2.1 Energy Flow in Ecosystems Student Notes

Transcription

1 2.1 Energy Flow in Ecosystems Student Notes General Information Biomass is Biomass is also sometimes used to measure the mass of organic materials that are used to produce biofuels such as biogas. Biomass is generally measured in g/m 2 or kg/m 2 Within an organism s niche, the organism interacts with the ecosystem by: Plants are called producers because they produce carbohydrates from carbon dioxide, water and the sun s energy, a process called photosynthesis. get their energy by feeding on producers or other consumers. is the break-down of wastes and dead organisms, by organisms called decomposers, through the process of biodegradation. Energy Flow Scientists use different methods to represent energy moving through ecosystems. Food chains Food webs Food pyramids

2 Food chains show the flow of energy in an ecosystem Each step is a Feeding & niche relationship = 1st trophic level = 2nd trophic level = 3rd trophic level = 4th trophic level Energy Flow and Types of Consumers Consumers in a food chain can be classified as: 1. - consumers that obtain energy and nutrients from dead organisms and waste matter and includes small insects, earthworms, bacteria and fungi Detrivores feed at trophic level Detrivores have their own, separate food chains, and are 2. - primary consumers herbivores eat plants (producers) only 3. - secondary or tertiary consumers Secondary consumers eat non-producers, such as herbivores Tertiary consumers eat secondary consumers o Aka top consumers, top carnivores or top consumers 4. - consumers that eat both plants and animals Examples include humans and bears Energy Flow - Food Webs Most organisms are part of many food chains. A food web is used to represent.

3 Food webs are models of the feeding relationship in an ecosystem. Arrows in a food web represent the and nutrients. Following the arrows This food web represents a terrestrial ecosystem that could be found in British Columbia Energy Flow - Food Pyramids Food pyramids show the from one trophic level to another in a food chain. Energy enters at the first tropic level (producers), where there is a amount of biomass, and therefore energy It takes large quantities of organisms in one tropic level to meet the energy needs of the next trophic level because: o Each level loses large amounts of the energy it gathers through basic processes of living. o of energy taken in by consumers (at each level) is used in chemical reactions in the body, and is lost as heat energy. o There is energy if left over for growth or increase in biomass.

4 Food pyramids are also known as ecological pyramids. Ecological pyramids may show. The amount of life an ecosystem can contain is of the ecological pyramid, where producers capture energy from the sun. Each level in the energy pyramid = a loss of of total energy available o Lower trophic levels have much larger populations than upper levels. o This shows the importance of maintaining large, biodiverse populations at the lowest levels of the food pyramid Practice Assignments: Complete crossword, quiz and Check your understanding questions at the end of the online notes.

5 2.2 Nutrient Cycles in Ecosystems Student Notes General Information Nutrients are. Nutrients move through the biosphere in, or exchanges. Nutrients often accumulate in areas called. Without interference, generally the amount of nutrients flowing into a store the amount of nutrients flowing out. Human activities can of nutrient cycles. Land clearing, agriculture, urban expansion, mining, industry and motorized transportation can all increase the levels of nutrients more quickly than the stores can absorb them. Excess nutrients in the biosphere can have unexpected consequences. There are five chemical elements required for life. cycle between living things and the atmosphere. Phosphorous cycles in from. The Carbon Cycle Carbon atoms are a fundamental unit in cells of all living things. Carbon is also an essential part of chemical processes that sustain life. Carbon can be stored in many different locations. is found in aquatic and terrestrial organisms, and in CO 2 in the atmosphere and top layers of the ocean. is found in middle and lower ocean layers as dissolved CO 2, and in coal, oil and gas deposits in land and ocean sediments. o Sedimentation traps many long-term stores of carbon o Layers of soil and decomposing organic matter become buried on land and under the oceans.

