Bio Question paper

• One adaptation that helps to prevent the cactus from being eaten by animals is the thorns or spikes
• A plant may produce poisons that make animals unwell as a chemical defence mechanism
• Some desert plants only grow leaves after it has rained, and the leaves fall off as soon as the soil dries out to reduce water loss
• The stem of a cactus is green due to chloroplasts or chlorophyll, allowing it to photosynthesize
• An organ is the name given to a group of tissues working together
• Water or minerals are substances transported through the xylem in the stem of the cactus
• The tissue that transports dissolved sugars through the stem of the cactus is the phloem
• The cell structure in a leaf mesophyll cell that is not found in a root hair cell is the chloroplast
• Guard cells control the rate of water loss in a leaf
• The scientific term describing the movement of water in plants is the transpiration stream
• The difference between xylem and phloem structure:

  • Xylem is made of dead cells, while phloem is made of living cells
  • Phloem cells have pores in their end walls, xylem cells do not
  • Xylem is hollow, phloem contains cytoplasm
  • Xylem contains lignin, phloem does not
  • Xylem transports water/mineral ions, phloem transports dissolved sugars
  • Xylem is involved in transpiration, phloem is involved in translocation
  • Xylem transports in one direction, phloem transports in two directions
• Diffusion is the movement of substances from an area of high concentration to an area of low concentration
• The human lungs are adapted for efficient gas exchange by diffusion:

  • Alveoli provide a large surface area: volume ratio
  • Capillaries have thin walls for a short diffusion path
  • Breathing maintains a concentration gradient
  • Large capillary network removes oxygenated blood quickly
  • Stomata let carbon dioxide into the leaf and oxygen out
• Water enters root hair cells through osmosis
• The function of stomata is to let carbon dioxide into the leaf and oxygen out
• Water is lost from a leaf by evaporation
• Water is transported in xylem and evaporates from leaves through stomata
• Cells in plant roots do not photosynthesize because they lack chlorophyll or chloroplasts
• An cell can become a new root hair cell by differentiation
• Scientists clone plants to protect endangered species from extinction
• Translocation is the process that transports sugars around a plant
• the removal of sugars from the stem can cause stunted growth due to less energy for respiration
• To reduce the spread of rose black spot, you should remove infected parts of the plant
• The heart is part of the circulatory system
• A tissue is a group of cells with a similar structure and function
• Root hair cells are adapted with a large surface area for faster osmosis and thin cell walls for shorter diffusion distance
• Root hair cells contain mitochondria for respiration and energy release for active transport against the concentration gradient
• Guard cells control the size of stomata