2024

• food chain (e.g)for algae,crabs and limpets

  algae---->limpets---->crabs
• Why throwing a quadrat is not a random method to estimate population size

  Location of the sample will be biased; therefore, results will not be representative of the actual abundance.
• Describe one method the students could use to plan where the quadrant should be randomly placed each time

  Divide the area into a grid and use a random number generator
• One hazard students should be aware of when collecting data on the sea shore

  -throwing quadrants

  ---animals
• One type of pollution in water that affects the population of an animal

  fertiliser
• type of classification group is eukaryota

  Domain
• asexual reproduction

  offspring are genetically identical
• gamete

  A gamete contains half of the number of chromosomes
• Describe one way a new plant species could be identified as being in the same genus as potatoes

  It has similar DNA/genes
• heterozygous & homozygous

  Having two different versions, or alleles, of a gene at a particular location on a chromosome. This means one allele was inherited from each parent. The opposite of heterozygous is homozygous, where both alleles are the same. 
• mutation is

  a change in gene
• How can a mutation result in the production of a non-functioning enzyme

  mutation causes an incorrect sequence of amino acids, which causes the enzyme to be a different shape
• How the process of IVF can result in pregnancy

  FSH and LH are injected into females to stimulate the maturation of eggs. Collected eggs are fertilised in a laboratory. Fertilised eggs undergo mitosis. One or two embryos are inserted into the woman's uterus
• against embryo screening

  -risk to the embryo

  -stressful process

  -risk to mother

  high cost

  -religion(ethical reasons)
• Describe how basal metabolic rate is increased

  More thyroxine is released from the thyroid gland
• Definition of ecosystem

  The interaction of a community of living organisms and the non-living parts of the environment.
• Why might animal species be important for the stability of a whole community

  -maintain biodiversity

  -may disperse pollen

  -may provide shelter for other species(to survive)
• If there is a decrease in the concentration of dissolved oxygen in the river, water will affect the population of otters.

  decrease in oxygen concentration causes a decrease in the number of fish because fish need oxygen to respire (aerobically); therefore otter population decrease due to less food.
• Hormones are released

  from endocrine glands
• which gland releases hormones to control other glands

  pituitary
• Adrenaline can increase blood glucose concentration. What is 1 another effect of adrenaline?

  increased blood flow to muscles
• What type of cells in the body detect changes

  receptor cells or neurons
• Why are people with type 1 diabetes chosen instead of people who don't have diabetes?

  Blood glucose concentration varies more than in people who don't have diabetes because no insulin is produced when blood glucose concentration increases.
• control variable in investigating the blood glucose concentration affecting reaction time

  -age

  -sex

  -food and drink consumption before and during the test

  -amount of sleep

  -any distractions
• Why was it important for scientists to monitor the health of each person during the investigation

  high blood glucose conc is dangerous
• How is blood glucose concentration maintained within narrow limits in people who don't have diabetes ...(5 marks)

  When blood glucose concentration increases, the pancreas releases insulin. Insulin causes glucose to move/from the blood into muscle cells in muscle-excess glucose is converted to glycogen. When blood glucose concentration decreases, the pancreas releases glucagon. Glucagon causes glycogen to be converted into glucose and released into the blood.
• Q:Explain why genetic modification of crop plants may be important for the human population to survive climate change. [6 marks]

  
  

  effects of climate change

  • Causes flooding, drought, temperature changes

  • Reduces farming land (flooding, sea level rise, desertification)

  • Current crops may not survive new conditions

  
  

  benefits of GM

  •Crops can grow in more conditions

  • More resistant to pests/diseases

  • Can be stored longer

  • Higher yield/growth rate

  • Helps feed growing population

  • Useful if farming land is limited

  
  

  other relevant content

  • Less variation in current crops due to cloning/selective breeding

  • Evolution may be too slow to keep up with climate change
• Q:Explain the trends in the data when warfarin was being given and when warfarin was no longer given.Use Table 1. [6 marks]

  
  

  trends

  • Resistance increased for 6 months when warfarin was used

  • Then decreased when warfarin stopped

  • Decrease was slower than the increase

  • Change didn’t happen instantly at 6 months

  
  

  increase explanations

  • Some rats had resistance alleles due to random mutation

  • These rats survived warfarin and reproduced

  • Passed on resistance to offspring

  • Repeated over generations → most became resistant

  
  

  decrease explanations

  • Without warfarin, resistant rats were outcompeted by bigger, non-resistant rats

  • Non-resistant rats killed or outcompeted resistant ones

  • So non-resistant rats reproduced more
• Describe how an increase in the chemicals could decrease reaction time. [2 marks]

  • More chemicals means impulses are more likely to reach muscles

  • Diffusion of chemicals across synapses is faster