Which of the following is common to the development of both birds and mammals? a. holoblastic cleavage b. epiblast and hypoblast c. trophoblast d. gray crescent

Video transcript

Welcome back. The next problem says all of the following are common in the development of both birds and mammals. Except. So this except reminds us that we're looking for the one answer that is not found in both birds and mammals. So let's look at our choices choice A says ectodermal Mezza derm. And indeed all these describe the three layers of the gastro to And organisms that develop into this three layered structure are called triple A. Plastic. And both birds and mammals are indeed triple Bostic. So that is common to both and therefore is not our answer. So we can eliminate choice A choice B says a central nervous system formation. Well, both birds and the mammals are vertebrates. They have a central nervous system so that is common to both and therefore is not our answer. Choice C. Says placenta. Well, placenta's are found only in placental mammals. They are not found in birds. So here we have our correct answer. Something that is not common to both. Choice C. Placenta. And we'll just look at choice D. To see why that is not our answer. Trustees amniotic sac. Well, both birds and mammals are am notes they have that sack. Just mammals. It's enclosed within the uterus while birds it's within the egg. So amniotic sac also common to both. And that is why Choice D. Is eliminated. So are correct answer is placenta. See you in the next video