B1 - Variation Flashcards
What are the 2 types of variation?
Environmental variation
Genetic variation
What is variation?
How members of the same species have differences
What causes genetic variation?
Members of the species have different genes because they have inherited mixes of genes from different sets of parents
How do offspring inherit genes from their parents?
Genes from the parents are passed on to offspring on gametes (sex cells) which the offspring develop from
What is environmental variation?
How offspring develop because of the conditions they grow up in
How something develops depends on both types of variation
What does the human cell nucleus contain?
All of the genetic material in the form of 23 pairs of chromosomes
What do the chromosomes contain?
Genes
What are genes made from?
Long lengths of DNA
What is a gene?
The genetic material needed to control the development of one feature of the human
What is an allele?
Different versions of the same gene are alleles
For example, brown and blue are alleles for the gene for eye colour
What is the process of reproduction that happens with animals?
Sexual reproduction
What is sexual reproduction?
Reproduction involving the fusion of male and female gametes resulting in offspring with a mixture of the parents’ genes
Describe sexual reproduction
The gametes have only 23 single chromosomes
The gametes of the father (sperm) fertilise the gamete of the mother (egg) to produce a fertilised egg that develops into the offspring
The genetic variation comes from the mixture of genetic material from the sperm and egg
What is the process of reproduction that happens in plants?
Asexual reproduction
What is asexual reproduction?
Reproduction where there is only one parent so there is no mixing of genetic material resulting in offspring that are genetically identical to the parent
Describe asexual reproduction
X-shaped chromosomes have 2 identical halves
Each chromosomes splits down the middle to form two identical sets of half-chromosomes
A membrane forms around each set and the DNA replicates itself to result in full chromosomes
What is the other natural use of asexual reproduction?
It is how all plants and animals grow and produce replacement cells
