CLASS AVES - BIRDS
Birds. Extremely distinctive. 9,000 species known. Waterproof skin covered in feathers. Beak or bill (no teeth). Highly adapted for flight. More species of birds than any other vertebrate class. Modern descendants of dinosaurs. Waterfowl, hummingbirds, condors, gulls, doves, eagles, hawks, chicken, turkey, sparrows, pelicans, flamingos, albatross, parrots, parakeets, penquins, owls, ostriches to name a few.
IMPORTANCE OF FEATHERS AND HOLLOW BONES
Bones are extremely lightweight, as they are hollow. Hollow bones make the skeleton lighter for flying and allows more oxygen to be absorbed from the air into the blood for extra energy (for flying). Feathers are a more prominent feature on a bird's anatomy. Feathers provide insulation and allow for flight as well. Penguins have solid bones; hence, they cannot fly (at least not well). But, both hollow bones and feathers are adaptations that enable birds to fly.
REPRODUCTION
Sexual. Both male and female birds have a cloaca (an opening that serves digestive, urinary, and reproductive systems). When they mate, it's called the "cloacal kiss." All birds lay eggs with amniotic protective sheaths. So, the fertilization itself is internal; then, the egg is laid.
CIRCULATORY SYSTEM
Their circulatory system is very efficient. Closed cardiovascular system. This helps them meet the demands of flight and maintaining body temperature. The heart is four-chambered. Two ventricles keeps oxygenated and deoxygenated blood separate in the heart, which maximizes the amount of oxygenated blood that can be efficiently transported to all parts of the birds' bodies.
ENDOTHERMIC
Birds are endothermic or "warm-blooded." So, they generate their own heat internally by their own metabolism.
IMPORTANCE OF FEATHERS AND HOLLOW BONES
Bones are extremely lightweight, as they are hollow. Hollow bones make the skeleton lighter for flying and allows more oxygen to be absorbed from the air into the blood for extra energy (for flying). Feathers are a more prominent feature on a bird's anatomy. Feathers provide insulation and allow for flight as well. Penguins have solid bones; hence, they cannot fly (at least not well). But, both hollow bones and feathers are adaptations that enable birds to fly.
REPRODUCTION
Sexual. Both male and female birds have a cloaca (an opening that serves digestive, urinary, and reproductive systems). When they mate, it's called the "cloacal kiss." All birds lay eggs with amniotic protective sheaths. So, the fertilization itself is internal; then, the egg is laid.
CIRCULATORY SYSTEM
Their circulatory system is very efficient. Closed cardiovascular system. This helps them meet the demands of flight and maintaining body temperature. The heart is four-chambered. Two ventricles keeps oxygenated and deoxygenated blood separate in the heart, which maximizes the amount of oxygenated blood that can be efficiently transported to all parts of the birds' bodies.
ENDOTHERMIC
Birds are endothermic or "warm-blooded." So, they generate their own heat internally by their own metabolism.