Question

ALL of these questions are different. Please answer ALL of them. Thank you!

1. Explain three important embryonic components that result from gastrulation, including why they are important in bilaterian animals.

2. Explain why the notochord is especially important during the embryonic development of chordates.

3.  Molecular evidence suggests that hagfish and lamprey should form sister taxa. Explain why many phylogenies suggest that lamprey branched off after hagfish, and would thus be more closely related to jawed vertebrates.

4.  Explain why it may have been important for hagfish to have lost their backbone.

5. Explain why the life cycle of lamprey is said to be anadromous. In which part of their life cycle are they parasites?

Answer 1

1.The three important embryonic components that result from gastrulation are endoderm ,mesoderm and ectoderm and these three layers are important for differentiation of different cell lineages in the body .

2. The notochord provide primary axial support for the body throughout the life span . It is present during embryonic development to induce the development of neural tube and gives support to the developing embryonic body .  

3. According to lolecular evidence the lamprey and has fish share a chordate clade, which has the cranium or skeletal braincase. These are found more appealing because it implies a gradual assembly of vertebrate characters in the  supports of the hagfish and lampreys as experimental models for distinct craniate and vertebrate evolutionary models .However, this is based on  comparative morphology for this phylogenetic hypothesis.

4. Hagfish are bonafied vertebrae and has lost their backbone because they backbone instantly makes an animal's body more rigid. They possess a  ridge of cartilage called a "notochord" which makes their bodies more flexible.

5 .Lamprey is said to posses an anadromous life cycle because it started with larvae that feed in freshwater. And later followed by transformation into juveniles that migrate to the ocean where they parasitize hosts, and adults that migrate into freshwater to spawn and die.