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Leaving certificate biology

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  1. Unit 1
    Ecology theory
    5 Topics
    1 Quiz
  2. Nutrient recycling
    4 Topics
    1 Quiz
  3. Ecological relationships and population dynamics
    2 Topics
  4. Human impact on the ecosystem
    2 Topics
  5. Study of a grassland ecosystem
    3 Topics
  6. Responses in the Flowering Plant
    4 Topics
    1 Quiz
  7. Unit 3
    Sexual reproduction in the flowering plant
    1 Topic
  8. The human reproductive system
    3 Topics
  9. The menstrual cycle
    2 Topics
  10. Pregnancy
    2 Topics
  11. The circulatory system
    4 Topics
  12. Blood
    5 Topics
  13. The heart
    5 Topics
Lesson 1, Topic 2
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Factors affecting organisms

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Abiotic factors (non living factors)

Climatic factors

  • Light intensity: plants grow better in south facing aspects where there is more light
  • Rainfall: all organisms need water to live
  • Wind: wind damages plants and stunts their growth
  • Temperature: organisms grow faster in higher temperatures 
  • Humidity: When conditions are too humid, it may promote the growth of mold and bacteria that cause plants to die and crops to fail
  • Day length: longer days mean more light and plants can grow better

Aquatic factors (relating to water)

  • Light: light may not penetrate far down into water if it is murky
  • Currents: currents may wash away algae, plants and animals
  • Wave action: waves create currents and physically damage organisms
  • Oxygen concentration: There is less oxygen in water than air

Edaphic factors (relating to soil)

  • Soil type: some plants tolerate sandy soil (large particles) others tolerate clay soil (small particles)
  • Soil moisture: more water means more plant growth
  • Air content: air in soil helps roots to grow
  • Soil pH: different plants prefer different pH
  • Mineral content: the presence of various minerals are needed for plant growth
  • Humus content: humus is decaying organic matter, which increases the growth of plants by providing nutrients and oxygen to the plant

Biotic factors (living factors)

  • Competition: competition for resources tends to reduce the numbers of organisms
  • Predators: predation tends to reduce the number of prey
  • Food: the more plants in a habitat the more animals can live there
  • Parasitism: parasitism (feeding from a living host) may reduce the numbers of the host organism

Topic quiz