Natural Selection And Genetic Modification Flashcards
What was the theory of evolution?
- Variation exists within species due to DNA mutations
- Organisms with characteristics most suited to be environment are more likely to survive and reproduce
- The beneficial characteristics are passed on to the next generation
- Over many generations the frequency of alleles for this characteristic increase within the population
How does bacteria resistance support Darwin’s theory?
- Bacteria reproduce at a fast rate
- Random mutation occurs in the genes individual bacterial cells
- Exposure to antibiotics create a selection pressure and bacteria without the mutation will die
- Those with antibiotic resistance can reproduce and pass on the resistant gene
- Supports his theory as the new bacteria is selected by environment to have an advantageous feature for survival
When did the Ardi species live?
4.4 billion years ago
When did the Lucy species live?
3.2 million years ago
What evidence for human evolution did the Ardi skeleton give?
- Contains ‘humanoid’ features but resembles an ape so is phenotypically between the two
- Ardi’s bones show she was able to walk upright but had long arms
- Bone structure in Ardi’s feet is different from chimpanzees, suggesting they evolved separately
What evidence for human evolution did the Lucy skeleton give?
- Bone structure suggests she walked upright but she had a small chimp-like skull and brain
- Represents another intermediate between apes and early humans
What evidence for human evolution did Leakeys’ discoveries give?
- Discovered fossils from 1.6 million years ago
- The skeleton (homo habilis) looked more like a modern human than Ardi or Lucy
- They also discovered stone tools
How have stone tools developed over human evolution?
- Early Stone Age (Homo habilis 1.5 million years), used basic tools created by smashing rocks together
- Late stone Age (homo neanderthalensis 40,000 years), used pointed arrowheads, spears and hooks
What are the two methods that stone tools can be dated?
Radiometric carbon dating - by looking at the natural radioactive decay of a carbon isotope
Stratifying rock layers – looking at the layer of sediment in which a rock was found
How does the pentadactyl limb provide evidence for evolution?
- A pentadactyl limb has five digits
- This is seen in many organisms, implying they all come from a common ancestor
- They have each ‘branched off’ at some stage of evolution, due to different selection pressures of different environments
What was the five kingdoms system?
- All organisms were split into: animals, plants, fungi, prokaryotes, protists
- Each kingdom was then divided into: phylum, class, genus, order, species
- The binomial naming system was based on the genus and species e.g. Homo (genus) Sapiens (species)
What are the three domains?
Archaea: primitive bacteria, usually live in extreme environments, no nucleus
Bacteria: true bacteria, no nucleus
Eukaryota: organisms who have a nucleus enclosed in membranes, includes the kingdoms protists, fungi, plants and animals
What is are some reasons for selective breeding?
- Disease resistance
- Increased yield
- Better ability to cope with difficult conditions
- Faster growth
- Better flavour
What is the process of selective breeding?
- Parents or plants with desired characteristics are bred together
- The offspring with desired characteristics are bred together
- This is repeated many times until all the offspring have the desired characteristics
What is the issue with selective breeding?
- Inbreeding
- Reduces gene pool, as number of different alleles reduces
- If environment changes the species could become extinct because little variation
- Small gene pool means more chance of genetic defects, as recessive characteristics are more likely 
What is tissue culture?
- A method of culturing living tissue within a growth medium
- Used to grow many identical cells
What are the stages of tissue culture for a plant?
- Take a plant with desirable characteristics
- Remove a piece of tissue in a fast-growing region (e.g. the root or shoot tip)
- Using aseptic technique, place the tissue on a growth medium (containing hormones and nutrients)
- Once developed enough it is transferred to compost for further growth
What are the advantages of cell cultures for animals?
- To test the effect of drugs and other chemicals on cells
- To check for cancer cells in a sample from a patient
- To produce important proteins, e.g. antibodies
What are the advantages of cell cultures for plants?
- Produce thousands of identical plants from just one parent 
- To make plant products (e.g. to treat cancer)
- Produce disease free plants
What is genetic engineering?
Modifying a genome to introduce desirable characteristics
What are the stages of genetic engineering?
- Genes from chromosomes are ‘cut out’ using restriction enzymes
- This leaves a few unpaired bases at each end (called sticky ends)
- Restriction enzymes are used to cut the vector
- Ligase enzyme attaches the sticky ends of the gene and vector together producing a recombinant gene product
- Vector is placed in another organism at early stage of development
What are the uses of genetic engineering?
- In medicine to produce certain hormones in microorganisms
- Improve yields by improving growth rates, crops can grow in different conditions and make their own pesticide
- Crops with extra vitamins in areas where they are difficult to obtain
- Greater yields can help solve world hunger
What are the risks of genetic engineering?
- May transfer gene to other species, what benefits one plant may harm another
- Some believe its unethical to interfere with nature
- GM crops seeds are often more expensive so developing countries may not afford them
- Could lead to genetic engineering in humans (designer babies)
- Create a selection pressure which leads to increased resistance, creating super weeds and pests
How are Bt crops created?
- The bacteria naturally produces toxins that kill insect larvae
- The gene for Bt toxin is ‘cut out’ of the bacterial DNA using restriction enzymes
- It is then inserted into the DNA of a plant cell using ligase
- The crop will then produce the toxin and any insects that eat it will die
What are the benefits of selective breeding?
- Increased yield, produce higher quality or larger mass of food
- Can be bred to be resistance to a particular disease
- Cheaper than genetic modification
What are the disadvantages of selective breeding?
- May get rid of characteristics that would be useful in the future
- Animal welfare, ethical concerns
- Lack of genetic variation, susceptible to same diseases
- Can cause severe health problems
- Takes a while
What are the advantages of disadvantages of fertilisers?
Advantages:
- Provide useful nutrients (nitrates and phosphates)
- These help them grow and be resistant to environmental conditions
- Good way to use animal waste
Disadvantages:
- Excess fertiliser can pollute waterways, causing eutrophication
- Artificial fertilisers are expensive to make
- Artificial fertilisers can reduce soil biodiversity
What are the advantages and disadvantages of biological control?
Advantages:
- The pest cannot become resistant
- If well chosen, it is specific to the pest
- Avoids using chemical pesticides which can leave harmful residues
- Reduces work/effort
Disadvantages:
- May not completely get rid of the pest
- The control agent may become a pest itself