Biology Paper 2

• Homeostasis


  The maintenance of internal conditions to keep them at an optimum
• What internal conditions are controlled as part of homeostasis? (3)

  Blood glucose (sugar)

  Water levels

  Temperature
• Why is it important to maintain an optimum temperature?

  For optimum enzyme activity in the body
• What is the pathway of a nervous reflex?

  Stimulus --> receptor --> sensory neurone --> relay neurone --> motor neurone --> effector --> response
• What is a stimulus?


  A change in the environment
• Why are reflex actions important?

  Reflex actions aid survival by preventing harm to the body.
• Why does the reflex arc not go via the brain?

  As it does not require a decision to be made as the reflex is there to prevent harm

  and

  It is a shorter and therefore quicker path to skip out the brain
• What is a synapse?


  Junction between two neurons. Neurons do not touch.
• What is the peripheral nervous system (PNS)?


  This is the part of the nervous system outside the CNS. These are the nerves that extend from the brain and spinal cord
• What is the difference between nervous responses and hormonal responses?

  Nervous responses faster

  Hormonal responses longer lasting
• Endocrine system


  Consists of glands that control many of the body's activities by producing hormones.
• Where is the pituitary gland?

  In the brain

  
• Where is the thyroid gland?

  In the neck

  
• Where is the adrenal gland?

  On top of the kidneys

  
• Where are the ovaries?


  Lower abdomen

  
• Where are the testes?

  Suspended in scrotum

  
• What happens when blood glucose rises too high?

  1. Pancreas detects this and secretes insulin

  2. Insulin allows glucose to move from the blood into the muscle and liver cells

  3. Insulin also triggers the liver to store glucose as glycogen

  
  

  This lowers blood glucose
• What is type 1 diabetes?

  Where the pancreas cannot produce insulin so blood glucose can rise uncontrollably
• What is type 2 diabetes?

  Where the insulin is still being produced but is ineffective (does not bring about a response)
• How can type 1 diabetes be managed?

  Through regular insulin injections
• How can type 2 diabetes be managed?

  Diet and exercise
• Ovulation


  The process of releasing a mature egg every 28 days in the menstrual cycle
• What is the function of FSH?

  Maturation of eggs in ovaries
• Where is FSH secreted?

  Pituitary gland
• Where is LH secreted from?

  Pituitary gland
• What is the function of oestrogen?


  Maintain the lining of the uterus
• Where is oestrogen secreted from?

  Ovaries
• What is the function of progesterone?

  Maintain the lining of the uterus
• Examples of non-hormonal contraceptives

  Barrier methods such as condoms and diaphragms

  Spermicidal agents

  Abstinence

  Surgical methods (sterilisation)
• How do hormonal contraceptives work?

  Release a progesterone which inhibits FSH so no eggs can mature
• Meiosis


  Cell division that produces 4 genetically different gametes which have half the number of chromosomes (23 chromosomes) from the parent cell
• Mitosis


  Cell division that produces 2 genetically identical cells from the parent cell with 46 chromosomes in each
• Differences between mitosis and meiosis

  Mitosis vs meiosis

  1 division vs 2 divisions

  46 chromosomes vs 23 chromosomes (in the daughter cell)

  Genetically identical vs genetically different daughter cells

  Used to make new body cells vs used to make gametes
• Sexual reproduction


  A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents
• Structure of DNA


  Polymer (chain) of 2 strands forming a double helix
• Chromosomes


  Structures in a cell containing DNA
• Gene


  Small section of DNA on a chromosome coding for a specific protein (characteristic)
• Gamete


  Sex cells with half the number of chromosomes (23 in humans)

  Humans have egg and sperm

  Plants have ova and pollen
• Allele


  A type of gene (dominant or recessive)
• Dominant allele


  An allele which is always expressed if it is present in the genotype