4.4 Variation and Evolution Flashcards
What does variation mean?
Small differences within a species make some individuals better adapted to the environment
What are two different causes of variation?
sexual reproduction
environmental influences
Why are gametes haploid cells?
because it has half the normal number of chromosmes
When they join at fertilisation, a new cell is formed
What is continuous variation?
a characteristic that changes gradually over a range of values
What are examples of continuous variation?
height
weight
hand span
What is discontinuous variation?
a characteristic of any species with only a limited number of possible values
What are examples of discontinuous variation?
gender
eye colour
blood group
What is meant by an inherited disorder?
a disorder that is caused by a gene, which is passed down from parents to offspring
What are the effects of cystic fibrosis on the sufferer?
a build up of thick mucus causes breathing difficulties and digestive problems
Using the letter ‘N’, what is the genotype of the cystic fibrosis sufferer?
nn
Using the letter ‘N’, what is the genotype of the cystic fibrosis carrier?
Nn
Is the cystic fibrosis gene dominant or recessive?
recessive
because if you inherit two copies of recessive alleles, it shows the cystic fibrosis phenotype
What are the names of the scientists that put forward the theory of evolution?
Darwin
Wallace
What does mutation mean?
A spontaneous change to the base sequence in DNA which results in genetic variants
What is natural selection?
the natural process whereby the best adapted individuals survive longer, have more offspring and thereby spread their characteristics
