2.1 Energy Flow in Ecosystems

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1 2.1 Energy Flow in Ecosystems Organisms interact with the ecosystem by: 1. Obtaining food from the ecosystem (eating) Plants are called producers because they produce carbohydrates during photosynthesis. CO 2 + H 2 O + sunlight C 6 H 12 O 6 + O 2 2. Contributing energy to the ecosystem (being eaten) Consumers get their energy by feeding on producers or other consumers. - they use cellular respiration to release the energy from the food molecules. C 6 H 12 O 6 + O 2 CO 2 + H 2 O + energy Decomposers break-down wastes & dead organisms, through the process of biodegradation. 1

2 Energy Flow & Energy Loss There are three main methods to represent energy moving through ecosystems. 1) Food chains: show the flow of energy from one organism to the next. 2) Food webs: represent interconnected food chains. 3) Food pyramids: show the changes in available energy from one trophic level to another in a food chain. (also called ecological pyramids) Food Chains Each step is a trophic level Producers = 1st trophic level Primary consumers = 2nd trophic level Secondary consumers = 3rd trophic level Tertiary consumers = 4th trophic level Terrestrial & aquatic food chains Using a food chain, consumers can be classified as: 1. Detrivores (decomposers) - obtain energy & nutrients from dead organisms & waste matter. - have their own, separate food chains & they feed on every trophic level. Ex. small insects, earthworms, bacteria & fungi 2. Herbivores - primary consumers - eat plants (producers) only Ex. Horse eating hay This dung beetle is a detrivore. 3. Carnivores - eat non-producers a) Secondary consumers - eat herbivores Ex. Frog eating a grasshopper b) Tertiary consumers - eat secondary consumers - also called top predators, top carnivores or top consumers Ex. Lions eating humans 2

3 Food Webs 4. Omnivores - consumers that eat both plants & animals - recognized using a food web (not food chain) Ex. bears Most organisms are part of many food chains. Arrows in a food web represent the flow of energy and nutrients. the top carnivore(s) is the one with no predator identified Food Pyramids - energy enters at the first tropic level (producers) - producers have a large amount of biomass & therefore a lot of energy Biomass is the total mass of all living things in a given area. (measured in g/m 2 or kg/m 2 ) It takes large quantities of organisms in one tropic level to meet the energy needs of the next trophic level. 80% - 90% of energy taken in by consumers is used in chemical reactions in the body, or is lost as heat energy. 3

4 The amount of life an ecosystem can sustain is based on the bottom level of the ecological pyramid, where producers capture energy from the sun. Lower trophic levels usually have much larger populations than upper levels. important so all higher organisms can feed and survive 2.2 Nutrient Cycles in Ecosystems Nutrient cycles the flow of nutrients IN and OUT of the land, ocean, atmosphere and deep rock. The health of our ecosystems depends on the balance of many nutrients, but especially: Carbon, Nitrogen, Phosphorous, Hydrogen and Oxygen C N P H O 4

5 The Carbon Cycle Do the Nutrient Cycles Worksheet! Hint: Use your data booklet Carbon Facts: - is found in all living matter. Places that it is found are called stores or sinks Short-term Stores Long-term Stores - living things in water & on land - underground (oil, gas, - rotting tissue of plants/animals natural gas and coal) - atmosphere (air) - sedimentary rock - ocean (dissolved in the water) (limestone) - ocean floor (old shells) Carbon Changes Form through: 1. Photosynthesis (in plants, algae and cyanobacteria) CO 2 + H 2 O + sunlight C 6 H 12 O 6 + O 2 4. Ocean mixing -moves CO 2 around the world - CO 2 sinks in cold ocean waters and flows to the warm equator and evaporates into the air. 2. Cellular respiration (in cells of all living things) C 6 H 12 O 6 + O 2 CO 2 + H 2 O + ENERGY (energy is used for growth, repair etc.) 3. Decomposition (rotting) done by bacteria/fungi cellulose CO 2 5. Combustion - (burning, engines, volcanoes, forest fires) Fossil fuels + O 2 CO 2 + H 2 O + Energy (oil, gas, natural gas, coal) 5

