Chapter 4: Organising Animals & Plants

• List the structures air passes through when breathing in.

  mouth/nose ➞ trachea ➞ bronchi ➞ bronchioles ➞ alveoli
• Why is a leaf an organ?

  there are many tissues inside the leaf that work together to perform photosynthesis
• How is the upper epidermis adapted for its function?

  • single layer of transparent cells allow light to pass through

  • cells secrete a waxy substance that makes leaves waterproof
• How is the palisade mesophyll adapted for its function?

  tightly packed cells with lots of chloroplasts to absorb as much light as possible for photosynthesis
• How is the spongy mesophyll adapted for its function?

  air spaces increase the surface area and allow gases to diffuse quickly
• What is the function of the guard cells?

  control the opening and closing of the stomata
• What is the function of the xylem?

  transport water and mineral ions from the roots to the rest of the plant
• Give three adaptations of the xylem.

  • made of dead cells

  • no end wall between cells

  • walls strengthened by a chemical called lignin to withstand the pressure of the water
• What is the function of the phloem?

  transport dissolved sugars from the leaves to the rest of the plant
• What is the purpose of translocation?

  transport dissolved sugars from the leaves to other parts of the plant for respiration, growth, and storage
• Define the term transpiration.

  movement of water from the roots to the leaves through the xylem
• What is the purpose of transpiration? (3)

  • provide water to keep cells turgid

  • provide water to cells for photosynthesis

  • transport mineral ions to leaves
• Name four factors that affect the rate of transpiration.

  temperature, light intensity, humidity, and wind speed
• What effect does temperature have on the rate of transpiration?

  higher temperatures increase the rate of transpiration
• What effect does humidity have on the rate of transpiration?

  higher levels of humidity decrease the rate of transpiration
• Why does increased light intensity increase the rate of transpiration?

  stomata open wider to let more carbon dioxide into the leaf for photosynthesis
• What is the function of the stomata?

  allow diffusion of gases into and out of the plant
• Where are most stomata found?

  underside of leaves
• What is the advantage to the plant of having a high number of stomata at this location?

  reduces the amount of water loss through evaporation