Marine Mammals/Sharks Flashcards
What characteristics are needed to classify a marine mammal?
- must breathe air with lungs
- has hair at some point in its development
- warm blooded
- produce milk for young
What are the three taxonomic groups of marine mammals?
- cetaceans (mysticetes + odontocetes)
- carnivora (pinnipeds, polar bears, sea otters)
- sirenia (dugongs and manatees)
Which marine mammals are nektonic?
cetaceans and pinnipeds
What effects can mesopredators like pinnipeds put on an ecosystem?
top-down as direct predators or bottom-up as influencing other predators, providing nutrients via waste products
What nutrient cycle do whales contribute to?
carbon cycle (stores carbon and can provide carbon to abyssal zones via whale falls)
What struggles do marine mammals face by being in the water?
- weightlessness
- rapid heat loss
- infrequent gas exchange
- resistance to movement
- low light visibility
Which whale has the record for deepest/longest dives?
Cuvier’s beaked whale
What are three challenges from deep dives ?
- lack of oxygen
- high pressure/decompression sickness
- heat loss
How do marine mammals overcome a lack of oxygen?
- short aerobic dives to balance time spent underwater/at surface
- increased RBD/hemoglobin, higher hemoglobin affinity
- brachycardia (slow heart rate)
- blood restriction to brain/lungs
How do marine mammals prevent decompression sickness (buildup of gaseous nitrogen)?
collapses lungs via flexible ribcages and reduces nitrogen need by pushing air to central lung
How do marine mammals stay warm?
- insulation via fur/blubber
- reduced blood flow
- countercurrent heat exchange (arteries and veins close to each other, warm outbound blood warms inbound blood returning to heart)
- basking
What are some differences between mysticetes and odontocetes?
mysticetes (baleen)
- two blowholes
- larger females
odontocetes (toothed)
- one blowhole
- larger males
What are some adaptations cetaceans have that make them successful marine mammals?
- dorsal airway for brief gas exchange at surface
- low surface-to-volume ratio = heat retention
- smooth stiff bodies for lower drag
- horizontal flukes for propulsion, dorsal fins for counterbalance
- echolocation
What structures are involved in echolocation?
phonic lips (blowhole) –> melon (amplification) –> lower jaw –> middle ear (image)
How are cetacean eyes structured?
- curved cornea
- 2 high density areas of cells on retina
What are some adaptation of sirenians?
- nostrils on snout prevents easy gas exchange while moving
- dense bones to counter buoyancy of blubber
- teeth suitable for herbivorous diet
- no echolocation
What are some differences between a dugong and a manatee?
dugong
- fluked tail
- found in eastern pacific
- snout points down
- solitary
- feeds on seagrass
- stationary year round
manatee
- paddle tail
- found in americas/africa
- blunt snout
- social
- feeds on various plants
- migrates to warmer waters
What are the three groups within the pinnipeds?
phocidae (earless seals), otariidae (eared fur seals/sea lions), odobenidae (walruses)
Why is the distribution of pinnipeds different than other marine mammals?
- found in cold, highly productive waters vs warmer less productive tropics
- commonly found along pack ice edge and near upwelling zones vs. open water
What are some adaptations of pinnipeds?
- streamlined body
- sensory bristles around nostrils
- differentiated teeth
- reliant on vision/touch
- large eyes with nictitating membrane (third eyelid)
What is unique about a harp seal’s milk?
up to 45% is fat, which allows for fast growth of pups
Where are walruses found and what do they eat?
found in Arctic continential shelf and consume benthic invertebrates <100m deep
What is unique about sea otters?
- densest fur in animal kingdom
- no blubber
- fur is fully water repellant and has air pockets for buoyancy/insulation
- high metabolism
What is the difference between a shark and a ray?
shark = gills on sides
ray = gills underneath
What are some characteristics of a shark?
- skeletons made of cartilage
- sensory structures around snout called Ampullae of Lorenzini
- oil filled liver for buoyancy ($$)
- can reproduce in 3 different ways
What are the three reproductive methods of sharks?
- viviparous: young develop inside mother’s womb (live birth)
- oviparous: young develop from yolk sacs in eggs
- ovoviparous: young start in eggs within mother then hatch into live births
What ecosystem services do sharks/rays provide?
- landscape of fear + prey population regulation (top-down effect, sharks)
- regulate carbon sequestration (by keeping herbivores in check)
- bioturbation (rays) –> cycles nutrients, increases oxygen in sediment, rearranges sediment for habitat structures
What are some examples of top down effects of sharks?
- controlling sea turtle population keeps seagrass meadows thriving
- control of herbivores prevents tropicalization of temperate seagrass meadows
What are some examples of bottom up effects of sharks?
- nutrient cycling from travelling between systems
- provide food source for higher trophic consumers like orcas
What effect of macropredator extinction is there on smaller sharks?
as macropredator numbers dwindle, smaller species reproduce more rapidly and can replace them
What percentage of total ocean is covered in MPAs? What percentage of EEZs have MPAs?
8.35% total MPAS
~19% of EEZs have MPAs
What is the biggest threat to sharks?
overfishing/bycatch
How many species have at least 10% of their range within a no-take zone?
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