To help young children understand why animals become endangered, discuss the basic things we all need to survive, such as food, a safe home and enough friends and family to look after us. Then, explain that some animals don't have enough of these things because the places where they live are being destroyed. Show them pictures of endangered species, such as tigers and gorillas, and pictures of habitats such as a jungle, clean water and the different foods these animals need to live. Include pictures of things animals don't need, such as houses, airplanes and hamburgers, and get the children to get guess which are important for a specie's survival.
Explaining biodiversity -- the reliance all plants and creatures have on other parts of nature for survival -- is vital in understanding why it is important different species are protected. To make this understandable for small children, you need a simple prop such as a cheese sandwich. Explain that cheese is made from milk, milk comes from cows and cows eat grass. Draw pictures of these and lay the pictures out in order. Illustrate what happens when a species is lost, by taking away one of the pictures and breaking the link. Repeat with a similar simple food chain involving an endangered animal and its food chain.
Children can learn their alphabet and more about endangered species at the same time. Print out pictures of endangered animals whose names start with the different letters of the alphabet. Place them on the wall in alphabetical order with their names written underneath, and the first letter of each name written larger in a different colored ink so it stands out. This will involve using some of the lesser-known endangered species and so helps illustrate that all types of creatures are threatened.
It is important for children to understand they can help save endangered creatures. Explain there are people who are working hard to save these animals. Ask the children to pick one type of animal they want to help save and organize a fundraiser. Depending on how much raised, it may be possible to sponsor a particular animal through a conservation organization which will send pictures and a certificate to display on the classroom wall.