Ecosystems and Ecosystems and the Biospherethe Biosphere

Energy TransferAll organisms need energy to carry out essential

functions – growth, movement, maintenance, repair, and reproduction

In ecosystems, energy flows from sun to autotrophs to organisms that eat autotrophs to organisms that feed on other organisms.

Amount of energy ecosystem receives and the amount. transferred from organism to organism have an effect on the ecosystem’s structure.

Energy FlowWhenever one organism eats another,

molecules are metabolized and energy is transferred.

Energy flows through an ecosystem from producer to consumer

Trophic levelTrophic level indicates the organism’s level of

nourishment, or position in the sequence of energy transfer illustrationFirst level – all producersSecond level – herbivoresThird level – predators of herbivores

Food Chain single pathway of feeding

relationship that results in energy transfer to mouse to snake to hawk

Feeding relationships in ecosystems are usually too complex to be represented by a single food chain.

Many consumers eat more than one type of food and many organisms may feed on the same organisms.

Food Web Models of complex

feeding networks within ecosystems; series of food chains interwoven

Energy Pyramid distribution of energy and

matter in an ecosystem

Shows the distribution of energy in a food chain

Energy flows upwards from producers to consumers

Energy is lost as head between each tier of the pyramid; average of 10% of energy is passed from one level to the next level

Other Pyramids Biomass pyramid

shows the total mass or organisms at each tropic level Less biomass at higher

tropic levels than lower levels

Pyramid of numbers shows the actual number of organisms present in each trophic level

Water Cycle Crucial to life - ells are 70-

90% water

90% of water evaporates from terrestrial ecosystems passes through plants in a process called transpiration – plants take in water through roots and release water and take in CO2 through the stomata in their leaves

In pic to right note: evaporation, condensation precipitation, transpiration

Carbon Cycle

Photosynthesis and cellular respiration form the basis of carbon cycle

In photosynthesis, plants use carbon dioxide,

water, and solar energy to make carbohydrates and produce oxygen

Both autrotrophs and heterotrophs use oxygen to break down carbohydrates during cellular respiration

Nitrogen CycleThe most important thing about the nitrogen cycle

is that bacteria are involved All organisms need nitrogen to make

proteins and nucleic acids.

Nitrogen gas makes up about 78% of the atmosphere.

Bacteria break down the corpses and wastes of organisms and release the nitrogen they contain as ammonia – ammonification.

Bacteria in the soil takes the ammonia and oxides it into nitrites – nitrification.

Nitrogen is returned to the atmosphere through denitrification.

Plants can absorb nitrates from the soil, but animals cannot. Animals get nitrogen by eating plants and other organisms and then digesting the proteins and nucleic acids.