Populations in ecosystems

• What are ecosystems?


  Dynamic systems made up of a community and all the non-living factors of its environment.
• What are biotic and abiotic conditions? Give examples.

  Biotic are living factors like competition and predation; abiotic are non-living factors like temperature and rainfall.
• What is a population?

  A group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed.
• What is the carrying capacity?

  An ecosystem supports a certain size of population of species.
• What can affect the size of a population?

  The effect of abiotic factors and interactions between organisms, such as intraspecific and interspecific competition and predation.
• What is intraspecific competition?


  Competition within the same species.
• What is interspecific competition?


  Competition between different species.
• What is a community?

  A population of different species living together.
• What is a habitat?


  The place where an organism lives.
• What is a niche?


  The role of a species in its habitat, including all the abiotic and biotic conditions to which it is adapted to survive, reproduce, and maintain a viable population.
• What is the population size?


  The number of individuals in a population.
• How can temperature affect the size of a population?

  Each species has a different optimum temperature for survival; the further away from the optimum, the fewer individuals can survive.
• How can temperature affect enzyme population size?

  Too low temperatures slow down enzyme activity, reducing metabolic rate; too high temperatures denature enzymes.
• How are warm-blooded animals affected by temperature?

  If the temperature is too far from the optimum, organisms expend more energy to maintain normal body temperature, leaving less energy for growth.
• How can light affect population size?

  As light intensity increases, photosynthesis increases, leading to faster plant growth, which can increase animal population size up the food chain.
• How can pH affect population size?

  Enzymes have an optimum pH, and population size will be larger when conditions are optimal for enzyme activity.
• How can water and humidity affect population size?

  Little water leads to small populations of species adapted to dry conditions; dry air allows species adapted to low humidity to thrive.
• What factors affect the growth and size of human populations?

  Birth rate and death rate.
• What affects individual human populations?

  Migration, which includes immigration (individuals joining a population) and emigration (individuals leaving a population).
• How can you work out population growth?

  Population growth can be calculated using the formula: [births + immigration] - [deaths + emigration].
• How can you work out percentage population growth?

  Percentage population growth is calculated as: pop change during the period/pop at the start of the period times 100
• What is the competitive exclusion principle?

  When two species compete for limited resources, the one that uses these resources most effectively will eliminate the other; no two species can occupy the same niche.
• What is a predator?


  An organism that feeds on another organism, known as their prey.
• Describe the relationship between predator and prey and its effect on population size.

  Predators eat prey, decreasing prey population; fewer prey lead to competition among predators, reducing their population, which allows prey to increase again.
• What are the two sampling techniques used to study habitats?

  Random sampling using frame or point quadrats and systematic sampling along a belt transect.
• How do you random sample?

  Lay out two long tape measures at right angles to create a grid, use a random number generator for coordinates, place a quadrat, and record species.
• When is systematic sampling used?

  When estimating the population size of slow-moving or non-moving organisms.
• How are quadrats on a line transect used?

  Place a tape measure at a right angle, place the quadrat every 5 meters, collect data, and repeat with additional transects.
• What is abundance?


  The number of individuals of a species within a given area.
• What is frequency?


  The likelihood of a particular species occurring in a quadrat.
• What is percentage cover?


  An estimate of the area within a quadrat that a particular plant species covers.
• How do you obtain reliable results in sampling?

  By using a large sample size, obtaining many quadrats, and calculating a mean to be more representative of the community.
• When would you use mark-release-recapture techniques?

  When measuring the abundance of motile animals.
• Explain the mark-release-recapture method.

  Capture a sample of species, mark and release them, then collect a second sample after allowing time for random distribution.
• What is the equation for mark-release-recapture?

  Population size = number in sample 1 x number in sample 2 / number marked in sample 2
• What are some assumptions made during mark-release-recapture?

  There has been no immigration or emigration, few deaths and births, and the mark is not lost.
• What does it mean that ecosystems are dynamic?

  They change day to day as populations fluctuate, sometimes slowly and sometimes rapidly.
• What is succession?


  The change in an ecosystem over time.
• What generally happens at each stage of succession?

  A new species colonizes the area, changing the environment, making it less suitable for existing species and more suitable for others with different adaptations.
• What is the first stage of succession?

  Colonization of bare rock or sand by organisms called pioneer species.