What does it mean?

Warm vs. Cold-blooded

Warm-Blooded

Warm-blooded animals have a constant body temperature and must eat a lot of food so they have the energy to maintain that temperature.

Cold-Blooded

Cold-blooded animals have a body temperature close to the temperature of their surroundings.

Cold-blooded animals can and do experience big swings (changes) in their body temperature. When the temperature warms up, cold-blooded animals become more active. If the temperature is too cold, these animals aren't active at all!

Three out of the five vertebrate groups are cold-blooded:

Fish -

Fish live and breathe in water. They use "gills" to take oxygen from the water. All fish lay their eggs in the water. Most fish have fins to help them swim and eyes located on the sides of their head. Fish are usually covered with scales.

Amphibians -

Amphibians start out in water and, as they grow older, they spend more time on land. They are similar to reptiles but, unlike reptiles who have scale scale or armour, most amphibians have smooth skin. All amphibians take in oxygen through their skin and most also breathe with lungs and/or gills.

Examples of amphibians include: salamander, toad and frog.

Reptiles -

Reptiles are covered with scales and breathe air with lungs. They usually lay hard-shelled or soft-shelled eggs. Many reptiles spend most of their lives in the water.

Examples of reptiles include: sea turtles, snake, lizard, alligator and crocodile.

Two out of the five vertebrate groups are warm-blooded:

Birds -

Birds are covered with feathers and have wings. Not all birds can use their wings to fly (e.g. ostrich, penguin, kiwi, emu). Hollow or partially hollow bones make birds lighter than if they had more solid bones like mammals. Birds have large appetites (they eat a lot!). They need great amounts of food energy to fly.

Mammals -

Mammals have some hair on their body, nurse their young and have a highly developed brain. Most mammals give birth to live young (instead of incubating an egg). Mammals are the only animals with a "diaphragm" -- a muscle in the chest that actively allows air to enter the lungs.