6 o o Slowly, under great pressure over many years, form. Layers of shells also are deposited in sediments on the ocean floor, forming rocks like limestone over long periods of time. Carbon stores are also known as carbon sinks Carbon is cycled through ecosystems in a variety of ways. Photosynthesis: energy from the sun allows CO 2 and H 2 O to react Carbon in the is transformed by plants into carbohydrates. Photosynthesis also occurs in cyanobacteria and algae in oceans. Cellular respiration: in consumers. (opposite of photosynthesis) The energy is used for growth, repair and other life processes. Decomposition: decomposers break down large quantities of cellulose o Cellulose is a carbohydrate most other organisms Ocean Processes: CO 2 dissolves in cold, northern waters and sinks Ocean currents flow to the tropics, the water rises and releases CO 2 o This process is called ocean mixing. Eruptions and fires: volcanic eruptions can o Forest fires also release CO 2

7 Many human activities can influence the carbon cycle Since the start of the Industrial Revolution (160 years ago), CO 2 levels have from the increased burning of fossil fuels. The increase in CO 2 levels in the previous years was 1% - 3% Carbon is being more quickly than it naturally would as we mine coal and drill for oil and gas. CO 2 is also a, which traps heat in the atmosphere. Nitrogen Cycle Nitrogen is very important in the structure of. In animals, proteins are vital for function. In plants, nitrogen is important for. The largest store of nitrogen is in the atmosphere in the form N 2.

8 Approximately of the Earth s atmosphere is N 2 gas. Nitrogen is also stored in oceans, and as organic matter in soil. Smaller nitrogen stores are found in terrestrial ecosystems and waterways. Nitrogen is cycled through processes involving plants is the conversion of N 2 gas into compounds containing nitrate (NO 3 ) and ammonium (NH 4 + ) Both nitrate and ammonium compounds are usable by plants. Nitrogen fixation occurs in one of three ways 1. - lightning provides the energy for N 2 gas to react with O 2 gas to form nitrate and ammonium ions. Compounds formed by these ions then enter the soil via precipitation This only provides a small amount of nitrogen fixation nitrogen-fixing bacteria like Rhizobium in the soil convert N 2 gas into ammonium ions These bacteria grow on the root nodules of legumes like peas. The plants provide sugars, while bacteria provide nitrogen ions some species of cyanobacteria also convert N 2 into ammonium during the process of photosynthesis. - occurs when certain soil bacteria convert ammonium. Ammonium is converted into nitrates (NO 3 ) by nitrifying bacteria. Ammonium is converted to nitrite (NO 2 ), which is then converted to nitrate.

9 - enter plant roots via uptake These nitrogen compounds compose plant proteins. Herbivores then eat plants, and use nitrogen for DNA and protein synthesis. Nitrogen is returned to the atmosphere via. Nitrates are converted back to N 2 by denitrifying bacteria. N 2 is also returned to the atmosphere through volcanic eruptions. Excess nitrogen, enters the waterways, and washes into lakes and oceans. The nitrogen compounds eventually become trapped in sedimentary rocks, and will not be released again until the rocks weather.

10 Human activities can also affect the nitrogen cycle. Due to human activities, the amount of nitrogen in the ecosystem has in the last 50 years. Burning fossil fuels and treating sewage releases nitrogen oxide (NO) and nitrogen dioxide (NO 2 ). o Burning also releases nitrogen compounds that increase in the form of nitric acid (HNO 3 ). o Agricultural practices often use large amounts of. o Excess nitrogen is washed away, or, into the waterways. This promotes huge growth in aquatic algae = These algal blooms use up all, killing many aquatic organisms. The algal blooms can also produce neurotoxins that poison animals. Clearing land for agriculture and urban development plants that can absorb and convert CO 2. o Farmed land CO 2 as natural vegetation does. Phosphorous Cycle Phosphorous is essential for life processes in plants and animals. Phosphorous is a part of the molecule that carries energy in living cells. Phosphorous promotes root growth, stem strength and seed production. In animals, phosphorous and calcium are important for strong bones. Phosphorous is not stored in the atmosphere. Instead, it is trapped in phosphates (PO 4 3, HPO 4 2, H 2 PO 4 ) found in rocks and in the sediments on the ocean floor. Weathering releases phosphates from rocks. Chemical weathering, via acid precipitation or lichens, releases phosphates.

