Presentation on theme: "1 Bi 1 Lecture 29 Thursday, June 2, 2005 Evolution 3. Voyages to the Galapagos; The physiology of Diving Mammals “Study nature, not books” (Louis Agassiz)"— Presentation transcript:
1 Bi 1 Lecture 29 Thursday, June 2, 2005 Evolution 3. Voyages to the Galapagos; The physiology of Diving Mammals “Study nature, not books” (Louis Agassiz)
2 Announcements on the Bi 1 Web page: http://www.its.caltech.edu/~bi1/schedule.html Review Session takes place here, today, here, 4 - 6 PM. Sections meet as usual today and tomorrow. The final exam is posted Thursday (today) 6 PM; Due Fri 6/10 4:30PM in the Bi 1 Closet Graduating seniors: papers are due today 5 PM in the Bi 1 Closet
3 Acknowledgements “It takes a village to teach Bi 1 at Caltech” TAs, both grads and undergrads Professional staff: Dr. Jane Mendel, Head TA: Sections and grading Patricia Mindorff, communications David Mathog, Molecular Graphics Eric Slimko, Webmaster Biology Electronics shop computer support: Mike Walsh and Pam Fong Guest lecturers: Robert Freedman David Anderson Cameo appearances from Biology Faculty Advice from other Core Curriculum Resources You, the students
4 Galapagos Islands 35 day visit Azores Cape Verde Islands Bahia Rio de Janeiro Montevideo Falkland Islands Valparaiso Canary Isles Cape Horn Cocos Islands New Zealand The Voyage of the HMS Beagle 1831-1836 Charles Darwin (born 1809), unpaid naturalist journey out journey home Cape of Good Hope King George Sound Tasmania Tahiti
5 British Admiralty chart of the Galapagos Islands, based on the Beagle’s observations Punta Espinoza Age of the archipelago: ~ 1 million yr Equator
6 Darwin’s Finches (5 genera, including Geospizia) cactus finch tree finch ground finch 13 Species, each endemic to the islands El Nino poses a survival challenge Highly specialized beaks Observable evolution in beak size Distinctive feeding habits
7 The voyage of the Beagle convinced Darwin that 1.Members of the same species often change slightly in appearance after becoming geographically isolated from each other 2.Organisms living on oceanic islands often resemble organisms found living on a close mainland 3.Factors other than or in addition to climate play a role in the development of plant and animal diversity 4.Organisms of the past and present are related to one another (but there are no fossils in the Galapagos)
8 "The distribution of the tenants of this archipelago would not be nearly so wonderful, if, for instance, one island had a mocking-thrush, and a second island some other quite distinct genus.... But it is the circumstance, that several of the islands possess their own species of tortoise, mocking- thrush, finches and numerous plants, these species having the same general habits, occupying analogous situations, and obviously filling the same place in the natural economy of this archipelago, that strikes me with wonder...." Darwin, The Voyage of the Beagle http://www.literature.org/authors/darwin-charles/the-voyage-of-the-beagle/chapter-17.html
12 Masked booby A recently discovered a behavior, called siblicide, occurs among booby chicks. The larger chick always kills the younger chick, sometimes aided by the parents. Scholars debate the selective advantage of such behavior. Perhaps the parents succeed better by insuring the survival of at least one chick.
13 Male Frigate Bird Displaying no oil on feathers cannot land on water steals other birds’ fish
14 Galapagos Waved Albatrosses in Courtship 2 m wingspan
15 Video of Galapagos Waved Albatrosses in Courtship
16 photo by Ben Lester Female Albatross on the nest
21 Marine Iguana feeding Marine iguanas feed once a day. The mature lizards swim out through the tidepools to dive to the bottom for algae; smaller iguanas feed off the rocks in the tidal zone. An iguana may lose up to 10 degrees C of body temperature on these feeding missions. Because they are cold-blooded ("ectothermic"), iguanas must bask on the hot lava rocks throughout the day until they raise their internal temperature.
