Chapter 10 Ecosystems

What is an ecosystem? An ecosystem is a community of living organisms interacting with one another and with the nonliving components of the environment that they inhabit. Examples of ecosystems: – Forest – Lake – Island

Interactions within an ecosystem: trophic relationships Trophic relationships are the feeding connections among the living organisms in an ecosystem. Often represented by a food chain or food web The position of each organism in a chain corresponds to its trophic level. Food chains contain: – Producers – Consumers – decomposers Trophe = nourishment

Food Chain

Producers Producers are organisms with the ability to create organic matter from inorganic matter – Organic matter that enters into the composition of living organisms and that is usually created by them (proteins, lipids) – Inorganic matter is not necessarily produced by living organisms (water, minerals, salts) Producers are also called autotrophs Autotrophs are at the bottom of the food chain because they are the organisms that bring energy into the ecosystem Auto= self Trophe = nourishment

In nature, photosynthesis is the process in which producers transform energy from the sun into organic matter. – In this way plants can feed themselves and grow. Photosynthesis

Consumers Consumers are heterotrophic organisms that feed on other living organisms. Primary, or first order consumers feed on producers or their seeds and fruit. – Herbivores are primary consumers.

Second, third and fourth order consumers eat consumers of the respective preceding order. – Species in the second order or higher are usually carnivorous.

Some animals are omnivorous. They are consumers of several orders at once. Bears are an excellent example of this because they will eat berries one day and salmon the next.

The same animal can be a consumer of a different order depending on its position in another food chain.

DECOMPOSERS Decomposers are organisms that feed on the waste and remains of other living organisms. They feed on detritus, which is dead organic matter. – Ex: fallen leaves, dead animals, excrement

TROPHIC NETWORK (food web) A representation of all these relationships is called a TROPHIC NETWORK...or food web. More than one food chain is possible in an ecosystem.

ECOSYSTEMS DYNAMICS Matter is transformed in an ecosystem Matter and energy within an ecosystem are exchanged from one organism to another in a process that is called material energy flow According to the LAW OF CONSERVATION OF MASS, nothing is lost and nothing is gained; matter is transformed

Producers convert energy from the Sun and inorganic matter from the environment into organic matter. When producers die (or the consumers that eat them), decomposers break down the organic matter in the detritus that they eat, producing new inorganic matter. This is called CHEMICAL RECYCLING Chemical recycling: a natural process by which decomposers make inorganic matter available by breaking down organic matter

PRIMARY PRODUCTIVITY The biomass is the total mass of organic matter in an ecosystem at any given time. The primary productivity of an ecosystem is the amount of new biomass generated by its producers.

The factors that influence primary productivity are: The amount of light The amount of water available Access to nutrients Temperature

DISTURBANCES A disturbance is an event that damages an ecosystem. It can lead to the elimination of organisms and alter the availability of resources. Disturbances can vary in three ways: – Type – Frequency – Seriousness

NATURAL DISTURBANCES These are events triggered by natural phenomena rather than by human activity. Examples of natural disturbances are: – Storms – Volcanic eruptions – Droughts – floods

HUMAN DISTURBANCES Many human activities have a damaging effect on ecosystems. Examples of human disturbances are: – Oil spills – Deforestation – Ozone depletion – Flooding (hydroelectric dams)

ECOLOGICAL SUCCESSION Ecological succession is the series of changes that occur in an ecosystem after a disturbance and that continue until the balance of the ecosystem is restored. After a disturbance, an ecosystem will go through a series of gradual changes until balance is restored…if possible.