Year 4: Animals, including humans
Animals, including humans
Curriculum Requirement
- describe the simple functions of the basic parts of the digestive system in humans
- identify the different types of teeth in humans and their simple functions
- construct and interpret a variety of food chains, identifying producers, predators and prey.
Pupils should be introduced to the main body parts associated with the digestive system, for example, mouth, tongue, teeth, oesophagus, stomach and small and large intestine and explore questions that help them to understand their special functions.
Pupils might work scientifically by: comparing the teeth of carnivores and herbivores, and suggesting reasons for differences; finding out what damages teeth and how to look after them. They might draw and discuss their ideas about the digestive system and compare them with models or images.
National Curriculum in England: primary curriculum, Section: "Animals, including humans", p. 162.
The Human Digestive System
It's a long tube that runs all the way through your body, from your mouth to... well, the other end! Its job is to break down the food you eat into tiny nutrients that your body can use for energy, growth, and repair. Think of it as your body's own food-processing factory.
The Journey of Your Food
1. The Mouth
This is where the journey begins! Your teeth, tongue, and saliva all work together.
Its job is to:
Grind, chop, and mash the food (mechanical digestion) and mix it with saliva. Saliva has special chemicals (enzymes) that start breaking down the food (chemical digestion).
💡 Fun Facts
- You make about 1 to 2 litres of saliva (spit) every single day. That's enough to fill a big bottle of lemonade!
- Your tongue is a super-strong muscle that pushes the food around your mouth and helps you swallow.
- Chewing your food properly makes the rest of the journey much easier for your digestive system.
2. The Oesophagus
This is the food pipe that connects your mouth to your stomach.
Its job is to:
Squeeze the ball of food (called a 'bolus') down into your stomach, a bit like squeezing toothpaste from a tube.
💡 Fun Facts
- It doesn't matter if you're standing up or hanging upside down; this squeezing motion, called 'peristalsis', will always get your food to your stomach.
- It only takes about 7 seconds for food to travel down your oesophagus.
- A little flap called the 'epiglottis' cleverly covers your windpipe when you swallow to make sure food goes the right way.
3. The Stomach
This is a J-shaped, muscular bag. When it's empty, it's quite small, but it stretches to hold your food.
Its job is to:
Churn and mix the food with strong acid and more enzymes, turning it all into a soupy mush.
💡 Fun Facts
- The acid in your stomach is strong enough to dissolve some metals!
- Don't worry, your stomach is protected from its own acid by a thick layer of slimy mucus.
- Your stomach 'growls' when you're hungry because it's squeezing air and any leftover bits around.
4. The Small Intestine
This is a very, very long, coiled tube. It's not called 'small' because it's short, but because it's narrow.
Its job is to:
Absorb all the tiny, useful nutrients from the food mush into your blood. This is where your body gets its energy!
💡 Fun Facts
- If you stretched out an adult's small intestine, it would be about 6 or 7 metres long – that's longer than a giraffe is tall!
- The inside is covered in tiny, finger-like bumps called 'villi' which give it a huge surface area to soak up nutrients.
- Food can spend up to 4 hours on its journey through the small intestine.
5. The Large Intestine
This is the last main part of the tube. It's wider than the small intestine, but much shorter.
Its job is to:
Soak up all the water from the leftover food that your body couldn't digest. It then gets the waste (poo) ready to leave the body.
💡 Fun Facts
- This is where trillions of friendly bacteria live. They help by munching on undigested fibre and making certain vitamins for you.
- It takes about 36 hours for waste to get through the large intestine.
- The waste that leaves your body is mostly made of water, bacteria, and fibre your body didn't need.
All About Teeth
Humans are omnivores, which means we eat both plants and meat. Because of this, we have different types of teeth to do different jobs.
Your Set of Teeth
Incisors
These are your four front teeth, top and bottom. They are thin and sharp, like little chisels.
Their job is to:
Bite and chop food, like when you bite into an apple.
💡 Fun Facts
- The word 'incisor' comes from the Latin word 'incidere', which means 'to cut'.
- Rabbits have very large incisors that never stop growing, which is why they need to gnaw on things.
- You have eight incisors in total.
Canines
These are the pointy teeth next to your incisors.
Their job is to:
Rip and tear tougher foods, like meat.
💡 Fun Facts
- They get their name from dogs ('canine' means 'dog-like'), which have large, pointy canine teeth.
- You have four canine teeth.
- In vampire stories, these are the teeth that are shown as long fangs!
Molars and Premolars
These are all the big, flat teeth at the back of your mouth.
Their job is to:
Crush, grind, and mash food into a paste that is safe to swallow.
