B2.2 challenges of size (animal)

• alveoli are small air sacs in the lungs that serve as the gaseous exchange surfaces. They provide a large surface area for efficient exchange.
• the aorta is the main artery that takes oxygenated blood away from the heart to the body
• arteries are a blood vessel that carries blood away from the heart under high pressure
• atriums are the upper chamber of the heart that recieves blood from the veins
• the shape of red blood cells are biconcave to increase surface area for oxygen to diffuse into the cell
• blood is a tissue that contains red blood cells, white blood cells, plasma and platelets
• a double circulatory system is a circulatory system in mammals in which the blood passes through the heart twice in in s full body circuit
• the heart is an organ that pumps blood round the body
• a multicellular organism is an organism that has more than one cell
• plasma definition


  a pale yellow liquid found in the blood that carries water, enzymes, salts, nutrients, protiens, urea and hormones
• whats the pulmonary artery


  the main artery that carrys deoxygenated blood away from the heart to the lungs (A for away)
• whats the pulmonary vein


  the main vein that carrys oxygenated blood back to the heart from the lungs
• what are red blood cells


  cells in the blood that carry oxygen blood and remove carbon dioxide
• whats a single circulatory system


  a circulatory system in which the blood passes through the heart only once in a full body circuit
• what are heart valves


  structures found at each end of both ventricles that prevent backflow of blood (ensuring blood flows in one direction). Valves are also in the veins
• a vein is a blood vessel that carries deoxygenated blood to the heart at low pressure
• the vena cava is the main vein that carries deoxygenated blood back to the hearts from from the body
• ventricles are the lower chambers of the heart that recieve blood from the atria and pump it to the arteries. The human heart has two ventricles
• villi are small projections of the intestinal wall that increase the surface area of the intestine for food absorption
• surfaces are better for exchanging when they have a higher surface area
• the bigger the surface area to volume ratio is, the more quickly will substances travel across the membrane by diffusion
• as size increases, the SA:V ratio decreases
• when organisms grow, their cells divide. explain why it is more efficient for cells to remain so small, rather than just grow bigger.


  because then the cells have more surface area for diffusion
• explain why single-celled organisms can rely on diffusion to obtain substances (such as oxygen) from their surroundings, but larger organisms usually need specially adapted exchange surfaces and transport systems, for example, lungs or gills, and blood


  Because they have a higher SA:V ratio meaning that it can absorb substances more efficiently and faster
• how is amoeba adapted for surface exchange?


  single celled organism with short diffusion path and high SA:V ratio, diffusion is faster
• how is alveoli adapted for substance exchange?


  the alveoli share a membrane with the capillaries, increasing surface area of the lungs to increase the diffusion of gases (O2 and CO2)
• how is villi adapted for substance exchange?


  increases the surface area of the intestines increasethe rate of diffusion of food molecules. Thin walls for short diffusion path
• how has a flatworm adapted for substance exchange?


  flat so it has a large surface area for diffusion, making sure every cell in the body is close to the membrane
• how have root hair cells adapted for substance exchange?


  single celled to take up water and minerals by having a large surface area to increase rateof absorption
• how have leaves adapted for subtance exchange?

  the leaves are thin for short diffusion path for gas exchange (carbon dioxide and oxygen) and its flat for large surface area to volume ratio
• how have fish gills adapted for substance exchange?


  highly folded and surrounded by blood capillaries giving it a largersurface area to carry out gas exchange. Gill walls are only 1cm thick to aid with quick diffusion
• An axolotl is an amphibian that lives in water and absorbs oxygen through its external gills, which have a feathery shape. they are pink because a lot of blood flows through them. Describe how the axolotl’s external gills are adapted to be efficient at absorbing oxygen fron water.

  • feather shape to add more surface area to the gills
  • more surface area meaning quicker diffusion
  • gills only 1 cell thick to allow more efficient diffusion
• explain why most single-celled organisms do not need a transport system


  they are single celled so they don’t need a transport system their SA:V ratio is larger
• what substances are transported in/out of organisms?


  in : glucose and oxygen

  out : carbon dioxide, water and urea
• what is oxygen‘s role in humans 


  respiration
• what is the order oxygen goes through the body


  lungs -> alveoli -> blood -> respiring cells
• what is carbon dioxide’s role in humans?


  it has no role, it is a waste product
• what is the order carbon dioxide goes through the body?


  respiring cells -> bloodstream -> lungs -> air
• what is glucose’s role in the body?


  respiration/energy
• what is the order that glucose goes through the body?


  food in the intestines -> cells respiring