ecology and sampling

• What is the purpose of the investigation mentioned in the study material?

  To estimate the population size of daisies in a field
• What equipment is needed for the investigation?

  A quadrat and a trundle wheel
• How is the area of the field measured?


  By measuring the length and width and multiplying them
• How should the area be divided for sampling?

  Into a 1 meter square grid
• What is the purpose of using a random number generator in this investigation?


  To choose random coordinates for the quadrat and remove bias
• What percentage of the total area should ideally be sampled?


  5 to 10%
• How should daisies be counted when positioned on the edge of the quadrat?

  If over half of the flower is within the quadrat, it should be counted
• How do you estimate the total population of daisies in the field?

  By multiplying the mean average by the total number of meter squares
• What method can be used to compare population sizes in different areas?

  Random sampling
• What is the purpose of using a transect in this investigation?


  To observe how population density varies between two points
• How long is the tape measure laid out for the transect?


  10 meters
• At what intervals is the quadrat sampled along the transect?

  At 1 meter intervals
• What type of graph can be used to show how population density changes with distance?


  A line graph
• What is the difference between biotic and abiotic factors?


  Biotic factors are due to living organisms, while abiotic factors are not
• Give an example of an abiotic factor mentioned in the study material.

  Light intensity or pH of the soil
• What determines the size of a quadrat


  size of the species being investigated
• Factors to consider when selecting sample area

  • population size
  • soil type
  • vegetation type
• Habitat


  The place where an organism lives
• Population


  All the organisms of one species living in one habitat
• Community


  The populations of different species living in a habitat
• Abiotic Factors


  Non-living factors of an environment E.g. temperature
• Biotic Factors


  Living factors of the environment E.g food
• Ecosystem


  The interaction of a community of living organisms (biotic) with non-living (abiotic) parts of their environment.
• Competition


  Organisms compete with other species and members of their own species for the same resources.

  Plants need light, space, water and mineral ions

  Animals need space(territory), food and water
• Interdependence


  Where each species depends on other species for food, shelter, pollination and seed dispersal. This means any major change in the ecosystem can have far reaching affects on population on every other species.
• Stable Community


  Species and environmental factors are in balance so population sizes are roughly constant. E.g ancient oak woodlands and rainforests
• Abiotic Factors Examples

  • Decrease in light intensity, temp or carbon dioxide levels decreases photosynthesis rate which would affect plant growth and cause a decrease in population size
  • Decreases in soil mineral content could cause nutrient deficiencies
  • moisture level, wind intensity and direction, oxygen level, soil pH
• Biotic Factors Examples

  • A new predator could cause a decrease in prey population for example red and grey squirrels eat the same food and live in the same habitat- grey squirrels outcompete and so red squirrel population decreases
  • Competition, new pathogens, food availability
• Abiotic and Biotic Factor Effects


  A change in environment could be the arrival of a new biotic factor or the increases or decrease of an abiotic factor, this can affect the size of populations in a community which has knock on affects because of interdependence.
• Distribution of Organisms


  An organism may be more common in one area due to a difference in environmental factors.
• Random Sampling


  Find the area of your sample space and then divide the area into 1m cubed sections and number each one of these. Then use a random number generator to chose one of these areas and measure here.
• Quadrats to Study Distribution

  1. Place quadrat on given spot from random sampling
  2. Count all organisms within the quadrat (over half-way in)
  3. Repeat this until 10% of the field has been measured
  4. Work out mean number of organisms per quadrat in this area
  5. Repeat 1-4 in second sample area
  6. Compare the two means
• Mean of Organisms in a quadrat


  Total organisms/number of quadrats
• Population size of organisms

  1. Work out the mean per m squared
  2. multiply the mean by the total area
• Transects

  1. Mark out a line in the area you want to study using a tape measure
  2. Then collect data along the line by placing a quadrat at 1m squared intervals or count how many organisms touch the line
• Percentage Cover

  1. Count the number of squares covered
  2. Divide the number of squares covered by the organism by the total number of squares in the quadrat then multiply by 100