Kids Learning Science V Term-III

5th Standard Science Term-III

AIR Continue...

  2. Effects of Air Pollution  

Air pollution affects all living organisms including man.  It causes serious health problems to human beings and affects both plants and animals.  It brings about a lot of changes in the climate and environment also.  In this section, let us learn about some of the effects of air pollution.

✧ Diseases

Air pollution causes several respiratory problems.  Many people have died due to air pollution.  Air pollutants cause pneumonia and asthma in children.

✧ Global Warming

Air pollution results in the accumulation of carbon dioxide in the atmosphere.  When gases like carbon dioxide are present in the atmosphere in large amount, they increase the atmospheric temperature.  With increased temperature, melting of ice and icebergs in polar regions and increase in sea levels are taking place.  It affects the organisms living there.

✧ Acid Rain

As we saw earlier, harmful gases like nitrogen oxides and sulphur oxides released into the atmosphere while burning fossil fuels.  When it rains, the water droplets combine with these gases nd fall on the ground in the form of acid rain.  Acid rain affects human, animals, and crops.

✧ Depletion of Ozone Layer

Ozone molecules are present in the Earth's stratosphere and they protect humans from harmful ultraviolet (UV) rays.  Chlorofluorocarbons, released into the atmosphere by human activities deplete the ozone layer.  As the ozone layer is depleted, UV rays reach the earth and they cause skin and eye related problems to us.

✧ Marine Life

Large amount of nitrogen present in some fertilizers in washed into the water bodies.  They cause the growth of green algae in the water bodies.  This is called Eutrophication.  This adversely affects fish, plants and animal species.

✧ Effect on Wildlife

Harmful substances present in the air affect wild animals.  Wild animals move to a new place when the air is polluted.  When their habitat is changed they face extinction.

  3. Prevention of Air Pollution  

If the air pollution increases at this rate, then there will be no life on the earth in the future.  Future generation will be affected very badly.  So, we need to take some measures to avoid air pollution.  Some of them are discussed below.

➜ Major pollutants which cause air pollution come from automobiles.  Using public modes of transport can reduce the rate of pollution.  We should encourage others to use public transport.

➜ By reducing the usage of fossil fuels we can save the environment.

➜ Using non-renewable energy resources like solar energy and wind energy instead of conventional energy can reduce air pollution.

➜ We need to reduce our usage of things.  We can reuse of recycle few items.

➜ Switch off fans and lights when you are not using them.

➜ CFL bulbs consume less electricity.  By using these bulbs we can save energy.

➜ Planting more trees can reduce the amount of carbon dioxide in the atmosphere.

  IV. Airborne Diseases  

Diseases which are caused by microorganisms and communicated through air are called airborne diseases.  When we breathe in air, there are chances for the microorganisms present in the air to get into our body.  Bacteria, virus and fungi are the microorganisms which cause airborne diseases.  These microorganisms are transmitted through droplets caused by coughing or sneezing, breathing and talking.  Let us study about some of the airborne diseases here.

  1. Diseases caused by Bacteria  

Diphtheria, Whooping Cough and Tuberculosis are some of the common airborne diseases caused by bacteria.

✧ Tuberculosis

Tuberculosis is caused by the bacteria, Mycobacterium tuberculosis.  When we breathe, the bacteria present in the air get into the lungs and affect it.  Infected person has to be treated with anti-tuberculosis drugs for a period of 6 months to 1 year.

✧ Whooping Cough

Whooping cough is caused by Bordetella pertussis.  It also affects the respiratory tract and causes mild fever severe cough ending in whoop.

✧ Diphtheria

It is caused by the bacteria, Corynebacterium diphtheriae.  It generally affects the upper respiratory tract (nose and throat) and causes fever, sore throat and chocking of air passage.

