Ecosystems

Explain this statement: "An ecosystem is the simplest entity that can sustain life."

"sustained life" does not refer to one organism or population. An ecosystem has a nonliving component as well as a living component, therefore and ecosystem is an "entity"; and needs to be a complete one, no matter how small, to be considered an ecosystem. The processes that occur in an ecosystem are necessary for the life of the ecological community, but no memeber of the community can carry out these processes alone. That is why we have said that sustained life on Earth, rather than individuals or populations, is a characteristic of ecosystems.

Describe the 2 basic processes that must occur for an ecosystem to function.

-A cycling of chemical elements--CHNOPS (Carbon, hydrogen, nitrogen, oxygen, phosporous, sulfur) -A flow of energy, such as in a food web or a series of trophic levels (basically, stuff eating other stuff, or photo/chemosynthesis.)

. How many trophic levels are possible in an ecosystem? What limits the number of trophic levels?

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What is a food chain?

A food chain shows a simple, linear flow of 'who eats who' and therefore the energy and matter that is transferred through the links.

What is a food web and how is it different from a food chain?

A food web is a more accurate portrayal of the complex relationships between organisms in an ecosystem. It consists of several overlapping food chains.

How is a community different from a population?

A population is all of the members of one type of organism (same species) in a community. A community is made up of all of the organisms in an ecosystem. There are many different populations in a community.

What is an indicator species?

A species that is more susceptible to change is is an early indicator of change in an ecosystem, whether it be by dying, moving or changing. Examples: Songbirds for rain forest destruction, raptors for pesticides, lichen for air quality, mussels for air quality.

What is a "mast" year? (The Acorn Connection)

A year of high acorn production, or bumper crop. Only happens occaisionally.

decomposer

An organism that breaks down already-deceased plants and animals into their basic chemical components and make these components available again to the ecosystem. Feed on all trophic levels.

autotroph

An organism that can directly make their own food from inorganic chemicals, from the sun or otherwise, is a source of energy for the rest of the food chain/web/ecosystem.

scavenger

An organism that eats already-deceased heterotrophs. Not considered a decomposer.

omnivore

An organism that eats both heterotrophs and autotrophs.

carnivore

An organism that eats other heterotrophs.

heterotroph

An organism that must eat an autotroph or another heterotroph to gain energy.

Why is it difficult to define or delineate the boundaries of an ecosystem?

Ecosystems differ in size, and some boundaries are gradual (such as change of lanscape from desert to forest)

What are ecosystem services?

Important environmental benefits that ecosystems provide to people; include clean air to breathe, clean water to drink, and fertile soil in which to grow crops.

What are community level interactions (indirect trophic interactions)?

Indirect (or immensely complicated) trophic interactions in an ecosystem, such as when an organism interacts with and changes its nonliving surroundings. Another example would be when an action from a certain organism affects animals in several different trophic levels.

How would you design an experiment to test the connection between acorn crops, gypsy moths, and mouse populations? Identify your control treatment and dependent and independent variables. (The Acorn Connection)

Manipulate the number of acorns in the ecosystem would be a good way to start a basic experiment. Control: average acorn production year; maybe take the average of several years of data Then, test situations with bumper crops and situations where oak trees produce very little. Constants would be anything in the environment that could be kept constant; not particularly easy if working with a real ecosystem, but something like climate could be a constant. Independent variable--Number of acorns Dependent variables--Population of gypsy moths and population of mice

What is an ecosystem?

Many organisms functioning together in ecosystems and interacting through their physical and chemical environments.

herbivore

Organisms that feed on plants, algae, or photosynthetic bacteria.

List and explain the three fundamental characteristics of ecosystems.

Structure-An ecosystem is made up of two major parts: living and nonliving. The nonliving part is the physical-chemical environment, including the local atmosphere, water, and mineral soil (on land) or other substrate (in water). The living part, called the ecological community, is the set of species interacting within the ecosystem. Processes-Two basic kinds of processes must occur in an ecosystem: a cycling of chemical elements and a flow of energy. Change-And ecosystem changes over time and can undergo development through a process called sucession.

What is a primary consumer?

The first organism in a food chain that consumes another organism;usually herbivores but can also be omnivores.

What is an ecological community?

The living part of an ecosystem-all species found in an area, whether or not they are known to react. (another definition is all living things that interact with each other; the hard part of this is that sometimes we don't know that/understand how certain things interact.)

What is a secondary consumer?

The organism(s) that eat the primary consumers; carnivores or omnivores.

Why is it useful to use the concept of a watershed to illustrate the delineation of an ecosystem?

When a watershed is used to define the boundaries of an ecosystem, the system is unified in terms of chemical cycling. Ecosystems are not defined by shape or size but by chemical cycling and flow of energy.

What is a direct trophic interaction?

When an organism is directly affected by the actions of another organism. Ex: being eaten.

What is a trophic level?

consists all those organisms in a food web that are the same number of feeding levels away from the original source of energy.

What does trophic mean?

of or relating to feeding and nutrition, stimulating growth of cells

What is a keystone species?

species whose impact on its community is much larger than its total mass or abundance indicates. An organism whose removal or a change in its role within the ecosystem changes the basic nature of the community. Example: Harp seals