biology

• Plants have organs, leaves are where photosynthesis takes place producing food for the plant, water also leaves the plant through them allowing transpiration to take place
• Roots are where water and mineral ions enter the plant, the meristem is where new cells are made
• Xylem are the long continuous tubes which water rises up, it is unidirectional
• Phloem are the conveyor belts of cells that transport sugars, food and sap up and down the plant, it is bidirectional
• Factors that increase the rate of transpiration

  • Increasing temperature
  • Decreasing humidity
  • Increasing air movement
• Layers of a leaf cross-section

  • Waxy cuticle
  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Vascular bundle
  • Lower epidermis with stomata
• Stomata

  Holes in the lower epidermis of a leaf that allow gases to enter and exit
• Guard cells

  Cells that flank the stomata and control their size to regulate the rate of gas exchange
• Photosynthesis

  1. Chlorophyll and chloroplasts in cells

  2. Light energy is needed (endothermic reaction)

  3. Glucose is produced

  4. Glucose is used for respiration, stored as starch or fat, or used to make cellulose and amino acids
• Factors that can limit the rate of photosynthesis: temperature, light intensity, CO2 concentration
• Measuring the rate of photosynthesis

  1. Submerge pondweed in an inverted measuring cylinder

  2. Measure the volume of oxygen produced over time
• Plant hormones

  • Gibberellins cause seed germination and promote flowering and fruit growth
  • Auxins control shoot and root growth, inhibit growth on the illuminated side causing phototropism
  • Ethylene induces fruit ripening
• Homeostasis is the regulation of internal conditions even when external conditions change
• Examples of homeostasis

  • Blood glucose concentration
  • Body temperature
  • Water levels
• Thermoregulation

  Body's control of internal temperature through sweating, vasodilation, vasoconstriction, and shivering
• Endocrine glands

  • Pituitary
  • Pancreas
  • Thyroid
  • Adrenal
  • Ovaries/Testes
• Insulin

  Hormone produced by the pancreas that causes glucose to move from the blood into cells
• Glucagon

  Hormone produced by the pancreas that causes the liver and muscles to convert glycogen back into glucose
• Type 1 diabetes

  Pancreas cannot produce enough insulin
• Type 2 diabetes

  Cells no longer absorb glucose properly
• Kidneys regulate water and nitrogen balance by filtering blood, reabsorbing useful substances, and excreting urea and excess water
• Antidiuretic hormone (ADH)

  Hormone produced in the pituitary gland that causes the kidneys to reabsorb more water
• Menstrual cycle

  1. FSH causes egg maturation and estrogen production

  2. LH causes egg release

  3. Progesterone maintains uterus lining
• Contraception methods

  • Hormonal pills, injections, implants
  • Condoms
  • Diaphragms
  • IUDs
  • Sterilization
• In vitro fertilization (IVF)

  Eggs are harvested, fertilized in a lab, and implanted in the uterus
• The heart is at the centre of the circulatory system, blood enters the heart twice in the double circulatory system
• Path of blood through the heart

  • Deoxygenated blood enters right atrium
  • Passes through right ventricle to lungs
  • Oxygenated blood enters left atrium
  • Passes through left ventricle to body
• There is also the risk that there could be more than one baby born which might not be desirable
• Heart

  At the center of the circulatory or circulatory system, the transport system of your body
• Double circulatory system

  Blood enters the heart twice every time it's pumped around the body
• Blood flow through the heart

  1. Deoxygenated blood from the body enters the right side of the heart through the venina Cava

  2. Valve between the right atrium and the right ventricle stops backflow

  3. Heart muscles contract and blood goes through the pulmonary artery to the lungs to be oxygenated

  4. Blood comes back to the heart through the pulmonary vein into the left atrium

  5. Blood goes into the left ventricle then out to the body through the aorta
• Left side of the heart

  • Has thicker walls as the left ventricle has to pump blood to the whole body while the right ventricle only pumps to the lungs
• Pacemaker

  A group of cells that create electrical pulses to cause the heart muscles to contract and the heart to beat
• If the pacemaker isn't working properly, you can be given an artificial pacemaker to do the same job
• Arteries

  Blood vessels that carry oxygenated blood away from the heart, have thicker walls to withstand higher pressure
• Veins

  Blood vessels that carry deoxygenated blood towards the heart, have thinner walls due to lower blood pressure but have valves to stop backflow
• Blood vessel structure

  Arteries split and get smaller and smaller until they end up as tiny capillaries with one cell thick walls to allow fast diffusion of molecules in and out of cells
• Coronary artery

  Supplies the heart muscle with its own supply of oxygen and blood to keep the muscle pumping
• If the coronary arteries are blocked by the buildup of fatty deposits, a heart attack can occur
• Stents

  Little tubes inserted into blood vessels to keep them open so blood can flow