2023

• name type of cell division that produces egg cells and sperm cells


  Meiosis
• sexual reproduction produces

  offspring that are genetically different from each other
• Give 2 reasons why sexual reproduction causes variation in the offspring


  -Gametes are not genetically identical

  -genetic information from both parents
• Genotype DD is homozygous

  Genotype Dd is heterozygous
• Give 2 advantages of embryo screening

  -can find out if the embryo has an inherited disorder

  -can decide whether to continue the pregnancy
• Why is the percentage of species that are extinct only an estimate

  Humans have not found evidence of every species
• What evidence is used to study species that have become extinct

  fossils
• What is an abiotic factor that could affect the number of different plant species found near the river

  Moisture levels in the soil
• genus name of salmon

  oncorhynchus
• domain are sea lice classified in

  eukaryote
• Explain the disadvantage of selectively breeding salmon


  can be cost or time

  -All fish are genetically similar therefore,all may have the same inherited disorder
• Which hormones is given to women having IVF treatment

  FSH and LH
• target organ of the hormones used for IVF

  Ovaries
• Why is microscopes needed in the process of IVF

  to see if the egg has been fertilised
• one factor that can affect the probability of women having a child as a result of IVF treatment

  Age
• argument against IVF treatments

  -cost or religion

  -The success rate is low

  -Multiple births are a risk to the mother (Or baby)
• internal condition controlled by homeostasis

  -body temp

  -blood glucose
• Why is the control of body temperature important?


  to maintain optimum temperature for enzyme action
• Q:Explain how the evolution of antibiotic-resistant C. difficile can be slowed down. [6 marks]

  
  

  • Only use antibiotics when necessary – reduces exposure of C. difficile to antibiotics

  • Don’t use antibiotics for viral infections – they don’t work and increase resistance

  • Hand washing after toilet use – reduces spread of C. difficile

  • Keep infected people off school/work – limits transmission

  • Develop vaccines – reduces antibiotic use

  • Create new antibiotics – kills resistant strains

  • Resistant strains may evolve more slowly
• Q:Describe a method to investigate how the distance from the river affects the number of different plant species in the field.You should explain how to use a transect in your method. [4 marks]

  
  

  • Lay out a transect line at right angles from the river edge

  • Place quadrats at regular intervals along the transect

  • Count the number of different plant species in each quadrat

  • Repeat using two more transects
• Explain the environmental implications of increasing numbers of cows being farmed. [6 marks]

  
  

  • Fewer plants due to trampling and cows eating them

  • More methane released (from cows) – methane is a greenhouse gas

  • More CO₂ from respiration – contributes to global warming

  • Deforestation for grazing space – reduces biodiversity
• Some salmon have genes that result in fewer sea lice attaching to the skin.

  Describe how fish farmers can selectively breed salmon that sea lice cannot attach to.

  [3 marks]

  • Selective fish get less attached to sea lice.

  • Selected offspring breed together.

  • Repeat over so many generations until all offspring have no sea lice attached.
• Explain the advantages to salmon farmers of producing salmon that do not have sea lice attached to their skin.[3 marks]

  • Sea lice will not be feeding on salmon (skin/blood)

  • So salmon grow faster & larger.

  • So salmon can be sold for more expensive
• Describe how the hormones given to women during IVF treatment interact with other hormones to prepare the body for pregnancy.[3 marks]

  • hormones (FSH/LH) used in IVF cause an increase in progesterone and oestrogen

  • Progesterone maintains uterus lining.

  • Uterus lining is ready for embryo to be inserted.
• Which gland secretes hormones to stimulate the adrenal glands?[1 mark]

  • Pituitary (gland)
• Explain the role of the adrenal glands in responding to a decrease in body temperature.

  [5 marks]

  • Adrenal glands produce adrenaline

  • to increase heart rate

  • so faster delivery of oxygen and glucose to muscles

  • because more oxygen needed for respiration

  • to move muscles to increase body temp!
• Explain how the thyroid gland controls the response to a decrease in body temperature by negative feedback.

  [3 marks]

  • decreasing body temp causes thyroid gland to produce thyroxine

  • which increases metabolic rate

  • so increasing body temp, which decreases the production of thyroxine