Biology

• Population: organisms of the same species that live in the same place at the

  same time.
• Community: all the populations that live in the same place at the same time.
• Ecosystem: dynamically interacting system of organisms, the communities it

  makes up, and the non-living components of its environment.
• The physical location where an organism lives in an ecosystem is called its habitat
• the role of an organism or species in an ecosystem is its niche.
• Biodiversity is defined as the variability within species, between species, and between

  ecosystems.
• Biodiversity


  • Increases the chance of organism's survival in the ecosystem
  • Decreases the danger of species extinction
• Medicinal values of biodiversity

  • Production of anticancer drugs and antibiotics
• Agricultural values of biodiversity


  • Production of different strains of crops such as rice, wheat and corn to provide food
• Commercial values of biodiversity

  • Production of fibers, beeswax, and seaweeds
• Biodiversity


  • Plays an important role in biogeochemical cycles including the water cycle, nitrogen cycle and carbon cycle
• Biodiversity

  • Helps to prevent soil erosion
  • Regulates the climate
• Biodiversity

  • Helps in the recycling of wastes
• Main components of an ecosystem

  Ecosystems are the dynamically interacting systems of organisms, the

  communities they make up, and the nonliving components of their environment.

  The main living components of an ecosystem are producers, consumers and decomposers.

  • Producers are organisms that produce their own food using sunlight energy.

  • Consumers are organisms that feed on other organisms
• Herbivores


  Animals that eat plants
• Carnivores


  Animals that eat other animals
• Omnivores


  Animals that eat other animals and plants
• Decomposers


  Organisms that obtain energy decomposing the remains,products, or wastes of other organisms after they die
• main role of decomposers in an ecosystem

  To decomposers release enzymes to break down the remains of organic matter into smaller molecules that can be readily absorbed by the decomposer or return back to the ecosystem (e.g. soil).
• how energy is transferred and lost from one trophic level to another.

  An average of 90% of the energy is lost when energy flows

  from one trophic level to another and only approximately 10% is passed on. Energy is

  lost in many forms, which includes heat produced by respiration, and through body

  excretions such as feces, which contain undigested material.
• two main types of ecological pyramids

  pyramids of numbers and pyramids of biomass.
• A pyramid of numbers

  depicts the number of organisms at each trophic level of the food chain; the width of each bar represents the number of organisms at that level.
• A pyramid of biomass

  depicts the biomass of all the members at each trophic level; the

  width of each bar represents the biomass of organisms at that level.
• When a very large producer supports a large number of herbivores, a pyramid of

  numbers has a very small/narrow base.
• pyramid of biomass

  A pyramid of biomass is a graphical representation of biomass (mass oforganic matter) present in a unit area of various trophic levels.

  • The pyramid of biomass always has the right shape. It shows that the

  primary producers contain the greatest amount of energy.

  • It is an accurate depiction of the available energy at each trophic level by

  measuring the dry mass of organisms.

  • Biomass decreases in each trophic level from the base to the apex (top).
• Food chain


  illustrates how energy flows through a sequence of organisms
• food web


  is a network of interlinked food chains that shows different possible

  feeding relationships among organisms in an ecosystem or part of it.
• Pyramid of numbers


  A pyramid of numbers depicts the number of organisms at each trophic level of the food chain. The width of each bar represents the number of organisms at that level