(bio 2) variation

• variation is the differences in characteristics due to random mutations
• there are 3 main causes to variation

  1. genetics, the alleles inherited determine your phenotype
  2. environmental, the colour of flowers depends on the ph of the soil and the language a person speaks

  3. combination of both genetics and environmental, a person may have the alleles for height but if they dont have enough calcium in their diets their bones cant fully develop
• evolution is the change in characteristics in a population over time by natural selection
• first life forms were simple single cells
• every population of a species has a different combination of alleles. eg some rabbits have thick fur some have good hearing ect
• natural selection happens when theres a change in the environment or a threat to the species (eg. cold environment). rabbits with thicker fur will survive and reproduce as they have the advantage phenotype they will reproduce and their ofspring will inherit the alleles and the other rabbits will die out. over many generations most of the population will have the advantage phenotype
• 4 examples of selective breeding is in dogs to have a gentle nature, food crops to be resistant to disease, cows to have more meat or produce more milk and flowers to have larger flowers
• how selective breeding works

  (eg.larger cows for meat)

  1. take the largest male and female cows and breed them together
  2. sexual reproduction produces variation
  3. offspring will have a variation of small and large cows
  4. breed the largest male and female offspring
  5. continue over generations till the populations are large cows
• a problem of breeding is if they are closley related you can get inbreeding which leads to breeds being prone to disease or inherited defects
• genetically modifying plants to make them resistant to disease and insects, produce bigger fruits and become resistant to herbicides
• cloning plants using asexual reproduction to produce genetically identical organisms
• another way to clone animals is

  2. adult cell cloning

  • remove adult cell (eg skin cell) from desired animal
  • remove the nucleus
  • take an unfertilised egg from the same species and remove its nucleus so it has no genetic material
  • insert the nucleus taken out from the adult cell into the emptey egg cell
  • give the egg and electric shock so it stimulates the egg to divide into an embryo the instert into a host mother
  • the clone will look nothing like the host mother

  advantage: because we are cloning from an adult cell we will know the characteristics it will be born with
• darwins theory was gradually accepted

  at first it challenged the idea of God and that he created all living animals and at the time darwin didnt have enough evidence. people didnt understand how inheritance worked and thought genes were blended it was after lamarcks theory was proved wrong people gradually accepted darwins theory
• wallace was intrested in warning colour on animals like the bright colours on a frog to warn predators and came to the same theory as darwin about evolution by natural selection
• many scientists disagreed with mendels work and it was forgotten. years later scientist researched how chromosomes worked in cell division they realised the chromosomes behaved similiarly to mendels 'units'. scientists realised genes must be located on chromosomes and later on scientists were able to determine the structure of dna
• FOSSILS can be used as evidence of evolution. fossils are remains of organisms rom millions of years ago found in rocks. the are formed when organisms have not decayed.
• there are three ways for fossils to form:

  1. when conditions are cold with little oxygen and water, the decay process can not take place
  2. some parts of the organism may be replaced by minerals
  3. fossils can be preserved traces of an organism eg. footprints, nests , burrows
• a problem with fossils is that many early organisms are soft bodied with no shells or skeletons so they very rarely formed fossils .

  many early fossils were also destroyed by volcanic eruptions so scientists cant be certain on how life began
• evidence for evolution is ANTIBIOTIC RESISTANT BACTERIA

  
  

  mrsa is a common resistant strain of bacteria

  penicillin is an antibiotic
• research for new antibiotic is long and expensive . it is very hard to keep up with new resistant strains
• evelutionary trees show how closley related organisms are
• how does speciation occur

  
  

  in a population of 1 species of snails if they are seperated they can no longer interbreed so mutaions arent spread the the seperated groups change so differently the can no longer interbreed with eachother
• mendel determined that characteristics were determined by 'units' (genes) that dont change when passed on. he found that some characteristcs can be masked or reappear later these are identifed as recessive genes
• due to development of microscopes and our understanding of biochemistery we can analyse similiarties of internal organs. WOES developed the ' three domain system'
• speciation is how species form and change. for speciation to occur you need a geographical barrier (eg river) to prevent interbreeding
• darwins theory is that species evolved by natural selection. he researched and colleted animals and plants from all over world and analysed fossils , he went on to write a book on the origin of species
• there are two ways to clone plants

  1. using cuttings . take a small piece of the plant and dip the end in rooting powder . the powder contains growth hormones. this only works for a small amount of clones
• another way to clone plants is

  tissue culture

  2. divide the plant into hundreds of tiny pieces . each piece contains cells. incubate them with plant hormones. conditons must be sterile
• two populations of the same species can be so different in phenotype they can not interbreed
• you get the binomial name using genus + species
• species can become extinct by

  • geological changes, like changing weather patterns
  • catastrophic events, like asteroids
  • new diseases
  • new predators
  • new species evolves and compete for food and water
• the three domain system includes

  1. archae - (primitive bacteria) found in extreme conditions such as hotsprings
  2. true bacteria - the kind that lives in human digestive systems
  3. eukaryota - animals , plants ,fungi and protists
• 3 ways to reduce resistant strains

  1. should not take antibiotics unecessarily
  2. patients should complete their course to ensure all the bacteria die and none can mutate
  3. restrict antibiotic usage in farming
• linnaeus's classification system

  • all living organisms divided into 2 groups, the animal kingdom and plant kingdom
  • each kingdom was divided into smaller groups

  kingdom

  phylum

  class

  order

  family

  genus

  species
• genetic engineering is cutting out the desired gene of an organism and transferring it to another , modifying the genome of the organism
• there are two ways to clone animals

  1. embryo transplant

  • start with a sperm and egg from (horses) with desired characteristics
  • allow the egg to fertilise and develop into an early embryo , cells must not differentiate
  • use a glass rod to split the embryo in two
  • transplant the embryos into the host mothers

  disadvantage: because we start with the sperm and egg and its sexual reproduction u cannot guarantee the offspring will have the desired characteristic s
• lamark suggested that when a characteristic is regularly used (eg. girraffes long neck) it will become more developed and this strengthened characteristic will be passed down to its offspring. however we know that changes that occur within an organisms lifetime will not be pass down. eg abs the baby will not have abs
• mendel carried out breeding experiments on pea plants. at the time inheritance was not understood and many believed characteristics were blended. mendel realised this was wrong and eg. the shape of the pod had no effect on the colour of the flowers
• steps for genetic engineering

  1. cut out desired gene with an enzyme ( ligase )
  2. then transfer the gene into a vector ( plasmid or virus)
  3. the desired gene is transfered into the cells of the target organism
  4. its transfered at the early stages of an organisms development eg and embryo to make sure all the genes are transferred to all the new cell
• how do bacteria become resistant?

  • within a population of bacteria, one might randomly mutate into a resistant strain
  • if you use an antibiotic all the bacteria apart from the resistant strain will die
  • this created less competition for food and space, the resistant strain will start multiplying rapidly by binary fission
  • the resistant strain spreads