Fish have been on earth for over 400 million years.  Over their existence, different fish evolved into mammals, birds, and reptiles.  There are over 31,000 species of fish today.  They have adapted to all bodies of water, fresh and salt.  They use gills to breath, and most fish are cold blooded.  To reproduce, they lay eggs.  Some fish have evolved to be carnivorous (like sharks).  Others eat plant matter (like carp).  And some eat both (like catfish).  Some fish grow to lengths of about 1 inch long, others to over 50 feet!  In this section of my blog, we learn about the interesting adaptations of fish.