bio ecology Flashcards
(314 cards)
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Biology notes
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Photosynthesis can be summarized in this word equation:
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light and chlorophyll
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Carbon dioxide + water ——————–> glucose + oxygen
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The balanced chemical equation for photosynthesis is:
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light and chlorophyll
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6CO2 + 6 H2O ——————–> C6H12O6 + 6 O2
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This equation suggests that photosynthesis is one simple reaction. This is not the case. There are many reactions in photosynthesis
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each catalyzed by a different enzyme.
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Light energy is absorbed by chlorophyll. The energy from light is transferred by chlorophyll as chemical energy to drive the reactions that form carbohydrates from water and carbon dioxide. During this process the energy is used to split water into hydrogen ions and oxygen. The hydrogen ions are used to reduce carbon dioxide to carbohydrate. As a result
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the light energy absorbed by chlorophyll becomes the chemical bond energy in the simple sugars that are produced. Glucose is one simple sugar that is produced; it is converted to starch as a store of energy in leaves and other parts of plants.
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Photosynthesis provides energy for plants and for all other organisms that feed on plants directly or indirectly. The equations show that oxygen is produced as a by-product. The plant may use oxygen in its own respiration or it may diffuse out into the atmosphere where it is used by other organisms.
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You can use iodine solution to test for the presence of starch in leaves. We can use this test to find out whether photosynthesis has been happening or not.
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Leaves
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The shape of a leaf makes it ideally adapted to carry out its functions of absorbing light for photosynthesis and allowing gasses to diffuse into and out of the leaf tissues.
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Leaves have:
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* a large surface area - to absorb light rays
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* a thin shape - so gasses can diffuse in and out easily
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* many chloroplasts - to absorb light for the reactions that take place in photosynthesis
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* veins - to support the leaf surface and to carry water and ions to the leaf cells
and to take sucrose and amino acids away from the leaf to all other parts of the plant.
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Inside a leaf
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To find out how a leaf works we can look at the structure of a typical leaf.
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Some of the internal features are adaptations for photosynthesis.
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* Palisade mesophyll cells are packed tightly together near the surface of the leaf to maximize absorption of light where its intensity is highest.
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* There are many chloroplasts in the palisade mesophyll cells to absorb as much light as possible.
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* Stomata (usually in the lower epidermis) open to allow carbon dioxide to diffuse into the leaf. Carbon dioxide is a raw material for photosynthesis.
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* Leaves are thin so that carbon dioxide does not have to diffuse far from the atmosphere to the cells of the palisade and spongy mesophyll.
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* There are large intercellular air spaces within the spongy mesophyll layer. This makes it easy for carbon dioxide to diffuse to all the mesophyll cells. Diffusion through air is much faster than diffusion from cell to cell.
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* Xylem in veins brings water and ions to the mesophyll cells. Water is a raw material for photosynthesis and magnesium ions are needed by the cells to make chlorophyll.
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* The sugar produced in photosynthesis is converted to sucrose and transported away from the leaf in the phloem in veins.
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Stomata
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Stomata are small pores (holes) in the epidermis that allow gasses to diffuse into and out of the leaf. Stomata are usually in the lower epidermis
but some plants like water lilies have them in the upper epidermis.
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In sunlight:
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* Carbon dioxide diffuses in for photosynthesis
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* Oxygen made in photosynthesis diffuses out
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* Water vapor diffuses out
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Opening and closing
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Stomata are opened and closed by guard cells.
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Stomata usually open during the day. Water passes into the guard cells by osmosis. This makes them bend so the stoma opens.
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Carbon dioxide diffuses into the leaf for photosynthesis and oxygen diffuses out. Water vapor also diffuses out.
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At night the stomata close. Water passes out of the guard cells by osmosis and they straighten and move closer together
closing the stomata pores. The stomata also close in hot
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Aerobic Respiration
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When we burn fuel such as petrol
oxygen is used up and carbon dioxide is made. The flame gives off a lot of light and heat.
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Every cell in every living organism needs energy. A fuel used to provide energy in cells is called glucose
but unlike burning petrol
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In aerobic respiration oxygen is used in the breakdown of glucose.
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glucose + oxygen → carbon dioxide + water + energy released
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Cells also respire fats and proteins to provide energy
but you only have to know about the respiration of glucose
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Using Energy
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Your body needs energy for many different things. Energy is used in the following processes:
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* Muscle contraction
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* Cell division
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* Absorption of nutrients in the gut by active transport
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* Sending impulses along nerves
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* Protein synthesis for making enzymes
some hormones and antibodies
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* Making new cell membranes and cell structures like the nucleus during growth
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* Keeping the body temperature constant. Some of the energy released is in the form of heat.
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Respiration takes place in all living cells all of the time because cells need a constant supply of energy to stay alive. The balanced chemical equation for aerobic respiration is:
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C6H12O6 + 6O2 → 6 CO2 + 6 H2O + energy released
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Most of the energy released in aerobic respiration is released in mitochondria. Cells that require a lot of energy have many mitochondria. For instance
insect flight muscle has numerous mitochondria located between the muscle fiber. The mitochondria provide the energy for the muscles to contract during flight. Liver cells have a high metabolism and have many mitochondria. The epithelial cells of the small intestine absorb glucose and other molecules by active transport
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The Carbon Cycle
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Processes Involved
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1. Photosynthesis
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* Description: Plants
algae
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* Equation: 6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂
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* Importance: This process captures carbon from the atmosphere and incorporates it into organic molecules
forming the basis of the food chain.
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2. Respiration
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* Description: Organisms (plants
animals
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* Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
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* Importance: Returns carbon to the atmosphere and provides energy for living organisms.
