1. Embryology and Anatomy
Comparative
Embryology and Anatomy

2. Comparative Embryology
Embryology is the study of embryos. An embryo is an organism in its earliest phase of development.
Comparative embryology is a branch of embryology that compares and contrasts embryos of different organisms.

3. Comparative Embryology
Can you guess which is which?
Scientist often compare the embryos of different animals. They do this to try and determine evolutionary relationships between animals.
Comparative embryology tells us that the basic plan for an animal’s development is practically the same for all animals, this suggests that all animals are related and have a common ancestor. a. b. c. d. e.
Human Pig
Chicken Shark
Lizard

4. a.) Shark b.) Lizard c.) Chicken d.) Pig e.) Human a. b. c. d. e.
List all of the steps used in completing your experiment.
Remember to number your steps. a. b. c. d. e.

5. Comparative Anatomy
Scientist often compare the structure, or anatomy, of different species. This is called comparative anatomy.
There are three types of structures scientist study when comparing anatomy of different species: homologous, analogous, and vestigial structures.

6. Homologous Structures: structures that look the same but have different functions. (Humans, cats, birds, and whales all have forelimbs, but it is used for different purposes)
These structures imply evolutionary relationships. Organisms with homologous structures are closely related.
Different species possess these structures because they descended from a common ancestor, but they look different because they are adapted for different purposes.

7. Analogous Structures: structures of different species that are adapted to perform the same function (exm. Birds, bats, and butterflies all have wings)
These structures do not imply evolutionary relationships.
Different species develop analogous structures because of common evolutionary or selective pressures from the environment.

8. Vestigial Structures: structures within organisms that are functionless. These are structures that are remnants of once functioning structures.
Vestigial structures imply evolutionary relationships. Specifically they demonstrate evolutionary divergence from a species with a past function.
For example, the appendix is a vestigial structure that is believed to have helped digest food in early human species.
The tailbone is also a vestigial structure that is the remnant of tail bones found in mammals that have a tail.