Biological Community • Interactions between plants and animals • Includes food chains and life cycles within the soil.
Nitrogen Cycle Explained • Nitrogen is critically important to life, as it is a basic building block for amino acids and proteins. • The chief reservoir of nitrogen is the atmosphere, which is about 78% nitrogen. • Nitrogen gas in the atmosphere is a fairly non-reactive gas; it takes a lot of energy to get nitrogen gas to combine with other elements, such as carbon or oxygen.
Nitrogen Fixation Nitrogen gas can be taken from the atmosphere (fixed - reacted) in two basic ways. • 1. Lightning provides enough energy to "burn" the nitrogen and fix it in the form of nitrate, NO3-. This process is duplicated in fertilizer factories to produce nitrogen fertilizers. • 2. Nitrogen fixing bacteria use special enzymes to fix nitrogen (react the nitrogen with oxygen or hydrogen). The NH4+ produced is converted to NO3- by nitrifying bacteria found in the soil.
The Cycle Begins • 1. Most plants can take up nitrates and convert it to amino acids and then possibly proteins. • 2. Animals acquire all of their amino acids when they eat plants (or other animals). • 3. When plants or animals die (or release waste) the nitrogen is returned to the soil. • 4. The nitrogen that is usually returned to the soil in animal wastes or in the output of the decomposers, is ammonia. Ammonia is rather toxic. • 5. Nitrifying bacteria in soil or water convert ammonia to nitrates, which are taken up by plants to continue the cycle.
Cycle Completed Soil also contains bacteria the uses NO3- as a fuel source. These Denitrifying Bacteria release N2 back to the atmosphere.
photosynthesis respiration CO2 + H2O C6H12O6 + O2
Photosynthesis • Photosynthesis starts with water present in the soil and carbon dioxide from the atmosphere (the product of respiration, combustion). • Chlorophyll is the green pigment in plants (gives them their color). This uses the light from the sun as the energy needed to transform carbon dioxide and water into sugar (made into starch, cellulose and lignin – woody fibre). • Photosynthesis also produces oxygen which the plant releases into the atmosphere.
Respiration The cell works constantly to stay alive. • It constructs macromolecules • It transports substances into and out of the cell • It moves (some cells) • It grows • It reproduces To accomplish these tasks and many others, the cell needs energy that it must get from it’s environment. We know that the sun is the energy for plants and other photosynthetic organisms, but what about the consumers?
What happens to the Carbon? • Plants take up carbon dioxide and convert it into sugar (carbohydrates) through photosynthesis. • This carbon in the plants now has 3 possible fates: (i) it can be liberated to the atmosphere by the plant through respiration; (ii) it can be eaten by an animal, (iii) it can be present in the plant when the plant dies • Animals obtain all their carbon from their food, and, thus, all carbon in biological systems ultimately comes from plants (autotrophs). In the animal, the carbon has the same 3 possible fates as in plants.
heterotrophes. use organic molecules in their food to get the energy they need. • Respiration uses the sugar in food to make energy. The byproducts of respiration are water and carbon dioxide.
Water is one of the components needed for photosynthesis and a very important component in living things. How is water cycled around the earth?
A Summary of the Hydrologic Cycle Water covers 70% of the earth's surface. The oceans contain 97.5% of the earth's water, land 2.4%, and the atmosphere holds less than .001%. There is rapid recycling of water between the earth's surface and the atmosphere. Water Cycle Components •Evaporation of water •Condensation of water •Transportation of water The cycle begins with the evaporation of water from the surface. Approximately 80% of all evaporation is from the oceans, with the remaining 20% coming from inland water and vegetation. Moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported and returns to the surface as precipitation. On the ground water may; 1) evaporate back into the atmosphere 2) the water may become groundwater or runoff. Groundwater and runoff gather into the oceans, rivers, and streams. Water is absorbed by plants, which then release it back into the atmosphere through transpiration. Water evaporates from the surface to begin the cycle again.
Importance of Soil • Soil: the layer of material that covers the land • Where plants anchor and grow • Made of weathered rock, decomposing plant and animal matter • Has spaces for air and water movement
Layers of composition • 3 major types of soil • Horizon A: • Horizon B: • Horizon C • Each layer has different characteristics depending on where it is found.
Grasslands • Horizon A is deep and supports root growth • Horizon B is the subsoil (mix of dirt and rock) • Horizon C is mostly rock formation
Deserts • Horizon A: limited plant growth so little decomposition, so thin top soil or none at all.
