TEST ON BIO

ECOSYSTEM

• Levels of Organization

• Organism is a single living thing

• Population is all of the organisms of the same species in the same place at the same time

• Community is all populations in the same place at the same time (all living things)

• Ecosystem is the area where living and nonliving things interact with each other

• Biosphere is made up of the parts of the Earth where life exists

• Abiotic factors are the nonliving things in an ecosystem (water,
  Sun, rocks, soil)

—> TYPES OF ORGANISMS IN ECOSYSTEMS

• Autotrophs are organisms that make their own food using light, water and carbon dioxide (Producers)

• Heterotrophs are organisms that feed on other organisms (Consumers)

• Herbivores (plant-eaters), carnivores (meat-eaters) and omnivores (plant and meat eaters) are consumers

• Decomposers (bacteria, fungi, earthworms)are organisms that break down dead plants and animals into carbon and nitrogen; they make the soil healthy

  —> FOOD CHAINS AND FOOD WEBS

  • Energy flows through ecosystems in one direction, typically from the Sun, through photosynthetic organisms including green plants and algae, to herbivores to carnivores and decomposers.

  • Arrows indicate the flow of energy from food (energy source) to the organism that eats it

  • In all environments, organisms compete (fight for the same vital resources).

  • At each link in a food web, some energy is stored in newly made structures but much is dissipated (released) into the environment as heat.

Trophic Levels in an Ecosystem

• Trophic levels are positions that organisms have in a food web

• Producers are at the base (bottom) of the food web and are at the first trophic level

• Primary consumers are organisms that eat producers (herbivores)

• Secondary consumers are organisms that eat primary consumers (carnivores/omnivores)

• Tertiary consumers are organisms that eat secondary consumers (top predators)

• Decomposers are at the final trophic level

• As you move up trophic levels, energy is lost as heat and as an organism performs metabolism (life processes)

CARRYING CAPACITY

• The number of organisms any habitat can support (carrying capacity) is limited by the available energy, water, oxygen, and minerals, and by the ability of ecosystems to recycle the residue (left overs) of dead organisms through the activities of bacteria and fungi.

• In any particular environment, the growth and survival of organisms depend on limiting factors that keep populations in check

• Examples: light intensity, climate, mineral availability, soil/rock type, and relative acidity (pH).

BIODIVERSITY

There is an enormous variety of life on Earth

As a result of evolutionary processes like mutation

and natural selection, there is a diversity of

organisms and roles in ecosystems.

This diversity of species increases the chance that at

least some will survive in the face of large

environmental changes.

Biodiversity increases the stability of the

ecosystem.

Biodiversity also ensures the availability of a rich

variety of genetic material that may lead to future

agricultural or medical discoveries with significant

value to humankind.

ECOLOGICAL SUCCESSION

All ecosystems go through a sequence of changes

during which one ecological community modifies

(changes) the environment, making it more

suitable for another community.

Succession may start after a lava flow, a severe

landslide or by some form of disturbance (e.g.

fire) of an existing community.

These long-term gradual changes result in the

community reaching a point of stability that can

last for hundreds or thousands of years.