive isolation
The most comedic species of the Galapagos Islands is the Blue Footed Booby, what a ridiculous outfit and expression! Their name is in fact taken from the Spanish 'bobo' which means clown.
The Blue Footed Boobies above display part of their humorous courtship ritual whereby they raise their feet one at a time and then swivel their heads away from the prospective mate looking to the sky.
Other interesting Booby features are the highly evolved airbag systems in their skulls which allow them to dive bomb into the sea for fish from great height, and the egg and hatchling nesting boundaries they make which are rings of Boobie poop. They aren't the only Booby on the island — there are also Masked and Red Footed Boobies about.
Blue footed boobies mate only after a courtship display unique to their species

15. Recognizing your own species
courtship songs of sympatric species of lacewings
courtship display of Gray-Crowned Cranes, Kenya
firefly courtship displays

16. E. Mechanical isolation
sympatric speciation
Morphological differences can prevent successful mating
Plants
Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. (You have to have the RIGHT pollinator!)
The most comedic species of the Galapagos Islands is the Blue Footed Booby, what a ridiculous outfit and expression! Their name is in fact taken from the Spanish 'bobo' which means clown.
The Blue Footed Boobies above display part of their humorous courtship ritual whereby they raise their feet one at a time and then swivel their heads away from the prospective mate looking to the sky.
Other interesting Booby features are the highly evolved airbag systems in their skulls which allow them to dive bomb into the sea for fish from great height, and the egg and hatchling nesting boundaries they make which are rings of Boobie poop. They aren't the only Booby on the island — there are also Masked and Red Footed Boobies about.

17. For example: Black sage (left) v White Sage (right)
Only smaller bees (honeybees) can pollinate Black Sage; larger bees cannot be supported by smaller flowers
Filaments stick out above petals making it impossible for little honeybees to access anthers: larger bumble bees OK!

18. F. Gametic isolation
sympatric speciation
Sperm of one species (or group) may not be able to fertilize eggs of another species
mechanisms
biochemical barrier so sperm cannot penetrate egg
receptor recognition: lock & key between egg & sperm
chemical incompatibility
sperm cannot survive in female reproductive tract
Ex. Sea urchins release sperm & eggs into surrounding waters where they fuse & form zygotes. Gametes of different species— red & purple sea urchins —are unable to fuse.

19. 3. POST-zygotic barriers (ex. Hybrids)
These will prevent hybrid offspring from developing into a viable, fertile adult
(3 ways)
reduced hybrid viability
reduced hybrid fertility
hybrid breakdown
zebroid

20. A. Reduced hybrid viability
sympatric speciation
Genes of different parent species may interact & impair the hybrid’s development
Or recent divergence of genes cause some missing or some extra genes; incompatible!
Species of salamander genus, Ensatina, may interbreed, but most hybrids do not completely develop; those that do are frail.

21. B. Reduced hybrid fertility
Even if hybrids are vigorous they may be sterile
chromosomes of parents may differ in number or structure & meiosis in hybrids may fail to produce normal gametes
Mules are vigorous, but sterile
What’s wrong with having 63 chromosomes?
Odd number! Cannot pair up in meiosis.
Horses have 64 chromosomes
(32 pairs)
Donkeys have 62 chromosomes
(31 pairs)
Mules have 63 chromosomes!

22. C. Hybrid breakdown
sympatric speciation
Hybrids may be fertile & viable in first generation, but when they mate offspring are feeble or sterile
In strains of cultivated rice, hybrids are vigorous but plants in next generation are small & sterile.
On path to separate species.

23. How Fast can we go from Species A to Species B?

24. Current debate: Does speciation happen gradually or rapidly
Phyletic Gradualism
Charles Darwin
Charles Lyell
Punctuated equilibrium
Stephen Jay Gould
Niles Eldredge
Niles Eldredge
Curator
American Museum of Natural History

25. Stephen Jay Gould ( )
Harvard paleontologist & evolutionary biologist
punctuated equilibrium
prolific author
popularized evolutionary thought
Stephen Jay Gould (September 10, 1941 – May 20, 2002) was a New York-born American paleontologist, evolutionary biologist, and historian of science. He was the most influential and widely read writer of popular science of his generation. He served as a member of the faculty at Harvard University beginning in Toward the end of his life he served as the Alexander Agassiz Professor of Zoology at that university. He helped Niles Eldredge develop Eldredge's theory of punctuated equilibrium 1972, wherein evolutionary change occurs relatively rapidly in comparatively brief periods of environmental stress, separated by longer periods of evolutionary stability. According to Gould, this overthrew a key tenet of neo-Darwinism; according to most evolutionary biologists, the theory was an important insight but merely modified neo-Darwinism in a way fully compatible with what had been known before. Gould became widely known through his popular science essays in Natural History magazine, collections of essays like The Panda's Thumb and The Flamingo's Smile, and extended studies like Wonderful Life and others.Gould was an emphatic advocate of evolution and wrote prolifically on the subject, trying to communicate his understanding of contemporary evolutionary theory to a wide audience. A recurring theme in his writings is the history and development of evolutionary (and pre-evolutionary) thinking. His early research involved the study of the fossil record of snails (detailed in one of his essays). He was also an enthusiastic baseball fan and made frequent references to the sport (including an entire essay) and a very wide range of other topics.

27. Phyletic Gradualism – Darwin and Lyelle
Gradual divergence over long spans of time
Species stay stable for long periods of time
assume that big changes occur as the accumulation of many small ones

28. Punctuated Equilibrium – Gould/Eldridge
Rate of speciation is not constant
rapid bursts of change
long periods of little or no change between
Occurs with drastic change in environments
Time

29. Is Evolution goal-oriented? No!
An evolutionary trend does not mean that evolution is goal-oriented.
Surviving species do not represent the peak of perfection. There is compromise & random chance involved as well
Remember that for humans as well!
Evolution is not the survival of the fittest. Rather it is the survival of the just good enough.

30. View Mr. Anderson’s “Speciation and Extinction”

31. Any Questions??