10.4- independence

• Population is the number of individuals of a species in a particular area at a given time.
• community is a group of populations that live in the same area and interact with each other
• Producers are the members of an ecosystem community that bring energy from an external source into the ecosystem. 
• consumers are organism that obtain enegry rather eating matter
• decomposers are organisms that break down dead organisms and release nutrients back into the environment
• keystone species are species that are essential to the functioning of an ecosystem
• What is intraspecific competition?


  Competition for resources between members of the same species
• Give an example of intraspecific competition.


  Wheat crops competing for soil and nutrients
• What is interspecific competition?


  Competition for resources between members of different species
• Provide an example of interspecific competition.

  Leopards and lions competing for the same prey
• What is amensalism?


  One organism is inhibited or destroyed, the other is unaffected
• Give an example of amensalism.

  Elephants stepping on ants — the elephant is unaffected, however the ant dies
• What defines a predator-prey relationship?

  One species kills and eats the other
• Provide an example of a predator-prey relationship.

  Polar bears (predator) eat seals (prey) in the Arctic
• What is the herbivore-plant relationship?

  An animal eats a plant
• Give an example of a herbivore-plant relationship.

  Koalas eating eucalypt leaves
• What is parasitism?


  An organism living on or within another organism to derive a benefit, whilst harming the host
• Provide an example of parasitism.

  A flea living on a golden retriever — the flea obtains food, however the golden retriever loses nutrients
• What is mutualism?


  A beneficial relationship between two species
• Give an example of mutualism.

  Hummingbird and bee balm flower — the hummingbird gets nectar, the balm flower spreads its pollen
• What is commensalism?


  One member gains a benefit from the relationship, the other is unaffected
• Provide an example of commensalism.


  The clown fish and the sea anemone — the clown fish obtains shelter and food scraps, and the sea anemone is unaffected
• intraspecific competition competition for resources in an ecosystem involving members of the same species
• Interspecific competition competition for resources in an ecosystem involving members of one species and members of other species
• Clumped distributions occur in:

  • plant populations when only some areas within a sample area are suitable for germination and survival of a plant species; the areas without plants are unsuitable for survival because of the pH of the soil, a lack of water or the ambient temperature
  • plant populations that reproduce asexually by runners or rhizomes, with new plants appearing very close to the parental plant
• an example of uniform distribution

  A uniform distribution may indicate a high level of intraspecific competition so that members of a population avoid each other by being equidistant from each other.
• random distribution is the least common form of distribution in nature and occurs when the members of a given species are found in environments in which the position of each individual is independent of the other individuals:
• The four primary ecological events that determine population size are:

  1. births
  2. deaths
  3. immigration (movement of individuals into the population)
  4. emigration (movement of individuals out of the population).

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• What is a positive growth rate in a population?

  Positive growth rates occur when population size increases over a stated period, such as 200 organisms per year.
• What is a negative growth rate in a population?

  Negative growth rates occur when the population size decreases over a stated period.
• What does zero population growth mean?

  Zero population growth occurs when growth by births and immigration matches losses by deaths and emigration over a stated period.
• What characterizes open populations?

  Open populations experience migration of individuals into the population (immigration) or out of the population (emigration).
• Can you give an example of an open population?

  Wildebeest living in the open woodlands and grassy plains of Africa are an example of an open population.
• What happens during the wildebeest migration?

  Each year, one and a half million wildebeest migrate north in May/June in search of food.
• What defines closed populations?

  Closed populations do not experience migration (immigration or emigration) as they are isolated from other populations of the same species.
• Can you provide an example of a closed population?

  A lizard population on an isolated island is an example of a closed population.
• Why are closed populations less common among bird species?

  Closed populations are less common among bird species because birds often migrate between different habitats.
• secondary ecological events in population dynamics, abiotic or biotic factors that influence changes in population density, such as temperature
• density-independent factors factor whose impact on members of a population is not affected by the size of the population
• density-dependent factors factor whose impact on members of a population is dependent on the size of the population