Content standard:
Support, movement and growth in animals
Learning standard:
Explain with examples the types of support in animals
Lesson activity:
Hi students. Welcome back! I hope everyone is in good condition. Ok, let's start. Oh ya, make sure you have your Science text book with you too.
In the past few weeks, we have learnt about cell division. In today's lesson, we are going to learn new chapter that is Movement.
I will start the lesson with two simple questions:
- Why do we move?
- How do we move?
I believe you know the answer. We move so that we can get food, we can go from place to place, we can play and even find new friends. Now let us focus on animals. It is very important for animals to move. It is not just to find food, escape from their predators but it also help them to find mate during mating season.
Different animals have different ways to move. Most of the animals have four legs so they can walk and run. There are some animals do not have legs for examples snakes and worm but they still can move. How about birds? They have two legs to walk and two wings to fly. Some can move very fast and some move very slow for examples sloth. Have you ever seen how sloth move? Let us watch this interesting facts about sloth.
Students, have you watch Zootopia movie? There are sloth cartoon character in it. I found it very funny. If you haven't watch the movie yet, it is time for you to watch with your family. Here is a short clip of this movie.
Animals can move because they have support system. Skeletal is a support system in all animals. There are three types of support in animals which are hydrostatic skeleton, exoskeletons and endoskeletons.
Hydrostatic skeletons is a volume of fluid enclosed in a body cavity surrounded by muscle. It is primarily found in soft bodied invertebrates, both terrestrial (on land) and aquatic (in water). The fluid is held under pressured in compartments surrounded by muscles. Since the liquid cannot escape, it forms a skeleton which cannot be compressed. Earthworm is an example of animals that have hydrostatic skeleton. Can you name others?
Diagram 1: Earthworm
Exoskeletons is a hardened outer surface to which muscles attach. Since it is an outer surface of the body, it protects all the soft tissues of the animals such as crab. Do you love to eat crab? (I'm sorry if you are allergic to seafood). To eat crab, we need to remove the outer skin. Well, it is not easy to remove the skin because it is hard and covered the whole body tissues. So the skin is the exoskeleton of the crab. Let us watch the video below. The video shows a woman cracking the crab to eat the crab meat. It is not easy because the exoskeleton is hard but the crab meat taste soooooo good. (hihihi)
If you cannot remember the meaning of exoskeleton, look at the photo below. We have Iron man and Crab man. They have one thing in common. Both are protected and covered by outer surface and of course it is hard and solid surface.
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| Iron man |
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| Crab man |
Even though exoskeleton is effective to protect the soft body tissues of the animals, they will face problems when they need to grow bigger and increase in mass. So, they need to have their own way to grow. We will discuss this in our next lesson.
Endoskeletons is an internal scaffolding to which muscles attach and against which they can pull. It provides a rigid framework that supports the body and protects the internal organs. Muscles can only contract and relax. So they need something rigid to pull against. Without endoskeleton, muscle would just be a formless mass. Just imagine ourself without bones. Most probably we will not look like as we are right now.
Diagram 3: Endoskeleton in mammals
You already know there are three types of support system in animals. So now I want you to watch this video. While watching the video, I want you to identify the animals support system.
That's all for our lesson today. Thank you for participating and please leave comments below.
Exercise:
1. Form a group of 5 people.
2. Create a powerpoint presentation (.ppt) about:
- types of support system
- functions of each support system
- examples of animals for each type of support system
3. Group leader post the presentation in WhatsApp group today (29thApril) before 4pm.
