Chapter 22 Flashcards
List the 5 main characteristics of mammals described in class.
*Mammary glands -> enlarged, modified sweat glands -> produce food for baby (like breast milk)
*Endothems -> internal body temp
*Hair (in most species exception dolphins and whales)
*Viviparous -> live brith with placenta (exception platypus & echidnas)
*Large brain size / body size
What are the three groups of pinnipeds?
Sea Lions and eared fur seals -> otariidae
True earless seals -> phocidae
Walrus -> odobenidae
Who are the three groups of pinnipeds closest relatives?
Ursidae (bears)
List the main functions of blubber.
Insulation, food reserve, buoyancy
How do pinnipeds reproduce?
Males mate with a bunch of females
What is polygamy?
One male mates with many females
What is a harem?
Bunch of females with one dominant male that fought for area
(Not fighting till death but until one scares the other male to leave)
What is a baculum?
Penis bone
Advantage -> don’t get tried, keeps on mating
Disadvantage -> can break
Be able to compare “true seals” (Phocidae) and sea lions (Otariidae).
True Seals
-part of family Phocidae
-no pinnae
-cannot place hind slippers under abdomen
-short neck (hydrodynamic)
-internal testes (hydrodynamic + doesn’t drag on surface when on land)
-propulsion by hind-flippers
Eared Seals & Sea Lions
-part of family Otariidae
-pinnae present (ear flaps)
-hind flippers can be flexed (rotated) under abdomen (hold own weight on land)
-long neck
-scrotum present (testes can descend into it when T is too high) (balls, hold weight = no dragging on land, temperature)
-propulsion by fore-flippers
*males have a bump on top of head
Why are sea otters endangered?
Because of humans hunting them for their fur, they have the thickest fur found
What impact did the reduction of sea otter populations have on the environment?
Sea otters are key stone species meaning that if the number of their species changes so does everything else in that environment.
When sea otters reduce, sea urchins increase, which makes kelp decrease, which effects animals that rely on kelp.
What are the sirenians?
Sirenia means mermaid which manatees and dugongs are apart of
How are the intestines and dentition of sirenians adapted to their diet?
-The intestines of sirenians are very long because they are strictly herbivores and plants are harder to digest which is why they need longer intestines.
-Flat snouts to reach food.
-only molars & premolars present (except dugong); manatees replace teeth throughout their life (from back to front as in elephants).
Compare the dugong and the manatees.
Manatees
-round tail
-short premaxillae (snout)
-only molars present and can be replaced
-absent tusks
-present nails
Dugongs
-truncated (whale-like) tail
-long and pointed downward premaxillae (more range for feeding)
-both molars and premolars present; premolars and a few molars lost in adults & not replaced
-present tusks in males and a few females
-absent nails
What happened to the Steller’s sea cow?
In 1741 there were 1500 of these animals and by 1768 they were extinct.
Reasons of extinction
-human hunting for products: skin (belts, shoes), fat (oil, butter)
-hunting of sea otters by aboriginals -> increase in sea urchins -> decrease in algae -> sea cows restricted to a few islands w/ algae
