Food chains and Food webs Objective: To understand where energy comes from and how it flows from organism to organism.

What would happen if? The sun disappeared

What would happen if? There were no insects?

What would happen if? There were no rats or mice?

What would happen if? We could grow no plants

All living things need energy to survive The flow of energy from organism to organism is called a FOOD CHAIN

A food chain is: A simple relationship that shows energy flow from one organism to another It is a flow chart All food chains start with the sun Plants get their energy from the sun to grow, Animals get their energy by consuming plants These relationships are actually quite complex, and they are shown in FOOD WEBS

Food chains and food webs http://www.youtube.com/watch?v=sbWyrcY5i3s

Producers consumers and decomposers Different organisms have different roles in the food chain Producers Consumers Decomposers FOOD WEBS start with the sun Sun gives out light energy Plants uses energy to make their food

Producers Plants are called producers because they can make their own food All organisms are dependent on the oxygen that plants produce

Producers (continued) Plants trap sunlight in their leaves and use chlorophyll to help them use sunlight to make carbohydrates. This is called photosynthesis:

Consumers Animals are called consumers because they are unable to make their own food and must eat plants or other animals There are 3 types of consumers: Herbivores Carnivores Omnivores

Types of consumers Herbivores: eat only plants

Types of consumers Carnivores: eat only meat

Types of consumers Omnivores eat both plants and animals

Decomposers: Decomposers get the energy they need as they break down dead matter If plants or animals die without being eaten, the body is broken down by bacteria and fungi http://www.youtube.com/watch?v=6Z2ZQDl2iJ4&feature=related

Food Chain

Energy flow through a food web Not all energy is passed on in the web Some is lost as heat, or used by the organism that consumes for growth and movement Energy is also lost in the cellular reactions each organism carries out to survive As you move up the web, there is less energy to be passed on This means fewer organisms at each level

Biomass pyramid If one organism is removed, another must replace it or it will upset the balance.

Your task Explain why all food webs start with the sun In you workbook, answer questions 1 – 4 on page 237 of your textbook