Ecosystems
What is an ecosystem?
all the living organisms in a given area as well as the abiotic factors with which they interact.
Many organisms on Earth do not have the capability to use the sun’s energy directly. What do these organisms do?
the energy that has been stored in the organic compound glucose (a type of sugar) as their source of energy.
What are heterotrophs?
Organisms that cannot make their own food.They rely on other organisms for their energy and food supply.
In what two ways can the productivity of an ecosystem be measured?
Gross primary productivity and Net primary productivity
What is a food chain?
A food chain is a series of steps in which organisms transfer energy from one organism to another by eating and by being eaten.
In an ecosystem, what is the ultimate source of energy?
the Sun
What is the definition of “chemosynthesis”?
Chemosynthetic autotrophs use the energy contained in the chemical bonds of inorganic molecules such as hydrogen sulfide to produce food.
Why are heterotrophs called “consumers”?
they must consume the food made by autotrophs in order to satisfy their energy requirements
Gross Primary Productivity
Gross primary productivity is the rate at which the producers (autotrophs) in an ecosystem capture energy. Gross primary productivity is the amount of light energy that is converted to chemical energy by photosynthesis per unit time.
What is the first step in every food chain?
All food chains begin with an autotroph.
What three factors are most important in determining net primary productivity in terrestrial ecosystems?
a) light
b) temperature
c) amount of rainfall
What are autotrophs?
organisms that have the ability to use energy from the sun to convert simple inorganic substances into complex organic substances. Autotrophs convert carbon dioxide and water into carbohydrates (glucose).
What are decomposers?
Decomposers are a class of detritivores that cause decay by breaking down organic compounds into simpler compounds.
What is “net primary productivity”?
Net primary productivity is equal to gross primary productivity minus the amount of energy used by the producers for respiration. it represents the amount of chemical energy (glucose) that will be available to consumers in the ecosystem
What is a food web?
The network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem. A food web links all the food chains in an ecosystem together.
What is “biomass”?
a term that is used to describe the amount of organic material in an ecosystem. Producers add biomass to an ecosystem by making organic compounds.
What organisms on Earth are considered to be autotrophs?
green plants, the algae, a few species of bacteria and a few protists
Why does life on Earth depend upon the decomposers?
some of these molecules are returned to the soil or water. The action of the decomposers makes the nutrients contained in the dead bodies and wastes of organisms available to autotrophs. The process of decomposition recycles the essential chemical nutrients.
What is an ecological pyramid?
A diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or a food web.
What is a trophic level?
Each step in a food chain is called a trophic level. The trophic level indicates the organism’s position in the sequence of energy transfers
What is photosynthesis?
the process by which green plants (and a few other organisms) use the light energy from the sun to convert water and carbon dioxide into glucose and oxygen.
A few autotrophs can produce glucose in the absence of light. What is this process called?
Chemosynthesis
Can energy be recycled?
No. Energy flows through an ecosystem in one direction, from the sun to autotrophs and then to various heterotrophs.
How does the biomass of one trophic level compare to the biomass of the next trophic level?
Organisms occupying the lower trophic levels are usually much more abundant than organisms belonging to the highest level. There are many more grasses, shrubs, and trees than there are herbivores. There are many herbivores (deer, antelope, gazelles) for each carnivore (lion).
What trophic level would be occupied by carnivores feeding upon herbivores?
These organisms are referred to as secondary consumers.