They leave no record of their existence because it's rare that fossils form. You need the right conditions in which the animal's remains are covered in silt, dirt, and rock layers in order for a fossil to form and therefore preserve the animal's remains in rocks. Otherwise, the animal's remains will be eaten by other animals or eventually rot away.
It should be the first one
Hydra and Obelia are cnidarians (species of aquatic organisms) that belongs to the Class Hydrozoa.
Several ways in which Obelia differs from Hydra are;
- Hydra is a predative species that lives on substrates such as wood, while Obelia is a colonial species that lives as polyps on branched frameworks.
- Hydra is found in freshwater habitats, while Obelia is found in marine habitats.
- Hydra undergoes the medusa form in its life cycle, while Obelia undergoes the two forms (polyp and medusa) in its life cycle.
- Hydra has great regenerative powers while Obelia does not have great regenerative powers.
Answer:
When you scrape your knee, skin cells are replaced by meiosis.
Explanation:
Answer:
The correct answer is - develop new methods to test the hypothesis.
Explanation:
Human produce offsprings long time and development also take a long time in general and then to test a hypothesis, regarding the gene therapy helps to treat a disease, would take even more time.
So testing this hypothesis required developing a new method as other options are not possible. You can not change the time it takes in reproduction. Giving up is not the option in science.
