Inhertitance and variation

• Mendel - studied inheritance of characteristics

  • experimented with pea plants : took a green pea plant and yellow pea planted and cross breeded - all yellow, then crossbreeded two of the yellow - 3/4 yellow + 1/4 green
  • hereditary units (genes) - recessive + dominant
  • same pattern with other characteristics such as flower colour and height
  • discoveries were only appreciated once in 90's chromosomes were discovered
• Charles Darwin

  Natural selection : random mutations create variations in species. This allows the creation of advantageous genes which make species better suited to their environment. This means that they are more likely to survive, reproduce and pass this gene on

  Evolution : inheritance of certain characteristics in a population could lead to a change for the whole species or create a new species ( they can no longer breed to from fertile offspring)

  • proven by MRSNA and fossils
• Darwin and Russel's theory

  wasn't believd because of : religious reason, lack of evidence, no discovery of DNA
• Lamark

  suggested that organisms aquired traits during their lifetime which would be passed onto their offspring

  e.g giraffes had short necks so had to eat low vegetation, they then stretched their necks during their lifetime, this was passed onto their offspring
• selective breeding = breeding best plants together to achieve better offspring

  1. select a desired characteristic
  2. find crops/animals which have this characteristic and breed them
  3. this will produce another generation of crops/animals with the desired characteristic
  4. repeat this process several times, eachtime picking the best ones drawbacks : reduces gene pool - can lead to imbreeding, less variation
• Genetic engineering

  Taking a desirable characteristic and transferring it into another organism through genetic modification
• Gene therapy


  Giving someone the healthy version of a gene to fix the inherited disorder
• Gene therapy process

  1. Find the desired gene

  2. Use an enzyme to cut it out

  3. Insert gene into a vector

  4. Introduce vector to the organism

  5. Organism takes up vector and starts producing gene which codes for the desired characteristic
• Pros of genetic engineering

  • Crops with desirable characteristics
• Cons of genetic engineering

  • Don't know how it could affect the human body
  • If crops get out into the wild they could affect ecosystems
• Human genome project = map out of human genetic code


  Importance : helps understand how genetic diseases work so can be prevented, helps diagnosis and treatment of inherited disorders, track human migration

  drawbacks : learning about genetic risk can cause stress, can lead to discrimination, misuse concerns
• Cloning animals

  1. take an egg cell from a doner and remove the nucleus to give enucleated cell
  2. take a cell you want to clone and remove nucleus
  3. fuse the enucleated cell and nucleus and give it an electric shock to encourage division
  4. once it has become an embryo implant into the uterus of the surrogate mother and allow to develop as normal
• transgenic organism = has DNA from another organism

  e.g insulin gene in cow
• Cloning by embryo transplant

  1. choose a male and female organism with the most desirable characteristics
  2. fertilise the egg with the sperm forming a zygote
  3. once an embryo is formed split it into many smaller embroys
  4. emplant each embryo into the uterus of a surrogate cow
  5. these offspring will be indectical clones
• Cloning through cuttings

  1. find a desirable plant
  2. cut a piece of the plant off a place in soil
  3. add growth hormones and nutrients allowing the new plant to grow into a clone of the previous one
• micropropagation (cloning using tissue cultures)

  1. find a plant with desirable characteristics of the plant you want to clone
  2. cut small pieces of plant tissue (explants) from tips of stem and sterilise
  3. place explants in agar (containing growth hormones) and let them grow into small groups of cells called calluses
  4. transfer calluses to soil where they can become plantlets (baby plants) which will grow into normal plants
• fossils

  • allow scientists to learn about extinct species
  • evidence for evolution
• formation of fossils

  • gradual replacement by minerals : organisms decay slowly and cells are slowly replaced by minerals forming rock-like substances
  • casts - organisms are buried in soft materials such as clay, when these harden the organism decays and a gap the same size of the organism is left behind
  • impressions - e.g footprints on the ground
  • preservation (no decay) - an organism is trapped in amber where there is no moisture or oxygen so the organism is intact
• why don't we have a full fossil record

  • early life forms were soft bodied so they decayed quickly
  • could've become destroyed
• reasons for extinction :

  • too warm
  • environment changes too quickly
  • habitat destroyed
  • new predator
  • human hunting
  • new disease
  • catastrophic event e.g meteriod
• Antibiotic resistance

  • random mutations in DNA lead them to be less affected by antibiotic
  • these can reproduce quickly as there is less competition for food
• super bug (MRSA) - resistant to many types of antibiotics
• factors leading to antibiotic resistance

  • unnecessary prescriptions - viral infecions, non-serious cases
  • farming - healthy animals are fed antibiotics to prevent illness and for increased growth
• classification = universal names for organisms


  linnean system, written in Latin

  kingdom - phylum - class - order - family - genus - specie

  Dear Kate Please Come Over For Great Spagetti
• binomial naming system

  • genus + species e.g homo sapiens
  • write in itallics
• Three domain system - placed above kingdom

  Eukaryota - eukaryotic cells e.g plants, fungi, animals

  Bacteria - prokaryotic, found everywhere

  Archaea - prokaryotic, found in extreme environments
• Evolutionary trees = evolutionary relationships between differeny groups through common ancestors

  splitting lines is an ancestor splitting into two different species

  
• Wallace

  • studying colouration in animals
  • speciation : formation of a new species
• speciation

  • isolation of species
  • these species live in different environments so have different environmental pressures
  • this means that different traits will be favorable so natural selection will make the groups look different
  • over time the two groups will evolve to be so different they will no longer be able to interbreed to produce fertile offspring