Disease	Causative Organism	Mode of Transmission	Tissue/Organ affected	Symptoms
Tuberculosis	Mycobacterium tuberculosis	Droplet infection from sputum of infected persons	Lungs	Persistent cough, Chest pain, Loss of appetite, Loss of weight
Whooping Cough	Bordetella pertussis	Droplet infection from sputum of infected persons, Direct contact.	Respiratory tract	Mild fever, Severe cough ending in whoop
Diphtheria	Corynebacterium diphtheriae	Droplet infection from sputum of infected persons	Upper Respiratory tract	Fever, Sore throat, Choking of air passage

 

  2. Diseases caused by Virus  

Some diseases are caused by the virus present in the air.  Common cold, influenza, measles, mumps and chicken pox are some of the diseases caused by virus.

✧ Common cold

Common cold is an infectious disease which affects the upper respiratory system like nose and throat and it is easily spread.  Symptoms of common cold include cough, painful throat, running nose and sometimes fever.  Though many viruses can cause this, it is generally caused by Rhinovirus.

✧ Influenza

Influenza is commonly found during childhood.  It is caused by the virus, Myxovirus and results in inflammation of nasal mucosa and pharynx.  It is also known as flu.

✧ Mumps

It is caused by Myxovirus parotitis and it affects the upper respiratory tract.  Some of the common symptoms of mumps include fever, headaches, sore throat and swelling of parotid glands which makes the jaw movement difficult.

✧ Chicken Pox

It is common among children but adults also may get it.  Affected people will have blisters or sports in the body and face along with fever.  Those blisters with fluid will drain but sometimes they may leave scars.

✧ Measles

Measles is caused by Rubeola virus and it is easily caught by people from other infected people.  Symptoms of measles include eruption of small rashes in skin cough, sneezing, redness of eye, pneumonia and bronchitis.  There is no cure for this disease.  Yet people can recover from this by proper rest and diet.

Disease	Causative Organism	Mode of Transmission	Tissue/Organ affected	Symptoms
Common Cold	Rhino virus	Droplet infection	Upper respiratory tract (Inflammation of nasal chamber)	Fever  Cough, Running nose, Sneezing and Headache
Influenza	Myxovirus	Droplet infection	Respiratory tract (Inflammation of nasal mucosa, pharynx)	Fever, Body pain, Cough, Sore throat, Nasal discharge, Respiratory congestion
Mumps	Myxovirus parotitis	Droplet infection, Contact with infected person	Upper respiratory tract	Enlargement of parotid gland, movement of jaw becomes difficult
Chicken Pox	Varicella Zoster virus	Droplet infection Direct contact with infected person	Respiratory tract	Eruptions of the skin, Fever and Uneasiness
Measles	Rubeola virus	Droplet infection, Direct contact with infected person	Respiratory tract	Eruption of small red spots or rashes in skin, Cough, Sneezing, Redness of eye, Pneumonia, Bronchitis

  3. Prevention  

Prevention is better than cure.  Airborne diseases can be prevented if we take certain measures.

➜ Avoid close contact with people who have active symptoms of disease.

➜ Maintain personal hygiene.

➜ Keep the patient in complete isolation.

➜ Cover nose and mouth while sneezing or coughing.

➜ Avoid touching the face with unwashed hands.

➜ Wash your hands thoroughly.

➜ Timely vaccination can prevent the diseases.

Kids Learning Science V Term-III

5th Standard Science Term-III

AIR 

  Introduction  

Air is present everywhere around us. Though we cannot see it, we can feel it.  Air is a mixture of gases like oxygen, nitrogen, carbon dioxide and hydrogen.  These gases act as an envelope around the earth form the atmosphere.  It is the presence of atmosphere that makes the earth a suitable place for living.  In the recent years more number of industries have been established and they release excess of harmful gases like carbon dioxide into the atmosphere.  Because of this, air is polluted more than ever before.  In this lesson, we are going to study about different layers of atmosphere, air pollution, air borne diseases and the measures to control air pollution.  

