Biology paper 2

• Homeostasis


  Organism's ability to regulate internal conditions even when external conditions change
• Nervous system response

  Receptor detects change due to a stimulus, electrical signal travels to the spine through sensory and relay neurons, signal travels across the synapse by a neurotransmitter, signal can go to the brain for a conscious decision, signal goes back to an affector via relay and motor neurons for action
• Internal conditions regulated by our bodies

  • Blood glucose concentration
  • Temperature
  • Water levels
• Glands as affectors


  • Produce specific chemicals your body needs depending on the situation
• MRI scans are a way of seeing the activity in your brain safely
• Eye structure

  • Pupil changes size depending on light intensity, cornea is the transparent outer layer, retina at the back consists of Rod and Cone cells responding to light
• Importance of homeostasis

  • Crucial chemical reactions involving enzymes can happen at an optimum rate
• Nervous system

  Consists of CNS (central nervous system) - brain and spinal cord, and PNS (peripheral nervous system) - nerves that go through the rest of the body
• Reflex is when the signal bypasses the brain and goes straight through the spine to the affector, known as a reflex arc
• Investigating reaction times


  Measure the distance a ruler falls before catching it, introduce independent variables like stimulants or depressants to observe changes in reaction time
• Accommodation of the eye

  • Ability to change the shape of the lens to focus light from objects at different distances
• Cone cells


  • Detect green, blue, or red wavelengths of light, a mix of which produces the colors we perceive
• Hyperopia is long-sightedness
• If too hot, sweat glands in the skin cause water to cover the surface, which evaporates taking heat away from the body quickly
• Shivering occurs when too cold, causing muscles to produce more heat
• Light reaching the eye


  Is focused on the retina at the back of the eye which consists of Rod and Cone cells
• The pituitary gland in the brain is considered the main or master gland as it produces hormones in response to stimuli that travel to other glands in the body
• Type 1 diabetes occurs when the pancreas can't produce enough insulin, requiring insulin injections; type 2 diabetes occurs when cells don't absorb glucose properly
• Reproduction involves menstruation in females after puberty, where eggs mature due to FSH and LH hormones
• Laser eye surgery aims to change the shape of the cornea to achieve the same effect as glasses or contact lenses
• The pancreas regulates blood glucose levels by secreting insulin to move glucose from the blood into cells for energy; excess glucose can be converted into glycogen by the liver
• If too cold, blood vessels dilate (vasodilation) to increase blood flow to the skin to increase the rate of heat loss; vasoconstriction occurs when too cold, causing paleness
• Glasses or contact lenses are usually used to mitigate hyperopia by slightly converging or diverging the light before it enters the eye
• Myopia is the medical term for shortsightedness
• Thermo regulation

  Your body controls its internal temperature by the brain sensing blood temperature and sending nervous and hormonal signals to various effectors around your body to regulate heat loss to the surroundings
• Rod cells

  • Detect light intensity but not color
• The endocrine system is a system of glands that produce or secrete hormones affecting various parts of the body via the blood
• If blood glucose levels are too low, the pancreas produces glucagon to convert glycogen back into glucose for use
• Endocrine glands

  • Pancreas (insulin production), thyroid (controls growth, heart muscle, digestive function), adrenal glands (produce adrenaline), ovaries and testes (release eggs or produce sperm)
• Water and nitrogen balance are triple science topics
• Thyroxin controls metabolic rate and is secreted by the thyroid
• Ethene induces ripening of fruits
• Contraception options

  • Pills that inhibit FSH production
  • Progestrone injections that stop any eggs being released
  • Implant that slowly releases progestrone
  • Condoms for men
  • Diaphragms for women
  • IUD or intrauterine device like a copper coil
  • Avoiding sex for some time after egg release
  • Clamping the UCT
  • Having tubes tied or cutting the sperm ducts
• Phototropism is when shoots bend towards the light source, while geotropism is when roots grow downwards
• IVF (In vitro fertilization)

  Eggs are harvested from the woman, fertilized in the lab with the prospective father's sperm, and inserted back into the uterus for potential implantation and growth of embryos
• Genome refers to all the genetic material in an organism, stored in DNA
• Sexual reproduction leads to variation in offspring, potentially making them better suited to their environment
• Meiosis is the process by which gametes are produced, leading to genetic variation in offspring
• Adrenaline increases heart and breathing rate in stressful situations for fight or flight response
• Ovarian cycle


  1. Ovaries produce estrogen causing the uterus lining to thicken

  2. Inhibits or stops the production of FSH so that no more eggs mature

  3. Causes the pituitary gland to produce LH luteinizing hormone which causes the egg to be released and travel towards the uterus via the UCT

  4. Progesterone is produced by the ovaries to maintain the uterus lining