Vertebrate Basics and Classification
Vertebrates are animals that have a backbone. They can be divided into two main groups based on body temperature. Ectotherms (cold-blooded animals) don't regulate their internal temperature, while endotherms (warm-blooded animals) can control their body heat.
Birds have special features that make them unique vertebrates. Some baby birds are altricial, meaning they're born helpless and weak, while others are precocial and hatch fully active and ready to go! Birds have two main types of feathers: soft, fluffy down feathers and longer contour feathers that give birds their shape.
Birds take care of their feathers through preening, using their beaks to spread oil and keep feathers clean and waterproof. Their digestive system includes a crop for storing food and a gizzard for grinding food since birds don't have teeth. When birds sit on eggs to keep them warm until they hatch, this is called brooding.
Fun Fact: Even though bats can fly like birds, they're actually mammals because they have fur instead of feathers and feed their babies milk!
