Evolution Flashcards
What causes genetic variation
Sexual reproduction and mutations
What is mutation
The change in the amount or structure of DNA
Cause of mutation
Mutagens are agents that increase the natural rate of mutations
Mutagens include radiation eg X-rays, uv light,
cigarette smoke, caffeine
Types of mutation
Gene mutation
Chromosome mutations
What are gene mutations
Effect only small sections of dna. Only their effects can be seen
Eg albinism (inability to produce melanin)
Eg cystic fibrosis (inability to clear mucus from lungs and other organs)
Eg sickle cell anemia (inability to form correct hemoglobin)
What are chromosome mutations
Effect a large section of chromosome (entire chromosome or groups of chromosomes)
Eg Down syndrome (a person has 47 chromosomes rather than 46) This is the result of a gamete with 24 chromosomes forming with a normal gamete with 23 chromosomes.
What is evolution
The way in which living things change genetically to produce new species over a long period of time
Evolution observations
Organisms produce large number of offspring buy the environment can only support a number of these eg providing food, water, light. THIS RESULTS IN COMPETITION
There are genetic variations amongst members of a population. The organisms that adapted the best live longer.
Organisms accumulate small changes over time, they evolve
What is natural selection
The organisms who have adapted best live on and those who didn’t adapt so well die. It’s survival of the fittest.
What is speciation ?
New species form from original species and the two cannot interbreed.
Evidence of evolution
Fossils, study of embryos, genetic evidence
How do fossils support the theory of evolution
Can be dated
Some species in fossils cannot be found alive anymore eg Dinosaurs
Some species have no fossil remains eg humans meaning we only fate back a few thousand years
Modern organisms are more complex than those in fossil fuels
name the mechanism proposed by the Darwin-Wallace theory which explains evolution
natural selection
explain the link between mutations and variations
mutations can be caused by variations
