Animals — Class 5 Science (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 5 Science. How animals are grouped, what they eat, and how energy passes between them.
1. The first big division
Run your fingers down the middle of your back and you can feel a row of small bones. That is the backbone, or vertebral column, and it splits the animal kingdom in two.
Vertebrates have a backbone. Invertebrates do not.
Vertebrates are the animals we notice — fish, frogs, snakes, birds, cats. Yet invertebrates are far more numerous: insects, spiders, worms, snails, crabs and jellyfish all manage without a backbone.
2. The five classes of vertebrates
| Class | Body covering | Blood | Young | Breathing | Examples |
|---|---|---|---|---|---|
| Mammals | Hair or fur | Warm-blooded | Live birth, fed on milk | Lungs | Human, dog, whale, bat |
| Birds | Feathers | Warm-blooded | Lay eggs | Lungs | Crow, eagle, penguin |
| Reptiles | Dry scales | Cold-blooded | Lay eggs on land | Lungs | Snake, lizard, turtle, crocodile |
| Amphibians | Moist skin | Cold-blooded | Lay eggs in water | Gills, then lungs | Frog, toad, salamander |
| Fish | Wet scales | Cold-blooded | Lay eggs in water | Gills | Shark, rohu, sardine |
Warm-blooded animals keep their body temperature steady whatever the weather. Cold-blooded animals take the temperature of their surroundings, which is why a lizard basks in the sun on a cold morning.
3. Two animals that break the pattern
A whale is not a fish. It lives in water and is shaped like a fish, but it breathes air through lungs using a blowhole, gives birth to live young, and feeds them milk. It is a mammal.
A bat is not a bird. It flies, but it has fur rather than feathers and feeds its young on milk. It too is a mammal.
The lesson is that where an animal lives, and how it moves, are not what decide its class. Body covering, blood and how the young are raised are.
4. What animals eat
| Group | Diet | Examples |
|---|---|---|
| Herbivores | Plants only | Cow, goat, deer, elephant, rabbit |
| Carnivores | Other animals | Tiger, lion, eagle, snake |
| Omnivores | Both plants and animals | Crow, bear, human |
5. Food chains
A food chain shows who eats whom, and how energy travels.
Grass gives energy to the deer; the deer gives energy to the tiger.
Every food chain begins with a producer — a green plant, which makes its own food by photosynthesis. Next comes the primary consumer, a herbivore. Then the secondary consumer, a carnivore that eats the herbivore.
Which way does the arrow point? This is the question most often got wrong. The arrow shows the direction in which energy flows, so it runs from the eaten to the eater — from the grass to the deer, not from the deer to the grass.
Decomposers — bacteria and fungi — break down dead plants and animals and return the nutrients to the soil, where plants can use them again.
6. Adaptation
An adaptation is a feature that suits an animal to where it lives.
- A camel stores fat in its hump, has long eyelashes against blowing sand, and can go days without water.
- A polar bear has thick fur and a layer of fat, and white colouring that hides it against snow.
- A fish has a streamlined body, fins for steering and gills for taking oxygen from water.
- A duck has webbed feet for paddling and oily feathers that shed water.
7. Worked examples
Example 1. What separates vertebrates from invertebrates?
Solution: Vertebrates have a backbone; invertebrates do not.
Example 2. Why is a whale a mammal and not a fish?
Solution: It breathes air through lungs, gives birth to live young and feeds them milk.
Example 3. Name the class of animals with moist skin that lays eggs in water.
Solution: Amphibians.
Example 4. In the food chain grass, deer, tiger, which is the producer?
Solution: The grass, because only plants make their own food.
Example 5. Which way does the arrow point in a food chain, and why?
Solution: From the eaten to the eater, because it shows the direction in which energy flows.
Example 6. Classify a crow by its food habit.
Solution: An omnivore, since it eats both plants and animals.
Example 7. Give two adaptations of a camel.
Solution: Fat stored in its hump for long journeys without food, and long eyelashes that keep out blowing sand.
8. Practice
- Name the five classes of vertebrates with one example each.
- What is the difference between warm-blooded and cold-blooded animals?
- Why does a lizard bask in the sun on a cold morning?
- Why is a bat a mammal though it flies?
- Which class of animals has feathers?
- Write a food chain with three living things.
- What is a producer, and why must every food chain start with one?
- What are decomposers, and what do they do?
- Give two adaptations of a fish.
9. Answers
- Mammals (dog), birds (crow), reptiles (snake), amphibians (frog), fish (shark).
- Warm-blooded animals keep a steady body temperature; cold-blooded animals take the temperature of their surroundings.
- Because it is cold-blooded, so it warms itself using the Sun rather than from within.
- Because it has fur rather than feathers and feeds its young on milk.
- Birds.
- Grass gives energy to the deer, and the deer to the tiger.
- A green plant that makes its own food. Every chain must start with one because all animals depend on that food.
- Bacteria and fungi that break down dead matter and return nutrients to the soil.
- A streamlined body for moving through water, and gills for taking oxygen from it.
10. Summary
- Vertebrates have a backbone; invertebrates do not, and invertebrates are far more numerous.
- The five vertebrate classes are mammals, birds, reptiles, amphibians and fish.
- Warm-blooded animals hold a steady temperature; cold-blooded ones follow their surroundings.
- A whale and a bat are mammals, judged by body covering, blood and how the young are raised.
- Herbivores eat plants, carnivores eat animals, omnivores eat both.
- A food chain runs producer, primary consumer, secondary consumer.
- The arrow points from the eaten to the eater, showing the flow of energy.
- Decomposers return nutrients from dead matter to the soil.
- Adaptations such as a camel's hump or a fish's gills suit an animal to where it lives.
