questions 3

• what might have caused a reduction in the heterozygosity(genetic diversity) of a population?

  • selection pressures would decrease frequency of different alleles in a population
  • due to natural selection
  • can lead to speciation
• what is a mutation?

  • a change of base sequence coding for different amino acids potentially causing different polypeptide chains
  • mutations occur via copying mistakes
• what is a niche?

  • the role an organism plays in an ecosystem
• what are the names of the different stages of classification?

  • kingdom, phylum,class,order,family,genus,species
• what is the structure of an amino acid?

  • carboxyl group, amine group and variable R group
  • peptide bonds form via condensation reactions between amino acids
• explain how proteins are formed at the ribosome(translation)

  • MRNA attaches to ribosome
  • TRNA binds to specific amino acid
  • TRNA anticodon binds to MRNA codon via complementary base pairing
  • ribosome holds 2 TRNA molecules/amino acids in place, these amino acids can form peptide bonds
• what is the difference between allopatric and sympatric evolution?

  • allopatric occurs via geographical barriers
  • sympatric occurs via mutation
  • for both, 2 populations are reproductively isolated
• symbiotic relationship

  • the close ecological relationship between members of two or more different species in which both species mutually benefit
• what is a metabolic rate

  • the amount of energy expended by that organism within a give n period of time
• describe the structure of an antibody

  • y shaped molecules
  • 4 polypeptide chains, 2 'heavy' attached by disulphide bonds to 2 'light'
  • each chain has a constant region and variable region
  • the amino acid sequence in the variable region are different for each antibody
• describe the structure of a virus

  • non cellular infectious particles
  • a nucleic acid core(DNA or RNA)
  • a protein coat called a 'capsid'
  • some have an outer layer called an envelope
• describe some aseptic techniques used in growing a culture

  • disinfect all surfaces and equipment
  • work close to a bunsen burner
  • sterilise the inoculating loop(pass through a flame)
  • open the petri dish only a little bit
• symbiotic relationship

  • when both species benefit from the relationship
  • sloths are camoflaged so arent seen by predators and the algae get shelter
  • also algae provide some kind of nutrition to sloths
• why might people want to keep sloths in captivity

  • because they are endangered so it conserves the species
• why is it important Seymour cited work carried out by other scientists

  • if they all find the same conclusions
  • then it strengthens the evidence for his theory
  • it is important that data can be replicated by other scientists and that they get similar results
• what are the advantages and disadvantages of only eating one type of food?

  • advantage is that there isnt much competition from other species as most can digest the leaves easily
  • disadvantage is that if food source ran low or died, then they wouldn't be able to adapt and survive
• why is it an advantage for an animal to take longer to digest their food

  • digestion is an active process thus requires energy
  • respiration also gives out heat to surroundings
  • taking longer to digest means less energy is needed in same amount of time, allowing lower metabolic rate
• explain how shivering helps to warm up the body

  • shivering involves contraction of muscles
  • more respiration in muscls occuring, respiration is an exothermic reaction
  • so heat is given off
• why would it be a disadvantage for sloths to be able to jump

  • jumping would mean more muscle contractions so more heat given off via respiration
  • the mean metabolic rate would increase
  • this is a disadvantage as they wouldnt be able to eat enough leaves to provide for the energy requirements
• what is a tendon

  • a non-elastic, fibrous connective tissue that attaches muscle to bone
• tendons are made of collagen, describe structure of collagen

  • it is a fibrous protein composed of 3 polypeptide chains wrapped around eachother to form quaternary structure, held together by hydrogen bonds
• explain how muscles contract using the sliding filament theory

  • CA+ released from sarcoplasmic reticulum upon stimulation
  • the bind to troponin, causing it to change shape and displace tropomyosin, exposing myosin binding sites
  • myosin and actin cross bridges form, ADP and PI released, myosin head moves forward which shortens the sarcolemma
  • free ATP binds, myosin head changes shape, ATPase in myosin head breaks ATP back into ADP+PI to restore original state
  • repeated stimulation causes continued contraction
• why would it be an advantage to have 'a heavy tolerance to accumulation of lactic acid'

  • lactic acid builds up during anaerobic respiration, cause a decrease in blood PH and causes pain in muscles
  • being tolerant would mean a longer period of anerobic respiration could occur