topic 6

• What happens during photosynthesis?

  Photosynthetic organisms (e.g green plants and algae) use the energy from the sun to make glucose.
• What is biomass?


  An organisms biomass is the energy stored within an organism which works its way up the food chain as animals eat eachother.
• Where does photosynthesis occur?

  Chloroplast they contain chlorophyll which absorbs light.
• What is the equation for photosynthesis?

  
• What is an endothermic reaction?

  A reaction where energy is taken in during the reaction
• What can the rate of photosynthesis be affected by?

  Intensity of light, Volume of CO₂ and Temperature
• How does light intensity affect the rate of photosynthesis?

  The rate of photosynthesis is directly proportional to light intensity. Up to a certain point and then either CO2 level or temperature becomes a limiting factor.
• How are the distance from the lamp and the light intensity related?

  They are inversely proportional. As the distance increases the light intensity decreases.
• How does the concentration of carbon dioxide affect the rate of photosynthesis?

  Similar to light intensity, increasing the concentration of CO2 increases the rate of photosynthesis up to a certain point then something else becomes a limiting factor.
• How does the temperature affect the rate of photosynthesis?


  Increased temperatures will increase the rate of photosynthesis until a maximum temperature is reached and if it becomes too hot the enzymes will be denatured . Decreased temperatures will decrease the rate of photosynthesis.
• How do root hairs take in minerals and water?

  The cells on the surface of the plant root grow into "hairs" which stick out into the soil- this gives the plant a large surface area for absorbing water and mineral ions from the soil.
• What process is used to absorb mineral ions and why?

  They are absorbed by active transport because the concentration of mineral ions is higher in the root hair cells than in the soil.
• What do phloem tubes transport?

  food substances mainly sucrose made in the leaves to the rest of the plant for immediate use or for storage.
• What are phloem tubes made of?

  They are made of columns of elongated living cells with small pores in the end walls to allow stuff to flow through.
• What are xylem tubes made of?

  Dead cells joined end to end with no end walls between them and a hole down the middle.
• What do xylem tubes transport?

  Water and mineral ions from the roots to the stem and leaves
• What is the transpiration stream?


  The movement of water from the roots through the xylem and out of the leaves
• What is transpiration caused by?

  The evaporation and diffusion of water from a plants surface
• What is the stomata?

  tiny pores in leaves where carbon dioxide enters and oxygen exits
• What do the guard cells do?

  open and close stomata
• When is the stomata open?

  During the day, the guard cells are swollen with water.
• When is the stomata closed?

  During the night, when the guard cells are low on water and limp.
• Transpiration is affected by which environmental factors?

  Light intensity, temperature and air flow
• How does the light intensity affect the rate of transpiration?

  The brighter the light, the greater the transpiration rate. The stomata closes as it gets darker, and photosynthesis can't happen in the dark so they don't need to be open.
• How does the temperature affect the transpiration rate?

  The warmer it is, the faster transpiration happens. When it's warm the water particles have more energy to evaporate and diffuse out of the stomata.
• How does the airflow affect the rate of transpiration?


  If there is a good air flow the water vapour surrounding the leaf is swept away maintaining a low concentration of water outside the leaf. Diffusion then happens quickly.
• How is leaves being broad an adaptation for photosynthesis?

  There is a large area exposed to light- which is needed for photosynthesis
• How is the palisade layer adapted?

  It contains lots of chloroplasts and are near the top of the leaf so that they can recieve the most light.
• How is the upper epidermis adapted?

  Transparent so that light can pass through it to the palisade layer
• How is the waxy cuticle adapted?


  Thin and made of wax - protects leaf without blocking out light and helps reduce water loss
• How are the tissues of leaves adapted for gas exchange?

  The lower epidermis is full of stomata to allow carbon dioxide to diffuse into the leaf, the stomata are controlled by guard cells to respond to environmental changes, the spongy mesophyll tissue had air spaces to increase surface area.
• Why do plants that live in hotter environments have fewer stomata?

  Reduces water loss by evaporation.
• Give two reasons why cacti have spines instead of leaves

  1. Reduces the surface area for water loss by evaporation.

  2. Spines stop animals from eating the plant to get water
• What are auxins?


  Plant growth hormones
• What are auxins involved in?

  The growth responses of plants to light (phototropism) and gravity (gravitropism)
• Why are shoots positively phototropic?

  Because they grow towards the light
• Why are roots positively gravitropic?

  Because they grow towards gravity
• Why are roots negatively phototropic?

  Because they grow away from light
• Name a part of a plant which is positively gravitropic

  Roots
• What is a use of gibberellins?


  They stimulate seed germination, stem growth and flowering