What is Ecology? ECOLOGY is a branch of biology that studies ecosystems.

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1 4.2 Energy Flow Through an Ecosystem Food Chains, Food Webs, and Ecological Pyramids What is Ecology? ECOLOGY is a branch of biology that studies ecosystems. Ecological Terminology Environment Ecology Biotic vs. Abiotic Population Community Ecosystem Biosphere Environment Ecology. Biotic Abiotic surroundings of an organism including the plants, animals and microbes with which it interacts. study of how living organisms interact with the physical and biological environments living organisms that are part of the environment. non-living chemical and physical factors of the environment (e.g. temperature, light, water, soil, nutrients). Population Community Ecosystem Biosphere a group of individuals of the same species living in the same geographic area. all interacting populations living in the same geographic area. all interacting communities of organisms and abiotic factors of the environment within a defined area. the global ecosystem, including all the earth s regions that can support life (land, air, water). ENERGY in the ecosystem ENERGY! BEGINS WITH SUNLIGHT 4.2U 1 Most ecosystems rely on a supply of energy from sunlight. 1

2 The 3-Step ENERGY Pathway of Ecosystems LIGHT 1. CHEMICAL ENERGY 2. HEAT U 1 Most ecosystems rely on a supply of energy from sunlight. photosynthesis CO 2 + H 2 O C 6 H 12 O 6 + O U 2 Light energy is converted to chemical energy in carbon compounds by photosynthesis. The chemical reaction by which green plants use water and carbon dioxide and light from the sun to make glucose. ENERGY is stored in glucose; glucose is stored as starch. 4.2 U 2 Light energy is converted to chemical energy in carbon compounds by photosynthesis. respiration Glucose O 2 + C 6 H 12 O 6 work for cells CO 2 + H 2 O HEAT 4.2 U4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat. 6O 2 + C 6 H 12 O 6 6H 2 O + 6CO 2 + energy CELLULAR RESPIRATION is the chemical reaction that releases the energy in glucose so the cell can do work. 4.2 U4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat. 2

3 Note: although the vast majority are, some ecosystems are not based around solar energy. For example, some organisms are able to use sulfur from hydrothermal vents as a source of energy. FOOD CHAINS and TROPHIC LEVELS 4.2U 1 Most ecosystems rely on a supply of energy from sunlight. Organisms that can make glucose during photosynthesis are called PRODUCERS. Organisms that cannot make their own glucose are called CONSUMERS. The transfer of energy from sun to producer to consumers can be shown in a FOOD CHAIN 3

4 (follow the ENERGY coming from the SUN) A food chain 1 A food chain ( capture ENERGY coming from the ) 1 2 PRODUCERS A food chain Primary consumers (herbavores that get ENERGY & MATERIALS from the PRODUCERS they eat) A food chain A food chain the numbers are called Trophic levels 2 Primary consumers 3 4

5 trophic levels tell how far away each feeding level is from Notice that the arrows point in the direction of energy flow. 2 1 THE 10% RULE and ECOLOGICAL PYRAMIDS The maximum amount of ENERGY that passes from one trophic level to the next is usually around 10%. About 90% of the ENERGY at each trophic level is used to keep the organisms alive and is converted to HEAT. Where does the energy go?? Energy not used 10 % Energy from lower trophic level Egested energy Urinary waste Gross energy intake Digested 90% energy Assimilated energy Resting energy Activity Growth Reproduction Maintenance or Production respiration 5

6 Where does the energy go?? Energy not used and available to be passed to the next level Energy from lower trophic level Urinary waste Gross energy intake Digested energy Assimilated energy Resting energy Activity Growth Reproduction Where does the energy go?? Energy not used 10 % Energy from lower trophic level Urinary waste Gross energy intake Digested energy Assimilated energy Resting energy Activity Growth Reproduction Always start with the SUN. PRODUCERS HERBIVORES 1st Order CARNIVORES 2nd Order CARNIVORES 3rd Order CARNIVORES Producers use most of the energy they make (90%) for themselves. The 10% of energy that is not used by producers can be passed on to organisms that cannot make their own energy. 6

7 a. Nutrients are recycled by the decomposers back to the producers. b. Nutrients are lost from the ecosystem when organisms die. c. The conversion of food into growth by an organism is not very efficient. d. Energy is recycled by the decomposers back to the producers. Most (90%) of the energy the primary consumer gets from the producer is used by the consumer. Some of the energy moves into the atmosphere as heat. Some energy in the primary consumer is not lost to the atmosphere or used by the consumer itself. This 10% of energy is available for another consumer. Ecological pyramids show: That the amount of available energy decreases down the food chain It takes a large number of producers to support a small number of primary consumers It takes a large number of primary consumers to support a small number of secondary consumers There are three types of Ecological Pyramids 1.Pyramid of Numbers 2.Pyramid of Biomass 3.Pyramid of Energy 7

8 Pyramid of Numbers Shows the number of organisms at each trophic level. Pyramids of numbers will often be pyramid-shaped - but not always. Pyramid of Biomass Shows the total mass of living tissue at each level e.g. shows that a large amount of tree mass is needed to feed a single caterpillar. Pyramid of Biomass Units are in mass per unit area. For example: g/m 2 grams per square meter Example Pyramid of Biomass The 10% rule applies to Pyramids of Biomass 8

9 1 lb. For every 1 lb. of halibut, how many lbs. of seals can be supported? 1 lb. For every 1 lb. of halibut, 0.1 lbs. of seal can be supported!? 0.1 lbs Pyramid of Energy shows the total amount of incoming energy ate each successive level based on the idea that 90% of the energy is lost as heat at each trophic level and only 10% of the energy is passed on. Pyramid of Energy energy units are in joules (J) or Kilocalories (kcal) 9

10 Typically decomposers (saprotrophs and detritovores) are placed beneath producers in the food web Oooops! What s wrong with this food web? Oooops! What s wrong with this food web? Construct a food web containing up to 10 organisms, using appropriate information. Using the information in the food web construct two individual food chains from the marine ecosystem, each with at least three linkages (four organisms) Identify each organism with its common name and state whether each is a producer, primary consumer, secondary consumer, etc. 1.No producers. 2.Arrows point backwards. Explain the energy flow in a food chain. 10

11 Explain why, in a food chain, a large amount of plant material supports a smaller mass of herbivores and an even smaller mass of carnivores. -Energy is lost at each trophic level. Only 10-20% of the energy made available by producers passes to primary consumers. This is because plants use energy for their own metabolic processes such as creating ATP. Consumers use energy in movement; the energy dissipates and is lost as heat into the surrounding environment. Also, not all the organic matter is consumed. -The total amount of energy available to top consumers is small; a large number of producers are required to provide tertiary and quaternary consumers with enough energy. Activity Suggest what trophic level humans occupy. Give examples. Trophic levels of humans depend on what they feed on: - When eating vegetables, cereals and fruits only: primary consumers - When eating meat from herbivores: secondary consumers - When eating other carnivore animals: tertiary or quaternary consumers Using a ruler, draw a pyramid of biomass to scale for the food chain in the table. Organism Biomass (g) Grass 100 Grasshopper 25 Mouse 10 Snake 5 Organism Biomass (g) Grass 500 Rabbit 50 Fox 1 11

12 The End! 12