Chapter 12 - Variation and natural selection Flashcards
What is continuous variation ?
There is a gradual change in the characteristic among the population
What graph do you use to show continuous variation
Histogram
What is discontinuous variation ?
The population can be clearly divided into groups or categories
What graph do you use for discontinuous variation ?
A bar chart
Name two examples of discontinuous variation
Tongue Rolling and hand dominance
Name two types of continuous variation
height and length
What are the two causes of variation ?
- genetic variation
- environmental variation
How do mutations affect variation ?
They are random changes in the number of chromosomes or type of gene. Which can affect the phenotype
How does sexual reproduction affect variation ?
Meisos mixes up the chromosome arrangements in gamete formation, this results in all gametes being genetically different .
Give an example of environmental variation
The actual height of a human will depend on the quality of their nutrition
How does competition for resources affect natural selection ?
When competing usually the stronger organism will survive and pass on their genes
What were Darwin’s 3 main conclusions from natural selection ?
- there are variation among the phenotypes in a population
- If there is competition there will be struggle for existence
- The better adapted phenotypes survive this struggle. The fittest are more likely to pass on their genes to the next generation
Why do some species go extinct ?
- hunting by animals
- hunting by humans
- spread of disease
- loss of habitat
How are fossils helpful to see the affects of natural selection ?
They showed what the plant or animal looked like millions of years ago and show then how they have changed
Or maybe even show that the organism hasn’t changed that much in a long time
define selective breeding
The selection and subsequent breeding of organisms chosen by man for their desirable qualities