11 Physical weathering, where wind, water and freezing release the phosphates. o Phosphates are then absorbed by plants, which are then eaten by animals. Weathering doesn t occur until there is geologic uplift, exposing the rock to chemical and physical weathering. Humans add excess phosphorous to the environment through components. Extra phosphorous, often along with potassium, then enters the ecosystems faster than methods can replenish the natural stores. Humans can also reduce phosphorous supplies. of forests removes phosphorous from trees, and it then is deposited as ash in waterways.

12 Nutrient Cycles and Biodiversity Any significant changes to any of these nutrients ( ) can greatly impact biodiversity. Carbon cycle changes are adding to climate change and global warming. o Slight temperature fluctuations and changes in water levels can drastically change ecosystems. o Changes influence every other organism in those food webs. levels of nitrogen can allow certain plant species to outcompete other species, decreasing resources for every species in those food webs. levels of phosphorous can inhibit the growth of algal species which are very important producers in many food chains. Review Assignments: Complete the crossword, 2.2 quiz and the 2.2 Check your Understanding questions at the end of the lesson. Required Assignment: Complete 2.2 Assignment B - Case Study of Nitrogen Loading pg in your textbook and then upload it to the appropriate drop box. Introduction 2.3 Bioaccumulation Student Notes Amphibians (like frogs) are valuable indicators of. They are also to chemicals changes in the environment. Since the 1980s, much of the world s amphibian species have suffered declines in population. There has also been alarming increases in amphibian birth deformities in that time. Many theories attempt to explain these changes, including drought, increased UV rays, pollution, habitat loss, parasites and diseases. Amphibians, like this frog, have exhibited drastic changes since the 1980s.

13 Bioaccumulation Bioaccumulation refers to an organism slowly the amount of chemicals in their bodies. Many harmful chemicals be decomposed naturally. These chemicals can be eaten or absorbed, and sometimes cannot be removed from the body of the organism effectively. If a keystone species suffers a chemical bioaccumulation, it can organism in its far reaching niches. o A keystone species is a vital part of an ecosystem. Biomagnification refers to the animals at the receiving huge doses of accumulated chemicals. At each level of the food pyramid, chemicals that do not get broken down in organisms. When the consumer in the next trophic level eats organisms with a chemical accumulation, they receive a huge dose of the chemical(s). An example of bioaccumulation in BC is the effect of PCBs on the Orca. are a chemical that were used for many industrial and electrical applications in the mid 20th century. PCBs were in 1977 because of fears of their environmental impact. PCBs bioaccumulate, and also have a long-half life ( ). PCBs will affect the reproductive cycles of Orcas until at least 2030.

14 The bioaccumulation of PCBs begins with the absorption of the chemicals by microscopic plants and algae. Chemicals like PCBs and DDT are called (POPs) POPs contain carbon, like all organic compounds, and remain in water and soil for many years. Many POPs are insecticides, used to control pest populations. o DDT was introduced in 1941 to control mosquito populations, and is still used in some places in the world. o Like PCBs, DDT also bioaccumulates and has a long half life. o At even low levels (5 ppm), DDT in animals can cause. ppm = parts per million also bioaccumulate. Lead, mercury and cadmium are the most polluting heavy metals. o Lead is found naturally at low levels, but levels have increased. Lead is. Many electronics contain lead, and must be recycled carefully. Lead can damage. o Cadmium is also found in low levels naturally. Cadmium is used in the manufacturing of plastics and nickelcadmium batteries. It is toxic to earthworms, and causes many health problems in fish. In humans, the main source of cadmium exposure is. Cadmium causes lung diseases, cancer, nervous and immune system damage. o Mercury also is found naturally. Much more has entered ecosystems through the burning of fossil fuels, waste incineration, mining and the manufacture of items like batteries. Coal burning adds of of the mercury released into the atmosphere. Mercury bioaccumulates in of many animals. Fish bioaccumulate mercury compounds, adding risk for any organisms eating fish.

15 Reducing the effects of chemical pollution can be accomplished in several ways. By trapping chemicals in the soil, they cannot enter the food chains as easily. Bioremediation is also used, are used to help clean up, and are then removed from the ecosystem. o The oil industry will often use bacteria to eat oil spills. o Certain natural species are also excellent at bioremediation.