  I. Atmosphere  

The earth is surrounded by a layer of gases which is called atmosphere.  It is composed mainly of nitrogen (78%) and oxygen (21%).  Other gases like carbon dioxide and argon comprise 1% of the atmosphere by volume.  The atmosphere is like a blanket that surrounds the earth.  It protects the Earth from getting too cold or too hot.  

Atmosphere divided into five different layers.  The layers from the bottom upwards are: Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.  

✧ Troposphere

The troposphere is the  lowest layer of the atmosphere.  From the sea level it extends upto about 10 km.  It is the densest layer and almost 75% of the air in the atmosphere is found in this layer.  This layer also has water vapour.  We live in the troposphere and most of the weather like clouds, rain, snow are found in this layer.  All weather changes also occur in this layer.  

✧ Stratosphere

It extends from the top of the troposphere to about 50 km above the ground. Ozone layer found in this layer absorbs harmful ultraviolet rays which can cause damage to our skin and eyes.  There is no water vapour in this layer.  The temperature in this layer is around -550 C. 

✧ Mesosphere 

The region above the stratosphere is called mesosphere.  It extends upward to a height of about 85 km from the ground.  The temperature in this layer decreases with height and it is -100⁰ C.  Most of the meteors found in the sky burn in this layer.  

✧ Thermosphere 

The layer of very rare air above the mesosphere is called thermosphere.  It is the fourth layer of the atmosphere.  

✧ Exosphere

The outermost layer of the atmosphere is called exosphere.  It lies between 400 - 1600 km above the earth. The air here is extremely thin.  

  II. Importance of Air   

Air is important for all the living organisms.  Without air no life can exist on the earth. We take in oxygen from the air an d release carbon dioxide.  Plants in turn use carbon dioxide present in the air to produce their food. The gases such as oxygen, nitrogen, carbon dioxide and hydrogen present in the air are important to us for many reasons.  Let us study about the importance of air in this section.  

✧ Water Cycle

Water vapour present in the air is important for the formation of water cycle.  Water from the water bodies such as rivers and oceans evaporates and becomes water vapour. This water vapour then forms the clouds.  These clouds move to the land and get cooled to give us the rain.  This movement of clouds is possible due to air.  

✧ Supplies Energy 

We breathe oxygen present in the air and it is supplied to the cells in our body.  Body cells burn the food molecules with the help of oxygen and produce energy.  With this energy we do all kinds of works.  

✧ Sound travels through air 

We hear many things from the surrounding and people hear what we speak.  This is possible due to air because sound needs a medium to travel.  Sound travels from the point of generation to the listener through air.  

✧ Useful for plants.

Nitrogen present in the air is useful for plants.  Nitrogen in the atmosphere is converted into easily absorbable nitrates by plants with the help of some microbes.  It is known as nitrogen fixation.  These nitrates are useful for the growth of plants.  Also, ir is helpful for the pollination of plants.  Pollen grains travel from one plant to another plant through air.  Thus, cross pollination is achieved with the help of air.  

✧ Transport

Movement of ir is called wind.  This is helpful for the ships and boats to sail on the water.  Airplanes and helicopters travel through air.  

✧ Sports

Para-gliding is the recreational and competitive adventure sport of flying.  In this sport, pilot sits in a harness suspended below a fabric wing.  Hang gliding is also an air sport or recreational activity in which pilot flies a light, non-motorized foot-launched air craft called a hang glider.  Para-gliding and hang gliding are possible with the help of air.  Other sports like wind surfing, kite surfing and sailing are also possible with the help of air. 

✧ Parachutes and Hot air balloons

Parachutes and hot air balloons are used to land from above.  In case of emergency, we can use parachutes and come down slowly and safely with the help of air.

✧ Wind energy

Air flows from high pressure region to low pressure region.  This flow of air at high speed is called wind.  This wind is used to generate electric power with the help of wind mills.

