Variation and Evolution Flashcards
Variation
Difference between members of the same species
Sources of genetic variation
Mutation - Gene muations, Chromosome mutations
Sexual reproduction - Independent assortment, Random fertilisation
Mutation
The change in DNA/Genotype in a cell
Gene mutation + Example
Change in structure of a single cell
Example: sickle cell anaemia
Chromosome mutation + Example
Change in structure or number of chromosomes
Example: Down’s Syndrome
Mutagen + Cause
Anything that can alter or damage DNA
Example: UV radiation, Asbestos, Viruses
Evolution
The slow change in inherited characteristics over a long period of time
Theory of natural selection
The process by which particular traits become more common in a population due to the trait becoming advantageous to the species
- Organisms struggle to survive
- Vary and some are better able to survive
- Become better adapted
- Pass on inheritable traits
Who proposed Theory of Natural Selection
Darwin and Wallace 1859
How Darwin developed his theory
Observations: Species overbreed Limited supply of resources Populations stay constant Species show variations that are inherited Conclusions: -Organisms struggle to survive -Vary and some are better able to survive -Become better adapted -Pass on inheritable traits
Evidence for the theory of natural selection
Palaentology - study of fossils - increased complexity the nearer they are to the surface
Comparative anatomy
Comparative embryology
Example of evolution - Change + Reason
The modern horse
Change: Molar teeth developed larger grinding surface
Reason: Grassland plants tougher than marshland plants
Species + Example
A group of similar organisms that are capable of interbreeding to produce fertile offspring
Example: Dogs
Speciation
Formation of a new species following many changes until the species cannot interbreed to produce fertile offspring of the original species
Heredity
Passing on of traits from parent to offspring through genes
