module 3

• Selection pressure 


  A change in the environment often results in some resources being limited, and individuals have to compete for these limited resources. Selection pressures drive natural selection.
• Biotic Factor 


  Living components of an ecosystem include, for example, organisms, such as plants and animals.
• Abiotic Factors 


  Living chemical and physical factors in the environment which affect ecosystems e.g. water, light, wind, soil, humidity, minerals, and gases.
• Ecosystem 


  A biological community of interacting organisms and their physical environment.
• Community 


  An interacting group of various species in a common location. E.g. A forest of trees and plants, inhabited by animals and rooted soil containing bacteria and fungi.
• Population 


  A group of organisms living in the same place at the same time. E.g. humans living in a city, pack of wild dogs.
• Habitat


  The natural home or environment of an animal, plant, or other organisms
• Organism


  A single living creature is composed of one or more cells. it is the simplest level in an ecosystem.
• Selection pressures are exerted by selecting agents 


  A selecting agent, is the specific environmental factor that creates a selection pressure for a particular phenotype.

  Example: The cheetah is a selecting agent. Predation by the cheetah is the selection pressure.
• Selective agent 


  An individual which has a feature, that helps it to survive or reproduce under a selection pressure (component to other members of the population) is said to have a selective advantage.
• Biotic selection pressure 


  Selection pressures created by a living (or biological) selecting agent.

  Includes: extreme temp, weather events etc
• Interspecific competition 


  competition for resources between individuals of the same species.
• Infectious disease


  Caused by pathogens (bacteria, virus, protozoan, prion, fungal) and can be transferred to individuals.
• Non-infectious disease


  Either environment, genetic or nutritional and can not be transferred between individuals.