2Boardworks KS3 Science 2008 Feeding Relationships Food chains and webs
3Boardworks KS3 Science 2008 Feeding Relationships Feeding typesBoardworks KS3 Science 2008Feeding RelationshipsDifferent types of organism can be grouped in several ways. One grouping system is based on how organisms obtain their food.Some organisms produce their own food. They are called producers.Plants produce their own food using light energy from the Sun. Some types of bacteria can also make their own food by using light or chemical reactions.Other organisms cannot make their own food. They are called consumers.
5Boardworks KS3 Science 2008 Feeding Relationships ConsumersBoardworks KS3 Science 2008Feeding RelationshipsConsumers can be grouped into different types:HerbivoresThese consumers eat producers.CarnivoresThese consumers eat other consumers.OmnivoresThese consumers eat other consumers and producers. Omnivores eat animals and plants. Most humans are omnivores.
7Predator-prey relationships Boardworks KS3 Science 2008Feeding RelationshipsAnimals that are high up in food chains, such as the fox, tend to be hunters that are skilled at locating and killing their food. These hunters are called predators.The animals on which the predator feeds are called their prey.Prey animals tend to be well adapted to avoid the predator.Photo credit: Jupiterimages CorporationCommon prey adaptations include camouflage or the ability to produce poisonous toxins.
8Prey population changes Boardworks KS3 Science 2008Feeding RelationshipsThe relationship between predator and prey population numbers in a food web is very close and follows a cyclical pattern. This means that it rises and falls in a fairly regular cycle. Why is this?The rabbit population changes due to both the vegetation growing season and changes in the fox population.Individual rabbits must compete for food and mates, and must also avoid being killed by their predators, the foxes.
9Predator population changes Boardworks KS3 Science 2008Feeding RelationshipsThe fox population also follows a cyclical pattern very similar to the rabbit population. Why is this?The fox is very dependent on rabbits for food, so as the rabbit population changes so does the fox population.This is why the fox population rises and falls slightly after the rise and fall of the rabbit population.How do cyclical rises and falls in population numbers affect the organisms in a larger food web?
11Food chains – who eats what? Boardworks KS3 Science 2008Feeding RelationshipsCan you see a food chain in this habitat?Feeding Relationship Worksheet1 accompanies this section.
12Boardworks KS3 Science 2008 Feeding Relationships Food chainsBoardworks KS3 Science 2008Feeding RelationshipsA food chain is a sequence that shows how each individual feeds on the organism below it in the chain. Each arrow means ‘eaten by’.leafcaterpillarbirdfoxWhat does this food chain show?A leaf is eaten by a caterpillar, which is then eaten by a bird, which is then eaten by a fox.Energy is transferred from one organism to another in the direction of the arrow.
13Food chains – draw your own Boardworks KS3 Science 2008Feeding RelationshipsDraw your own food chains based on the following guidelines:A food chain from a forest habitat.A food chain from an ocean habitat.A food chain with four organisms in it.A food chain that ends with you!Use arrows ( ) to show the transfer of energy between the organisms that you choose.
15Producer, herbivore or carnivore? Boardworks KS3 Science 2008Feeding RelationshipsFood chains always start with a producer.If the producer is a plant, only a small part of it might be involved in the food chain, such as its seeds, fruits, leaves or even dead leaves.From a food chain, we can tell if an organism is a producer, a herbivore or a carnivore.leafsnailbirdowlWhat are the feeding types of the animals in this food chain?
16Boardworks KS3 Science 2008 Feeding Relationships Name that feeding typeBoardworks KS3 Science 2008Feeding Relationships
17Boardworks KS3 Science 2008 Feeding Relationships Ranking consumersBoardworks KS3 Science 2008Feeding RelationshipsConsumers eat plants or animals, or both. A food chain can be used to rank different types of consumers.seaweedlimpetcrabhumanproducerprimaryconsumersecondaryconsumertertiaryconsumerProducers – make their own food.Primary consumers – eat producers.Secondary consumers – eat primary consumers.Tertiary consumers – eat secondary consumers.
18Primary, secondary or tertiary? Boardworks KS3 Science 2008Feeding Relationships
19Boardworks KS3 Science 2008 Feeding Relationships What is a food web?Boardworks KS3 Science 2008Feeding RelationshipsWhy is it a good idea for an organism to have different sources of food? Animals usually eat many different things and are involved in lots of different food chains:plantsaphidladybirdblue titowlplantsmothblue titowlplantsvolestoatplantsvoleowlTeacher notesWhy is it a good idea for an organism to have different sources of food? Reliance on only one source of food would make an organism vulnerable to variations in the availability of this food. Also, many food sources are not available all year round, so alternative sources of nutrition are needed.These food chains can be put together in a food web,which shows how the food chains are connected.What would the food web for these food chains look like?
21Boardworks KS3 Science 2008 Feeding Relationships Using a food webBoardworks KS3 Science 2008Feeding Relationships1. Name the producer in this food web.2. Name two herbivores in this food web.3. Name two species that are top carnivores.4. How many secondary consumers are there?Teacher notes1. Daisy (flower/plant)2. Vole and aphid (moth is also an acceptable answer – adult moths usually don’t eat, but their larvae do)3. Stoat and barn owl4. Four (ladybird, spider, stoat, blue tit)5. Daisy, moth, blue tit, barn owl Daisy, moth, spider, goldfinch, barn owl.5. Which food chains include the moth?
