Characters of Class Pisces
(fishes)
1. The class of fishes is called Pisces. They are
aquatic vertebrates.
2. According to their size and shape, the fishes are of many kinds.
3. They have a head, a trunk and a tail.
4. The head and trunk are directly jointed together and neck absent.
5. Body of fish is flexible tapering at both ends and streamlined. This type of
body helps in swimming.
6. They can swim with fins, which are attached to the trunk.
7. They body is covered with scales which remain moist by special type of
secretion of body.
8. Breathing organs are gills which are present in the hollow spaces found on
both sides of the head for exchange of gases i.e. oxygen and carbon dioxide.
9. Mouth has teeth, which is used for grasping instead of grinding of food.
10. In some fishes air pouch is present, which is called air bladder. The air
bladder is used for buoyancy.
Class Amphibia
1. This group of animals can live both in water and
on land.
2. They need water for reproduction. Therefore they are called Amphibians.
3. The skin is thin, moist and slimy.
4. Small teeth are present in the upper jaw which is only used for grasping the
prey.
5. Breathing organs are two lungs. Skin is also used for the exchange of gases.
6. Eggs are laid in water or moist places and their outer shells are not hard.
7. They are cold blooded animals e.g. they cannot maintain their body
temperature constant.
8. They become very slow and bury themselves in the mud. This process is called
hibernation.
9. During the process of reproduction fertilized egg is changed into adult
passing through a number of physical changes. This process is called
metamorphosis.
10. The fertilized egg develops into larva. The larva of frog is called
Tadpole. It has tail and gills. This larva later changes into adult.
Class Reptilia
The animals of this class are called reptiles. They
have following features.
Reptiles
1. Most of the reptiles are terrestrial and only a
few five in water.
2. They are also called crawlers.
3. They have thick, dry and rough skin.
4. The skin is covered with scales which originate from the ectoderm.
5. There are present lungs for respiration.
6. Teeth are present in their buccal cavity, which are used for cutting and
biting.
7. The locomotary organs are legs but snakes and a few types of lizards have no
legs.
8. Most of the lizards are not poisonous except members of the genus Heloderma
which are found in American desert.
9. All the reptiles lay their eggs on land. Water dwelling reptiles e.g. turtle
also lay their eggs on land.
10. Their eggs have a tough outer shell of calcium carbonate.
Class Aves
The animals included in this class are called
Birds. Their distinguishing characters are as follows.
1. Birds have a single unique feature, which makes them different from other
animals which is the presence of feathers. Their forelimbs are modified to form
wings while hind limbs help in walking, wading and sitting on the branches.
2. All the birds have horny beaks without teeth.
3. All the birds lay eggs.
4. All the birds must have two wings for support and propulsion, strong but
light and hollow bones.
5. Their digestive system is able to digest high caloric food.
6. They have a higher blood pressure and higher metabolic rate.
7. Nervous system and especially eye sight is very well developed so that they
can track their path even at a very high speed.
8. They migrate during winters towards warmer places covering thousands of
miles.
9. It is the most studied and most observable class in the world.
10. The birds are very beautiful and have melodious voices.
Types or Groups of Birds
Running Birds (Ratitae)
They have following characters:
1. They have flattened sternum.
2. Their pectoral muscles are weak.
3. Their examples are Ostrich, Emu, Rhea and Casso wary.
Flying Birds (Carinatae)
They have following characters:
1. A keel is present on sternum in these birds.
2. Keel is vertical bony part that is present below the sternum in the centre
from anterior to posterior end.
3. Pectoral muscles are very strong, powerful and are inserted on the keel.
These muscles help them to fly.
4. Their common examples are pigeon, hen, crow, kite etc.
Class Mammalia
All the animals included in this class are called
“mammals”. These animals are highly advanced vertebrates. There are almost four
thousand species of mammals including man.
Characteristics of Mammals
Their distinguishing characters are given below:
Hair
The body of mammals is covered with hair. In most of the mammals hair may cover
the whole body but in a few may be restricted to some areas. The hair conserves
heat of the body.
Glands
Their skin is provided with sweet glands, scent glands, sebaccous glands and
mammary glands.
Skeleton
Two occipital condyles, secondary bony palate, three bones in middle ear and
fused pelvic bones and seven cervical vertebrae are present in their skeleton.
External Ear
Fleshy external ears are present in mammals.
Eyelids
Moveable eyelids are present in mammals.
Teeth
Two sets of teeth are present. Milk teeth are replaced by permanent set of
teeth.
Brain
Brain is higly developed. It perform more functions than that of other
vertebrates.
Cranial Nerves
Twelve pairs of cranial nerves are present.
Circulatory System
Circulatory system has four chambered heart, persistent left aorta and non-nucleated
biconcave red blood corpuscles are present in female.
Sexes
Sexes are separate i.e. there are two individuals, male and female.
Fertilization
Most of them have internal fertilization and fetus developed inside the uterus
of female giving birth to their children.
Breast Feeding
They feed the children by milk from mammary glands.
Endothermic
They are endothermic i.e. they can maintain their body temperature according to
the environment. It means that they are warm-blooded animals.
Egg Laying Mammals
These mammals lay eggs. Mostly two eggs are laid in
one year. Fertilization of egg is internal i.e. inside the body of mother. Eggs
are laid in burrows of animals. Young ones are hatched from the eggs. Mother
feed their children with milk. Their egg laying character shows their
relationship with reptiles. Duck bill platypus and Spiny ant eater are the
examples of egg laying mammals.
