00:01
When you're looking at this transition from water to land for vertebrates, you're looking at fish, which are in the water zone, and obviously reptiles and animals that are on land or on land.
00:14
And the biggest problem with transitioning from water to land, as you can imagine, is drying out.
00:21
So every adaptation to living on land has to do with keeping from drying out.
00:29
And you can see, you know, even just comparing an amphibium like a frog here to a reptile, like a lizard or iguana, if you feel the skin of a frog, you're going to feel that it is very moist, both because frogs do rely someone on their skin for respiration so they have to have moisture in their skin, but that also ties them to water.
00:51
And because they are tied to water, they're not going to be losing water through their skin.
00:56
Whereas any organism that lives on land, whether it's plants or animals, must have a waterproof outer layer that does keep water in and doesn't allow them to lose a lot of water through their external morphology.
01:12
So looking at some key adaptations to living on land, as we said that waterproof outer layers is key, they must have waterproof epidermis.
01:26
Another key adaptation that first showed up and evolved in reptiles and continued on to birds and even some mammals is the development of the amniote egg...