B7 Variation And Evolution Flashcards
Environmental variation
Changes due to the environment Tattoos Scars Language Hair colour and length
Genetic variation
Differences from our genes Blood group Eye colour Shape of earlobe Natural hair colour
Genetic and environmental factors
A mixture of both Height Skin colour Weight Sporting abilities
Variation and survival
Variation is critical for survival and for evolution
Genetic variation
The product of 3 processes that lead to differences in genomes: mutations, sexual reproduction and meiosis
Most mutations have no effect and rarely change the phenotype
An early theory of evolution
French scientist Jean-Baptiste Lamarck in 1809
Organisms survived by adapting to their environment passed on this adaption to the next generation
Eg. Giraffes necks were stretched and then passed to next generation
How does evolution happen?
The environment does influence the phenotype but not in the way Lamarck suggested
Desired characteristics are passed to their offspring eg.resistant to antibiotics
Natural selection
When desired characteristics are passed to their offspring
Environmental changes
Geographical isolation, change in climate causes species to adapt differently
Overtime they will develop characteristics different to those or the original species
Darwin’s theory
He noticed that animal where the similar but not the same
This lead to the idea of natural selection and evolution
Natural selection
The most advantageous characteristics are passed on
Evolution
Species are changing and adapting through natural selection in order for survival
How are fossils formed?
By dead animal or plants being buried in mud,silt or sand
There is no oxygen so that organisms can not decay the body
Hard parts of animals like bones are fossilised
Can also be trapped in amber or volcanic ash
Evidence from fossil records
Older fossils are near the bottom
We can see which species have adapted, survived or died out
Radiometric dating
Allows us to identify the exact age of the fossil.
Incomplete fossil records
Geological activity has destroyed them
May be lost
Soft bodied organisms can not be fossilised
Missing links between species
Evolution of life
Some species have changed a lot whilst others have evolved very slowly
Some bacteria have changed very little as there is still chemical evidence of them in fossils
Warning colouration
To deter predators
Favoured by natural selection
Mimicry
Unrelated species develop similar warning colourations to help promote their survival
Isolation
Geographical isolation causes species to develop different advantageous characteristics
Eventually it will reach a point where the new species can no longer interbreed with the original species to form fertile offspring
Speciation
A species that evolves through natural selection to form a new species
Selection pressures
Pressures such as food, water, shelter creates competition to which only the best suited species survives and passes on its characteristics