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Bi 1 Lecture 29 Thursday, June 2, 2005 Evolution 3. Voyages to the Galapagos; The physiology of Diving Mammals

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“Study nature, not books” (Louis Agassiz) . Bi 1 Lecture 29 Thursday, June 2, 2005 Evolution 3. Voyages to the Galapagos; The physiology of Diving Mammals. Announcements on the Bi 1 Web page: http://www.its.caltech.edu/~bi1/schedule.html.

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slide1

“Study nature, not books” (Louis Agassiz)

Bi 1 Lecture 29

Thursday, June 2, 2005

Evolution 3. Voyages to the Galapagos;

The physiology of Diving Mammals

slide2

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

slide3

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

slide4

The Voyage of the HMS Beagle 1831-1836

Charles Darwin (born 1809), unpaid naturalist

Azores

Cape Verde Islands

Canary Isles

Cocos Islands

Tahiti

Bahia

Rio de

Janeiro

King George

Sound

Cape of Good Hope

Galapagos

Islands

35 day visit

Valparaiso

Montevideo

Tasmania

New

Zealand

Falkland Islands

journey out

journey home

Cape Horn

slide5

Equator

Punta Espinoza

Age of the archipelago:

~ 1 million yr

British Admiralty chart of the Galapagos Islands, based on the Beagle’s observations

darwin s finches 5 genera including geospizia

13 Species, each endemic to the islands

  • El Nino poses a survival challenge
  • Highly specialized beaks
  • Observable evolution in beak size
  • Distinctive feeding habits
Darwin’s Finches(5 genera, including Geospizia)

cactus finch

ground finch

tree finch

slide7

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)

slide8

"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

slide10

Finch family tree based on a 660-nt sequence

Molecular Biology and Evolution 18:299-311 (2001)

Darwin’s

Galapagos finches

.01 change per position

slide11

Red-Footed Booby

(Ben Lester)

Blue-Footed Booby

slide12

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.

slide13

Male Frigate Bird Displaying

no oil on feathers

cannot land on water

steals other birds’ fish

slide16

photo by

Ben Lester

Female Albatross on the nest

slide17

photo by

Ben Lester

slide18

The Galapagos tortoises reach sexual maturity at the age of 40

and have clutches of 2 - 26 eggs.

Eggs hatch at 85 -180 d.

slide19

Galapagos Penguins

World’s Northernmost population of penguins.

After "El Nino" in 1983 the population decreased from 12,000 to just 2,000 birds.

slide21

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.

slide22

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.

slide23

The fight against salt at Punta Espinoza:

marine iguanas

cormorants

sea lions

Marine Iguana

slide25

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)

slide33

Sally Lightfoot crab

Resembles black crab of Hawaii’s Big Island

slide35

Pinnacle Rock on Bartolome:

Excellent diving, lots of marine life

slide37

Emperor penguins

Aptenodytesforsteri

550 m

22 min

typical: 2-10 min, 50-500 m

slide38

Elephant seal

Mirounga leonina

1600 m

120 min

typical: 20-30 min, 200-800 m

slide39

Weddell seal

Leptonychotes weddellii

> 600 m

82 min

slide40

Bottlenose dolphin

Tursiops truncutus

210 m

5 min

typical 30 m, 120 s

slide41

Blue whale

Balaenoptera musculus

300 m

50 min

slide42

Sperm whale

Physeter macrocephalus

3000 m

90 min

slide43

In metabolism, electrons move around inside cells until they reach oxygen,

which has the highest electron affinity of the biological elements

Little Alberts 2-7

© Garland

slide44

Emperor penguin

Baikal seal

Weddell seal

In the absence of oxygen,

glucose ®

pyruvate and lactic acid.

~ 2 moles of ADP are converted to ATP.

In the presence of oxygen,

glucose + O2® H20 + CO2.

~ 24 moles of ADP are converted to ATP

enzymes and carriers transfer 40% of the bond energy to high-energy phosphate bonds, in small steps.

Diving mammals must store oxygen in order to conduct aerobic metabolism

slide45

two oxygen-carrying heme proteins

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.

slide46

two oxygen-carrying heme proteins

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.

slide47

Crittercam (UC Santa Cruz)

35 cm

batteries

and

computer

detachable

CCD

camera

8 mm

tape recorder

lens

float

transmitter

Ti or Al

housing

900 nm LEDs

fins

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.

slide51

Pressure effects on air gases

10 m = 1 bar

Sport diving is limited to ~ 40 m

1. The bends: N2 bubbles form in the blood

2. Nitrogen narcosis

3. Oxygen toxicity

tanks 200 bar
Tanks200 bar

Regulators

slide53

Some compressed air remains in the windpipes, but a collagen lining prevents absorption by the blood

complete peripheral collapse

at 20-50 m

Diving mammals don’t get the bends: adaptations to pressure

“Lungs are a liability for deep divers because, in contrast tomuscle and blood, they are a better nitrogen storethan oxygen store.”

a. flexible chest;

b. no collagen in the smallest branches

“The early occurrence of lung collapse in sealsmakes the lung almost useless as an O2 store, whereas it limitsN2 absorption during the dive.”

slide54

Other effects of water’s high density

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

slide55

apparent

object

q’

q’

q

q

2. Objects look larger to a diver (Phys 2a)

real

object

water

n’ ~ 1.3

air in mask

n = 1

nsinq = n’sinq’

slide56

Sound travels

3-4 times faster in water

3. A diver cannot judge sound direction

delay between the two ears

~ 7 sin q ms

(can be determined

to within ~ 10 ms)

q

20 cm

0.2 m/(300 m/s)

~ 7 ms

slide57

4. Objects look blue to a diver

a few m of water absorbs

long wavelengths

shorter wavelengths

penetrate further

slide58

A Summary of Adaptations in Diving Mammals

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

slide59

Darwin, The Voyage of the Beagle

Darwin, The 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

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