What is Classification?
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Classification means grouping living things into categories based on how they are
similar.
Scientists do this to make it easier to identify and study different kinds of organisms
(living things).
It helps us understand the diversity (many different types) of life on Earth.
� Animals Can Be Divided Into Two Main Groups:
1. Vertebrates
2. Invertebrates
� 1. Vertebrates
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Vertebrates are animals that have a backbone (a row of bones in their back).
Their bodies are firm because they have muscles (body parts that help us move) that are
connected to their skeleton (a hard inner body made of bones).
Examples: Humans, dogs, fish, birds, etc.
� Hard word explained:
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Skeleton – The hard inner framework of bones that supports the body.
� 2. Invertebrates
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Invertebrates are animals that do not have a backbone.
Their bodies are usually soft, but they may have:
o A flexible covering (a soft outer layer that can bend),
o OR a hard covering on the outside called an exoskeleton (a protective shell or
hard skin outside the body).
Examples: Jellyfish, crabs, worms, insects.
Classification of Vertebrates (Animals with a Backbone)
Animals in the Vertebrates group (those that have a backbone) are divided into five major
groups:
�� 1. Mammals
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Mammals are warm-blooded, which means they can keep their body temperature steady
even when it’s hot or cold outside.
They have lungs to breathe air.
Most mammals give birth to live babies (instead of laying eggs).
They feed their babies with milk produced by the mother.
Their bodies are covered with hair or fur (soft body covering).
� Examples: cats, dogs, squirrels, foxes, whales, and humans.
� Hard word explained:
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Warm-blooded – Animals that can keep their body temperature the same, no matter the
weather.
� 2. Reptiles
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Reptiles are cold-blooded, meaning their body temperature changes with the weather
around them.
They breathe through lungs.
Baby reptiles look like smaller versions of the adult. There is no metamorphosis (no big
change in body shape as they grow).
Their skin is rough and covered with scales (tiny, hard, dry plates like on a lizard or
snake).
They lay eggs.
Reptiles are oviparous, meaning they lay eggs outside their body.
� Examples: turtles, lizards, snakes, and alligators.
� Hard words explained:
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Cold-blooded – Animals whose body temperature changes with the surrounding air or
water.
Metamorphosis – A big change in the body of an animal as it grows (like a caterpillar
turning into a butterfly).
Oviparous – Animals that lay eggs, and the babies grow outside the mother’s body.
� 3. Fish (shown in the diagram)
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Live in water.
Breathe using gills (special parts that take oxygen from water).
Skin is covered with slimy scales (smooth, slippery covering).
Lay jelly-coated eggs in water.
� Hard word explained:
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Gills – Body parts that help fish breathe underwater.
� 4. Amphibians (like frogs)
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Can live both on land and in water.
Skin is moist (wet) and smooth.
Lay eggs in water.
Cold blodded
� 5. Birds
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Have feathers.
Lay hard-shelled eggs.
Have wings and most can fly.
They are also warm-blooded like mammals.
� FISH
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Fish are cold-blooded animals.
They are also called ectotherms, which means their body temperature changes with the
temperature of the environment.
Fish breathe using gills – special organs that take in oxygen from water.
Their bodies are covered with smooth, slimy scales that help reduce friction in water.
Fish have fins to help them swim and move.
Fish lay eggs outside their body – they are oviparous.
� Examples: goldfish, sharks, tuna, trout.
� Hard words explained:
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Ectotherms – Animals whose body temperature depends on the temperature of the
outside environment.
Gills – Special breathing organs in fish that take in oxygen from water.
Oviparous – Animals that lay eggs outside their body.
� AMPHIBIANS
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Amphibians are also cold-blooded animals.
They can live both in water and on land.
When in water, they breathe through their skin.
When on land, they breathe using lungs.
Amphibians go through metamorphosis – a big change in body form as they grow (e.g.,
tadpole turning into frog).
Their skin is thin, smooth, and moist, which helps in breathing.
They lay eggs in water – they are also oviparous.
� Examples: frogs, toads, newts, salamanders.
� Hard words explained:
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Metamorphosis – A major change in the body of an animal as it grows.
Oviparous – Lays eggs; babies grow outside the mother’s body.
� BIRDS
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Birds are warm-blooded – their body temperature stays the same even if it’s hot or cold
outside.
They breathe using lungs.
Birds have wings with feathers.
They have a beak, used to pick up and eat food.
Birds lay hard-shelled eggs – they are oviparous.
� Examples: eagles, sparrows, ostriches, chickens.
� Hard words explained:
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Warm-blooded – Animals that can maintain a steady body temperature.
Beak – The hard, pointed mouthpart of a bird.
Oviparous – Lays eggs outside the body.
Vertebrate
Group
Body Covering
How It
Breathes
Mammals
Hairy or furry skin
Birds
Feathers
Lungs
Tough skin with
Lungs
scales
Soft, moist skin (no Lungs
Reptiles
Amphibians
Lungs
How Offspring Are
Produced
Most young are born
Mostly on land
alive
On land
Lay eggs
Where It Lives
Mostly on land Lay eggs
On land and in Lay eggs (in water)
Vertebrate
Group
Fish
Body Covering
scales)
Scales
How It
Breathes
Gills
Where It Lives
water
In water
How Offspring Are
Produced
Lay eggs