Environmental studies Energy flow and nutrient cycles Energy

Environmental studies Energy flow and nutrient cycles

Energy Flow The sun is the source of all natural energy on earth Plants are able to absorb the energy from the sun by using a special pigment called chlorophyll. The chlorophyll is found in an organelle called chloroplast. The plant uses some of this energy for its own activities like growth, production of organic compounds and for chemical reactions. The rest of this energy is converted to chemical potential energy and stored in the plant.

Energy flow: Plants are able to trap enough energy from the sun for their own needs and for the needs of the animals. This is possible because there are more plants than animals. When herbivores feed on the plants this stored energy is transferred to the animal’s body. The animals uses some of the energy for their own activities like growth, movement, respiration. The rest of the energy is stored in the animals tissues. Animals will use more energy than plants because they are more active.

Energy flow The energy is transferred from animal to animal as the animals feed on each other. The energy is transferred from the herbivores and or omnivores to the carnivores. When the plants and animals die the energy still trapped in their bodies are released by the decomposers. The decomposers release the energy when they break down the dead plant and animal matter. This energy can be used by other plants and animal. This flow of energy from one living organism to the next is called energy flow.

Food chain: A food chain shows the transfer of energy from one organism to the next: grass worm spider frog In reality a food chain never exists alone. This is because a single organism may provide food to many different organisms. Therefore in nature there is usually a number of interwoven food chains: called a food web.

Something for you to do Try to complete this food chain

Trophic levels A trophic level may also be called a feeding level. All the plants and animals in any habitat can be grouped into trophic levels. There are generally four trophic levels. Tophic level 1 is made up of all the green plants because they are able to make their own food by photosynthesis. These plants also have the highest total energy. Trophic level 2 is made up of all the organisms that feed on the green plants. They have a slightly lower energy than the green plants. These organisms are the herbivores.

Trophic levels Trophic level 3 is made up of all the organisms that feed on the herbivores in trophic level 2. The organism that make up this trophic level are carnivores. This trophic level may also be made up of omnivores. In this trophic level organisms have less energy than the herbivores and of trophic level 2. Trophic level 4 is made up of organisms that feed on the carnivores in trophic level 3. The carnivores found in trophic level 4 are called top carnivores. They have less energy than the carnivores of trophic level 3. This trophic level can be made up of carnivores and omnivores.

Trophic level 1: Producers Trophic level 2: Primary consumers Trophic level 3: Secondary consumers Trophic level 4: Tertiary consumers

Something to do Can you name the organisms found in the different trophic levels? To which trophic level does the producer belong? Name all the trophic levels that the omnivores can be a part of.

Where do the decomposers fit? The decomposers can occur at any trophic level depending on which organism they are breaking down. In a food chain trophic levels occurring in the following order: Trophic level 1 trophic level 2 trophic level 3 trophic level 4

Something for you to do 1. Which food chain correctly describes the flow of energy in an ecosystem? A. grass-->cow-->human B. caterpillar-->leaf-->human C. cow-->grass-->human D. leaf-->bird-->caterpillar

2. Rabbits eat grass and other plants to survive, but they do not eat animals. What kind of animal are rabbits? A. decomposers B. carnivores C. producers D. herbivores

3. How do decomposers help other organisms in an ecosystem? A. They are food for consumers. B. Through photosynthesis they can make their own food. C. They return nutrients back to the soil. D. They eat plants

4. In what order do a hawk, grass, and rabbit form a food chain in a meadow? A. hawk-->grass-->rabbit B. grass-->hawk-->rabbit C. rabbit-->grass-->hawk D. grass-->rabbit-->hawk

5. Which of the following lists only consumers? A. hawks, lizards, chipmunks B. acorns, squirrels, rabbits C. grass, chipmunks, eagles D. mice, squirrels, grass

Solution: 1. A 2. D 3. C 4. D 5. A

Ecological pyramids An ecological pyramid is a graphical representation of the energy or matter contained within each trophic level.

Ecological pyramids From the diagram on the previous slide it is clear that there are 3 different types of ecological pyramids. 1. Pyramid of energy 2. Pyramid of numbers 3. Pyramid of biomass.

Pyramid of energy This pyramid shows the amount of available energy at each trophic level

Pyramid of energy The available energy gets less and less as we move up the pyramid. This means that the producers have the most available energy while the tertiary consumer has the least. Therefore the amount of energy available in each trophic level is less than the previous trophic level. The decreasing available energy results in the pyramid shape.

Why does the energy decrease at each trophic level? There are 3 reasons for the decrease in available energy: The organisms use some of the energy for their own activities. Some energy is lost because the organism does not consume the entire resource. Some energy is lost as faeces and urine.

