Populations in ecosystems

• what is a niche?


  the role of an organism in the environment. It refers to where an organism lives and what it does there. It includes all the abiotic and biotic conditions for an organism to survive, reproduce and maintain a viable population
• what is intra-specific competition?


  individuals of the same species competing with one another for food, water, breeding site etc
• what are decomposers and detritivores?


  organisms hat break down waste and dead organisms to obtain energy. In doing so they release minerals and elements in a form that can be absorbed by the producers. They enable an ecosystem to be self sustainable
• what is a producer?


  organisms that manufacture organic substances (e.g. glucose) from inorganic substances (e.g. carbon dioxide and water) using an energy source (e.g. light energy)
• what is a predator?


  an organism that hunts and feeds on another organism
• what is a trophic level?


  a stage in a food chain
• what is a population?


  all the individuals of the same species living together in the same habitat at the same time
• what is a community?


  all the populations of different species living and interacting in the same habitat at the same time
• what is abiotic?


  non living components of an environment
• what is sustainable?


  capable of being continued, resources are maintained through nutrient cycling
• what is biotic?


  living components of an environment
• what is an ecosystem?


  a community of living things and the non living components of its environment together form an ecosystem
• what is adaptation?


  a feature that increases an individuals chance of survival and reproduction
• what is natural selection?


  the process whereby an allele becomes common in a population because it codes for a characteristic that makes an organism more likely to survive, reproduce and pass on its genes to its offspring
• what is carrying capacity?

  the maximum stable population size of a species that an ecosystem can support
• what is interspecific competition?


  competition between organisms of different species for food, water, breeding site etc (resources)
• what is predation?


  where an organism (the predator) kills and eats another organism (the prey)
• what is abundance?


  the number of individuals of one species in a particular area (i.e. population size)
• what is distribution?


  where a particular species is within an area being investigated
• what is fundamental niche?


  the total area that a species could occupy without competition
• what is realised niche?


  the actual area occupied following infraspecific competition
• what is the equation for estimated population size?

  estimated pop size = (total no of individuals in 1st sample x total no of individuals in 2nd sample) / no of marked individuals recaptured
• when using mark release recapture method what factors do you need to consider when marking?

  - if the mark will wash off

  - if the mark will affect survival chances
• what affects reliability in mark release recapture method?

  - migration

  - time between cycles (life cycles)

  - time of day of trapping

  - how large and where the habitat is
• what are transects?


  used to study the distribution of organisms
• what are line transects?


  comprises of a string or tape stretched across the ground in a straight line. Any organism over which the line passes is recorded. A single line is unlikely to be representative so it is usually necessary to take a series of lines
• what are belt transects?


  a strip, usually a metre wide, marked by putting a second line parraliell to the first or it is done by placing quadrants alongside a single line. The species occurring within the belt between the lines is recorded
• what is a continuous quadratic?

  a line or belt transect where the whole line or belt is sampled
• what is an interrupted transect?


  samples are taken at points along the line or belt transect. The points are usually regularly spaced intervals. This could be done if the distance survey is too long. Interval widths need to be determined so that they are not so wide that he presence of a species or a change in one species abundance is missed out
• what are point quadrats?

  a long piece of wood with holes at regular intervals through which large metal pins are pushed through

  - record the species plant touched by the pins
• what is a frame quadrats?

  - a defined area with which data is collected

  - used for collecting data about plants or sessile organisms
• what is succession?


  - changes in (development of) a community overtime

  - due to species present causing changes in the environment i.e. levels of abiotic factors, that lead to new niches, and other species being able to colonise
• what is the process of succession?

  - colonisation by pioneer species occur

  - these species lead to changes in the environments, in the levels of the abiotic factors (e.g. changes in pH)

  - dead pioneer species are decomposed

  - humus levels increase and there are increased levels in mineral ion levels such as nitrate ions

  - the environmental conditions become less hostile (and more suitable for other species and less suitable for pioneer species)

  - new niches form and other species that are adapted to the new environmental conditions can then colonise

  - these new species ca outcompete previous species, reducing the population size and leading to their death and decomposition

  - further changes occur in the environment : more soil forms, humus levels and moisture levels in the soil increase, levels of nitrate ions for example increase

  - more new niches form, and more species can colonise leading to an increase in biodiversity over time

  - an increase in the diversity of plants leads to a greater variety of habitats and food sources for animals, increasing biodiversity

  - a climax community is established over time
• what is pioneer species?

  organisms which colonise early in successional process -- often small, fast growing and have short lifecycles
• what is a climax community?

  a stable community where no further succession occurs
• what are features of a climax community?

  - same species (biodiversity) reset over a long period of time / stable community

  - levels of abiotic factors being constant over time

  - population sizes are stable (are around carrying capacity)§
• what is primary succession?


  - succession that occurs where there is currently no soil i.e. new land formed volcanic activity , rock shores, sand dunes

  - this succession is slower as the soil building process takes time
• what is secondary succession?


  - is succession that occurs in an environment where soil already exists

  - for example, where a flood, fire or storm has occurred
• what is deflected succession?


  - the continuation of succession being prevented

  - gardening is an example, or the burning of heather or grasslands that conserves these environments