TOPIC 4 BIOLOGY

• Biodiversity


  the variety of living organisms in an area.
• Species diversity

  the number of different species and the abundance of each species in an area
• Genetic diversity

  the variation of alleles in the gene pool of a species
• Endemism

  when a species is unique to a single place
• How is species richness counted

  counting the number of species in a known area using a quadrat
• Why does biodiversity need to maintained


  loss of biodiversity means there are fewer species. Loss of endemic species leads to extinction. Some species have not yet been discovered that may be useful
• Structure of a cellulose cell wall

  cellulose is made of long unbranced chains of B glucose joined by 1-4 glycosidic bonds, the bonds are straight so the celluloe chains are straight. 50 to 80 cellulose chains are held together by many hydrogen bonds forming microfibrils, microfibrils arranged in a mesh, microfibrils held together by pectin and hemicelluloses
• Structure of starch

  mixture of two polysaccharides of alpha glucose. amylose is a long unbranched chain of a glucose. Coiled strcture which makes it compact so good for storage. amylopectin is a long branched chain of a glucose. its side brances allow enzymes to get at the glycosidic bonds easily so glucose can be released quickly. it is insoluble in water
• Secondary thickening of cell walls

  when some structural plant cells have finished growing they produce a second cell wall between the normal cell wall and the cell membrane. the secondary cell wall is thicker and has more lignin so makes plant fibres stronger.
• How does lignin add strength to xylem tissue


  lignin holds microfibrils together and keeps them parallel
• How does the structure of xylem allow them to transport water

  Hollow as no cytoplasm, vessels have no end walls and pits, vessels are strong so do not collapse, lignin makes the walls waterproof
• Why do plants need calcium

  to make pectin for the middle lamella
• Why are different enzymes needed to digest starch and cellulose

  different shape molecule requires a different enzyme as they have different active site shapes. cellulose is made of B gluclose and starch of alpha glucose. 1,6 glycosidic bonds are only in starch. starch is made of amylose and amylopectin, cellulose is linear and starch is unbranched
• How does the structure of sclerenchyma make them good for rope


  thick lignin walls for strength and makes them waterproof, flexible so do not break easily, light because are hollow
• How is the structure of starch related to its function


  made up of many glucose monomers so good energy storage. is large so is unreactive and insoluble
• Why is little genetic diversity bad

  no selective advantage when the enviroment changes, less likely to survive, so this increases risk of extinction
• Why is increased genetic diversity good

  greater chance of survival as higher chance of having beneficial alleles, increased mating with genetically different individuals decreases inbreeding
• Why would no plant develop if xylem was used to demonstrate totipotency

  xylem tissue is dead so no genetic material is present, it is not totipotent as it is already specialised, it is unable to undergo mitosis
• What do seedbanks do with seeds to ensure long term conservation

  assess seed viability - only select seeds with a living embryo. Use X rays to detect embryo presence, clean and dry seeds and store at low temperatures. regularly test viability of seeds.
• How are seeds selected for storage


  from different plants to provide genetic variation. x rayed to check for viability
• Why are seeds stored in dry and cold conditions

  reduces enzyme activity, prevents germination of seeds, prevents microbial growth
• Advantages of making rope from sustainable resources

  renewable so more can be grown
• Why are papers checked by scientists

  peer review to check conclusions drawn from data are valid
• How do scientists share their data with the scientific community

  Scientific conferences, journals and blogs
• What is critical evaluation of data by scientific community

  Checking methods, collecting more data and testing if the date can be replicated
• Why is it better to store seeds rather than the whole plant

  takes less space so can have more, more genetic variety, less maintainance costs, can freeze eggs
• How does the use of Hardy Weinberg equation allow us to see if evolution has occured

  identify changes in the allele frequency over time, if allele frequency has changed then evolution has occured
• How does no ATP production affect transport of substances

  translocation inhibited by transpiration stream not inhibited. Phloem contains cytoplasm but xylem does not. Cytoplasm has mitochondria involved in metabolism.
• Why is conservation important for endemic species

  they are vulnerable to extinction as they are only found in one place so cannot migrate if their habitat is threatened
• Why is it important to measure species diversity

  to compare different habitats or study how a habitat has changed over time
• Why is a sample of a population taken

  it is too time consuming to count every individual organism in a habitat. estimates about the whole habitat are based on the sample
• When is a quadrat used

  for plants
• When is a sweepnet used

  for flying insects
• When is a pitfall trap used

  for ground insects
• When is a net used

  for aquatic animals
• What does sampling involve

  choosing an area to sample. the sample should be random to avoid bias, use a random number generator to select coordinates for a grid, count the number of individuals of each species in the sample area, repeat the process as it gives a better indication of the whole habitat,
• Why may individuals of the same species vary

  they have different alleles
• gene pool

  complete set of alleles in a species
• How can looking at phenotype help to measure genetic diversity of a species

  different phenotypes are coded for by different alleles, so the larger the number of different phenotypes, the greater the diversity of alleles so the greater the genetic diversity
• How can looking at genotype help to measure genetic diversity of a species

  analyse the sequence of base pairs in DNA samples of organisms. the order of bases in different alleles is slightly different. by sequencing the DNA of individuals of the same species, you can look at similarities and dfferences in the alleles. The larger the number of dif alleles the greater the genetic diversity