1. Lec 7: Rhythms

• HW2

• In-class review and discussion of HW2

• Handout Guidelines for answering short answer questions

• Lecture clarification sympatric speciation, character displacement

Circadian Rhythms

2. Animal Behavior, Lec. 6, BIOL 4518 Sympatric speciation

Create a species - >

• How? restrict gene flow

• Who? Among members of thesamepopulation

3. Sympatric Speciation

• Sympatric speciation is a theory

• • Does this happen in nature?

• • Why is it controversial?

• • Is instantaneous or gradual more likely to be a mechanism used?

4. Sympatric speciation

Mechanisms for restricting gene flow in a population

• Polyploidy

• • How does this work?

• • Is behavioral isolation involved?

5. Reproductive character displacement

2 Components

• Female discrimination

• • females are choosy!

• • Females choose among variation in male traits

• • Receiver preference function

• Male character divergence

• • Over time key traits in males become more and more different

• • Bimodal distribution

6. Reproductive character displacement

How would it work?

What is reinforcement?

• Is low hybrid fitness required?

How do hybrid offspring have low fitness?

7. Reproductive character displacement

Evidence supporting this theory

• Polyploid frogs

• • Character:

• • Female discrimination:

• • Cause of low hybrid fitness:

8. Reproductive character displacement

Evidence supporting this theory

• Polyploid frogs

• • Character: vocalization

• • Value which females discriminate: frequency of pulses

• • Cause of low hybrid fitness: 3N are not viable

• Song bird

9. Summary Reproductive Character Displacement and Sympatric Speciation

Sympatric

• restrict gene flow within a pop.

• Low hybrid fitness

Mechanisms

• Instantaneous: Polyploidy

• Gradual: Female discrimination and male character divergence

Why controversial?

10. Geomagnetism: Earth's Magnetic Field Gary A. Glatzmaier 11. Geomagnetism: Earth's Magnetic Field Gary A. Glatzmaier

Why does the Earth have a magnetic field

How is it generated?

• Poorly understood

• Hypothesis:

• • Iron-rich magma in the earth's crust rises with heat and sinks with cooling generating the field

12. Geomagnetism: Earth's Geomagnetism: Earth's Magnetic Field: Animal navigation

Is it changing?

• Yes!

• Polarity changes

• • North and South magnetic poles reverse

• • Evidence in tectonic plates on sea floor that preserve the polarity as the new magma cools

• Field strengthens and weakens

• • • the dipole moment will decay in about 1,300 years.

How often does the magnetic field reverse?

• During the past 100 million years, the reversal rates vary (5 thousand years to 50 million years).

• Last reversed 750,000 - 780,000 years ago.

13. Geomagnetism: Pigeon navigation

Pigeons navigate in overcast skies

Suggest they are using magnetic field

14. Geomagnetism: Pigeon navigation

Pigeons navigate in overcast skies

Suggest they are using magnetic field

Evidence?

15. Geomagnetism: Pigeon navigation

Pigeons navigate in overcast skies

Suggest they are using magnetic field

16. Geomagnetism: Pigeon navigation

Pigeons navigate in overcast skies

Suggest they are using magnetic field

17. Electromagnetic Fields: Animals

In addition to the use of the geomagnetic field for navigation,

Some animals generate their own electric field for example for prey detection

18. Summary Geomagnetism, Electromagnetic fields

Geomagnetism

Electromagnetic fields generated by animals

19. Time circadian rhythm

Clock is affected by environmental cues

Clock is not affected by environmental cues

Evidence:

Conclusion somewhere in the middle; free-running cycle updated with some environmental cues

20. Organization of clocks and behavior

Chemical clock

Clock located in central place

Receives input and adjusts

Sends signals to other behaviors

21. Organization of clocks and behavior

Chemical clock

• perPER,tauCKl e

Clock located in central place

• Hypothalamus

• • Suprachiasmic nucleus (SCN)

Receives input and adjusts

• e.g., light on retina

Sends signals to other behaviors

• PK2

22. How is a clock made

Endogenous

Pacemaker, master clock

Free-running cycle

Gene product feedback

23. How is a clock made 24. Cycles/Rhythms

Single cycles

• Daily

• Lunar

• Tidal

• Seasonal

• Annual

• Multiple years

Combinations of cycles

25. Cycles/Rhythms 26. Circadian cycles

Absence of cues

• Human sleep patterns

27. Lunar Cycles

Lunar cycles

28. Lunar cycles - cues

Hydrostatic pressure

Temperature

Salinity

Turbulence

Vibrations

Immersion

29. Lunar Cycles - tides 30. Tidal cycles

Intertidal pools of various heights

Protists

Encysted (18hr) and free swimming (6hr)

Cycle remain in pools during flooding

Encyst for 2 high tides and one low tide

Faster rhythms and change in phase and duration on lower tide pools

31. Which cycle is the cue?

Intertidal brown shrimp live in pools created at high tide

They are exposed to both diurnal and tidal cycles

What are cue are they using?

32. Which cycle is the cue? 33. Which cycle is the cue? 34. Which cycle is the cue? 35. Which cycle is the cue? 36. Seasonal Cycles

Hibernation without external cues

37. Multiple Years

Cicadas

Only in North America

Spend most of life in ground in larval stages

Emerge every 13 or 17 years

Co-occur every 221 years!

Emerge within a few days of each other

Several species identified

38. Multiple Years

Can sympatric speciation occur by temporal displacement?

• Why would this be controversial, given what we have been discussing?

What would you expect to observe if sympatric speciation occurred?

39. Multiple Years 40. Multiple Years

Character divergence

41. Multiple Years 42. Multiple Years

Suggests single gene change speciation event

43. Summary on cicadas

Sympatric speciation through timing?

Character divergence

44. Combinations of cycles

Ocean

• Tidal cycles

45. Relative vs. absolute time 46. Clock shifts

Clock shifted pigeons change

47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64.