Variation and evolution

• variation is all the differences in the characteristics of individuals in a population
• What are the four main causes of variation

  Their alleles they inherited

  environmental Environmental and genetic Language
• Examples of genetic variation are hair colour and eye colour
• What is a example of environmental variation

  The colour of flowers to the ph of the soil
• What is a example of environmental and genetic variation in humans

  Height in humans
• All genetic variation is due to mutations
• mutations are random changes to DNA
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  very rarely, mutations can lead to a new phenotype. Sometimes the new phenotype can be beneficial as the environment changes and this can lead to a rapid change in the species
• A phenotype is the physical characteristics of a organism
• The first life forms on earth were very simple single cells and all living things have evolved from these life forms, this is called the process of evolution by natural selection
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  For example if the environment gets colder, rabbits which have inherited thicker fur are more Likely to survive the colder temperatures than rabbits with thinner fur. Because the rabbits with thicker fur survived they can reproduce and pass on the alleles for thicker fur so their offspring can survive and reproduce. This is called natural selection
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  Evolution is the change in the inherited characterises of a population over time through a process of natural selection
• What are the four main selective breeding types used for

  Dogs= gentle nature

  food crops= disease resistance

  cows= more meat/milk

  plants= larger flowers
• How is selective breeding carried out

  By taking a mixed population of the organism and select the male and female with the most wanted alleles (height weight etc). Then breed them together, as sexual reproduction produces a variation in offspring, they will have a variety. again select the male and female with the most wanted alleles from the offspring and breed them together. Continue over many generations until all offspring have the desired alleles.
• what is a problem with selective breeding

  inbreeding which can cause inherited defects
• Genes are sections of DNA in a chromosome
• each gene codes for the amino acid sequence of a specific protein
• what is insulin 


  a hormone involved in blood glucose regulation in humans
• People with type one diabetes can not produce their own insulin so they need to inject themselves with it regularly
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  Bacteria have been genetically modified to contain the human insulin gene. These bacteria now produce human insulin which can be purified and used for type one diabetes.
• In genetic engineering, genes from one organism are cut out and transferred to cells of a different organism. The genome of the second organism is modified and now includes a gene from the first organism.
• we can also transfer genes into plants to produce genetically modified crops. generally they produce a greater yeild than normal crops or are resistant to more diseases. some people think we need to do more research on these crops as they may effect the wildlife.
• Genetic modification is currently being explored as a way to treat inherited disorders in humans this is called gene therapy
• Main steps in genetic engineering:

  1. Identify the gene that needs to be transferred

  2. Use enzymes to isolate this gene

  3. Transfer the gene into a small circle of DNA called a plasmid or a virus (vector)

  4. Transfer the desired gene into the cells of the target organism
• Always transfer the gene at an early stage in the organism's development to ensure that all cells receive the transferred gene, allowing the organism to develop with the desired characteristic
• Fossils are the remains of organisms from millions of years ago found in rocks
• what are the three ways fossils form

  1 when parts of organisms have not decayed, this can happen when conditions needed for decay are absent

  2 even if an organism decays, if parts of the organism are slowly replaced by minerals during the decay process

  3 they can be the preserved traces of organisms eg foodprints
• why do we not have as many fossils from early life?

  because many organisms didn’t have skeletons so they rarely formed fossils, and if they did thy had been disTroyes by the changes in the earths crust. this means scientists cannot be certain how life on earth began
• fossils show the huge number of species that became extinct
• You can use fossils to eye how species have evolved over time
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  under ideal conditions bacteria can reproduce every 30 minutes, this means they can evolve rapidly
• An example of a antibiotic is penicillin
• what is a downside to antibiotics

  bacteria can make themselves antibiotic resistant and cannot be effected
• how does antibiotic resistance happen

  a group of bacteria create a pathogen (the population will have genetic variation due to mutations) a mutation could possibly make a bacterium resistant to antibiotics which could reproduce and cause a resistant strain.
• what are the three ways to stop antibiotic resistants

  1. doctors not prescribing antibiotics inappropriately
  2. patients should complete their course of antibiotics to make sure all bacteria are killed so none can mutate and form resistant strains
  3. restrict the use of antibiotics in farming
• creating new antibiotics takes a long time and is expensive
• Linnaeus divided all living organisms into two kingdoms, either plant or animal. he then divided each kingdom into a number of smaller categories in the order, kingdom phylym class order family genus species
• What does king Philip came over for good soup stand for

  kingdom phylum class order family genus species
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  Every organism is named from their genus and species this is called the binomial system
• Carl woese created the three domain system who compated the biochemistry of to different organisms