Pyramid of numbers This pyramid shows the number of organisms in each trophic level. Pyramid shape exists because the number of organisms decreases in each trophic level from the bottom to the top.

Rose bush Inverted pyramid of numbers Sometimes the pyramid of numbers can be inverted. This can be because a single plant ( e. g. fruit seeds) can provide food for many organisms. aphids bird Similarly many organisms can provide food for a single organism.

Pyramid of biomass This pyramid shows the total mass of organisms in each trophic level. This pyramid can also become inverted, if the ecosystem becomes imbalanced.

Assessment task Study the following paragraph and answer the questions that follow: A baboon was seen lifting stones and looking for food in a patch of grass. The baboon found some beetles and ate them. Every so often, the baboon would scratch himself, because he had a large number of fleas on his body 1. Draw a food chain which clearly illustrates the feeding relationships described above. [4]

2. Draw a pyramid of numbers to illustrate the description above. [4] 3. What is a pyramid of numbers? Comment on the shape of this pyramid of numbers in your answer. [3] 4. Draw a food web which illustrates a feeding relationship between at least ten organisms. Include the four organisms in the food chain you drew in number 1. [10]

5. Choose one organism in the food web you drew in number 4 and draw a circle around this organism. Imagine that this organism was eliminated (removed) completely from the feeding relationship. What impact would this have on the rest of the food web? Explain fully. [4] [25 marks]

Activity 3. 3. 3 pg 250 no 1 and 2 only

Solutions 1. Grass Beetle Baboon Flea 2. pyramid

Solutions 3. A pyramid of numbers shows the relative numbers of organisms in a particular food chain; usually a pyramid has the smallest portion on top, this one does not. 4. Learner responses will differ. Mark according to the web they produce. Check that arrows flow in the correct direction (in the direction of energy flow) and check that links are realistic. One mark per organism correctly inserted in the web. 5. Learners will vary. However they should indicate that the ecosystem will become imbalanced. They should indicate how trophic level before and after the chosen one is altered.

Nutrient recycling is the process that ensures that nutrients become available for reuse. Some examples of these important nutrients are carbon dioxide, water vapour, oxygen, minerals and energy. Nutrient recycling occurs in the following general way.

Nutrient recycling occurs in the following general way. During photosynthesis green plants use sunlight, carbon dioxide and water to make food in the form of glucose. When the primary consumers (herbivores and omnivores) feed on the green plants the food is transferred to their bodies. Remember this food contains carbon (glucose), water, and energy. When the secondary consumer (carnivores) feed on the primary consumer the food is transferred to their bodies from the primary consumer.

Role of decomposers in nutrient recycling When any of these organisms die (producer, primary, secondary or tertiary consumer) their bodies are broken down by decomposers. Decomposers release nutrients so that they can be reused. The decomposers releases carbon dioxide and energy in the form of heat into the atmosphere and water vapour and mineral salts into the soil. Without nutrient recycling important nutrients will become exhausted.

Water cycle

Homework Draw figure: 3. 3. 3 – page 253

Water cycle ensures that water supply is never exhausted. The water cycle occurs as follows: Water vapor from the atmosphere falls to the ground. This water vapors can fall to the earth as rain, dew, frost, mist and hail: precipitation. Some of this water reaches the soil and then runs off into the rives and streams Some of this water will also reach the dams, lakes and oceans.

Water cycle The ground water may soak into the soil. One of two things may happen to this water: It may remain in the soil as capillary water around the soil particles or it may reach the water table. Plants absorb the water from the soil using their roots. Animals obtain their water from the rivers, lakes and streams or from the food they eat. This water is then used by plants and animals for various functions. Plants lose some of the water as water vapour during the process of transpiration. Animals also lose some water as water vapour during the process of respiration. Animals also lose water during sweating and breathing.

Evaporation When the ground, air or water surface becomes heated the water changes from a liquid into a gas. This gas is called water vapour. The process by which water changes from a liquid to a gas is evaporation. The water vapour then rises into the atmosphere with the warm air that rises. As the water vapour goes to higher altitudes cooling of this water occurs.

Condensation As the water vapour goes to higher altitudes cooling of this water occurs. When the water vapour cools it changes from a gaseous state to a liquid state: condensation. This results in the formations of clouds. The air becomes saturated when more and more water collects at this level, clouds will form. The clouds then become heavy ( the clouds are holding the maximum amount of water in a specific volume at a specific temperature. ) Then the water begins to fall as precipitation. The cycle is completed and begins all over again.

