Good Science Victorian Curriculum Year 7

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BIOLOGICAL SCIENCES 3.2 FOOD CHAINS AND FOOD WEBS LEARNING INTENTION At the end of this lesson I will be able to describe interactions between organisms in terms of food chains and food webs. KEY TERMS ecosystem a community of living and non-living things food chain a path of energy through an ecosystem food web a system of interlocking food chains 1 All living organisms need energy to grow, repair damage and reproduce. Without energy, an organism cannot survive. Plants make their own food and energy, but other organisms – including humans – must feed on other organisms to gain energy. The feeding relationships between organisms, and the energy transfers in an ecosystem, can be shown in food chains and food webs. Food chains show the path of energy in an ecosystem Food chains are diagrams that show one possible path that energy can move through an ecosystem. Energy is transferred between organisms when they eat or are eaten. Food chains always begin with a producer – a plant or microorganism that can produce energy. This is because they provide the glucose for all other organisms to feed on. Every ecosystem includes producers. When you draw a food chain, you draw arrows between each organism to show the direction that energy moves. In a food chain for an Australian grassland ecosystem, a grasshopper gains energy from grass, so you would draw an arrow from the grass to the grasshopper. Figure 3.3 Each organism in a food chain provides energy for the next organism. LITERACY LINK SPEAKING Explain to another student the difference between a food chain and a food web. Ask them for ‘two stars and a wish’ – two things you did well in your explanation and one thing you could have done better. NUMERACY LINK CALCULATION Each level up in a food chain only receives 10% of the energy of the lower level. In Figure 3.3, the grass would have to store 10 joules of energy for the grasshopper to receive 1 joule of energy. How much energy would the grass need to store to eventually provide the wedge-tailed eagle with 100 joules of energy? Grass Producer The other organisms in the food chain – those that feed on organisms to gain energy – are consumers. They can be described in terms of the organisms they feed on. Table 3.1 Types of consumer and how they obtain their energy Consumer Obtains energy by … Examples Herbivore … feeding on producers Koala, grasshopper Omnivore Grasshopper Primary consumer Blue-tongue lizard Secondary consumer … feeding on producers and other consumers Eastern brown snake Tertiary consumer Sea star, most humans Carnivore … feeding on other consumers Kookaburra, brown snake Decomposer … breaking down dead matter Bacteria, fungi Wedge-tailed eagle Quaternary consumer Organisms can also be described by their position in a food chain. 38 GOOD SCIENCE VICTORIAN CURRICULUM 7
CHAPTER 3: ECOSYSTEMS Table 3.2 Organisms and their positions in a simple food chain Organism Position in food chain Investigation 3.2 Modelling a pond ecosystem Grass Grasshopper Blue-tongue lizard Eastern brown snake Producer Primary consumer Secondary consumer Tertiary consumer KEY SKILL Identifying limitations to the method and suggesting improvements Go to page 147 2 Wedge-tailed eagle Quaternary consumer What type of consumer is a herbivore? Food chains interact to form food webs Organisms are usually part of more than one food chain. This is because most organisms don’t feed on a single food source, or get eaten by a single consumer. Having more than one food source is important for the survival of a species in changing environments. If a food source runs out, a species is more likely to survive if it has another food supply. Food webs show all the feeding relationships in an ecosystem. These types of diagram show a much bigger picture of how each organism feeds and interacts. An organism may be a tertiary consumer in one food chain while being a secondary consumer in a different food chain within the ecosystem. When organisms feed, they only gain a small amount of energy from their food source. They use a large amount of their energy to move, grow, repair cells and reproduce. What is the difference between a food chain and a food web? Figure 3.4 This bushland food web shows how different food chains can connect. CHECKPOINT 3.2 1 Define the term producer. 2 What do the arrows in a food chain show? 3 Use the food web in Figure 3.4 to: a draw one food chain b identify the secondary consumer in your food chain. 4 Explain how an organism can be both a secondary and tertiary consumer. 5 If you removed one organism from a food web, what impact could this have on the populations that give and receive energy to that organism? 6 Can a secondary consumer ever be a herbivore (something that does not eat animals)? Explain your answer. CRITICAL AND CREATIVE THINKING Dingo Red-bellied black snake 7 Imagine you’re a tiny carbon atom stored in the leaf of a eucalypt tree. Describe a possible journey you could take as you cycle through an ecosystem. Kangaroo Sheep Possum Lizard Tree frog SUCCESS CRITERIA Moth Cricket I can explain what a food chain is and construct a simple food chain independently. Native grass Banksia I can explain what a food web is and construct a simple food web independently. 39
Page 1 and 2: GOOD SCIENCE VICTORIAN CURRICULUM Y
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Page 5 and 6: MAKE EVERY LESSON A GOOD LESSON
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CHAPTER 7: EARTH’S RESOURCES 23 S
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CHAPTER 7: EARTH’S RESOURCES FINA
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CHAPTER 8: FORCES 3 SEE-KNOW-WONDER
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CHAPTER 8: FORCES 3 What would happ
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CHAPTER 8: FORCES 2 We can predict
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CHAPTER 8: FORCES 2 3 Kinetic frict
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CHAPTER 8: FORCES Imagine a mattres
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CHAPTER 8: FORCES 3 On the surface
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CHAPTER 8: FORCES Figure 8.10 The f
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CHAPTER 8: FORCES 2 3 Pulleys redir
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CHAPTER 8: FORCES FINAL CHALLENGE 1
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INVESTIGATIONS KEY SKILLS Writing a
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INVESTIGATIONS Investigation 2.2 Su
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INVESTIGATIONS Investigation 2.6 Gr
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INVESTIGATIONS Investigation 3.2 Mo
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INVESTIGATIONS Investigation 4.1 Co
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INVESTIGATIONS Investigation 4.3 Ex
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INVESTIGATIONS Investigation 4.5 Ex
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INVESTIGATIONS METHOD 1 Copy the re
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INVESTIGATIONS RESULTS 30 min Level
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INVESTIGATIONS Investigation 5.6A E
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INVESTIGATIONS Investigation 5.6C D
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INVESTIGATIONS Investigation 5.7B S
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INVESTIGATIONS Investigation 6.2 Mo
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INVESTIGATIONS 30 min Level 2 TO MO
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INVESTIGATIONS Investigation 7.1 Cl
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INVESTIGATIONS Investigation 7.3A D
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INVESTIGATIONS Investigation 8.1 Pu
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INVESTIGATIONS Investigation 8.6 Me
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INVESTIGATIONS METHOD 1 Copy the re
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INVESTIGATIONS Investigation 8.9B I
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fractional distillation a method th
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INDEX Aboriginal and Torres Strait
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photosynthesis 30, 31, 36, 42, 109
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Good Science Victorian Curriculum Year 7

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