SECTION A CYCLES Flashcards
What is the Carbon Cycle?
The carbon cycle is a process by which carbon atoms are passed from one organism to another and to their environment.
What are the 5 steps in the carbon cycle?
Producers absorb carbon. Producers are eaten by consumers. Consumers respire, excrete and die. Decomposers feed and respire. Fossils are formed. Combustion and Deforestation.
- Carbon present in the atmosphere is absorbed by plants for photosynthesis.
- Carbon is transferred from producers to consumers and some is transferred back to the atmosphere through respiration, excretion and death.
- Decomposers feed saprophytically on dead and waste organic matter. During this process they release carbon dioxide.
- Fossils are formed when plant and animal matter die in a watery environment. Soft tissues decompose leaving the hard bones or shells behind.
- Combustion of fossil fuels and deforestation contributes to increased levels of carbon dioxide into the atmosphere. Increased concentration of carbon dioxide in the atmosphere is associated with global warming.
Why is the cycling of carbon important?
- Plants have a continuous supply of carbon dioxide to manufacture organic food by photosynthesis.
- Animals and decomposers have a continuous supply of organic food.
What is the nitrogen cycle?
The nitrogen cycle is a biogeochemical process through which nitrogen is converted into many forms as it circulates among the atmosphere, terrestrial and marine ecosystems.
In order to move through the different parts of the cycle, nitrogen must change forms.
What are the 5 steps in the nitrogen cycle?
- Nitrogen Fixation
The conversion of nitrogen gas (N2) into ammonium.
Some nitrogen is fixed by abiotic means (lightning).
Most fixation is done by nitrogen fixing, symbiotic bacteria, Azotobacter and Rhizobium. Azotobacter and Rhizobium have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia.
Nitrogen gas is deposited into soils from the atmosphere and surface waters, mainly through precipitation. Two nitrogen atoms get separated and combine with hydrogen to form ammonium (NH4+).
Types of Nitrogen Fixation
Atmospheric fixation: A natural phenomenon where the energy of lightning breaks the nitrogen into nitrogen oxides and is then used by plants.
Industrial nitrogen fixation: Is a man-made alternative that aids in nitrogen fixation by the use of ammonia. Ammonia is manufactured (under high temperature and pressure) by the direct combination of nitrogen and hydrogen and later, it is converted into various fertilizers such as urea.
Biological nitrogen fixation: We already know that nitrogen is not usable directly from the air for plants and animals. Bacteria like Rhizobium and blue-green algae transform the unusable form of nitrogen into other compounds that are more readily usable. These nitrogen compounds get fixed in the soil by these microbes.
Symbiotic nitrogen-fixing bacteria such as Rhizobium live in the root nodules of legumes forming a mutualistic relationship with the plant, producing ammonia in exchange for carbohydrates. Because of this relationship, legumes will often increase the nitrogen content of nitrogen-poor soils.
- Nitrification
In this process, the ammonia is converted into nitrate by the presence of bacteria in the soil. Nitrites are formed by the oxidation of Ammonia with the help of Nitrosomonas bacterium species. Later, the produced nitrites are converted into nitrates by Nitrobacter. This conversion is very important as ammonia gas is toxic for plants. - Assimilation
Primary producers – This is how plants get nitrogen. They absorb nitrates from the soil into their roots. It enters the food web when the primary consumers eat the plants. - Ammonification
When plants or animals die, the nitrogen present in the organic matter is released back into the soil. Decomposers like fungi and bacteria turn the nitrogen back into ammonium. - Denitrification
The process in which nitrate (NO3-) is converted to gaseous nitrogen (N2) (occurs in the absence of oxygen). Denitrification is carried out by the denitrifying bacterial species - Clostridium and Pseudomonas, which will process nitrate to gain oxygen and gives out free nitrogen gas as a byproduct.
Nitrogen cycled by human activities (combustion of fuels and the use of nitrogen fertilizers) increase the levels of nitrogen-containing compounds in the atmosphere. The fertilizers containing nitrogen are washed away in lakes and rivers and results in eutrophication.
Why is the cycling of nitrogen important?