Carbon cycle The concentration of carbon dioxide in the air 0, 03%. The carbon in the form of carbon dioxide is used by green plants to manufacture food by photosynthesis. Carbon dioxide is released by both plants and animals during the process of cellular respiration. While photosynthesis uses up carbon dioxide, cellular respiration releases it. In this way the levels of carbon dioxide is maintained.

Carbon cycle Carbon dioxide is absorbed by green plants from the atmosphere and water to be used during photosynthesis. The carbon is used to make glucose and then other organic material. When the consumers (herbivores, omnivores and carnivores) feed on the plant that organic material is transferred to these consumers. The carbon is now present in the bodies of both plants and animals.

Carbon cycle The carbon occurs in organic compounds such has carbohydrates, proteins, lipids, hormones, pigments, enzymes etc. REMEMBER: organic compounds contains carbon. During cellular respiration all living organisms release carbon dioxide. The carbon dioxide is released into the water or atmosphere. When plants and animals die decomposers break down their bodies and release carbon dioxide into the atmosphere or soil.

Carbon cycle Sometimes carbon becomes trapped in the bodies of dead plants and animals when these organisms do not decompose. These dead bodies become compressed and form fossil fuels such as coal, oil and gas. When these fossil fuels are burnt the carbon dioxide trapped in them is released. The cycle then starts over.

Carbon cycle

Draw figure: 3. 3. 4 – page 254

Oxygen cycle Oxygen is required by both plants and animals for cellular respiration. Oxygen is found in the atmosphere and dissolved in the water. The concentration of oxygen in the atmosphere is 21%.

Oxygen cycle Oxygen found in both the atmosphere and water is used by both plants and animals during cellular respiration to release the energy trapped in food. Oxygen is also used during the combustion (burning) of fossil fuels. The levels of oxygen decreases. Both combustion and cellular respiration releases carbon dioxide. This carbon dioxide is used by plants during photosynthesis to make organic compounds. During photosynthesis oxygen is released and the levels of oxygen return to normal. The cycle begins once more.

Oxygen cycle Oxygen in the water and atmosphere is To release oxygen Carbon dioxide is used by plants during photosynthesis Combustion of Fossil fuels enters the water and atmosphere Used by plants and animals during cellular respiration to Release carbon dioxide which

Draw figures: 3. 3. 5 – page 255

Nitrogen cycle About 79% of the atmosphere is made up of nitrogen. Nitrogen is required to manufacture proteins by both plants and animals. Plants cannot absorb nitrogen as it occurs in the atmosphere. The nitrogen must first be converted to nitrates before the plants absorbs it. Animals obtain their nitrogen when they feed on plants or feed on animals that feed on plants.

Nitrogen cycle Since plants can only absorb nitrogen in the form of nitrates, atmospheric nitrogen must first be converted into nitrates before it is absorbed by the plants. This conversion can take place in 2 ways: 1. Lightening and rain can convert the nitrogen into nitrate. 2. Nitrogen fixing bacteria found in the soil converts the nitrogen in the soil into nitrate which then can absorbed by the plants.

Nitrogen cycle Plants then uses the nitrates to manufacture proteins. Nitrates are transferred to animals when they feed on plants or animals that have fed on plants. When the plants and animals die the decomposers breaks down the dead and decaying matter to release nitrites. Other bacteria then converts the nitrites into nitrates.

Nitrogen cycle One of two things may happen to the nitrates: It maybe absorbed by plants to manufacture proteins. Denitrifying bacteria may convert the nitrates back into nitrogen and the cycle continues.

Nitrogen cycle

Homework Activity 3. 3. 5 Page 256

Environmental concerns and nutrient recycling

Effects of the enhanced greenhouse effect pg 257.

TERMINOLOGY This flow of energy from one living organism to the next is called energy flow. A food chain shows the transfer of energy from one organism to the next organism. A trophic level can also be called a feeding level. An ecological pyramid is a graphical representation of the energy or matter contained within each trophic level. Pyramid of energy shows the amount of available energy at each trophic level

Terminology Pyramid of numbers shows the number of organisms in each trophic level. Pyramid of biomass shows the total mass of organisms in each trophic level. Nutrient recycling is the process that ensures that nutrients become available for reuse. Precipitation is when water vapors can fall to the earth as rain, dew, frost, mist and hail. The process by which water changes from a liquid to a gas is called evaporation. Condensation is when the water vapour cools it changes from a gaseous state to a liquid state.

Terminology Water is an inorganic compound made up of hydrogen and oxygen. Nitrogen fixing bacteria converts the nitrogen in the soil into nitrate which then can absorbed by the plants. The nitrifying bacteria converts the nitrates into nitrates. Denitrifying bacteria converts the nitrates back into nitrogen and the cycle continues.