WHAT IS A FISH?

A limbless cold-blooded vertebrate animal with gills and fins living wholly in water.

Have a brain protected by a braincase and an obvious head region with eyes, teeth, and other sensory organs.

Are vertebrates with vertebrae protecting the spinal cord.

Live in water.

Breathe primarily with gills rather than lungs.

Have paired limbs, in the form of fins that aid in locomotion.

Are unable to regulate their own internal body temperatures.

Are covered with scales that protect their bodies.

There are many exceptions to these guidelines. For example, hagfish aren't vertebrates and don't have scales; mudskippers can live outside the water; lungfish use lungs to breathe; lampreys don't have paired fins; and tuna are warm blooded!

WHAT IS A MAMMAL?

A warm-blooded vertebrate animal of a class that is distinguished by the possession of hair or fur, females that secrete milk for the nourishment of the young, and (typically) the birth of live young.

Mammals live in all sorts of environments including the ocean, underground, and on land. Some mammals, bats for example, can even fly. 

Mammals are sometimes divided into three types based on how they give birth and take care of their young.

  Most mammals give birth to live young (instead of laying eggs like birds or reptiles).

 These mammals are called placental mammals.

 Marsupials are special types of mammals that carry their young in a pouch.

 Some marsupials include the kangaroo, the koala, and the opossum.

  A few mammals lay eggs, they are called monotremes. Monotremes include the platypus and the long-nosed spiny anteater.

NAME SOME MARINE MAMMALS

There are five groups of marine mammals: pinnipeds (seals,sea lions, fur seals, and walruses), cetaceans (whales, dolphins, and porpoises), sea otters, sirenians (dugongs and manatees), and polar bears.

Marine mammals have the same characteristics as all other mammals, but they have adapted to living all or part of their life in the ocean. To keep warm in the ocean, most of them depend on a thick layer of blubber (or fat). They have streamlined bodies to help them swim faster.  Many species can stay under water for a long time, but must come to the surface to breathe.  To be able to stay under water for long periods, they store extra oxygen in their muscles and blood.  They also have more blood than land mammals in proportion to their body sizes, can direct their blood flow to only their vital organs (such as their heart and lungs), and can slow their heartbeat down so they are using less oxygen in a dive.

All marine mammals are protected in the United States by the Marine Mammal Protection Act of 1972. There are also international laws and treaties that protect marine mammals. Unfortunately, many marine mammals are considered endangered species and there are still threats to most of their populations, such as illegal hunting, pollution, climate change, and habitat loss.  Learn more about these issues and tell others, including lawmakers, how you feel about them.  Together, we can solve or prevent many of the problems our ocean friends face.

By Reuben