Ecosystems and Energy Flow

The energy and trophic levels of an ecosystem are often depicted as ecological pyramids. Although all information could be shown on one pyramid, three are often used.

The energy and trophic levels of an ecosystem are often depicted as ecological pyramids. Although all information could be shown on one pyramid, three are often used.

Pyramid of EnergyPyramid of Energy

• The pyramid of energy shows the amount of available energy (represented as heat ) decreases at each succeeding trophic level. Note the conservation of energy.

Pyramid of Energy

Heat

Heat

Heat

Heat

0.1% Consumers

1% Consumers

10% Consumers

100% Producers

Parasites, scavengers, and

decomposers feed at each

level.

Pyramid of Energy explanation : Energy Transfer Pyramid of Energy explanation : Energy Transfer

• The total energy transfer from one trophic level to the next is only about 10 percent because cellular respiration “burns” food to release its energy, and in doing so, produces ATP, which carries some of the energy as well as heat, which carries the rest back into the environment.

Pyramid of Energy explanation : Energy Transfer • Organisms do not store the total amount of energy

due to this process and also do not eat all the energy available at the lower trophic level.

• Therefore, although a lot of energy may be taken in at any level, the energy that ends up being stored there – food energy for the next level — is much less.

Pyramid of BiomassPyramid of Biomass

• Biomass is the total weight of living matter at each trophic level. A pyramid of biomass represents the total weight of living material available at each trophic level.

Pyramid of Biomass

1 kilogram of human tissue

10 kilograms of beef

100 kilograms of grain

Pyramid of NumbersPyramid of Numbers• A pyramid of numbers

shows that populations decrease at each higher trophic level. Population sizes decrease in relation to biomass, energy and sustainability . Nature is balanced!

Pyramid of Numbers

Fox (1)

Birds (25)

Grasshoppers (250)

Grasses (3000)

The carbon cycleThe carbon cycle• Carbon is the building block of the

molecules of life.

• Linked carbon atoms form the frame for molecules produced by plants and other living things. The formula of photosynthesis is =

• 6CO2 +12 H2O + Light energy → C6H12O6 + 6 O-- + __H2O carbon dioxide + water +sunlight= glucose+ ________+______

The nitrogen cycleNitrogen in the atmosphere

Nitrogen-fixing bacteria in the

nodules on roots of leguminous plants fix atmospheric nitrogen.

Nitrogen-fixing soil bacteria

Some excess nitrogen evaporates from soil.

Nitrogen compounds

released into soils and acted

upon by soil bacteria

Released to the atmosphere

Assimilated by plants

Urine from animals

Dead plant matter

Decomposing organisms

Decomposers—bacteria and fungi—break down tissues and wastes and nitrogen-

containing compounds are released.

Converted to other nitrogen compounds

by soil bacteria

The phosphorus cycleThe phosphorus cycle• In the phosphorus cycle, phosphorus moves

between the living and nonliving parts of the environment.

• Phosphate is a nutrient that’s vital to all living things and is found naturally in our food, our water and our bodies.

• Cellular respiration uses phosphates to convert glucose into a more usable form of energy called ATP. The formula of cellular respiration is =

• P + ADP + C6H12O6 + 6 O2 → 6 CO2 + 6H2O + ATP

Biotic relationships- Symbiosis Biotic relationships- Symbiosis • symbiosis - a close and permanent

association between biotic factors organisms of different species is called.

• Symbiosis means living together. Three kinds of symbiosis are recognized: mutualism, commensalism, and parasitism.

• Other abiotic and biotic relationships include : predator/prey, and competition and succession (Lesson 9)

Mutualism- + + - good for both Mutualism- + + - good for both • A symbiotic

relationship in which both species benefit is called mutualism.

Commensalism - + 0

good for one, neutral for other

Commensalism - + 0

good for one, neutral for other • Commensalism is a

symbiotic relationship in which one species benefits and the other species is neither harmed nor benefited.

Parasitism - +-

Good for one , Bad for other

Parasitism - +-

Good for one , Bad for other

• A symbiotic relationship in which a member of one species derives benefit at the expense of another species (the host) is called parasitism.

ParasitismParasitism

• Parasites have evolved in such a way that they harm, but usually do not kill the host species. Why don’t the parasites want to kill their host?

Predation- + -

predator/prey relationship

Predation- + -

predator/prey relationship • Predation is found in all ecosystems and includes organisms

that eat plants and animals.

• A predator is a type of consumer. Predators seek out and eat other organisms (prey). Clearly good for one, not so good for the other