Biology Paper 2- Things im unsure on

• Why does the body need to maintain optimal conditions?

  For optimal enzyme action and cell function
• internal conditions

  Blood PH + BGC
• external conditions

  • The amount of fluids you drink
  • Room temperature 
• What is the role of a receptor?

  Detects changes in the internal or external environment 
• What is the role of a coordination centre? 

  Interprets changes and organises a response
• Name the two types of effectors and state what they do.

  muscles- contact

  glands- release hormones
• How does negative feedback work?

  reverses the change
• What is the role of effectors?

  carry out the response
• What is a reflex

  An automatic response to a stimulus
• examples of reflexes

  blinking when you get dust in your eyes + sneezing
• How the endocrine system works

  1. Glands are organs that release small chemicals called hormones.
  2. These chemicals are normally released into the bloodstream, allowing them to travel around the body.
  3. They can then bind to specific cells that have the correct receptors. 
  4. This will bring about some change within the cells.
• What is the role of thyroxine? 

  regulates metabolism
• If the level of thyroxine in the blood is too low, the pituitary gland will release more thyroid stimulating hormone (TSH). 
• Which hormones can hormonal contraceptives contain?

  progesterone + oestrogen
• How can oestrogen act as a contraceptive? 

  Inhibit FSH production, so that eggs can't mature
• How can progesterone act as a contraceptive?

  Stimulate the production of mucus in the cervix, so sperm can't enter the uterus
• What is a long lasting contraceptive method?

  Intrauterine device (more than 3 years)
• What is a short lasting contraceptive method?

  Contraceptive patch (has to change every week)
• What is an invasive contraceptive method?

  Contraceptive implant
• Condoms are the only contraceptives that protect against

  Sexually transmitted diseases/infections 
• The diaphragm sits over the cervix to prevent sperm from entering the uterus
• How does a spermicide act as a contraceptive? 

  Destroy the sperm cells
• If a man undergoes sterilisation, which structure is cut and tied? 

  sperm duct
• What does luteinising hormone do?

  Stimulate an egg to be released (ovulation)
• The stages of in vitro fertilisation

  1. First, a woman is given FSH and LH to stimulate their eggs to mature.
  2. These eggs can then be collected from the woman's ovaries. Sperm is also collected from the male.
  3. The eggs are then fertilised by the sperm.
  4. These fertilised eggs are then left to grow into embryos in a laboratory incubator.
  5. Once the embryos are large enough, they are transferred to the women's uterus, so that they can develop into a foetus.
• What is Intra-Cytoplasmic Sperm Injection (ICSI)

  Sperm is injected into an egg cell with a tiny needle
• Why are embryos kept in an incubator whilst in the laboratory?

  To provide the optimum temperature for enzymes and thus cell growth
• What are the cons of IVF?

  • It can be stressful and emotionally upsetting 
  • It doesn't always work
  • Can cause abdominal pain and vomiting 
  • High chance of multiple births and associated complications
• Why do some people think IVF is unethical?

  • Some embryos (which had the potential for human life) are destroyed 
  • It could lead to 'designer babies' if parents can select embryos with certain traits
• Adrenaline causes changes in the body to prepare for a ‘fight or flight’ response.

  Describe 3 of these changes. 

  Increase heart rate

  Increase blood pressure

  Increase blood flow to muscles 

  Increases blood sugar (glucose) level
• What is the main role of thyroxine?

  increase metabolic rate
• Describe what will happen when thyroxine levels are too high.

  Thyroxine inhibits the pituitary gland...

  ...from releasing TSH.

  Less TSH means the thyroid gland won't release as much thyroxine. 

  Thyroxine levels fall back to normal over time.

  Negative feedback
• What does the term 'haploid' mean?

  A cell that only has half the normal amount of genetic material
• When two haploid cells join, they form a diploid cell. 
• Which two factors contribute to the variation between organisms? 

  • The genes that individuals inherit 
  • The environment that individuals are exposed to
• Who is credited with developing and proposing the theory of evolution?

  Charles Darwin
• Describe a series of events that might result in zebras evolving to run more quickly

  There is variation among the zebra population so that some can run faster than others 

  A mutation arises that allows some zebras to run faster

  Those zebras that can run fastest are more likely to survive... 

  ...and are therefore more likely to reproduce and pass on their advantageous alleles 

  This repeats over multiple generations 

  So the advantageous allele spreads throughout the population, until the species has 'evolved' to run faster
• Speciation is the evolutionary process by which populations evolve to become distinct species.
• What is evolution?

  inherited characteristics of a population change over time due to natural selection. (forms a new species sometimes)
• What are fossils?

  remains of organisms from millions of years ago, which are found in rocks.