  III. Air Pollution  

The presence of harmful substances in the air which can have an adverse efffect on living beings and the environment is called air pollution.  When harmful substances including gases like carbon dioxide, carbon monoxide, sulphur dioxide etc., and particles like dust and aerosols are released into the earth's atmosphere, air pollution occurs.  These substances are released into the atmosphere at a rate which exceeds the natural capacity of the environment to absorb them.  Air pollution may cause diseases, allergies and even death to humans.  It may also cause harm to other living organisms such as plants and animals.  It may damage the natural environment also.

  1. Causes of Air Pollution  

Air pollution is caused by both natural and manmade activities.  Air pollutants are released into the atmosphere through human activities like burning of fuels, releasing industrial wastes, mining etc.  Natural events like volcanic eruption also cause air pollution.  Let us see about some of the causes of air pollution in detail.

✧ Industries

Many industries have been established to manufacture things.  Large amount of carbon monoxide, hydrocarbons, organic compounds, and chemicals are released into the air by these industries.  Because of these pollutants quality of air is affected very much.

✧ Burning of fuels

Combustion of fossil fuels like coal and petroleum release sulphur dioxide which is an air pollutant.  Major air pollutants are released by the vehicles including bus, cars, trains and airplanes.  Improper or incomplete combustion o fuel releases carbon monoxide.  Nitrogen oxides which are released by both natural and manmade processes, also cause air pollution.

✧ Agricultural activities

Use of insecticides, pesticides, and fertilizers in agricultural activities has increased in the modern days.  They emit harmful chemicals such as ammonia into the air causing air pollution.

✧ Mining

Extraction of minerals from the earth is called mining.  Mining processes release dust and chemicals into the air causing massive air pollution.  This affects the health conditions of workers and people living in the surrounding areas.

✧ Household activities

Air is polluted through household activities also.  While cleaning and painting, we use a lot of chemicals.  These chemicals pollute the environment.

Kids Learning Science V Term-III

5th Standard Science Term-III

ANIMALS Continue...

II. Endangered Species

An endangered species is an animal or a plant that is at the risk of extinction.  It means that they might extinct from the earth soon.  It is reported that nearly 132 species of plants and animals are critically endangered in India.  Snow leopard, Bengal tiger, Asiatic lion, Purple frog and Indian giant squirrel are some of the endangered animals in India.  Similarly, plants like Umbrella tree, Glory lily, Rafflesia flower, Indian mallow and Musli plant are endangered.

1. Causes for Endangerment

The following are the reasons why an animal or a plant is endangered or extinct. 

➜ Forests which provide food and shelter to animals are destroyed for human needs.  

➜ Large number of animals are hunted for their horns, skin, teeth and many other valuable products.

➜ Pollutions like air pollution and water pollution affect the animals.

➜ Sometimes animals are taken to new habitat by people.  They cannot survive there.

➜ Pesticides and chemicals which are used to get rid of insects, pests or weeds, poison the plants and animals.

➜ Natural disasters like flood, cyclone and fire also destroy animals.

2. Saving Endangered Species

Nature is beautiful and it is filled with varieties of plants and animals.  But they are endangered mainly due to human activities.  We need to take some measures to protect them.  

➜ Hunting and poaching of animals should be prohibited.

➜ We should not pollute the environment.

➜ Limiting the usage of plastic and recycling it can save the endangered animals.

➜ Pesticides and chemicals which pollute the environment should be avoided.

➜ Planting native trees will provide food to the animals. 

➜ We should buy eco friendly products only.

3. Red Data Book

The Red Data Book is a book maintained for recording rare and endangered species of animals and plants.  This book is created to identify and protect the species which are about to extinct.

It is maintained by the International Union for Conservation of Nature (IUCN), an international organization working in the field of nature conservation.  The Red Data Book contains colour-coded information sheets.

✧ Advantages of Red Data Book

➜ It helps to evaluate the population of a particular species.

➜ The data given in this book can be used at the global level.

➜ This risk of a species becoming globally extinct can be estimated with the help of this book.

➜ It provides the necessary guidelines for implementing protective measures.

