7.5.4 Comparative Embryology

Embryology: the study of embryos and their structures and development Embryo: an animal in the early stages of development before it is born or hatched. After fertilization in animals, the fertilized egg is called an embryo. Embryology: the study of embryos and their structures and development

This is an animal embryo. Can you tell what animal it is This is an animal embryo. Can you tell what animal it is? Make a list of possible animals that it might be. Look at your list. What is similar among the animals on your list? Why did you choose those animals?

Embryonic Development of Humans Week 4: heart begins to beat, arm buds appear, internal organs appear Week 5: Eyes start to form, leg buds appear, hands appear as paddles, blood circulates, face develops Week 6: Lungs start to form, fingers and toes form Week 7: Hair follicles form, elbows and toes form Week 8: Face looks human, external ears form

Comparative embryology: the study of similar patterns of embryos of different species. Some similarities are only present in the embryo form and not in the adult form. All animals that have a backbone also have gill slits and tails at some point in their embryonic development. As the animal grows, these characteristics disappear in animals that live on land, but are still present in the animals that live in or near the water. Organisms that share traits are more closely related. These similarities in embryonic development show how some animals may share a common ancestor, and therefore gives evidence for the theory of evolution.

Construct an explanation as to why it is sometimes difficult to identify the species when looking at the embryos. How do scientists use embryos to show how closely related animals are?