💡 Fun Facts
- 'Molar' comes from the Latin word 'molaris', which means 'millstone', a stone used for grinding grain.
- The 'premolars' are the ones just behind your canines, and the 'molars' are right at the back.
- Your wisdom teeth, which appear when you're a teenager or adult, are a third set of molars.
Teeth in the Animal Kingdom
Carnivore Teeth (e.g., Cat or Lion)
.jpg)
Carnivores only eat meat.
Their teeth are:
- Very long, sharp canines to grab and kill prey.
- Sharp, scissor-like molars (called carnassials) to slice meat off bones.
- They have very small or no incisors.
💡 Fun Facts
- A cat's jaw can only move up and down, which is perfect for slicing.
- They don't have flat molars because they don't need to grind food; they swallow their meat in chunks.
- A lion's canines can be over 7 cm long!
Herbivore Teeth (e.g., Cow or Sheep)
.jpg)
Herbivores only eat plants.
Their teeth are:
- Wide, flat molars at the back to grind tough grass and leaves.
- Sharp incisors at the front to chop and clip plants.
- They often have no canine teeth at all, leaving a gap.
💡 Fun Facts
- A cow's jaw can move side-to-side, which helps with grinding.
- Cows spend a large part of their day just chewing and re-chewing their food (called 'chewing the cud').
- A sheep's teeth are constantly worn down by chewing tough grass, but they also keep growing to replace what's lost.
Food Chains
A food chain shows how energy moves in an ecosystem. It shows what an animal eats, and what eats that animal. All energy in a food chain originally comes from the Sun!
The Links in the Chain
1. Producer
This is the start of every food chain.
Its job is to:
Produce (make) its own food using energy from the Sun. All plants are producers.
💡 Fun Facts
- The process plants use to make food is called 'photosynthesis'.
- Without producers, there would be no life on Earth!
- Seaweed and algae are the main producers in ocean food chains.
- Humans grow a lot of food in fields. Some of this is for us to eat and some is for us to feed animals we eat!
2. Primary Consumer (Prey)
.jpg)
.jpeg)
This is the first animal in the chain. It is an animal that eats producers.
Its job is to:
Eat plants to get energy. These animals are also called herbivores.
💡 Fun Facts
- Examples include rabbits, caterpillars, cows, and snails. Also some kinds of turtle and fish.
- These animals are often eaten by other animals, which makes them prey.
- They have to eat a lot of plants to get enough energy.
3. Secondary Consumer (Predator)
.jpg)
This animal eats the primary consumer.
Its job is to:
Eat other animals to get energy. These animals are predators.
| facts =
- Examples include a fox (which eats a rabbit) or a blue tit (which eats a caterpillar).
- These animals can be carnivores (meat-eaters) or omnivores (eat plants and meat).
- A food chain can have more links, like a 'tertiary consumer' that eats the secondary consumer (e.g., an owl eats a stoat, which ate a blue tit).
An Example Food Chain
Here is a simple food chain you might see in a British garden or field:
Lettuce ➡️ Snail ➡️ Thrush ➡️ Sparrowhawk (Producer) ➡️ (Primary Consumer / Prey) ➡️ (Secondary Consumer / Predator & Prey) ➡️ (Tertiary Consumer / Predator)
Activities & Reflections
Activities
Food Chain Links
Write the names of different producers (grass, leaf, algae), consumers (rabbit, snail, fox, owl, small fish, shark), and the Sun on separate pieces of card. In groups, ask pupils to arrange them into different food chains, using arrows drawn on paper to show the flow of energy.
Cracker Digestion
Give each pupil a plain, unsalted cracker. Ask them to chew it for a full 30 seconds without swallowing. They should notice it starts to taste sweet. This is the saliva (enzyme) in their mouth turning the cracker's starch into sugar – chemical digestion in action!
Tooth Detectives
Hand out small, safe mirrors. Ask pupils to look at their own teeth and try to identify their incisors, canines, and molars. They can draw a map of their own mouth and label the different types of teeth they find.
Reflections
Self-Reflection (Exit Ticket)
On a piece of paper, ask pupils to draw a simple food chain with three links. They must label the producer, prey, and predator.
Paired Reflection (Think-Pair-Share)
Ask pupils to turn to a partner and explain: Why does a cow have large, flat molars, but a cat has pointy, sharp molars?
Whole Class Share-Out
As a class, discuss: What is the most important part of the digestive system? (There is no right answer! This is to encourage them to justify their ideas, e.g., "The mouth, because it starts everything," or "The small intestine, because it soaks up the food.")
Back to: Science