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Leaving certificate biology

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  1. Ecology theory
    5 Topics
    |
    1 Quiz
  2. Unit 1
    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 3 of 13
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Ecological relationships and population dynamics

Populations

  • A population comprises all the members of a species in an area

Biotic factors that control population size

1. Competition:

  • Competition is the struggle between two or more organisms for a resource that is in short supply 

Animals compete for:

  • Food
  • Water
  • Shelter
  • Territory
  • Mates

Plants compete for:

  • Space
  • Light
  • Water
  • Minerals

 Types of competition

  • Contest competition:

Contest competition occurs when there is an active, physical struggle between different organisms

Example: male deer compete with each other for females

  • Scramble competition:

Scrample competition means that all the competing organisms get some of the resources

Example: Seedlings growing in overcrowded conditions compete for resources but none get enough

2. Predation: 

Predation occurs when an animal (predator) kills and eats another animal (prey) for food. 

Adaptations of predators:

  • The colour of a fox’s coat helps to camouflage
  • Hawks excellent eyesight helps them tom see their prey

Adaptations of prey:

  • Rabbits have large hind legs so they can run very fast
  • Mice are very flexible, which allows them to hide in very small spaces

3. Symbiosis: 

Symbiosis is a close relationship between different species that involves benefit to at least one of them

Types of symbiosis:

  • Mutualism  is where two different species live together and both benefit

Example: bacteria in the large intestine of humans that produce vitamin K 

  • Parasitism is where two different species live together and one (the parasite) benefits and causes the other (the host) harm

Example: Fleas on a dog

  • Commensalism is where two different species live together and one benefits and the other neither benefits or is not  harmed

Example: Birds nesting in a tree

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