Classification of animals
Animals which have a backbone are known as vertebrates whereas whose who do not have a
backbone are known as the invertebrates.
The main groups of vertebrates are : mammals, birds, reptiles, amphibians, fish
Mammals
• Mammals are warm-blooded organisms with body covered with hair or fur.
•
Leopards, bats, dolphins, bears, lemurs, whales, platypus, spiny ant-eater, wolves and
man are all examples of mammals.
•
They are endothermic that is they maintain a relatively high and constant body
temperature
•
Fertilisation is internal and so is development. The young develop in a womb (uterus)
and they are born already well developed. Their young develop in uterus, attached to
their mother by a placenta. They feed their young with milk produced from mammary
glands.
• They have lungs for breathing.
• They have external ears (pinnae).
• They have sweat glands.
• They have different types of teeth (incisor, canine, premolar and molar).
Birds
Like mammals they are warm blooded organisms and have feathers on their bodies.
Their front limbs are modified as wings but not all birds can fly e.g penguins and ostriches.
They are able to maintain a constant internal temperature
Fertilisation is internal and development is external as females lay eggs that are protected
by hard shells
Like mammals they also have a heart with four chambers.
Their young develop in eggs
Depending on the species the type of food fed is different. Birds have no teeth but have
beaks. Each species of bird is adapted to deal with a specific type of food.
Amphibians
•
Reptiles are cold-blooded organisms.
•
They have a tough, dry and scaly skin. Crocodiles, lizards, chameleon, snakes, turtles
•
and tortoises are all examples of reptiles.
•
They cannot maintain a constant body temperature. Hence, to prevent overheating,
most of the time they stay submerged in water, buried in soil and hidden in shade
•
Fertilisation takes place inside the female’s body. However, development is external
as they lay eggs with leathery, waterproof shells that stop them from drying out. The
eggs hatch into tadpoles which live in water, but adults live on land.Tadpoles breathe
using gills while adults have lungs for gas exchange.
•
Tadpoles change into adult by a process called metamorphosis.The young develop in
eggs .Reptiles don't typically feed their young.
•
They have lungs for breathing. On land, the adult amphibians breathe using lungs.
However, when they are in water, they can breathe through their skin.
•
Their eggs are laid in water and have no shells.
•
The teeth vary in their form, their attachment, and whether they are shed. The teeth of
herbivorous species are broadly flattened with crushing surfaces. Those of most
carnivorous reptiles are tapered to sharp points.
•
They are cold-blooded that is they cannot maintain a constant body temperature
•
•
They have soft skin with no scales e.g frogs, toads, newts and salamanders.
They swallow their prey whole.
Fish
•
Cold -blooded.
•
They have eyes and a lateral line for detecting pressure changes in water. Their skin is
covered with scales. They have swim bladders which is a specialised organ filled with
air that helps to ensure fish maintain a stable buoyancy .Ex:Goldfish, tuna, herring,
tilapia, shark, eel, catfish, and cod.
•
Some are endothermic some are ectothermic.
•
Nearly all fish reproduce by sexual reproduction - the fusion of sperm produced from
testes and eggs produced from ovaries.
•
They breathe dissolved oxygen from the water using their gills.
•
Most fish release thousands of eggs, scattering them in the water where the male fish
fertilize them. The eggs develop and hatch into larvae (baby fish) .A few kinds of fish
keep their eggs inside their bodies, so when they hatch they give birth to live young.
•
No parental feeding
•
All fishes have teeth