- Plants have a continuous supply of nitrates to synthesize chlorophyll and manufacture proteins.
- Animals and decomposers have a continuous supply of proteins.
- In the process of ammonification, the bacteria help in decomposing the animal and plant matter, which indirectly helps to clean up the environment.
Nitrogen availability affects the rate of key ecosystem processes, primary production and decomposition.
What is recycling?
Recycling is the process of converting waste material into reusable material.
Biodegradable Material Can be decomposed by the action of bacteria and fungi. 1. waste from food industry 2. farmyard and garden waste 3. bagasse
Non-biodegradable Material Cannot be decomposed by the action of living organisms. 1. glass 2. plastic 3. rubber 4. nylon 5. iron, copper, steel, lead, aluminium
What are five reasons why recycling important?
- Prevents wastage of potentially useful materials.
- Conserves natural resources by reducing the quantity of raw materials used in manufacturing.
- Reduces energy use.
- Reduces pollution of air, land and water.
- Reduces the quantity of waste requiring disposal.
What are five difficulties experienced in recycling?
- It can be difficult to persuade households and industries to separate their waste into different types.
- It can be difficult to collect, transport and store waste items.
- It can be time consuming because items have to be cleaned before they are recycled. Different manufactured materials have different properties and as such, they have to be stored into different types before recycling, example there are many different types of plastics.
- it can be hazardous because recyclable materials have to be separated from any toxic materials before they can be recycled, example the acid has to be removed from lead batteries before the lead can be recycled.
- It can be uneconomical in small countries because it is labour and energy intensive.
What are renewable resources?
What are non-renewable resources?
Renewable resources are resources that are present in the earth in finite amounts that cannot be replaced (fossil fuels, radioactive fuels, iron ore, bauxite (aluminium ore), copper, tin).
Non-renewable resources are resources that can be replaced by natural processes.
What is the impact of human activities on natural resources?
- Overfishing for food (lobster, whales, turtles, sea eggs).
- Overhunting for fur and ivory.
- Deforestation for land, housing, agriculture and materials for fuel, building and the manufacture of paper.
- Bad agricultural practices such as leaving the soil barren after harvesting, using chemical fertilizers instead of organic fertilizers, overgrazing of animals and ploughing down hillsides instead of contour ploughing.
- Pollution - release of waste and harmful substances into the environment which can damage the environment, harm living organisms and have a negative effect on human health.
What are 2 consequences of soil erosion?
- A reduction in the number of trees and other plants that can be grown.
- A reduction in the quantity of agricultural crops that can be grown.
What are 4 consequences of deforestation?
- The loss of habitat for plants and animals.
- The destruction of plants and animals living in the forests. Some of these may eventually become extinct.
- A reduction in photosynthesis resulting in a gradual increase in atmospheric carbon dioxide levels which is contributing to the greenhouse effect.
- Soil erosion caused by the absence of leaves to break the force of the rain and roots to bind the soil.
What is pollution?
Pollution is the contamination of the natural environment by the release of harmful or poisonous substances into the environment.
Pollution caused by pesticides?
(insecticides)
(fungicides)
(herbicides)
Pesticides are used in agriculture to control pests, diseases and weeds. It is also used to control vectors of diseases like mosquitoes.
Pesticides become higher in concentration up the food chains and can be harmful to top consumers. I can also harm useful organisms as well as the harmful ones such as bees which are important for pollination in plants.
Pollution caused by chemical fertilizers?
Nitrate ions NO3-
Phosphate ions PO4 3-
Chemical fertilizers causes eutrophication.
What is eutrophication?
Eutrophication is the nutrient enrichment of aquatic environments such as lakes, ponds and rivers which stimulates the rapid growth of green plants and algae causing the water to turn green. The plants and algae begin to die and are decomposed by aerobic bacteria that multiply and use up the dissolved oxygen. This causes other aquatic organisms like fish to die.
Pollution caused by carbon dioxide?
Burning fossil fuels in industry, motor vehicles, power stations and airplanes.
Carbon dioxide builds up in the atmosphere enhancing the greenhouse effect which leads to global warming.
Some carbon dioxide is absorbed by oceans causing ocean acidification.