Pouched Mammals or Marsupial Mammals
These mammals have a pouch outside the belly called
marsupium, this is the reason that they are also known as Marsupial mammals.
1. Fertilization of eggs and development of embryo is internal.
2. The embryo is at first encapsulated by shell membrane and floats free for
several days in the uterine fluid.
3. There is no placenta.
4. After hatching from the shell membranes, the embryo does not implant or
“take root” in the uterus and absorb nutrient secretions from the vascularized
yolk sac.
5. The gestation period is brief and the marsupials give birth to tiny young
that is effectively still an embryo.
6. These young creeps into the marsupium where it gets milk from mother through
nipple.
7. It lives in marsupium until it can take care of itself.
8. Examples are Kangaroo, Koala, Tasmanian wolf and Wombat etc. These are found
in Australia and Tasmania, Opossum is found in America. It lives on trees.
Placental Mammals
This is common group of mammals in which embryo
completes its development inside the mother’s uterus. After gestation period
young ones are born. Embryo remains in the uterus and gets its nourishment from
mother through umbilical cord and placenta. Gestation period of these mammals
is longer than those of other mammals. Pregnancy is called Gestation Period. In
man it is of 9th months.
In mice it is 21 days, in rabbit 30 to 36 days, in cats and dogs 60 days, in
cattle 250 days and in elephants 22 months. It is lengthier in large mammals.
The conditions of young ones at time of birth are different in different
mammals. For example in antelope, at the time of birth, the body of young is
covered over, with heavy fur, eyes are open and it can walk about. In case of
rat, young is very weak, eyes are closed and has no hair on the body.
Flora and Fauna of Pakistan
Flora
Definition
“Different types of plans present in a particular region constitute its flora.”
Details
1. Hilly regions of Pakistan have snow fall and low temperature. These regions
have thick forests where trees of Juniper (Sanober), Cedar, Chir, Chalghoza,
Olive Apple, Plum Peach and Loqaut are very common.
2. Plain areas of Pakistan have fertile and less fertile soils. In areas where
rainfall is low, desert environment is present in which Aeacia (Babool), Kikar,
Ber, Pilas etc grow.
3. Fertile plains have trees of Sheesham, Bakain, Cane, Bamboo and Eucalyptus.
These are source of timber whereas; fruit trees include mango, banana, Kino,
Orange, Grapes, Jamman etc.
4. Plain and hilly areas have natural pasture lands that provide fodder for
cattle.
5. In sea, rivers, ponds, canals and streams, algae are abundant, which on one
hand are the source of food for aquatic animals and on the other hand they
provide oxygen to atmosphere.
6. A large number of plants are used as ornamental plants. These include
flowering plants like rose, motia, jasmine, lady of night, chrysanthemum etc.
7. Besides this wheat, maize, rice, oats, burley, grams garlic, onion,
potatoes, carrots, cabbage and turnips etc are cultivated in plains and hilly
areas to meet our food requirements.
Fauna
Definition
“Different
kinds of animals present in a particular region are known as its Fauna.”
Detail
1. In the seas adjoining our coastal areas numerous types of animals are found
starting from protozoa to mammals. The most noticeable are octopus, mussels,
star fish, sea urchins, crabs, prawns, fishes, amphibians, whale, dolphin etc.
2. Many animals are used as food e.g. prawns, crabs and fish etc. Our rivers
are rich in fish life particularly Rohu, Khagga, Malhi, Trout, and carps are
abundant and used as human food, as well as a source of earning lively hood.
3. Frogs and toads are abundant.
4. The tortoises, turtles, snakes, crocodiles are also common.
5. On the plains of Pakistan we have very rich wild life. There is a great
diversity of land fauna starting from earthworms, almost all kinds of insects,
spiders, myriapods, snails, slugs to toads, lizards, snakes and enormous
variety of birds and mammals.
6. Some of the birds peculiar to Pakistan are Houbara bustard, partridge,
pheasant, falcons etc.
7. The mammals peculiar to Pakistan include Black buck, Blue ball, Brown bear,
Musk deer, Urial, Ibex, Asiatic ass.etc.
8. Most of the animals provide milk, meat, hide and wool. Some are used for
transportation. Some of the animals are now endemgered species because of their
excessive hunting and pollution.
WARM BLOODED ANIMALS
The animals which do not change their body
temperature with the change of temperature in environment are called as Warm
Blooded Animals. Their body temperature remains constant.
Example
Common examples of warm blooded animals are following.
(i) Parrot
(ii) Sparrow
(iii) Pigeon
(iv) Ostrich
(v) Kiwi
(vi) Duck billed platypus
(vii) Kangaro
(viii) Oppossum
(ix) Elephant
(x) Whale
(xi) Monkey
(xii) Man
COLD BLOODED ANIMALS
The animals in which the body temperature is
changed with the changes of temperature in the environment are called Cold
Blooded Animals.
Example
Common example of cold blooded animals are following.
(i) Shark
(ii) Labeo (Rohu)
(iii) Trout
(iv) Hilsa (Pullah Fish)
(v) Cat Fish (Khagga)
(vi) Frog
(vii) Toad
(viii) Snake
(ix) Wall-Lizard
(x) Crocodile
0 comments :
Post a Comment