Animal Evolution & Development

1. What defines members of the Kingdom Animalia?

They are eukaryotic, primarily multicellular, heterotrophic, and most exhibit motility.

2. What are the two unique types of tissues found only in animals?

Nervous tissue and muscle tissue.

3. How do most animals reproduce?

Most reproduce sexually, with the diploid stage usually dominant in their life cycle.

4. What occurs during fertilization in animals?

A small flagellated sperm (n) fertilizes a larger, non-motile egg (n), forming a diploid zygote.

5. What is cleavage in animal development?

A series of rapid cell divisions by mitosis and cytokinesis, increasing the number of cells while the total surface area remains the same.

6. What is the blastula stage?

In humans, it is comprised of about 100 cells and occurs roughly one week after fertilization, allowing for the harvesting of embryonic stem cells.

7. What happens during gastrulation?

The invagination of the blastula creates the gastrula, and the opening is called the blastopore, which leads to the development of germ layers into adult body parts.

8. What is the developmental sequence from zygote to gastrula?

Zygote → Eight Cell Stage → Morula → Blastula → Gastrula.

9. From which germ layers do nervous tissue and cardiac tissues develop?

Nervous tissue develops from the ectoderm, and cardiac tissues develop from the mesoderm.

10. What is the fate of the blastopore in deuterostomes?

The first opening (blastopore) becomes the anus.

11. What is the fate of the blastopore in protostomes?

The first opening (blastopore) becomes the mouth.

12. How do most deuterostomes exhibit cleavage?

They exhibit radial cleavage, such as in humans.

13. How do most protostomes exhibit cleavage?

They exhibit spiral cleavage, such as in mollusks.

14. How are animals classified based on their body plans?

By tissue, symmetry, body cavities, and fate of the blastopore.

15. What are tissues?

Groups of cells that have a common, specialized function.

16. What is Parazoa?

Organisms that lack true tissues, are mostly asymmetrical; an example is Phylum Porifera (sponges).

17. What is Eumetazoa?

Organisms that have true tissues, including all other animals.

18. What type of symmetry do "Radiata" exhibit?

Radial symmetry and are diploblastic (2 germ layers: endoderm and ectoderm).

19. What type of symmetry do "Bilateria" exhibit?

Bilateral symmetry and are triploblastic (3 germ layers: endoderm, mesoderm, and ectoderm).

20. What are acoelomates?

Animals that lack a body cavity altogether; an example is Platyhelminth (flatworm).

21. What are pseudocoelomates?

Animals with a body cavity partially derived from mesoderm; an example is a nematode.

22. What are coelomates?

Animals with a true coelom completely lined by mesoderm; an example is crayfish.

23. What is schizocoelic coelom formation?

Coelom is formed by the splitting of the mesodermal layer between the ectoderm and endoderm.

24. What is enterocoelic coelom formation?

Coelom is formed by “pinching off” a portion of the endoderm that develops into mesoderm.

25. How can bilateral organisms be classified further?

By the presence of a body cavity and the fate of their blastopore.

26. What is a protostome?

An organism in which the mouth develops from the blastopore; examples include octopuses, earthworms, and insects.

27. What is a deuterostome?

An organism in which the anus develops from the blastopore, and the mouth develops later; examples include sea urchins and mammals.