What do fossil records say about birds?
are the last surviving dinosaurs
What did they evolve from?
from feathered ancestors
What group?
theropod group of saurischian dinosaurs
When did they first appear?
during the Cretaceous period
How long ago was that?
around 100 million years ago
What group are they classified as?
endothermic vertebrates
What are their characteristics?
feathers, toothless beaked jaws,
Anything else?
the laying of hard-shelled eggs, a high metabolic rate,
How many chambers does their heart have?
Four
Where do they live?
Birds live worldwide
How big are they?
range in size
What is the smallest?
bee hummingbird
How big are they?
5 cm (2 in)
What is the largest?
ostrich
What is their size?
2.75 m (9 ft)
What is their class rank?
tetrapods
How many living species are there?
approximately ten thousand
What are half known as?
passerines
What is another name for that?
perching birds
When did they diversify dramatically?
Cretaceous–Paleogene extinction event