Question

1. What accounts for the scarcity of fossils? What conditions and types of specimens favor fossil formation?

2. How do studies in biogeography show the influence of continental drift on the rise of new species?

3. Name the 5 groups of Excavates. Which of the Excavates are amitochondriate? Did they never have mitochondria or did they loose them? Does that have any bearing on the number of parasites in this group? Excavates are almost* all unicellular. What feature gives Diplomonads their name? What does Giradia cause? What structure enables this organism, which does not usually tolerate much oxygen, persist even for months out in an external environment?

Answer 1

Question 1:

Answer: Fossils became scarce because their formation and discovery depend on chains of geological and ecological events that occur over time. Most organisms decompose quickly after their death, and for an organism to be fossilized, the remains usually need to be covered by the sediment soon after they die. Only a small portion (fraction) of the primates that have ever lived have been preserved as fossils.

To become a fossil, the remains of an organism should not decay away to anything but instead, they must be buried in some medium such as mud, ash, sand, which generally happens in water, which doesn't always happen.