Australian curriculum focus
Science / Year 7 / Science Understanding / Biological sciences / ACSSU112
Content Description: Interactions between organisms can be described in terms of food chains and food webs; human activity can affect these interactions
Elaboration:
· Using food chains to show feeding relationships in a habitat
· Constructing and interpreting food webs to show relationships between organisms in an environment
everyday exposure
Students should have prior knowledge about food chains and have a general idea of animal food chains (e.g. small fish eat the plankton, bigger fish eat the smaller fish & sharks eat the bigger fish etc).
Students may also have been exposed to:
Students may also have been exposed to:
- Animal farming (e.g. breeding cows for food, chickens for eggs)
- Personal pets (feeding snakes live mice)
- Own vegetable gardens etc
- Fishing
- Affects of humans (news reports of oil spillages etc)
Misconception Explored
Misconception Two: Food chains have a start and an end
Students often think of feeding relationships as linear. They may misunderstand the food chain model in several ways:
1. They think organisms high up the chain eat everything that is lower on the chain;
2. They see only linear food chains as unconnected to a food web. (Munson,1994)
Misconception explained: Food chains are used to represent the interactions between organisms. 25% of school aged children believe that animals exist on the sole basis for human benefits (Leeds national curriculum science support project, 1992). The food pyramid depicts how children may see the flow of food chains as direct from bottom (producers) to the top (predator). Students need to be able to see the food chains a cycling process where the Predator then decompose and are included in the transferring of energy (food) to the producers to start the chain again (Leeds national curriculum science support project, 1992). There needs to also be a direct link of food chains and food webs and how they can be altered due to external factors (what happens if secondary consumers population increased? or how does human activity affect the food chain?).
Students often think of feeding relationships as linear. They may misunderstand the food chain model in several ways:
1. They think organisms high up the chain eat everything that is lower on the chain;
2. They see only linear food chains as unconnected to a food web. (Munson,1994)
Misconception explained: Food chains are used to represent the interactions between organisms. 25% of school aged children believe that animals exist on the sole basis for human benefits (Leeds national curriculum science support project, 1992). The food pyramid depicts how children may see the flow of food chains as direct from bottom (producers) to the top (predator). Students need to be able to see the food chains a cycling process where the Predator then decompose and are included in the transferring of energy (food) to the producers to start the chain again (Leeds national curriculum science support project, 1992). There needs to also be a direct link of food chains and food webs and how they can be altered due to external factors (what happens if secondary consumers population increased? or how does human activity affect the food chain?).
Trophic levels of food chains
The sun is the source of all the energy in food chains. Green plants, usually the first level of any food chain, absorb some of the Sun’s light energy to make their own food by photosynthesis. Green plants (autotrophs) are therefore known as ‘Producers’ in a food chain (eSchooltoday, 2015).
The second level of the food chains is called the Primary Consumer. These consume the green plants. Animals in this group are usually herbivores (eSchooltoday, 2015). Examples include insects, sheep, caterpillars and even cows.
The third in the chain are Secondary Consumers. These usually eat up the primary consumers and other animal matter. They are commonly called carnivores and examples include lions, snakes and cats (eSchooltoday, 2015).
The fourth level is called Tertiary Consumers. These are animals that eat secondary consumers.
Quaternary Consumers eat tertiary consumers.
At the top of the levels are Predators. They are animals that have little or no natural enemies. They are the ‘bosses’ of their ecosystems. Predators feed on preys. A prey is an animal that predators hunt to kill and feed on. Predators include owls, snakes, wild cats, crocodiles and sharks. Humans can also be called predators (eSchooltoday, 2015).
When any organism dies, detrivores (like vultures, worms and crabs) eat them up. The rest are broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues. Decomposers start the cycle again (eSchooltoday, 2015).
The second level of the food chains is called the Primary Consumer. These consume the green plants. Animals in this group are usually herbivores (eSchooltoday, 2015). Examples include insects, sheep, caterpillars and even cows.
The third in the chain are Secondary Consumers. These usually eat up the primary consumers and other animal matter. They are commonly called carnivores and examples include lions, snakes and cats (eSchooltoday, 2015).
The fourth level is called Tertiary Consumers. These are animals that eat secondary consumers.
Quaternary Consumers eat tertiary consumers.
At the top of the levels are Predators. They are animals that have little or no natural enemies. They are the ‘bosses’ of their ecosystems. Predators feed on preys. A prey is an animal that predators hunt to kill and feed on. Predators include owls, snakes, wild cats, crocodiles and sharks. Humans can also be called predators (eSchooltoday, 2015).
When any organism dies, detrivores (like vultures, worms and crabs) eat them up. The rest are broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues. Decomposers start the cycle again (eSchooltoday, 2015).
Where to start- unit/lesson plans
A food web describes the flow of energy and nutrients through an ecosystem, while a food chain is a linear path through a food web (Boundless biology, 2015).
The lesson plan below is a great starting tool for teachers to help students to discover the differences between food webs and chains. The lesson plan outlines clear learning objectives, scientific terms, and detailed information that students can use to explore their ecosystems. Boundless is an free educational learning website that can be used to connect with and assign unit readings to the class. This website includes PowerPoints and quizzes to aide the students learning. Progress reports can be forwarded on to the teacher as well. |
This unit is a more in depth look into Ecosystems and provides a wide range of resources and information. The unit includes videos, interactive games and simulations, visuals, online textbooks, detailed glossary and extensive amount of valuable information at a click of a button. This unit is a complete package that not only includes food chains/webs but also looks into other factors of the environment (soil, water etc) that effect ecosystems. Cross curriculum opportunities can be found within this unit to link Year seven geography: Water in the world and Place and liveability.
Hands On activities
Online simulator that is located within the unit plan above. There are lesson guides and questioning that allows students to explore and engage in the activities to develop a greater understanding of food webs and the impact that changes have to an ecosystem (Appleton, 2003).
This is a great idea that can be adapted for students to work together by placing their own food chains (variety of colours) and seeing where they lay within the food webs. The cards should include organisms from all trophic levels (producers, consumers, predators etc). This link will take you to a basic idea that can then be expanded to incorporate a year 7 understanding of ecosystems. Instead of using rubber bands cotton wool could be used and a whole class food web could be produced.
A fun hands on way to explore various food chains/webs and how the animals all connect and interact with each other. To extend this activity why not have the students write observational notes about their engagement and identify the organisms involved and explain their interaction.