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III. Conversation of Animals

Biodiversity is the term used to describe different plants, animals, microorganisms, and insects etc., that are found on the earth.  Conservation of biodiversity helps us to protect, maintain and recover the endangered animal and plant species.  Conservation of biodiversity is the protection, preservation, management of wildlife and natural resources.  Endangered species are maintained in certain protected areas such as national parks and wild life sanctuaries.  In India, there are about 73 national parks and 416 wild life sanctuaries.

1. National Parks

A national park is an area which is strictly reserved for the betterment of wild life.  In these areas, activities like forestry, grazing or cultivation are not permitted.  Even private ownership rights are not allowed in these areas.  The national parks cover an area of 100 - 500 square kilometers.

✧ Jim Corbett National Park

Jim Corbett National park is located close to Nainital, in Uttarakhand.  Tigers are found in this park.  Other animals found here include several species of deer, leopards, jackals red foxes, black bear, sloth bear, and monkeys.

✧ Gir Forest National Park

It is located in Gujarat.  Asiatic lions in their natural habitat can be seen here.  Other animals that are found here include sambar, chinkara, chital, porcupine, wild boar and black buck.

✧ Kaziranga National Park

It is located in Assam.  Wild animals such as rhinoceros, tiger, elephant, wild buffalo and swamp deer are seen here.  This park also has bears, leopards, and several species of local and migratory birds.  This park is famous for one horned rhino.

✧ Sundarban National Park

Located in West Bengal, Sundarban National Park is a tiger and biosphere reserve on the Ganges delta.  Bengal tiger, saltwater crocodile, wild boars, foxes, leopard cats, huge turtles, Ganges river dolphins and several other varieties of mammals and reptiles, along with a huge variety of local and migratory birds can be seen here.

✧ Kanha National Park

Kanha National Park, located in Madhya Pradesh was established as a part of Project Tiger.  Apart from tiger, animals such as elephants, jackals, leopards, striped hyenas, monkeys, and several varieties of deer including black buck, swamp deer, chital and sambar are seen here.

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✧ Periyar National Park

Periyar National Park is in Thekkady, Kerala.  Various species including the majestic elephants, royal tigers, fishes, reptiles and birds can be seen here.

Name of the Park	District
Gulf of Mannar National Park	Ramanathapuram
Indira Gandhi National Park	Coimbatore
Mudumalai National Park	The Nilgiris
Mukurthi National Park	The Nilgiris

✧ Guindy National Park

This park is located at the heart of the Chennai city, the capital of Tamilnadu.  It is a home to spotted deer, black bucks, white bucks, river otter, hyena, bonnet monkey, civet cat, jackals, pangolin, hedgehog and common mongoose etc.

2. Wildlife Sanctuaries 

A sanctuary is a protected area which is reserved for the conservation of animals.  Harvesting of timber, collection of forest products and private ownership rights are allowed here.  Tourist visit is also allowed in these places.

✧ Kalakkad Wildlife Sanctuary

Kalakkad wildlife sanctuary is famous for tigers.  Lion tailed macaque, Nilgiri langur, bonnet macaque, langur, Nilgiri tahr, sambar, sloth bear, gaur, elephant, flying squirrel, panther, wild dog and pangolin are some of the animals found here.

✧ Mudumalai Wildlife Sanctuary

It is located in Ooty.  Bengal tiger, giant elephant and leopard are found here.  Elephant safari is famous in this sanctuary.

✧ Mundanthurai Wildlfe Sanctuary

It is located in Thirunelveli district.  Major wild life animal found here is tiger.

✧ Anaimalai Wildlife Sanctuary

It is also called as Indira Gandhi Wildlife Sanctuary.  It is situated in Coimbatore district.  Dhole, wild dog and giant squirrel are seen here.

