Cetaceans - Marine Biology

What are Cetaceans?

• Includes species of whales, dolphins, and porpoises
• Cetaceans are white, black, gray, bluish-gray, or pink in color, many are spotted, mottled, streaked, or boldly patterned
• Key characteristics:
  • Fully aquatic lifestyle
  • Streamlined body shape
  • Often large size
  • Exclusively carnivorous diet

Tetrapods

• Cetacea are predominantly adapted to marine life, cannot survive on land at all
• Evolved from four legged animals (tetrapods), for which limbs played a primary role in movements, into virtually limbless aquatic creatures living in an environment where the back muscles are more important

Where can cetaceans be found?

• In almost the entire ocean as a whole, though there are some species that only appear in locally or broken populations
• Habitats include all oceans, arctics, and brackish water (salt/freshwater but mostly salt)
• Can live in just about any climate for there are species that are able to live in water that is near-freezing temperatures

Key Adaptations

• Rather than in a horizontal plane, they use vertical strokes when they swim instead of horizontal like a crocodile or fish (locomotive system)

  • It is made up of the skeleton, skeletal muscle, ligaments, tendons, joints, cartilage, and other connective tissues. It makes sure that these parts work together to allow their body to move

• Their adaptations can be seen through characteristics such as:

  • Dorsal blowhole: allows animals to breathe
  • Baleen teeth: allows animals to "filter feeds
  • Cranial "melon" organ: organ for aquatic echolocation 

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Body Systems

• Locomotive system, which they use to swim, one of the most important body systems
• Because of their descendants from mammals, they now swim using vertical strokes instead of horizontal
• Cetaceans are relatively known for their extremely efficient lungs and circulatory system, which allows them to dive for extended periods of time, allowing them to use about 12% of the oxygen they inhale compared to 4% used by terrestrial mammals
• Cetaceans’ flippers and flukes have a countercurrent heat exchange system, wherein heat from arterial blood warms venous blood as it returns to the heart. Both small and large cetaceans are insulated by their thick blubber layer

Key Orders

• Cetaceans provide a greater understanding of brain functioning in intelligent/social animals
• Already helped us understand so much about the brain function, learning, culture, and communication within the animal kingdom, including ourselves
  • Ceteacean’s keystone species is the blue whale
  • Blue whales help to keep the number of krill and phytoplankton in balance
  • This is key to the functioning of their aquatic ecosystem because phytoplankton are the core of the food pyramid
  • They are indicator species in the marine environment-- they are used to monitor changes in our environment

What Phylum do Cetaceans Belong To?

• Belongs to Phylum Chordata
  • Made up of animals w/ vertebrates or a spinal column and a cranium
  • Also known as “Chordates”
  • All have bilateral symmetry
  • All at one point have had a notochord, dorsal nerve chord, and gill slits
• Belongs to Class Mammalia

What Makes Them Unique?

• Cetaceans known for breathing through the blowhole on top of their head

• Although they live completely underwater, cetaceans use their blowhole to inhale/exhale oxygen, much like humans use nostrils

• They are mammals. They breathe air, have hair, are warm-blooded, give birth to their live young, and feed their babies milk

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