22 The increased rainfall that accompanies El Niño results in greater food availability for most terrestrial organisms in the Galápagos, but marine life generally suffers from the higher water temperature, which decreases the amount of dissolved oxygen. Green and red algal species, which are the marine iguanas' preferred food, disappear and are replaced in intertidal areas by brown algae which iguanas find hard to digest. Up to 90% of marine iguana populations on islands can die of starvation as a result of these environmental changes. During a recent El Niño event (1997–98), larger individuals of the two island populations shrank more than smaller individuals. The scale of the shrinkage — up to 20% of body length — means that it cannot simply be explained by decreases in cartilage and connective tissue, which together make up only 10% of total body length. Apparently bone absorption accounts for much of the reduction.
23 Marine Iguana The fight against salt at Punta Espinoza: marine iguanas cormorants sea lions
25 Flightless Cormorant drying its feathers at Punta Espinoza large flightless birds are common on islands, e.g. kiwi (New Zealand) extinct: Great auk (north Atlantic), dodo (Mauritius), solitaire (Reunion, Rodrigues), moa (New Zealand)
44 Emperor penguin Baikal seal Weddell seal In the presence of oxygen, glucose + O 2 H 2 0 + CO 2. ~ 24 moles of ADP are converted to ATP In the absence of oxygen, glucose pyruvate and lactic acid. ~ 2 moles of ADP are converted to ATP. Diving mammals must store oxygen in order to conduct aerobic metabolism enzymes and carriers transfer 40% of the bond energy to high-energy phosphate bonds, in small steps.
45 Diving mammals have much higher: blood volume hemoglobin concentration and especially myoglobin than other mammals. More than 80% of the oxygen is in the blood and muscle. two oxygen-carrying heme proteins
46 Diving mammals have much higher: blood volume hemoglobin concentration and especially myoglobin than other mammals. More than 80% of the oxygen is in the blood and muscle. two oxygen-carrying heme proteins
47 lens detachable CCD camera 8 mm tape recorder Ti or Al housing batteries and computer fins float transmitter 35 cm 900 nm LEDs Audio channels (1) accelerometer (2) microphone Transducers for pressure, water speed, and compass bearing are sampled once per second, and the data are stored on a PCMCIA card. A separate housing (17 cm long and 5.5 cm in diameter) for the gimbaled flux-gate compass is positioned behind the main housing and connected to it with a cable. Crittercam (UC Santa Cruz)
53 “Lungs are a liability for deep divers because, in contrast to muscle and blood, they are a better nitrogen store than oxygen store.” Some compressed air remains in the windpipes, but a collagen lining prevents absorption by the blood “The early occurrence of lung collapse in seals makes the lung almost useless as an O 2 store, whereas it limits N 2 absorption during the dive.” a. flexible chest; b. no collagen in the smallest branches complete peripheral collapse at 20-50 m Diving mammals don’t get the bends: adaptations to pressure
54 1.Heat capacity and heat conduction Diving mammals solve this problem with blubber. Scuba divers use exposure suits (wet suit, dry suit). Both of these materials compress at depth, increasing the animal’s density and providing negative buoyancy. 2.Greater index of refraction 3.Greater speed of sound 4.Greater light absorption Other effects of water’s high density
55 ’’ air in mask n = 1 water n’ ~ 1.3 ’’ nsin = n’sin ’ real object apparent object 2. Objects look larger to a diver (Phys 2a)
56 3. A diver cannot judge sound direction 20 cm 0.2 m/(300 m/s) ~ 7 ms delay between the two ears ~ 7 sin ms (can be determined to within ~ 10 s) Sound travels 3-4 times faster in water
57 a few m of water absorbs long wavelengths shorter wavelengths penetrate further 4. Objects look blue to a diver
58 1. Compressible lungs: decrease buoyancy, decrease bends 2. High myoglobin concentration 3. Blubber 4. “Intermittent locomotion” = gliding 6. Decreased heart rate decreases heat flow 5. Wave riding and jumping 6. Countercurrent cooling devices for testes A Summary of Adaptations in Diving Mammals
59 Darwin, The Voyage of the BeagleThe Voyage of the Beagle Darwin, The Origin of SpeciesThe Origin of Species Michael Jackson, Galapagos, University of Calgary Press, 1994 Jonathan Weiner, The Beak of the Finch: a Story of Evolution in our Time, Knopf, 1995