18. Variation and Selection Flashcards
What is variation?
The difference between organisms in the same species.
What causes variation?
Mutations in the genetic code.
What is discontinuous variation?
Variation that produces distinct categories (e.g. eye colour or blood groups)
What is continuous variation?
Variation that cannot be placed into distinct categories and instead produces a spectrum (e.g. height, weight)
What is a mutation?
A random change in the base sequence of the DNA of an organism.
State 2 things which may increase the rate of mutation
- Ionising radiation
- Certain chemicals (like those found in cigarette smoke)
State 4 sources of genetic variation in a population
- Mutation
- Meiosis
- Random mating
- Random fertilisation
What is an adaptive feature?
Any inherited feature which helps an organism to survive in its environment and pass on its genes.
What are hydrophytes?
Plants which are adapted to live in aquatic conditions
State 3 adaptations of hydrophytes
- Wide and flat leaves
- Stomata positioned on top of the leaves
- Thin/no waxy cuticle
What are xerophytes?
Plants which are adapted to live in very arid and dry conditions
State 3 adaptations of xerophytes
- Rolled leaves
- Thick waxy cuticle
- Small needle shaped leaves
Describe the process of natural selection
- Populations are naturally varied due to random genetic mutations
- Some of these mutations provide a selective advantage
- These organisms survive and reproduce, passing on
the successful genes
What is the process of adaptation?
Populations become more suited to their environment over time due to natural selection
What is the development of antibiotic resistance an
example of?
Evolution by natural selection
Describe how antibiotic resistance arises
- A random genetic mutation causes a bacterium to become resistant to the antibiotic
- When the antibiotic is used, all the bacteria that do not have the mutation are killed
- The population containing just the resistant bacteria then begins to grow
Describe how selective breeding is carried out
- Organisms with the desired traits are selected
- These organisms are bred together
- This process is repeated until the offspring have the desired characteristics
What is the difference between natural selection and artificial selection?
Natural selection occurs when the selection pressures are created by the environment whereas artificial selection is when humans deliberately create selection pressures
