Biology - Unit 1a

Cards for AQA GCSE Biology unit 1a

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Responding to Change

  • Your nervous system enables you to react to your surroundings + co-ordinate your behaviour
  • Nervous system carries electrical impulses - travel 1-120m/s
  • Impulses help you to react to your surroundings quickly
  • Hormones - chemical substances that control many processes in the body
  • Glands - secrete hormones into the body
  • Hormones are carried in the blood stream to target organs
  • They can act v. quickly or slow + long lasting
  • Stimuli - changes in surroundings
  • Receptors - cells that pick up stimuli
  • Receptors are usually clustered together in sense organs
  • When a sensory receptor detects a stimulus, it passes along neurones
  • Neurones found in bundles - nerves
  • It travels to CNS - brain + spinal cord
  • Sensory neurone - cells which carry impulses from sense organs to CNS
  • Relay neurone - passes the impulse from the sensory to motor neurones
  • Motor neurone - carries impulses from CNS to effector -a muscle or gland
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Reflex Actions

  • Reflex actions - responses to stimuli that are automatic + rapid
  • The run everyday bodily functions + help you avoid danger
  • They do not involve the brain

The gap between two neurones is called a synapse. Chemicals diffuse across the gap which stimulate the impulse on the other side.

Stimulus > Receptor > Co-ordinator > Effector > Response

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The Menstrual Cycle

  • The cycle takes about 28 days with ovulation about 14 days in
  • The cycle is controlled by 3 hormones
  • Hormones control the release of an egg from the ovary + the build up of the lining of the womb in the menstrual cycle
  • The main hormones involved are FSH and LH from the pituitary gland and oestrogen from the ovaries
  • FSH is made in the pituitary gland and causes the egg to mature and oestrogen to be produced
  • Oestrogen is produced by the ovaries + inhibits the further production of FSH. It stimulates the production of LH + also stimulates the womb lining to develop to receive the fertilised egg
  • LH is made by the pituitary gland + stimulates the mature egg to be released
  • If the egg is not fertilised, the lining is shed in the monthly period
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The Artificial Control of Fertility

  • The contraceptive pill contains oestrogen that prevents the production of FSH so no egg matures
  • FSH can be given to a woman to help her to produce eggs
  • Hormones can be used to control fertility

IVF Treatment:

  • Fertility drugs are used to make lots of eggs mature at the same time for collection
  • The eggs are collected and placed in a special solution in a petri dish
  • A sample of semen is collected
  • The eggs and semen are mixed in the petri dish
  • The eggs are checked to make sure they have been fertilised + early embryos are developing
  • When the eggs have formed tiny balls of cells, 1 or 2 of the embryos are placed in the mother's uterus
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Advantages & Disadvantages of Artificial Control o


  • Pill - smaller families therefore less poverty
  • Pill - controls population growth e.g. China
  • IVF - helps women have children


  • Pill - health risks e.g. weight gain
  • Fertility drugs - large multiple births - often premature therefore expensive
  • Pill - ethical - denying life
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Controlling Conditions

It is very important that the internal conditions of the body are kept within certain limits.

Water and ion content, as well as temperature and blood sugar level, are all carefully controlled.

  • Water is leaving the body all the time as we breathe out and sweat.
  • We lose any excess water in the urine (produced by the kidneys).
  • We also lose ions in our sweat and in the urine
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Very detailed, perfect note-taking skills, everything tightly packed and condensed.

+Professional material, well done. -Rated 5*

Good Job!



To gain extra marks from me, you could include the ethical issues.

Those questions ALWAYS come up and they trip you up easily.



Stright to the point notes. This really helped, thank you!

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