Distribution of organisms

• Biotic factors- factors of living orgin that can affect the distribution of organisms
• Abiotic factors- non living factors thst can affect the distribution of organisms (important in ecosystems as they dictate where an organism lives)
• Biotic Factors: competition for resources, disease, food avalibility, grazing, preditation
• Abiotic Factors: light intensity, moisture, PH, tempreture
• SAMPLINGS- ABIOTIC FACTORS

  Light intensity- light meters Meter is held at soil surface and light sensitive panel is pointed in dircetion of maximum light intensity ERRORS- may stand in the way and cast a shadow, light intensity may change due to time of day HOW TO MINIMISE- make sure shadow is not blocking light, take readings at same time of day
• SAMPLINGS - ABIOTIC FACTORS

  Soil moisture and PH-soil moisture and PH meter can be used by pushing probe into the soil and reading the meter ERRORS-moisture/soil from previous measurements may be left on probe and affect the reading HOW TO MINIMISE- Wipe the probe before each use
• SAMPLINGS- ABIOTIC FACTORS

  tempreture- soil thermometer can be used to measure soil tempreture and thermometer is placed in soil and reading is taken ERRORS-tempreture recorded was inncorrect HOW TO MINIMISE-ensure probe is inserted at same depth each time, allow time for thermometer to adjust to soil tempreture
• Human influinces on biodiversity- deforestation, overfishing, desertification
• Inticator species- an organism whos presence or absesnce can be used to show levels of pollution in the enviroment
• What is a quadrat used for in ecological studies?

  To measure the variety and abundance of plant species
• How is a quadrat sampled in an ecological study?

  A quadrat is placed in a random location and the number of organisms within each square is counted
• What are some errors that can occur when using quadrats for sampling?

  Errors include taking too small a number of samples and underestimating the number of plants due to some being half in or out of the quadrat
• How can researchers minimize errors when using quadrats?

  • Take many samples
  • Establish rules for counting
  • Count plants half in/out only if they are on the bottom or right-hand side of the quadrat
• What are pitfall traps used for in sampling?

  To sample the variety and abundance of invertebrates living on the surface.
• How is a pitfall trap set up?

  A hole is dug, and a pot is placed inside level with the soil.
• What happens to animals that pass by a pitfall trap?

  They fall in and get trapped.
• What are some errors that can occur when using pitfall traps?

  Traps being too high above soil, too low below soil, left too long, or not camouflaged.
• How can errors in pitfall trapping be minimized?

  By ensuring traps are level with the ground, checking traps regularly, and disguising them.
• What are the key steps to minimize errors when using pitfall traps?

  • Ensure traps are level with the ground
  • Check traps regularly
  • Disguise traps to blend with the environment