Lecture 24 - Water Mammals Flashcards
What are some of the major adaptations made by tetrapods to adapt to life on land?
ability to walk breathing air amniotic egg/live birth different thermoregulation hearing airborne sounds
What are the problems with returning to the water for tetrapods?
- Buoyancy
- Slow and inefficient
- Can’t breathe
- Lose heat faster
- Won’t be able to smell, see, or hear
- Can’t eat without swallowing sea water
- Pressure (the bends)
How many different times have marine tetrapods colonised the ocean?
30 times throughout history
How is a terrestrial vertebrates Buoyancy a problem underwater?
They are too buoyant
How do dugongs and other marine mammals overcome the issue of being to buoyant?
Dense bones
What advantage does returning to the water bring?
taking advantage of open niches(usually the lack of large species)
How did marine tetrapods make themselves faster and more efficient underwater?
evolution of Hydrodynamic forms. Includes streamlined bodies, flippers rather than hands or wings and the loss or reduction of hindlimbs
How do marine tetrapods prevent heat loss?
Insulating fur, feathers, blubber and Counter-current heat exchange
What are the groups of marine mammals?
Cetaceans
- Mysticetes: Baleen whales
- Odontocetes: Toothed Whales
Pinnipeds
- Phocids: True seals
- Otariids: Fur seals and sea lions
- Odobenids: WalrusesWhat order are Cetaceans from?
Artiodactyl: Even-toed ungulates
What are Archaeocetes?
Ancient whales
What order are Pinnipeds from?
Carnivora
Can whales smell?
No, the mammalian sense of smell does not work underwater so whales have lost it.
When Transitioning to Life in Water, What Features did Marine Mammals Initially Evolve?
- Initially evolved larger eyes.
- Eye size (and orbit) now varies
- Relied more on their sense of touch (e.g. - whales use sensory organ on their jaw, seals use undulating whiskers to detect fine movement in water)
Why do Marine Mammals Need to Hear in Water?
Ideally to communicate with others (e.g. - mating, finding other members of same species) and to locate prey (hunting).
How do Terrestrial Mammals Hear in the Air?
- Air-filled passages and chambers
- Ear drum only vibrates in response to sound travelling through air.
What is the Direction of Travel of Sound Energy for Terrestrial Mammals?
Ear canal > ear drum > middle ear bones > oval window > inner ear (cochlea) > round window
How do Marine Mammals Hear Underwater?
- Whales hear via fat pads in their mandibles
- Toothed whales use echolocation (clicking sounds via blowhole and picked up by fat pads)
- Pinnipeds can hear in air and underwater through the use of a tissue called the cavernous sinus lines (fill with blood when seals dive to match density of water).
What are Some Issues Marine Mammals Face When Hunting Prey?
- Modified senses to detect prey
- Hydrodynamic body forms to catch up to prey
- Altered anatomy and physiology to hold breath (e.g. - extra haemoglobin and collapsed lungs)
- How would they eat their prey once caught?
What are the Six Feeding Strategies for Aquatic Mammals?
- Terrestrial feeding
- Semi-aquatic feeding
- Aquatic “raptorial” feeding
- Suction feeding
- Suction filter feeding
- Ram filter feeding
Explain the Process of Terrestrial Feeding:
- Capture prey using teeth and claws
- Consume prey on land (in air)
- Often using sharp cutting teeth
Explain the Process of Semi-Aquatic Feeding:
- Prey is separated from seawater
- Can still breathe
- Can break apart (process) prey
Explain the Process of Aquatic “Raptorial” Feeding:
- Swim until prey is in jaws (ram)
- Snap mouth shut, trapping prey between teeth
- Swallow prey whole
Explain the Process of Suction Feeding:
- Generate suction by opening mouth and moving tongue
- Suction feeders sometimes have non-functional teeth
- Once prey is in mouth, need to remove seawater
Explain the Process of Suction Filter Feeding:
- Suck in mouthful of small prey
- Expel water through fine sieve to trap prey inside mouth
- Specialised filtering apparatus used to filter out small prey
Explain the Process of Ram Filter Feeding:
Two Strategies:
- Skimming: Swim slowly through the water collecting tiny zooplankton in fine baleen sieve.
- Lunge Feeding: Swim fast toward prey and engulf huge volume of water along with evasive prey like fish and krill
