biology task 2 notes

• Alveoli


  Microscopic structure in mammals that enables gas exchange
• Alveoli


  • Each alveolus is composed of an air sac and is surrounded by tiny thin-walled blood vessels called capillaries
• Diffusion of oxygen and carbon dioxide in the blood

  1. Movement of particles along a concentration gradient, from an area of high concentration to an area of low concentration

  2. Seen in humans through gas exchange of carbon dioxide and oxygen

  3. Partial pressure of carbon dioxide is much greater in the capillaries than in alveoli, causing carbon dioxide to diffuse down a concentration gradient from the capillaries into the alveoli

  4. Partial pressure of oxygen is higher in the alveoli than the capillaries, causing oxygen to diffuse from the alveoli into the capillaries down the concentration gradient
• Stomata


  Pores on the leaves of plants that are often found on the upper and lower epidermis bordered by two guard cells
• Stomata


  • Open and close to control the exchange of gases such as oxygen, carbon dioxide and water vapour (open = gases can diffuse through them, closed = no gases are transported and no water can be lost)
• Lenticels


  Porous tissue found on woody structures e.g. on the bark, allowing gas exchange in the stem e.g. carbon dioxide, oxygen and water vapour
• Guard cells


  • Two bean-shaped cells that border the outside of the stomata, have chloroplasts allowing them to conduct photosynthesis
  • Become turgid when filled with water causing the outer walls to stretch outward, separating the pore between the walls and allowing gas exchange to occur
  • When water leaves the stomata the outer walls don't bulge, causing the inner walls to contract and the pore to close, preventing gas exchange
• Sunlight is the main factor controlling the size and shape of stomata, with stomata typically opening in the day (when exposed to sun) and closing at night
• Parts of the human respiratory system

  • Upper respiratory tract: Nose, Pharynx, Larynx, Trachea
  • Lower respiratory tract: Lungs, Bronchi, Bronchioles, Alveoli
• Human respiratory system


  • Divided into upper and lower respiratory tracts
  • Nose is the primary entry point for air, with vellus hairs filtering the air
  • Pharynx directs airflow from the nose through the larynx to the lungs, contains the epiglottis to prevent food from going down the larynx
  • Larynx protects the lower respiratory tract from aspirating food, contains vocal cords/voice box
  • Trachea is the passage where air is taken towards the lungs
  • Lungs allow oxygen in the air to be taken into the body, while also letting the body get rid of carbon dioxide in the air breathed out
  • Bronchi carry air to and from the lungs
  • Bronchioles deliver air to a diffuse network of alveoli in the lungs
  • Alveoli are the location of gas exchange of oxygen and carbon dioxide
• Bird respiration


  • Have air sacs connected to the lungs which bellow to continually pump air through the lungs distributing oxygen and expelling carbon dioxide
  • Exchange gases through pulmonary respiration where efficient distribution of oxygen is caused by the thin walling of the bird's lungs
• Amphibian respiration


  • Exchange gases through cutaneous respiration, a form of respiration that occurs through the skin rather than lungs or gills
  • Internally, amphibians have a simple respiratory system which includes lungs that take in oxygen and release carbon dioxide
• Reptile respiration


  • Respire both through cutaneous respiration and their lungs as they have a complex internal respiratory system
  • Cutaneous respiration in reptiles is less efficient than in amphibians due to the thick, coarse skin that reptiles possess
  • Reptiles have heightened senses on their tongues allowing for minimal gas exchange to occur
• Fish respiration


  • Respire through their gills, where oxygen is diffused from the water into the fish's bloodstream
  • Also able to conduct cutaneous respiration as their skin is thin and permeable
• Insect respiration


  • Take in oxygen through the pores called spiracles, with tubes called tracheae taking this oxygen from the spiracles directly to the insect's cells
• Identify the microscopic structure in mammals that enable gas exchange to occur.


  microscropic structure is called the alveoli. a