23Changes in the food chain Boardworks KS3 Science 2008Feeding RelationshipsNearly every species of animal is dependent on a number of other species for survival – this is called interdependence.Currently human activity is damaging the natural habitats of many animals.This will not only affect the animals in the area, but it could have far-reaching effects on the rest of the species in the food web.Photo credit: Jupiterimages CorporationTeacher notesSee ‘Ecosystems’ presentation for more about how changes in the environment can have an impact on animals.If the population of a species declines dramatically how might this affect the other species that depend upon it?
24Boardworks KS3 Science 2008 Feeding Relationships Changes in a food webBoardworks KS3 Science 2008Feeding RelationshipsTeacher notesThis activity is designed to show students that a decline in one species can have a significant impact on others. These values and outcomes are completely speculative.
27Boardworks KS3 Science 2008 Feeding Relationships Food for energyBoardworks KS3 Science 2008Feeding RelationshipsWhy do organisms need to feed?Most animals get their energy from food. If the producers at the bottom of the food chain are small organisms, then the consumers at the top of chain need to eat many of them to gain enough energy.Much of the energy that prey generate is lost on a daily basis through heat, growth and waste.Very little energy is actually transferred to the predator.
28Food chains and pyramids Boardworks KS3 Science 2008Feeding RelationshipsWhat can a pyramid of numbers show about energy transfer?Teacher notesThis illustration contains several discussion points relating to food chains and pyramids, including:Oak tree containing caterpillars, shrews and an owl: This represents a food chain with an oak tree as the primary producer, caterpillars as primary consumers, shrews as secondary consumers and an owl as the tertiary consumer. The balancing act illustrates the dependence of organisms on a food supply. Although the amount of biomass decreases at each stage of the food chain, representing this chain as a pyramid of numbers would result in a pyramid with a base narrower than its middle, because this system is supported by one oak tree.Ring master balancing on cows: This represents a food chain with cereal crops as the primary producer, cows as the primary consumer and humans as the secondary consumer. Students could be asked to consider if it would be more energy efficient for the human to eat the cereal crops directly.Setting sun: The Sun provides energy for photosynthesis, the process used by plants to make food.Antelope and lions: The antelope are grazing on grass. They are being closely watched by a hungry-looking pride of lions. This represents a food chain with grass as the primary producer, antelope as the primary consumer and lions as the secondary consumer.
29What are pyramids of numbers? Boardworks KS3 Science 2008Feeding RelationshipsPyramids of numbers are a numerical way of representing food chains.They record the number of organisms at each level in the food chain.What are the problems of representing food chains in pyramids of numbers?Pyramids of numbers only give an accurate impression of the flow of energy in a food chain if the organisms are of similar size. Measuring the biomass (living material that makes up all organisms) at each level in the food chain can give a more accurate picture.
30Boardworks KS3 Science 2008 Feeding Relationships Numbers or biomass?Boardworks KS3 Science 2008Feeding RelationshipsTeacher notesThis activity provides illustrated examples of pyramids of biomass and pyramids of numbers. It could be used to allow students to draw comparisons between these two methods of representing food chains.
31Understanding pyramids of numbers Boardworks KS3 Science 2008Feeding RelationshipsIn a pyramid of numbers, the length of each bar represents the number of organisms at each level in the food chain.As a single tree can support many organisms, this food chain produces an unbalanced pyramid.
32Understanding pyramids of biomass Boardworks KS3 Science 2008Feeding RelationshipsIn a pyramid of biomass, the length of each bar represents the biomass at each level of the food chain.Feeding Relationships Worksheet 2 accompanies this slide.At each level, the amount of biomass and energy available is reduced, giving a pyramid shape.
33Boardworks KS3 Science 2008 Feeding Relationships Death benefits?Boardworks KS3 Science 2008Feeding RelationshipsWhen animals and plants die, they are decomposed by microbes.In this way, the nutrients that were stored in animals and plants are eventually returned to the soil.The nutrients fertilize the soil, helping producers, such as plants, to grow better.Photo credit: Jupiterimages CorporationAs the number of producers increases, how will this affect the populations of organisms higher up in the food chain?
34Food chains and pyramids Boardworks KS3 Science 2008Feeding RelationshipsTeacher notesThis completing sentences activity provides the opportunity for some informal assessment of students’ understanding of food chains and pyramids.
36Boardworks KS3 Science 2008 Feeding Relationships GlossaryBoardworks KS3 Science 2008Feeding Relationshipsbiomass – The living material that makes up all organisms.carnivore – An organism that only eats other animals.consumer – An organism that feeds on plants or animals.food chain – A sequence that shows feeding relationships and the transfer of energy between organisms.food web – Food chains that are linked to show the complex feeding relationships in a habitat.herbivore – An organism that only eats plants.omnivore – An organism that eats both plants and animals.producer – An organism that makes its own food.population – The number of organisms of a species living in an area.pyramid of biomass – A diagram, in which the length of each bar represents the biomass at each level of the food chain.pyramid of numbers – A diagram, in which the length of each bar represents the number of organisms present at each level of the food chain.