biology aqa gcse - inheritance,variation and evolution
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- Created on: 31-01-19 14:31
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- inheritance, variation and evolution
- DNA
- DNA - deoxyribonucl-eic acid. its a chemical that all genetic material is made up of.
- your DNA decides what genetics you inherit, your characteristic
- chromosomesnormally come in pairs. every human being has 23 pairs of chromosomes
- DNA is a polymer, its made up of two strands coiled together in the shape of a double helix
- only 20 amino acids are used, genes tell cells what order to put amino acids together
- a gene is a small section of DNA found on a chromosome, each gene codes for a particular sequence.
- Reproduction
- the mother and father produce gametes
- sexual reproduction is where genetic information from two organisms is combined to produce offspring which is genetically different to either parent
- asexual reproduction produces genetically identical cells
- there's only one parent, so the offspring are genetically identical to that parent
- asexual reproduction happens by mitosis - an ordinary cell makes a new cell by dividing in two
- the new cell has the same genetic information - this is called a clone
- meiosis
- before the cell begins to divide, it duplicates its genetic information.
- in the first division the chromosome pairs line up in the centre of the cell
- the pairs are then pulled apart so each new cell has only one copy of each chromosome
- in the second division, chromosomes line up in the centre of the cell and the arms are pulled apart
- you end up with four gametes each with only a single set of chromosomes in it.
- Genetics
- to transfer a gene responsible for a desirable characteristic form one organisms genome into another organism
- bacteria has been modified to to produce human insulin to treat diabetes
- there are worries about the long term effects of modifying genetics
- fossils
- three ways fossils form in rocks:
- form in rocks from gradual replacement by minerals
- form in rocks from casts and impressions
- form in rocks from preservation
- fossils are remains of plants and animals
- three ways fossils form in rocks:
- classification
- K - Kingdom P - Phylum C - Class O - Order F - Family G - Genus S - Species
- or
- clean
- frogs
- ponds
- sick
- get
- keep
- every organism is given its own two - part Latin name so that scientists all over the world can understand and don't need to translate
- ie. humans were given the name Homo sapien
- K - Kingdom P - Phylum C - Class O - Order F - Family G - Genus S - Species
- evolution
- Charles Darwin's theory of evolution - evolution by natural selection
- natural selection - the process in which evolution takes place. organisms produce more offspring than the land can manage, only those that adapt to the land can survive and produce their own offspring
- theory of evolution - all of today's species have evolved from simple life forms that started to develop over 3 billion years ago.
- survival of the fittest
- selective breeding
- organisms are selectively bred to develop features that are useful or attractive
- animals that produce meat or milk
- crops with disease resistance
- dogs with a good, gentle temperament
- decorative plants with big or unusual flowers
- take the best plants or animals and breed them together to get the best possible offspring
- organisms are selectively bred to develop features that are useful or attractive
- DNA
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