why bat is a mammal and penguin is an Aves?

if you observing the video above you can see the body of a bat is covered with fur not with feather and the bats give birth while Aves should lay eggs.

A penguin on the other hand, looks like it covered with fur, but if you take a closer look.....the penguin's body is covered by small and stiff feathers, and they also lay eggs (click it if you want to see the movie).

picture taken from:

http://www.seaworld.org/animal-info/info-books/penguin/images/pic-incubating-single-egg.jpg

visit this web to observe their feathers:

http://www.penguinscience.com/education/adaptations_feathers.php

Those are the characteristics that you can easily see....how about the other characteristics too distinguish them?

please look at your notes to get the right answers:)

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