Living Things Around Us
Primary 5 · Science and Elementary Technology
Living Things Around Us
Lesson 2 of 3
14 min
Let's begin
On the way to school Keza passes a cow chewing grass by the road, a lizard doing press-ups on a warm stone, a butterfly over the flowers, and a long line of ants carrying crumbs to their hole.
Four animals in five minutes. A scientist would not simply call them “animals”. A scientist would sort them into groups — because once you know which group an animal belongs to, you already know a lot about it before anybody tells you. Today you learn how that sorting works.
Reach behind you and run your fingers down the middle of your back, from your neck to your waist. You can feel a line of hard bumps under the skin. That is your backbone — a chain of small bones, also called the spine. It holds your body up and protects the nerves running inside it.
A cow has one. A tilapia has one too (you have picked the bones out of a fish at dinner). A lizard has one.
A butterfly does not. An ant does not. A snail does not either — and be careful here, because a snail has a hard shell. But that shell is on the outside. Outside armour is never a backbone.
So the very first question a scientist asks about any animal is simply: does it have a backbone, or not?
Which group do you think is bigger? Most people guess vertebrates, because cows and goats and people are big and easy to notice. In fact the invertebrates win by an enormous margin. Most animals on earth are insects, worms, snails and their relatives.
Body covered in hair or fur. Breathe air with lungs. The mother gives birth to live young instead of laying eggs, and she feeds them on her own milk. Their bodies stay warm.
Cow, goat, dog, mountain gorilla, bat — and you. Yes, you are a mammal.
Feathers. Two wings, two legs, and a beak with no teeth in it. They lay eggs with hard shells. Their bodies stay warm.
Chicken, crow, and the grey crowned crane — umusambi — that you can spot standing in Rwanda's marshes, such as Rugezi.
Live in water all their lives. Body covered in scales, with fins and a tail for swimming. Breathe with gills, which take oxygen out of the water. They lay eggs.
Tilapia, and the small isambaza that the fishermen of Lake Kivu bring in at dawn.
Dry, scaly skin. Breathe air with lungs. Most lay eggs. Their bodies go cold unless they warm themselves up — which is exactly why that lizard was lying flat on a hot stone in the morning sun.
Lizard, chameleon, snake, tortoise, and the crocodiles of Akagera.
The word means “two lives”, and that is precisely right. Moist, smooth skin with no scales. The young hatch in water and breathe with gills; the adults live on land and breathe with lungs.
Frogs and toads — you hear them start up after the rains.
A bat comes flitting out at dusk over Kigali. Plenty of people call it a bird. Let us do it properly, one step at a time.
A bat is a mammal that happens to fly. Flying was never the test. Feathers, fur, milk, eggs, scales, gills — those are the tests. Take the features one at a time and nobody can trick you.
Mugisha finds a spider in a web in the corner of the classroom and calls it an insect. Let us check.
8 legs and 2 body parts → it is not an insect. A spider belongs to a group of its own called the arachnids. It is still an invertebrate — just not an insect. Mugisha was half right, and now you know which half.
Tip
Two quick tests do most of the work for you.
And remember the trap: a snail's shell is on the outside. Outside armour is never a backbone.
Do each one, then tap Show answer to check.
A crocodile in Akagera spends much of its day in the water. Is it a fish? How do you know?
Answer: No — it is a reptile. It has dry scaly skin, it breathes air with lungs, and it lays its eggs on land. A fish would breathe with gills and never leave the water.
An animal has feathers, a beak, two legs and lays eggs with hard shells. Which group?
Answer: A bird. Feathers alone are enough — no other group has them.
A grasshopper and a spider are both invertebrates. Give one difference that puts them in different groups.
Answer: The grasshopper has 6 legs and 3 body parts, so it is an insect. The spider has 8 legs and 2 body parts, so it is an arachnid. (Its wings and antennae are another clue.)
Sort these into vertebrates and invertebrates: goat, ant, tilapia, earthworm, chameleon, snail.
Answer: Vertebrates — goat, tilapia, chameleon. Invertebrates — ant, earthworm, snail.
A young animal lives in water and breathes with gills. The grown-up sits on the bank and breathes with lungs. Which group is it, and why does the name suit it?
Answer: An amphibian, such as a frog. The name means “two lives” — one life in the water when young, one on land as an adult.
What you learned today
Quick check
A snail has a hard shell. Is it a vertebrate?
