Carbon, Nitrogen, and H2O

Energy Flow  Without a constant flow of energy, living systems cannot function. Sunlight is the main energy source for life on Earth.

 Some types of bacteria rely on the energy stored in inorganic (non-living) chemical compounds instead of the sun.  These organisms use chemical energy to produce food in a process called chemosynthesis.

 autotrophs, or producers, have the ability to make their own food.  Most autotrophs convert light energy to chemical energy (food). They accomplish this through photosynthesis.

 The bacteria that perform chemosynthesis are also autotrophs (ex: bacteria in deep sea thermal vents, hot springs, and marshes)

 Heterotrophs get their energy from the things they consume (eat) or absorb.  There are five major types of heterotrophs.

 Herbivores – obtain energy from eating plants  Carnivores – obtain energy from eating animals  Omnivores – obtain energy from eating plants and animals (most humans)

 Detritivores – feed on plant and animal remains and other dead matter (detritus)  Decomposers – organisms that break down organic matter (once living stuff) into simple products.  Generally, fungi and bacteria are the decomposers.

FOOD CHAINS AND FOOD WEBS  Energy flows through an ecosystem in one direction, from the sun or inorganic compounds to autotrophs and then to many different heterotrophs.

 A food chain is a series of steps in which organisms transfer energy by eating and by being eaten.  Each step in a food chain or a food web is called a trophic level.  There are basically four trophic levels to food chains:

 Producers (autotrophs that perform photosynthesis or chemosynthesis)  Primary consumers (herbivores)  Secondary consumers (carnivores or omnivores)  Tertiary consumers (carnivores or omnivores)

 A food web shows all the food chains and relationships in an ecosystem.

Ecological pyramids  An ecological pyramid is a diagram that shows the amount of energy or matter within each trophic level in a food chain or web. There are three major types of ecological pyramids.

 Energy Pyramid – shows the relative amount of energy available at each trophic level.

 The 10% Rule – In a food chain, only about 10% of the energy is transferred from one trophic level to the next.  The other 90% is used for things like respiration, digestion, running away from predators, etc.  The producers will have the most energy in an ecosystem, the tertiary consumer will have the least energy.

100% 10% 1%.1% PRODUCERS Autotrophs 1 st Level CONSUMERS Heterotrophs 2 nd Level CONSUMERS 3 rd Level CONSUMERS Copyright 2011 – Rachel Miller – No part of this presentation may be duplicated

 Biomass Pyramid – represents the amount of living organic matter at each trophic level. Typically, the greatest biomass is at the bottom of the pyramid (producers).

 Pyramid of Numbers – Shows the relative number of organisms at each trophic level. This is not always the same as the biomass pyramid.

Hydrological (Water) Cycle  Water vapor is transferred into clouds through condensation, which leads to precipitation (rain, snow, sleet, hail).

 The process by which water changes from liquid to water vapor is called evaporation.

 Water can also enter the atmosphere by evaporating from the leaves of plants in a process called transpiration.

Carbon Cycle  Animals and plants add carbon dioxide (CO2) to the atmosphere through respiration.  Plants take in the atmospheric CO2 to use during photosynthesis.

 When plants and animals remove waste or die, the carbon in their bodies enters the soil. Over millions of years the carbon is turned into fossil fuels.

 Humans release carbon dioxide into the atmosphere when they burn fossil fuels, mine coal, and cut or burn forests.

 Since the industrial revolution, the levels of atmosphere CO2 have steadily risen. Which has lead to an increase in the greenhouse effect.

 Greenhouse effect – when heat is trapped in the Earth’s atmosphere by carbon dioxide, methane and other greenhouse gases.  A drastic rise in greenhouse gases could increase the greenhouse effect and lead to global climate change.

Nitrogen Cycle  Most of the Earth’s nitrogen exists as atmospheric nitrogen (N2). Plants and animals cannot use this form of nitrogen.

 Atmospheric nitrogen (N2) is transferred to the Earth’s soil by precipitation.  Once in the soil, special bacteria in plant roots convert N2 into ammonia in a process called nitrogen fixation.

 Other bacteria in the soil then change the ammonia into nitrate or nitrite.  Producers (plants) and animals use the nitrate or nitrite to make proteins.

 When organisms die, decomposers return the nitrogen to the soil as ammonia.

 Other bacteria convert nitrates back into atmospheric nitrogen (N2) in a process called denitrification.