Ecosystem Energy Flow

• Energy flow in the ecosystem supports the survival of many organisms
• Solar energy serves as the primary energy source for almost all organisms

Cellular Respiration

• Process during which stored energy in nutrient molecules is released for use by cells

Energy Flow

• The passage of energy is in a one-way direction in an ecosystem

Food Chain

• The sequence of transfers of matter and energy in the form of food from one organism to another
• Food chains intertwine locally into a food web because most organisms eat more than just one type of animal or plant

Food Web

• A complex network of interconnected and overlapping food chains that shows the feeding relationships in a community

Trophic Levels

• Food webs are divided into trophic levels
• Tropho is Greek for nourishment

Food Chains and Poisons

• Toxic substances like pesticides, radioactive isotopes, heavy metals, and industrial chemicals enter food chains
• The effect of the pesticide DDT on certain bird species drew attention to the problem
• In 1962, U.S biologist Rachel Carson published "Silent Spring" which heightened public awareness about the dangers of DDT and other pesticides

Ecological Pyramid

• Shows the relative amounts of various parameters like the number of organisms, energy, and biomass across the trophic levels
• Can also be called trophic pyramids or energy pyramids

Pyramid of Numbers

• Displays the total number of individual organisms at each level in the food chain of an ecosystem

10% Rule

• Approximately 10% of the energy "harvested" at a lower trophic level is transferred to the next higher trophic level

Pyramid of Biomass

• Represents the total living biomass or organic matter present at different trophic levels in an ecosystem
• Calculated as the mass of organisms present at each trophic level in a given sample size.

Pyramid of Energy

• Represents the amount of energy retained or stored in the form of new biomass at each trophic level
• The energy originally comes from the sun

Biogeochemical Cycles

• Matter moves in cycles from one part of an ecosystem to another one.
• Matter moves from one organism to another and from organisms to the abiotic environment.
• There are four cycles of matter: carbon, nitrogen, phosphorus, and water

Carbon Cycle

• The process that moves carbon between plants, animals, microbes; minerals in the earth as well as in the atmosphere.
• Carbon is abundant in the universe.
• Since it is able to form complex molecules like DNA and proteins, carbon makes life on Earth possible

Nitrogen Cycle

• A biogeochemical process through which nitrogen is converted into many forms
• Consecutively, the nitrogen passes from the atmosphere to the soil to the organism and back into the atmosphere
• Involves several processes such as nitrogen fixation, nitrification, assimilation, denitrification, decay, and putrefaction

Nitrogen Fixation Steps

• Step 1 Nitrogen fixation is a process that transforms of non-reactive atmospheric N2 into reactive compounds like nitrates, nitrites, or ammonia
• Step 2 Nitrification is a microbial process by which reduced nitrogen compounds are sequentially oxidized to nitrite and nitrate
• Step 3 Assimilation is the process by which plants and animals incorporate NO3- and ammonia formed through nitrogen fixation and nitrification
• Step 4 Ammonification occurs when an organism excretes waste or dies by the process of ammonification, the nitrogen becomes organic
• Step 5 Denitrification converts nitrogen compounds like nitrate, into gaseous forms such as nitrogen oxides and nitrogen gas

Phosphorus Cycle

• A biogeochemical cycle that describes the transformation and translocation of phosphorus in soil, water, and living and dead organic material

Hydrologic Cycle

• Refers to the continuous circulation of water through the earth's land, ocean, and atmosphere
• It involves the exchange of mass, matter, and energy
• Plays a crucial role in the earth's ecosystem, climate, and energy budget

Definitions

• Estuaries are where fresh water meets the ocean
• Runoff is surface movement from land to ocean
• A watershed is an area of land drained by runoff
• Aquifers are underground caverns and porous layers of rock in which groundwater is stored
• Aquifer depletion is the removal of more groundwater than precipitation or melting snow recharges