Name of the Santuary	District
Meghamalai Wildlife Sanctuary	Theni
Vandalur Wildlife Sanctuary	Chengalpattu
Kalakkad Wildlife Sanctuary	Thirunelveli
Grizzled Squirrel Wildlife Sanctuary	Virudhunagar

✧ Vedanthangal Bird Sanctuary

It is a very old sanctuary in Tamil Nadu.  It is located in Chengalpattu district.  It has many migratory birds like spoon bills, open billed storks, pelicans etc.

 

3. Advantages of Conservation

➜ Species can be adapted to their habitat.

➜ Species can interact with each other.

➜ Natural habitat of the animals is maintained.

➜ It is a less expensive and easy to manage.

IV. Prevention of Cruelty to Animals

Cruelty to animals includes capturing, trapping, poisoning of any wild animal collectively.  There are many animal welfare organizations concerned with the health, safety and psychological wellness of animals.  They include animal rescue groups which help animals in distress, and others which help animals suffering from some epidemic.  Animal Welfare Board of India and National Institute of Animal Welfare are the government organizations which work for the welfare of animals.  There are some private welfare organizations also.

1. Blue Cross

Blue Cross is a registered animal welfare charity in the United Kingdom.  It was established in 1897 with the vision that every pet will enjoy a healthy life in a happy home.  This charity provides support for pet owners who cannot afford private veterinary treatment, helps to find homes for unwanted animals, and educates the public in the responsibilities of animal ownership.  

Blue Cross of India was established at Chennai in the year 1959.  Now, Blue Cross of India is one of the largest animal welfare organizations in India.  Its main office is located at Guindy, Chennai, with all amenities like hospitals, shelters, ambulance services and animal birth controls etc.  Activities of the organization include, providing shelters, adoption, maintaining hospitals and mobile dispensary and providing ambulance services.

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Kids Learning Science V Term-III

5th Standard Science Term-III

ANIMALS

Introduction

Our planet earth has countless number of organisms including plants and animals.  Among them, animals are the most advanced organisms.  Animals are a gift of nature to human beings.  They are very closely associated with us in our daily life and contribute a lot to us.  Man is exploiting nature nowadays more than ever before.  Hence animals are affected and many of the plant and animal species are disappearing from the earth.  We are going to study about this in this lesson.  This lesson will also deal with reproduction in animals, extinction of animals and the ways to preserve them.

I. Reproduction in Animals

Reproduction is the biological process by which an organism gives rise to a new organism.  This process is seen in all living organisms - both plants and animals.  Reproduction is essential for the continuation of similar kinds of species, generation after generation.  In animals, two types of reproduction are seen.  They are : sexual reproduction and asexual reproduction.

1. Sexual Reproduction

Sexual reproduction is a natural way of reproduction in humans, animals and also in most of the plants.  This type of reproduction is more complex and lengthy as compare to asexual reproduction.  Different and unique offspring are produced by sexual reproduction.  Sexual reproduction consists of the following stages.

a. Pre-fertilization b. Fertilization c. Post-fertilization   

 

a. Pre-fertilization

This is the first stage of sexual reproduction.  In this stage, gamete (sex cells formation and transfer of gametes take place.  In animals, males and females have different reproductive organs.  The male reproductive organ is called testes and the female reproductive organ is called ovary.  The testes produce the male gametes known as sperms and the ovaries produce the female gametes known as ova or eggs.  The male gamete reaches the female gamete during this stage.

b. Fertilization 

When the male gamete reaches the female gamete they begin to fuse together.  The fusion of gametes is known as fertilization.  During fertilization, the nuclei of the sperm and the egg for a single nucleus together, resulting in the formation of a fertilized egg, known as zygote.

Fertilization in animals takes place in two ways.  They are : External fertilization and Internal fertilization.

External fertilization takes place outside the animal's body.  It usually takes place in aquatic environments where both eggs and sperm are released into the water.  Fertilization in frogs and fish takes place by this method.  When the fertilization takes place inside the animal's body, it is called internal fertilization.  Internal fertilization takes place in animals like cat, dog, cow etc.

c. Post - fertilization

The zygote (fertilized egg) further divides repeatedly into group of cells.  These cells develop into different tissues and organs constituting a full body.  This structure is known as embryo.