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3. Decomposition
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* Description: Decomposers (bacteria and fungi) break down dead organisms and waste products
releasing CO₂ into the atmosphere or soil.
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* Importance: Recycles carbon from dead organisms back into the ecosystem.
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4. Combustion
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* Description: The burning of fossil fuels (coal
oil
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* Equation: Hydrocarbon + O₂ → CO₂ + H₂O + energy
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* Importance: Adds significant amounts of CO₂ to the atmosphere
contributing to global warming.
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5. Ocean Uptake
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* Description: Oceans absorb CO₂ from the atmosphere. Marine organisms use dissolved CO₂ to make shells and skeletons
which eventually form sedimentary rock.
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* Importance: Oceans act as a major carbon sink
helping to regulate atmospheric CO₂ levels.
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The Nitrogen Cycle
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Processes Involved
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1. Nitrogen Fixation (nitrogen gas represents 78% of the atmosphere)
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* Description: Conversion of nitrogen gas (N₂) from the atmosphere into ammonia (NH₃) or related compounds by nitrogen-fixing bacteria in soil or legume root nodules
and by lightning.
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* Equation: N₂ + 3H₂ → 2NH₃
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* Importance: Makes atmospheric nitrogen available to living organisms in a usable form.
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2. Nitrification
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* Description: Conversion of ammonia into nitrites (NO₂⁻) and then into nitrates (NO₃⁻) by nitrifying bacteria.
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* Steps:
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* Ammonia to nitrites: NH₃ → NO₂⁻
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* Nitrites to nitrates: NO₂⁻ → NO₃⁻
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* Importance: Nitrates are a form of nitrogen that plants can readily absorb.
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3. Assimilation
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* Description: Plants absorb nitrates from the soil and incorporate them into organic molecules like amino acids and proteins.
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* Importance: Transfers nitrogen from the soil into the food web.
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4. Ammonification
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* Description: Decomposers convert organic nitrogen in dead organisms and waste back into ammonia.
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* Importance: Returns nitrogen to the soil in a form that can be used by plants.
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5. Denitrification
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* Description: Conversion of nitrates back into nitrogen gas by denitrifying bacteria
releasing it into the atmosphere.
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* Equation: NO₃⁻ → N₂ + O₂
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* Importance: Completes the nitrogen cycle by returning nitrogen to the atmosphere.
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The Phosphorus Cycle
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Processes Involved
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1. Weathering
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* Description: Phosphate rocks break down due to weathering
releasing inorganic phosphate (PO₄³⁻) into the soil and water.
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* Importance: Releases phosphate into the ecosystem where it can be used by organisms.
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2. Absorption by Plants
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* Description: Plants absorb inorganic phosphate from the soil through their roots.
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* Importance: Incorporates phosphorus into biological molecules such as ATP
DNA
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3. Consumption
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* Description: Animals obtain phosphorus by eating plants or other animals.
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* Importance: Transfers phosphorus through the food web.
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4. Decomposition:
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* Description: Decomposers break down dead organisms and waste
returning phosphorus to the soil or water.
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* Importance: Recycles phosphorus back into the ecosystem.
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5. Sedimentation:
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* Description: Phosphorus can settle in water bodies and form sedimentary rock over geological time scales.
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* Importance: Acts as a long-term storage of phosphorus
completing the cycle.
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Food Chains
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* Definition: A linear sequence of organisms where nutrients and energy pass as one organism eats another.
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* Components:
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* Producers (Autotrophs): Organisms that produce their own food through photosynthesis (e.g.
plants
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* Consumers (Heterotrophs): Organisms that consume other organisms for energy.
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* Primary Consumers (Herbivores): Eat producers (e.g.
rabbits
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* Secondary Consumers (Carnivores): Eat primary consumers (e.g.
snakes
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* Tertiary Consumers: Eat secondary consumers (e.g.
eagles
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* Decomposers (Detritivores): Break down dead organisms (e.g.
bacteria
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Food Webs
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* Definition: A complex network of interconnected food chains in an ecosystem.
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* Importance: Shows how different organisms are related through feeding relationships and how energy flows through an ecosystem.
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* Biodiversity: Higher biodiversity results in a more stable food web.
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Energy Pyramids
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* Definition: A graphical representation showing the energy flow at each trophic level in an ecosystem.
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* Structure:
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* Base: Producers (most energy)
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* Middle: Primary and Secondary Consumers
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* Top: Tertiary Consumers (least energy)
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* Biomass: The total mass of living organisms at each trophic level decreases as you move up the pyramid.
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Predation
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* Definition: An interaction where a predator hunts and kills prey for food.
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* Impact: Helps control population sizes and maintain ecosystem balance.
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Symbiosis
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* Definition: A close relationship between two species where at least one benefits.
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* Types:
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* Mutualism: Both species benefit (e.g.
bees and flowers).
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* Parasitism: One species benefits at the expense of the other (e.g.
ticks on dogs).
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* Commensalism: One species benefits while the other is neither helped nor harmed (e.g.
barnacles on whales).
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Additional Terms
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* Biomass: The total mass of all living organisms in a given area.
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* Biosphere: the region on
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* Autotrophs: Organisms that produce their own food.
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* Heterotrophs: Organisms that obtain food by consuming other organisms.
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* Herbivores: Animals that eat plants.
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* Carnivores: Animals that eat other animals.
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* Omnivores: Animals that eat both plants and animals.
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* Detritivores: Organisms that feed on dead organic matter.
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* Eutrophication: The enrichment of water bodies with nutrients
leading to excessive plant growth and oxygen depletion.
