B4

• 4.2 Explain Darwin's theory of evolution by natural selection- evolution

  evolution is the gradual change in the characteristics of a species over time.
• genetic variation


  the characteristics of individuals vary (due to differences in genes)
• environmental change


  conditions in an area change, ie the lack of food may cause a competition between organisms
• 4.3 Explain how the emergence of resistant organisms supports Darwin's theory of evolution including antibiotic resistance in bacteria

  bacteria in a population show variation in the amount of resistance to warfarin. With time, the antibiotics kills more and more bacteria. The more resistant bacteria take the longest to die. if the bacteria course finishes too early and the resistant bacteria survive and reproduce. the new population of bacteria are all now resistant to the antibiotic, so the individuals have the 'better adapted variations
• 4.4 Describe the evidence for human evolution, based on fossils, including: a Ardi from 4.4 million years ago


  Ardi is a fossil of the species Ardipithecus ramidus, found in Ethiopia and is 4.4 million years ago.

  - Structure of feet suggest she climbed trees

  - long arms and legs (more ape than human)

  - brain size the same size as a chimpanzees

  - structure of legs suggested she walked upright. Structure of hand bone suggest she didn't use hands to walk
• 4.4 Describe the evidence for human evolution, based on fossils- Lucy from 3.2 million years ago


  Lucy is a fossil of the species Australopithecus afarensis . Found in Ethiopia and is 3.2 million years old.

  -arched feet more adapted for walking than climbing

  -size of arms and legs similar to apes and humans

  -brain slightly larger than Ardi's but still small (chimp's brain)

  -leg bone structure walked upright and more efficient than Ardi)
• 4.4 Describe the evidence for human evolution, based on fossils, including: Leakey's discovery of fossils from 1.6 million years ago


  Leaky and his team found fossil hominids 1.6 million years old.

  1) Turkana Boy - 1.6 million years old skeleton of homo erectus. Ape and human like features, more like Lucy

  2) Short arms and long legs much like human, less ape. Brain size much larger than Lucy's

  3) Structure of legs and feet - better adapted to walking upright than Lucy
• 4.5 Describe the evidence for human evolution based on stone tools, including: how these can be dated from their environment.

  1. Looking at structural features of tool or fossil - simpler tools more likely to be older

  2. Stratigraphy - the study of layers of rock. The deeper the rock the older it is so tools in deeper layers of rock tend to be older.

  3. Carbon-14 dating - Stone tools are often found with carbon-containing material.
• 4.5 Describe the evidence for human evolution based on stone tools, including: the development of stone tools over time

  The oldest stone tools are very simple, but would have helped with skinning animal or cutting up meat. Tools found in more recent rock are more sophisticated (more smaller and sharper).
• 4.7 Describe how genetic analysis has led to the suggestion of the three domains rather than the five kingdoms classification method

  The development of genetic analysis means we are able to determine and compare sequences of DNA bases and also RNA sequences in a similar way

  Using RNA sequencing, scientists found that some of Prokaryote kingdom were not as closely related as first thought. It was proposed that this kingdom should be split into two groups called Archaea and Bacteria.
• What are the five kingdoms of living things?

  -Animals (fish, mammals, reptiles)

  -Plants (grasses, trees)

  -Fungi (mushrooms and toadstools, yeasts)

  -Prokaryotes (all single-celled organisms without a nucleus)

  -Protists (eukaryotic single-celled organisms)
• Three Domains


  -Archaea (cells with no nucleus, genes contained unused sections of DNA

  -Bacteria (cells with no nucleus, no unused sections in genes)

  -Eukarya (cells with a nucleus, unused sections in genes
• inheritance


  survivors breed and pass on their variations to their offspring, meaning the next generation contains more individuals with the 'better-adapted variations
• evolution


  if the environmental conditions remain changed, natural selection occurs over and over agains, so a new species evolves with the individuals all having the 'better- adapted variations
• natural selection


  by chance, the variations of some individuals make them better at coping with the change than others, and more likely to survive
• 4.8 Explain selective breeding and its impact on food plants and domesticated animals

  selective breeding is by selecting the most desirable animals in a species and breeding them together. Then, select the most desirable offspring and breed them together over and over again so that you produce new breeds and varieties of species and plants
• what plants and animals are selectively bred for

  disease resistance

  
  

  yield

  
  

  coping with certain environmental conditions

  
  

  fast growth

  
  

  flavour
• genetic engeneering


  changing the DNA of one organism (genome) by inserting genes from another. this creates GMOs (genetically modified organisms). much faster than natural selection but much more expensive
• GMOs


  golden rice produces beta-carotene in it's grains, which humans need to make vitamin D. a lack of this can cause blindness.

  
  

  Scientists are developing goats and sheep to produce proteins in their milk which can treat human illnesses.

  
  

  GM pigs are being developed with human-like organs to use in organ transplants
• 4.10 Describe genetic engineering as...


  a process which involves modifying the genome of an organism to introduce desirable characteristics
• 4.11 Describe the main stages of genetic engineering - 1

  restriction enzymes make staggered cuts in DNA molecules, producing sections with a few unpaired bases at each end - sticky ends. a section of DNA containing the gene for making insulin is cut out this way
• 4.11 Describe the main stages of genetic engineering - 2

  restriction enzymes are also used to cut plasmids open. by using the same restriction enzyme as was used on the human chromosome of DNA, the cut plasmids have the same sticky ends
• 4.11 Describe the main stages of genetic engineering - 3

  sections of DNA containing the insulin gene are mixed with the cut plasmids. the complementary bases on the sticky ends pair up. an enzyme called ligase is used to join the ends together
• 4.11 Describe the main stages of genetic engineering - 4

  the plasmids are then inserted back into the bacteria, which are then grown in huge tanks. the insulin they make can now be easily extracted
• Recombinant DNA


  DNA produced by combining DNA from different sources
• vector


  any DNA molecule used to carry new DNA into another cell
• 4.14 Evaluate the benefits and risks of genetic engineering and selective breeding in modern agriculture and medicine, including practical and ethical implications


  genes exist in different forms (alleles) which cause variation in characteristics. in selective breeding, only certain characteristics are selected, causing others to become rare or disappear. therefore, alleles that may be useful in the future are no longer available
• more selective breeding risks

  farming huge numbers of the same breed or variety is a problem. all the organisms are very similar, so if a change in condition (eg disease) affects one organism, all the others are affected

  
  

  animal welfare is also a concern. some selectively bred chickens produce so much breast meat they can hardly stand up
• genetic engineering - benefits

  some produced to be resistant to some insects (less insecticide needed) and others resistant to certain herbicides (so will kill the weed and not the crop)
• genetic engineering - risks

  GM plants are expensive

  some think that GM crops will reproduce with wild plant varieties and pass on their resistance genes, having unknown consequences in wild plants.

  others think eating GM organisms will be bad for health (no evidence to support this)
• GM bacteria - benefits

  produce many useful substances, such as insulin, which is needed to treat type 1 diabetes. used to be extracted from dead pigs and cows, but it was expensive and not suitable for vegans or religious diets. however it is slightly different to mammal insulin so not all diabetics can use it.