Disturbing soils • Soils change over time naturally • Human impact: deforestation leads to increased erosion of topsoil (no roots to hold soil in place)
Productivity of Ecosystems • Ecosystems have different productivities, based on light availability, soil types, precipitation, temperature, nutrients. • Productivity: the quantity of biomass of plants produced each year on a given area (g/m2)
Sustaining life • Biotic: living part of the environment. Ex: plants and animals • Abiotic: non-living part of the environment. Ex: elements, air, and water.
The key events - respiration and photosynthesis • Photosynthesis takes carbon dioxide, water and energy to produce carbohydrates and oxygen. • Respiration takes carbohydrates and oxygen, combines them to produce carbon dioxide, water, and energy.
The Ecological Footprint of a population is equal to: Area of land and water occupied by the population + Land and water used to produce resources for the population + Land and water used to dispose of wastes for the population
The Food we Eat The food we eat contributes 11 percent of the total household output of greenhouse gases which cause global warming; 21 percent of common and 13 percent of toxic air pollution; 47 percent of common and 26 percent of toxic water pollution; and 78 percent of aquatic and 54 percent of terrestrial habitat alteration
Most of the world's fresh water and land is used in agriculture. • Our North American diets are particularly water intensive. It takes 5,020 liters of water per person per day to produce what we eat. Compare this to 2,810 liters per person per day in Latin America, 2,530 liters in China, and 1,760 liters in Africa. • Much of this difference is accounted for in the quantities of meat (production and processing of meat takes a lot of water) and irrigated crops we eat. • Meat production and processing contributes four times more water pollution than fruits, veggies and grains. • Pesticide contaminants to water are roughly the same in both categories.
Livestock production in Canada over the past five years has increased, in some cases dramatically (cattle 4.4%, pigs 26,4%, chickens 23.4% and sheep 46%), and the per capita demand for meat worldwide is growing. This has led to the development of giant feedlots or mega-barns where animal husbandry is replaced by mechanized production. Unlike the traditional mixed farms where livestock raised was well-matched with crops that could use the manure, these feedlots generate huge amounts of liquid manure that must be stored and disposed of. Most often, the volumes of manure overwhelm the ability of local cropland to absorb it all safely. Gigantic liquid manure lagoons can leak or rupture, contaminating groundwater, streams, rivers and estuaries with nitrates, phosphates, antibiotics and other drugs, and disease vectors like bacteria and viruses. Factory farms are also a source of toxic air pollution and noxious odours.
Aquaculture has developed along the same trajectory. Over 20 years, small family fish farms including those in the Bay of Fundy have become huge industrial-scale feedlots with control or ownership increasingly concentrated in a few large hands. Chemical inputs - drugs, pesticides, feed contaminants, anti-foulants (preventing the accumulation of microorganisms, plants, algae on submerged surfaces), dyes - and fish excrement have become a huge source of pollution to coastal waters where aquaculture is practiced. Now even shellfish aquaculture is growing so large that there are localized impacts on the seafloor. • Industrial scale growing of monoculture crops also has a huge environmental impact. Overworked soils cause irreplaceable topsoil to erode and soil health to decline. Chemical fertilizers used to compensate for degraded soil pollute groundwater and surface water. Toxic pesticides used to control insects and kill weeds inject poisons into the air, water and food we eat. This chemical-dependent crop production has become dominant over the past thirty years.
Succession • One ecosystem is gradually replaced by another over time. • Primary succession: • Sequence of changes that begins with bare landscape and ends with a climax community • Climax community is one at maximum productivity and support
Secondary Succession • Restores a community back. • Ex: fire • Fire will destroy a forest, but over a 10 year period that forest can return to its original state. • Quicker than primary succession
Irreversible Change • Frequent and severe change can cause the destruction of any ecosystem • Remediation: can be restored so it is suitable for wildlife and forestry
Protecting land • Wetlands: • Believed by humans to be worthless because could not use for farming or building home/business • Humans changed the land to be useful, so they drained the water and filled in the land
Would this affect the environment? Yes! • Wetlands act like sponges, holding in lots of water, but slowly releasing it when needed. • They improve water quality by trapping (filtering) particles out.
Wetlands provide peat (a valuable source of nutrients) • Can be used for soil improvement • Burned as a fuel source • Peat is sold for lots of money ($100 million a year)
Protecting Wetlands • Loss of an area leads to loss of the entire ecosystem (plant and animal biodiversity) • Loss for the scientific community • Loss for cultural groups that consider the land sacred.