biology

• Circulatory system


  An example of an organ system whose role is to transport oxygen and nutrients to the body's tissues
• Circulatory system


  • Relies on 3 main things: blood, blood vessels, heart
• Circulatory system


  1. Blood carries oxygen and nutrients

  2. Blood vessels hold the blood

  3. Heart pumps the blood through the vessels
• Double circulatory system


  Two distinct loops: 1) Deoxygenated blood from heart to lungs, then back to heart 2) Oxygenated blood from heart to body, then back to heart
• Heart


  • Consists of 4 chambers with thick muscular walls
  • Veins and arteries come in and out
• When looking at a diagram of the heart, the left side is on the right and the right side is on the left
• Atria


  Top chambers of the heart
• Ventricles


  Bottom chambers of the heart
• Valves


  Prevent blood from flowing backwards, ensure blood flows in the right direction
• Blood flow through the heart

  1. Flows into right atrium and left atrium

  2. Atria contract, pushing blood into ventricles

  3. Ventricles contract, pushing blood into pulmonary artery and aorta

  4. Atria refill with new blood, cycle repeats
• Pacemaker cells


  Group of cells in right atrium that produce electrical impulses to make the heart contract
• Artificial pacemaker


  Small device implanted under skin above heart that carries electrical current to make heart contract regularly
• Artery


  Vessel that carries blood away from the heart
• Vein


  Vessel that carries blood to the heart
• Arteries don't always carry oxygenated blood, and veins don't always carry deoxygenated blood
• Coronary arteries


  Small arteries that branch off the aorta to supply the heart muscle with oxygenated blood
• Growth


  The permanent, typically irreversible increase in size of an organism by the increase in dry mass or any number of cells
• Plant growth


  • Height of the plant (growth of the meristem stems)
  • Length of the roots and growth of lateral roots
  • Number of leaves
  • Thickness or diameter of the bark
  • Presence of flowers and fruits
• Phototropism


  1. Plants grow towards sunlight

  2. Auxins enable rapid cellular growth in the shoot tips

  3. Causes the plant to bend towards the sunlight
• Phototropism is a growth movement or partial movement, while animal locomotion is a whole movement
• Removing the shoot tip or covering it prevents phototropic movement
• Gravitropism/Geotropism


  1. Roots have a positive response, growing in the direction of gravity

  2. Shoots have a negative response, growing in the direction opposite to gravity
• Animal growth occurs in almost all tissues and regions, while plant growth mainly occurs in meristematic regions
• Germination


  The development of a plant from a seed after a period of dormancy
• Components of a seed

  • Embryonic plant
  • Endosperm (nutrient storage)
  • Seed coat (testa)
  • Radicle (rudimentary root)
  • Plumule (rudimentary shoot)
  • Cotyledons (rudimentary leaves)
• Germination is triggered by warmth, moisture, and oxygen, but not sunlight
• Autotrophic nutrition


  Organisms produce food from inorganic raw materials, e.g. plants producing glucose through photosynthesis
• Heterotrophic nutrition


  Organisms depend on consuming other organisms for their food requirements, e.g. animals eating plants or other animals
• Photosynthesis


  1. Light-dependent stage: Light energy splits water, releasing hydrogen and oxygen

  2. Light-independent stage: Hydrogen combines with carbon dioxide to form glucose
• Leaf structure


  • Large surface area of leaf blade
  • Petiole to orient leaf towards sunlight
  • Dense network of veins to transport water
  • Stomata on lower epidermis for gas exchange
• The palisade mesophyll layer is where most photosynthesis occurs due to the high concentration of chloroplasts
• Spongy mesophyll cells


  • Loosely irregularly packed
  • Air spaces facilitate gaseous exchange between the spongy mesophyll and the stomata
• Gaseous exchange in spongy mesophyll

  1. Carbon dioxide diffuses into the stomata

  2. Passes through the spongy mesophyll layer

  3. Goes to the palisade mesophyll cells
• Palisade mesophyll cells


  • Where majority of photosynthesis occurs
  • Contain large number of chloroplasts for light absorption
• Palisade mesophyll cell structure

  • Transparent upper epidermis allows sunlight penetration
  • Large vacuoles keep chloroplasts on outer edges to maximize light exposure
  • Adjacent to vascular bundles with xylem to enable water flow
  • Thin cell walls facilitate rapid gas diffusion
• Limiting factors


  Factors that when increased or decreased influence the rate of a reaction
• Requirements for photosynthesis


  • Light energy
  • Carbon dioxide
  • Water
  • Reasonable temperature
  • Chlorophyll
• Light intensity increases


  Rate of photosynthesis increases
• Light intensity reaches saturation point

  Rate of photosynthesis plateaus
• Removing carbon dioxide by placing plant in potassium hydroxide results in negative starch test