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The embryo continues to develop in the uterus and it is developed into body parts such as head, face, hands, legs, etc.  Based on whether the embryo develops outside or inside the body, animals are classified into oviparous animals and viviparous animals respectively.

✧ Oviparous animals

Animals in which embryo develops outside the body are called oviparous animals.  They produce their offspring by laying eggs.  In the case of birds new ones are produced from the eggs.  The egg shell protects the embryo from outer environment and the embryo receives its nutrients from the egg yolk.  In some of these animals the new born one will have different developmental stages.

For example, in butterfly, there are different developmental stages like egg, larva, pupa and adult.  Each stage is different.  The process in which a butterfly becomes an adult is called metamorphosis.  The life cycle process can take a month to year.

State 1 - Eggs

In the first stage a butterfly lays eggs on the leaf.  These eggs are very small and round.  About five days after the eggs are laid, a tiny worm-like creature will hatch from the egg.

Stage 2 - Caterpillar (Larva)

The second stage is the caterpillar.  It is also called larva.  The caterpillar starts to eat leaves and flowers once it has hatched.  It grows very fast because it eats a lot.  As it grows fast, it sheds its old skin and gets new skin.  A caterpillar shedding its outgrown skin is called moulting.

Stage 3 - Chrysalis (Pupa)

The third stage is the pupa.  It is mostly brown or green.  This is the resting stage as well as the changing stage.  The caterpillar turns into a butterfly.

Stage 4 - Butterfly (Adult)

In the fourth stage, the pupa opens and a butterfly comes out.  A butterfly is sometimes called an imago.  It is also called as adult.  Butterflies are very colourful.  When the butterfly first comes out it is very tired and so it rests.  Then the butterfly will lay eggs and the life cycle will start all over again.

✧ Viviparous animals

Animals in which the embryo develops inside the body are called viviparous animals.  These animals give birth to the young ones.  The developing embryo gets its nutrients from the mother.  Human, cow, deer and dog are examples for viviparous animals. 

Oviparous animals	Viviparous animals
The development of the embryo takes place outside the animal.	The development of the embryo takes place inside the animal.
They produce their young ones by laying eggs	They directly give birth to the young ones.
The embryo receives the nutrients from the egg yolk.	The embryo receives the nutrients from the mother.
Examples for oviparous animals are insects, fish, reptiles, birds etc.	Examples for viviparous animals are cat, dog, lion, human etc.

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2. Asexual Reproduction

The type of reproduction in which only a single parent gets divided into two or more new offspring is known as asexual reproduction.  This type of reproduction takes place in micro organisms like hydra and amoeba.  Asexual reproduction produces offspring that are identical to the parent.  There are several ways by which animals reproduce asexually.  Some of them are explained below.

✧ Fission

Fission occurs in some invertebrate (organisms without back bone), multi-celled organisms.  In this method, an organism splits itself into two parts.  For example, flatworms, sea anemones and sea cucumbers divide into two halves and regenerate the other half in each of the resulting individuals.

✧ Budding

Budding is a form of asexual reproduction that results from the outgrowth of a part of the body.  Then, the bud is separated from the original organism forming two individuals.  Budding occurs commonly in some invertebrate animals such as hydras and corals.

✧ Fragmentation

Fragmentation is the breaking of an individual into parts followed by regeneration.  Reproduction through fragmentation is observed in sponges and sea stars.  Fragmentation may occur through accidental damage, damage from predators, or as a natural form of reproduction.

✧ Spores

Some protozoan, bacteria, plants and fungi reproduce via spores.  Spores are the structures that naturally grow as part of an organism's life cycle.  They are separated from the organism and dispersed through a medium such as air or water.  In a suitable environment, the spores will develop into a fully grown organism.

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