6 Human Activities & CO 2 Burning Fossil Fuels releases CO 2 CO 2 in the atmosphere has increased 30% in past 160 years. Carbon is removed from long-term storage as we mine coal & drill for oil and gas. CO 2 is also a greenhouse gas, (traps heat in atmosphere) Removing Trees releases CO 2 Trees absorb and store CO 2, so when they are cut down. Other crops don t remove and store as much CO 2 as forests The Nitrogen Cycle Nitrogen Facts Makes up DNA & proteins. Help plants grow. Nitrogen is Found in the: Atmosphere (78% is N 2 ) Oceans Organic matter in soil Lakes, marshes, organisms - N 2 (nitrogen gas) is not usable by plants or animals, so it has to be converted to NO 3 - (nitrate) and NH 4+ (ammonium) Nitrogen Changes Form Through: 1. Nitrogen Fixation takes N 2 out of the air Happens because of A) Lightning - changes N 2 NO 3 - and rain then washes NO 3- into soil B) Bacteria in soil (rhizobium) & water (cyanobacteria) - changes N 2 NH most of nitrogen fixation happens this way 6

7 2. Nitrification: - done by nitrifying bacteria. NH 4 + NO 2- (nitrite) NO 3 - Nitrogen Cycle 3. Uptake: - NO 3- is sucked into plants & used for growth. Herbivores eat plants & use N for making proteins & DNA. 4. Denitrification: -Puts N 2 back in the atmosphere - done mostly by denitrifying bacteria, but also volcanic eruptions NO 3 - N 2 Human activities affect the nitrogen cycle through: 1. Burning fossil fuels, burning forests to clear land & sewage treatment. All release NO & NO 2 which cause acid rain containing nitric acid (HNO 3 ) 2. Overfertilization NH 4 + & NO 3- leach into soil & waterways. Causes huge growth in aquatic algae = eutrophication These algal blooms use up all CO 2 & O 2, block sunlight & produce neurotoxins which kill many aquatic organisms. The Phosphorous Cycle Phosphorous Facts is a part of the molecule that carries energy in cells (ATP). in plants, it helps root growth, stem strength and seed production. in animals, it is important for strong bones. it is NOT in the atmosphere, but in phosphate rocks (PO 4 3, HPO 4 2, H 2 PO 4 ) and sediments on the ocean floor. 7

8 Phosphorous Changes Form through: 1. Weathering (breaking down rock into smaller pieces). a) Chemical weathering where acid rain or lichens releases phosphates (PO 4 3- ) b) Physical weathering where wind, water and freezing release the phosphates. 2. Uptake: plants suck up PO 4 3-, then are eaten by animals. 3. Decomposition: Bacteria break down organic matter & phosphorous is returned to soil. 4. Geologic Uplift: when rocks under the ground are pushed up and exposed so weathering can occur. The Phosphorous Cycle Humans affect the Phosphorous Cycle through: 1. Mining: increases P in ecosystems quickly. 2. Slash-and-burn forest practices: turns P into ash, which runs into waterways. Changes in Nutrient Cycles Affect Biodiversity Significant changes to any of these nutrients (C, H, O, N or P) can greatly impact biodiversity. 1. Carbon cycle changes are causing climate change & global warming. 2. Too much nitrogen can allow certain plant species to out-compete other species. 3. Decreased levels of phosphorous slow the growth of algae (important producers). 8

9 2.3 Effects of Bioaccumulation on Ecosystems Bioaccumulation: a slow build up of chemicals in the bodies of organisms. If bioaccumulation occurs in a keystone species, it can affect every other organism in its niche. Amphibians are used as indicators of environmental health because they are very sensitive to chemical changes. Since the 80s the world amphibian population has declined & birth deformities have increased. This may be due to: pollution, drought, increased UV rays, habitat loss, parasites & diseases. Ex. PCBs were banned in 1977, but will continue to affect the reproductive cycles of Orca whales until at least Spraying DDT, 1958 Heavy metals also bioaccumulate. Lead, cadmium & mercury are the most dangerous. Lead - is not considered safe at any level, it can cause anemia, nervous & reproductive system damage. Chemicals like PCBs and DDT & other insecticides are called persistent organic pollutants (POPs). POPscontain carbon, & remain in water & soil for many years DDT, even at low levels like 5 parts per million (ppm) causes nervous, immune & reproductive system disorders in animals. Cadmium - is toxic to earthworms & causes many health problems in fish. - causes lung diseases, cancer, nervous & immune system damage in humans - it is in cigarette smoke. 9

10 Mercury - enters ecosystems through burning of fossil fuels, waste incineration, mining & the manufacture of batteries. - it bioaccumulates in the brain, heart & kidneys of many animals Reducing the effects of chemical pollution: Trapping chemicals in the soil - then they cannot enter the food chains as easily. Bioremediation: micro-organisms or plants are used to help clean up, and are then removed from the ecosystem. - Fish readily bioaccumulate mercury, adding risk for any organisms eating the fish. Ex. The oil industry will often use bacteria to eat oil spills. Biomagnification Biomagnification: the individual consumers in each trophic level receive larger doses of accumulated chemicals than those in lower levels. 10