Biology-Term 2 '23

• Natural factors that affect the balance within an ecosystem: Light intensity, Temperature, Rainfall, Epidemic and Natural disasters.
• Human factors that affect the balance within an ecosystem: 'The Six Mass Extinction'; Desertification, Deforestation, Invasive Species, Draining wetlands, Monoculture, Urbanisation, Poaching, Loss of biodiversity, Pesticides, Pests and Infertile soil.
• What is adaptations?

  Traits or characteristics that help an organism survive and reproduce in its environment.
• Mimicry: A form of camouflage where one species mimics the appearance of another.
• Camouflage: The use of natural or artificial colors to make an organism less noticeable to predators.
• Hydrophytes: Plants that live in water, they are not capable of living in dry conditions
• Mesophytes: Plants that can grow in both dry and wet conditions.
• Xerophytes: Plants adapted to dry environments, have thick waxy cuticle to reduce water loss
• Hydrophytes leaves:

  • Large round and thin leaves to increase surface area for water and nutrient absorption, photosynthsis and to float.
  • Leaves contain an upper waxy top surface to ensure water droplets roll off and to prevent water loss.
• Hydrophytes stem:

  • Long and flaccid stems accommodate the movement of water.
  • Absorb water and nutrients from the surrounding environment.
  • Doesn't contain wood as the plant is supported by water.
• Hydrophytes roots:

  • Poorly developed as it only serves an anchoring function.
  • Less branched than those of xerophytes as they do not absor any water.
• Mesophytes leaves:

  • Contain a waxy cuticle on the upper surface to reduce water loss.
  • Contain stomata on the lower surface to allow for gaseous exchange.
  • In winter, leaves fall off to prevent water loss.
• Mesophytes stems:

  • Well-developed woody stem to support the plant.
  • Branched to increase the surface area for the leaf attachment to increase the rate of photosynthesis.
• Mesophytes roots:

  • Well-developed root system with a long taproot for anchorage and to increase water and nutrient absorption.
  • Fin ehairs on branched roots to increase the surface area for water absorption.
• Xerophytes leaves:

  • Spirally arranged to direct rain/dew water towards stem and roots.
  • Thick and fleshy to store water.
  • The leaf edge is modified into hard thorns for protection.
• Mesophytes stem:

  • Single unbranched vertical stem to reduce the surface area exposed to direct sunlight.
  • Dead leaf base provides shade to prevent dehydration.
• Mesophytes roots:

  • Adventitious shallow roots grow out from the base of the stem.
  • Roots near the soil surface maximise water absorption from the envirment.
• Adventitous: Roots grow from the stem, there is no taproot.
• Natural selection: The process by which individuals with certain inherited characteristics are more likely to survive and reproduce than others.