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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
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Population dynamics

  • Population dynamics refers to the factors that cause population numbers to rise and fall

What causes populations to rise and fall ?

  • Population numbers rise due to births or immigration
  • Population numbers fall due to death or emigration

Predator - prey relationships

  • There is a correlation between predator and prey numbers
  • We see a cyclic pattern between predator and prey numbers as shown in the graph

Factors affecting predator and prey numbers

Availability of food

  • When predators first feed on prey the predator numbers rise and the number of prey falls
  • The lower number of prey results in a fall in the predator numbers due to a lack of food
  • As the predator numbers fall the number of prey can rise again and the cycle resumes


  • Prey may not be completely wiped out 
  • A small number may hide ad survive allowing them to repopulate  

Movement to new locations

  • If prey numbers in an area decrease too much predators may leave to find new hunting grounds
  • Fewer predators in the area allows those prey who survive to repopulate

Factors affecting human population numbers

Decreasing population 

  • War

  • Famine

  • Contraption

  • Disease

Increasing population

  • Vaccination

  • Improved sanitation

  • Insecticide that kill insects that spread disease like malaria

  • Improved surgical methods

  • Drugs such as antibiotics