Ecosystems

• Studying Ecosystems


  . A group of organisms of one species living in a habitat is called a population.

  . Scientists often want to estimate the size of a population.

  . This might involve sampling using a square frame called a quadrat
• What is the purpose of the required practical described in the study material?

  To measure the population size of a common species in a habitat
• What are the steps involved in the sample method for measuring plant population size?

  1. Place a quadrat on the ground at random.
  2. Count the number of individual plants of one species in the quadrat.
  3. Repeat this process a number of times and work out the mean number of plants.
  4. Work out the mean number of plants in 1m².
  5. Measure the area of the whole habitat and multiply the number of plants in 1m² by the whole area.
• Why is it important to place quadrats at random during the experiment?

  To ensure that the sample is representative of the entire habitat
• How can random numbers assist in the placement of quadrats?

  They can act as coordinates to ensure random placement
• What is the relationship between the number of samples taken and the accuracy of the estimate?

  The more samples that are taken, the more accurate the estimate should be
• What is the dependent variable in the experiment?

  The number of plants in the quadrat
• What is a key safety consideration after conducting ecology work in a habitat?

  Care should be taken to wash hands
• What safety measure should be taken when throwing quadrats?

  Throw low to the ground, not up in the air
• What is the purpose of using a transect in the study of plant distribution?

  • To see how plants are spread or distributed in a habitat
  • Involves stretching a long tape (transect line) across the area
  • Place a quadrat down at regular intervals along the line
  • Count the plants in the quadrat each time
• What is an ecosystem?

  All organisms and non-living parts in a habitat
• What are the different levels of organization in an ecosystem?

  • Individual organism
  • Populations (groups of the same species)
  • Communities (many populations living together)
• What do organisms require from their habitat to survive and reproduce?

  Certain resources from their habitat and other organisms
• What results from organisms trying to get enough resources?

  Competition
• What do plants in a community often compete for?

  Light, water, space, and mineral ions
• What do animals often compete for?

  Food, mates, and territory
• What is interdependence in an ecosystem?

  Species relying on each other for resources
• What can happen if one species is removed from a habitat?

  It can affect the whole community
• What characterizes a stable community?

  Species and environmental factors are in balance
• Key Point

  All ecosystems should be self-supporting, but they do need energy. Energy is usually transferred into the ecosystem as light energy for photosynthesis in green plants, which are the start of the food chain.
• What are the two types of factors that can affect communities?

  Abiotic and biotic factors
• What are adaptations in organisms?

  Features that enable survival in their environment
• What types of adaptations do organisms have?

  • Structural adaptations
  • Behavioural adaptations
  • Functional adaptations
• What are organisms that live in extreme environments called?

  Extremophiles
• How do extremophiles differ from other organisms?

  They thrive in extreme environmental conditions
• Key Point

  Bacteria that live at high temperatures have enzymes that are very resistant to denaturing.