evolution help?

Question

*how do fossils form?
* Why is the fossil record incomplete?
*What causes phenotypic variation and how does it relate to natural selection?
*Describe adaptation and fittness in genetic terms.

Answer 1

1. Fossils form when organisms die and are covered with sediments.
2. The fossil record is incomplete because we have not discovered all the types of fossils and because many organisms decay without being fossilized.
3. Phenotypic variation is a result of genotypic variation. Variation can be due to mutation or to the ordinary genetic recombination of meiosis, crossing-over, and sexual reproduction.
4. Adaptations are features that help an organism survive in its environment. The adaptation is genetic and can be passed on to offspring. The organism does not adapt in the genetic sense during its lifetime. It either has beneficial characteristics or it doesn't.

Fitness describes how well-suited an individual is to the environment and situations that arise. Fitness takes on different forms depending on what forms the pressures to survive take on. Fitness for a rabbit involves holding still to avoid a predator's notice. Fitness for a zebra involves running fast.

Answer 2

I want to add one thing to what ecolink says: MOST remains do not fossilize. It is only a rare instance when an animal dies in the exact right place with the exact right conditions for the bones to turn to stone. That's why there are gaps in the fossil record. It is only in a few very isolated instances that there are any fossils, much less that they are found.