Speciation NICE.ppt
- 1. AP Biology Mom, Dad… There’s something you need to know… I’m a MAMMAL! WHAT IS SPECIATION?
- 2. AP Biology So…what is a species? defined by Ernst Mayr (Evolutionary Biologist) A population whose members can interbreed & produce viable, fertile offspring Being reproductively compatible is a key component Western Meadowlark Sturnella magna Eastern Meadowlark Sturnella neglecta Distinct species: songs & behaviors are different enough to prevent interbreeding
- 3. AP Biology How and why do new species originate? New species are formed by a series of evolutionary processes which cause reproductive isolation. Reproductive Isolating Mechanisms Pre-zygotic barriers are various forms of isolation Post-zygotic barriers are generally related to fertility & viability of offspring
- 4. AP Biology This means there is an obstacle to mating or to fertilization if mating occurs PRE-Reproduction (pre-zygotic) Barriers behavioral isolation geographic isolation ecological isolation temporal isolation mechanical isolation gametic isolation
- 5. AP Biology 1. Geographic isolation New species occur in different areas physical barrier separated ancestor species 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 Ammospermophilus spp
- 6. AP Biology 2. Ecological isolation Species occur in same region, but occupy different habitats so they rarely encounter each other 2 species of garter snake, Thamnophis, occur in same area, but one lives in water & other is terrestrial lions & tigers could hybridize, but they live in different habitats: lions in grasslands tigers in rainforest
- 7. AP Biology 3. Temporal “time” isolation Species that breed during different times of day, different seasons, or different years cannot mix gametes. Eastern spotted skunk (L) & Western spotted skunk (R) overlap in range but eastern mates in late winter & western mates in late summer
- 8. AP Biology 4. Behavioral isolation Unique behavioral patterns & rituals isolate species identifies members of species attract mates of same species courtship rituals, mating calls Blue footed boobies mate only after a courtship display unique to their species That’s hot…
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- 10. AP Biology firefly courtship displays courtship display of Gray-Crowned Cranes, Kenya courtship songs of species of lacewings (that live in the same area) Recognizing your own species
- 11. AP Biology 5. Mechanical isolation Morphological differences can prevent successful mating Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. These 2 species of monkey flower differ greatly in shape & color, therefore cross-pollination does not happen. Plants
- 12. AP Biology Mechanical isolation For many insects, male & female sex organs of closely related species do not fit together, preventing sperm transfer lack of “fit” between sexual organs: hard to imagine for us… but a big issue for insects with different shaped genitals! Damsel fly penises Animals Get that thing away from me!
- 13. AP Biology 6. Gametic isolation Sperm of one species may not be able to fertilize eggs of another species biochemical barrier: sperm cannot penetrate egg receptor recognition: lock & key between egg & sperm chemical incompatibility sperm cannot survive in female reproductive tract Sea urchins release sperm & eggs into surrounding waters where they fuse & form zygotes. Gametes of different species are unable to fuse.
- 14. AP Biology POST-Reproduction (Post-Zygotic) Barriers Prevent hybrid offspring from developing into a viable, fertile adult
- 15. AP Biology Post Zygotic: Reduced hybrid viability Genes of different parent species may interact & impair the hybrid’s development Species of salamander genus, Ensatina, may interbreed, but most hybrids do not complete development & those that do are frail.
- 16. AP Biology Mules are vigorous, but sterile Post Zygotic: 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 Donkeys have 62 chromosomes (31 pairs) Horses have 64 chromosomes (32 pairs) Mules have 63 chromosomes!
- 17. AP Biology Post Zygotic: Hybrid breakdown 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.
- 18. AP Biology Rate of Speciation Current debate: Does speciation happen gradually or rapidly? Or both? Gradualism Punctuated equilibrium
- 19. AP Biology Gradualism Gradual divergence over long spans of time assume that big changes occur as the accumulation of many small ones
- 20. AP Biology Punctuated Equilibrium Rate of speciation is not constant rapid bursts of change long periods of little or no change species undergo rapid change when they 1st bud from parent population Time
- 21. AP Biology Modes of Speciation: Allopatric Speciation A physical barrier arises and prevents gene flow between populations Reproductive isolating mechanisms evolve in the genetically diverging populations Speciation occurs when the members of the divergent populations no longer interbreed
- 22. AP Biology Modes of Speciation: Sympatric Speciation A new species may form within the home range of an existing species (there is no physical barrier) May be: Temporal Mechanical Behavioral
- 23. AP Biology Modes of Speciation: Parapatric Speciation Daughter species form a small proportion of individuals along a common border between 2 populations. Hybrid Zone is formed BULLOCK’S ORIOLE BALTIMORE ORIOLE HYBRID ZONE Figure 18.10
- 24. AP Biology The two types of plants are close enough that tolerant and non-tolerant individuals could potentially fertilize each other—so they seem to meet the first requirement of parapatric speciation, that of a continuous population. However, the two types of plants have evolved different flowering times. This change could be the first step in cutting off gene flow entirely between the two groups
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- 27. AP Biology EVALUATION (1/8 sheet of paper) Directions: Choose the letter of the best answer from each given item.
- 28. AP Biology Test I. Multiple Choice
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- 34. AP Biology Test II. Identification
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- 39. AP Biology 4. A type of isolation which potential mates occupy different areas or habitats thus, they never come in contact .
- 40. AP Biology 5. A type of isolation where there are differences in reproductive organs prevent successful interbreeding .
- 41. AP Biology 6. A part of post-zygotic isolation where hybrids are sterile because gonads develop abnormally or there is abnormal segregation of chromosomes during meiosis.
- 42. AP Biology 7. It a mode of speciation that occurs when members of a population that initially occupy the same habitat within the same range diverge into two or more different species. It involves abrupt genetic changes that quickly lead to the reproductive isolation of a group of individuals.
- 43. AP Biology 8. A mode of speciation that occurs when the groups that evolved to be separate species are geographic neighbors. Gene flow occurs but with great distances is reduced. There is also abrupt change in the environment over a geographic border and strong disruptive selection must also happen.
- 44. AP Biology 9. occurs when some members of a population become geographically separated from the other members thereby preventing gene flow. Examples of geographic barriers are bodies of water and mountain ranges.
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- 61. AP Biology Group Activity Directions: The class is subdivided into eight (8) groups. Each group must have six (6) members. Gather as many bills and coins in your group and identify organisms present in the bills/coins.
- 62. AP Biology Identify the name of the organisms found and write the correct scientific name by following the guidelines.
- 63. AP Biology Bills/Coins Local Name Scientific Name Example: Human Homo sapiens
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Editor's Notes
- #3: Humans are 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
- #9: 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.
- #12: 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.
- #13: The selection is intense because it directly affects offspring production -- it is affecting sex itself
- #17: What’s wrong with having 63 chromosomes? Odd number! Cannot pair up in meiosis.