Interactions within the Environment
Ecology is the study of the responses and interactions of living things with their
environment. The word ecology comes from the Greek word ecos, which means home.
The habitat, or home where an organism lives, must contain resources to provide
energy, water and gases for survival. In order to stay alive, organisms must interact
constantly with their surroundings by responding to living and non-living parts of the
environment. The combined living and non-living parts of an environment make up an
ecosystem.
The non-living parts of the ecosystem are called abiotic. The letter “a” in front of a word
means “without”, so abiotic means without life. Some of the abiotic parts or factors of
the environment include water, light, air, temperature, soil, rocks, and wind. The living
parts of the environment are called biotic, with “bio” meaning living.
Food Chains
A food chain shows how the energy in food is passed from one organism to another in
an ecosystem. An aquatic food chain often begins with tiny phytoplankton, which are
organisms that photosynthesize as they float at the top of the ocean.
Phytoplankton serve as the plants of the ocean, because they transform sunlight
energy into food. Small organisms called water fleas and copepods eat the
phytoplankton. The arrows in a food chain show the direction of energy flow. The
animals that eat plants are called herbivores. Animals that eat other animals are called
carnivores. Decomposers, such as bacteria, break down dead plant and animal matter
and return nutrients back to the marine ecosystem.
Remember the formula for photosynthesis is as follows:
6 CO2 + 6 H2O
→ C6H12O6 + 6 O2
Carbon dioxide + Water + Light energy → Glucose + Oxygen
Every living thing has a special job or role in the ecosystem. This role is called a niche,
which is very similar to an occupation for a person. An organisms niche is the way it
gets food energy and how it might give energy to others in a food chain or food web.
The niche of a plant is to be a producer for the food chain. The producer is always
shown as the first link in the chain. As energy moves through a food chain or food web,
much of the energy is transformed into different forms through the life processes of
living things.
Plants convert the Sun’s energy into food energy, but their cells also must use some
energy for growth and repair of tissues. Herbivores much chew to ingest grass, so even
the process of grazing to obtain food uses energy. Digesting the grass and getting the
energy to cells also requires energy.
Many herbivores and carnivores are warm-blooded animals which require great
amounts of energy to maintain a constant body temperature. Energy pyramids can be
used to show the amount of biomass, or food that is available to be eaten by another
organism at the next level of a food chain.
Pyramids can be used to show the amount of food that is available to be eaten by
another organism at the next level of a food chain. A single water flea needs to eat
many phytoplankton to support its daily activities, and only about 10% of the energy
present in the phytoplankton is available to the carnivore that eats the herbivore. Most
of the energy is transferred to the environment in other forms, such as heat.