4.2 Energy flow. Essential Idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat..

Transcription

1 4.2 Energy flow Nature of Science: Use theories to explain natural phenomena the concept of energy flow explains the limited length of food chains. (2.2) Essential Idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat.. By Darren Aherne

2 4.2 The Kidney & Osmoregulation Essential Idea: All animals excrete nitrogenous waste products and some animals also balance water and solute concentrations. Assessment Statement 4.2 U1 Most ecosystems rely on a supply of energy from sunlight. 4.2 U2 Light energy is converted to chemical energy in carbon compounds by photosynthesis. 4.2 U3 Chemical energy in carbon compounds flows through food chains by means of feeding. 4.2 U4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat U5 Living organisms cannot convert heat to other forms of energy. 4.2 U6 Heat is lost from ecosystems. Guidance

3 Assessment Statement 4.2 U7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels S1 Skill: Quantitative representations of energy flow using pyramids of energy. Guidance Pyramids of number and biomass are not required. Students should be clear that biomass in terrestrial ecosystems diminishes with energy along food chains due to loss of carbon dioxide, water and other waste products, such as urea.

4 4.2 U1 Most ecosystems rely on a supply of energy from sunlight. 4.2 U2 Light energy is converted to chemical energy in carbon compounds by photosynthesis. Producers capture the sun s light energy and convert it to chemical energy in the process of photosynthesis. CO 2 + H 2 O + light C 6 H 12 O 6 + O 2 light energy is captured And converted to chemical energy Chemical energy is used to create BIOMASS. The stored energy in biomass is passed on when consumers feed. Biomass is the total dry mass of organisms within an area or volume. Organisms in most ecosystems get their energy from the sun, though consumers get it indirectly by feeding.

5 4.2 U3 Chemical energy in carbon compounds flows through food chains by means of feeding. A food chain shows a linear sequence of organisms, starting with a producer and ending with a predator, that feed on each other. There are between 2-5 organisms in a food chain, but not more. Arrows show the flow of energy between organisms. Why aren t there more organisms in a food chain?

6 4.2 U4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat. Cell respiration is the conversion of chemical energy into a form that cells can use. Heat is produced too C 6 H 12 O 6 + O 2 CO 2 + H 2 O + ATP Sugar- stored chemical energy ATP- the energy currency of the cell Cell respiration releases heat when organic compounds are converted to ATP. Where does the heat go?

7 4.2 U5 Living organisms cannot convert heat to other forms of energy.. Organisms can convert many types of energy: Light energy to chemical energy in photosynthesis. Chemical energy to kinetic energy in muscle contraction. Chemical energy to electric energy in neurons. Chemical energy to heat energy in heat generating adipose tissue (for homeostasis) But once the energy becomes heat, organisms cannot convert it to any other form of energy.

8 4.2 U5 Heat is lost from ecosystems. The heat generated by cell respiration is useful to organisms. It makes ectothermic (cold-blooded) animals warmer, which allows them to be more active. It is used by endothermic (warm-blooded) animals to maintain a constant body temperature in homeostasis. Image: Wikipedia Cold-blooded reptiles can be more active when they are warm Heat moves from warmer areas to colder areas, so the heat is lost to the environment. The heat in the ecosystem is eventually lost into space.

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10 4.2 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels. Trophic level: the position of the organism in a food chain. Producers are on the first trophic level, primary consumers on the second. When biomass is consumed, energy is transferred. Energy transfers between trophic levels is inefficient. Only about 10% of the energy available at one trophic level is passed on to the next. Energy is lost: As heat from respiration Not consumed (bones, fur, etc.) As feces /ecosystem_organization.swf

11 From I-Biology.net

12 Problem: The production of a rainforest is 2.56 X 10 5 KJm -2 yr -1. Construct a pyramid of energy, assuming that 10% of energy is passed on to each trophic level.

13 Problem: The production of a rainforest is 2.56 X 10 5 KJm -2 yr -1. Construct a pyramid of energy, assuming that 10% of energy is passed on to each trophic level. Why are food chains and biomass limited by energy loss between trophic levels? Tertiary Consumers: 256KJm -2 yr -1 Secondary Consumers: 2,560 KJm -2 yr -1 Primary Consumers: 25,600 KJm -2 yr -1 Producers: 256,000 KJm -2 yr -1

14 Problem: The production in a tropical rainforest biome is 2.56 X 10 5 KJm -2 yr -1. Construct a pyramid of energy, assuming that 10% of energy is passed on to each trophic level. Because there is not much energy available at higher trophic levels- just 0.1% or less Tertiary Consumers: 256KJm -2 yr -1 Secondary Consumers: 2,560 KJm -2 yr -1 Why are food chains and biomass limited by energy loss between trophic levels? That s why you see fewer tigers (apex predators) than trees (producers)! Primary Consumers: 25,600 KJm -2 yr -1 Producers: 256,000 KJm -2 yr -1

15 Outline how energy is passed through ecosystems. (6 marks)

16 Outline how energy is passed through ecosystems. (6 marks) The sun is the initial source of energy for most ecosystems; Producers capture the sun s energy in photosynthesis; Light energy is converted to chemical energy; Energy is passed from producers to consumers in feeding; Energy transfer between trophic levels is inefficient/only about 10% of energy is passed between trophic levels; Energy is lost as heat/materials not eaten/waste as feces/not assimilated; Organisms cannot convert heat energy to other forms of energy; Food chains & biomass are limited by energy availability at top trophic levels