1.9 Flashcards
What is the main idea of Darwin’s theory regarding change in species?
Change occurs gradually in small steps over many generations.
What does the fossil record suggest about Darwin’s gradual change theory?
The fossil record does not show the progression of change that Darwin had suggested.
What are the two possible answers proposed by gradualists for the lack of intermediate fossils?
- We have not found them yet.
- The fossils were not preserved.
What is the punctuated equilibrium model?
A theory suggesting that evolution happens so fast that we will never find intermediate forms.
What does the concept of Genetic Equilibrium refer to in the context of species ‘A’?
Species ‘A’ remained stable for long periods (20-50 million years) before undergoing rapid evolution.
What resulted from a successful mutation in species ‘A’?
Species ‘B’ emerged from a successful mutation.
What happens to species ‘A’ when species ‘B’ and ‘C’ emerge?
Species ‘A’ could no longer compete and eventually died out.
Define extinction.
When all known members of a species have passed out of existence.
List two reasons why extinction occurs.
- Could not cope with changes in the environment.
- Changed (evolved) over time so they were no longer recognizable.
What is a mass extinction?
Extinction of many species due to a major climate change.
What can mass extinction leave empty?
Some niches in the environment.
What may happen to members of surviving species after a mass extinction?
They may take over empty niches and evolve/adapt to their new environment.
What do scientists at Mount St. Helens suggest about large disturbances?
Large disturbances make large changes, producing habitat that species can adapt to.
Fill in the blank: Extinction occurs when all known members of a species have _______.
[passed out of existence]
