Just biology hw review

• A plant's rate of photosynthesis

  • Affected by light intensity, concentration of carbon dioxide, and temperature of surroundings
  • If one of these is slowing the rate of photosynthesis, it is a limiting factor
• Types of pollination

  • Self-pollination: Pollen grain lands on the same flower it originated from
  • Cross-pollination: Pollen grain lands on a different flower to the one it originated from
• Farmers try to get maximum growth out of crops

  1. Use greenhouses made of glass to trap sun's heat and increase temperature to optimum for photosynthesis

  2. Use heaters to increase temperature to optimum and pump extra carbon dioxide

  3. Provide enclosed space to reduce pests and pathogens

  4. Add fertilisers full of minerals to help crops grow

  5. Use pesticides to kill unwanted pests

  6. Balance cost of these against crop yield to sustain successful business
• Fertilisation

  Joining of gametes
• Pollen

  • Male sex cell in a plant
  • Pollen grains land on stigma with help of wind, water, insects or animals
  • Pollen tube grows down through style to ovary
  • Nucleus from male sex cell moves down tube to join with female sex cell (ovule) in ovary
  • Fertilisation is when the two nuclei join
• Methods of pollen transfer

  • Wind-pollinated plants let pollen blow in wind and hope it reaches another plant
  • Insect-pollinated plants use insects and other animals to carry pollen grains to other plants
• Many crops depend on pollination by insects to survive
• Bees, butterflies, beetles, moths and flies are all pollinators
• Without pollinators, food security would be threatened and there would be a worldwide shortage of fruit; especially apples, plums and pears
• Many plant species could also decline or become extinct along with the organisms that directly or indirectly depend on them
• Bees are facing many threats globally including habitat loss, climate change, toxic pesticides and disease
• The culmination of these threats makes an unpredictable future for bees and many other pollinators