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Story of our Environment and   Diseases caused by Environmental Factors

           Dr Sampurna Roy MD


Story of our Environment:

Life exists all over the surface of the Earth, even in the most unlikely places.

The conditions in which a plant or animal lives and everything that affects its life form what is known as its environment.

Each type of natural environment contains its own kinds of living things.

Every wild animal and uncultivated plant is suited to the particular conditions in which it lives and is able to survive in them.

There are five distinct kinds of environment - in the sea, the seashore, fresh water, land and living things.

The sea: The open sea is an unchanging environment for many kinds of life, particularly the millions of tiny plants and animals called plankton floating near the surface.

The tiny plants provide food for the tiny animals and some of these animals are eaten by bigger fish.

The bottom of the deep sea is quite different, being dark, cold, and silent.

There are no green plants because they cannot live where there is no light.

The animals have to feed on other animals and any decaying matter they may find.

Deep sea fishes have huge jaws and stomachs so that they can eat a lot in one time, as they can seldom find food.

Their bodies are adjusted to the great pressure of water in the depths of  the sea.

The seashore: This is a very interesting environment between the sea and dry land. Plants and animals there have to be able to live sometimes in water (when the tide is in) and sometimes out of it (when the tide retreats).

Those near low tide mark are only exposed to the air for a short while, but those near the high tide mark get wet only with salt water at intervals.

Between these two extremes the kinds of living things vary according to the amount of exposure to the air they can stand.

While the tide is down there are many hiding places from the drying sun and wind.

They include rock pools, cracks in the rocks, under stones and burrous in sand and mud.

Limpets (aquatic snails with shells) , however, stick themselves to the rock surface and pull their shells down tight over their soft bodies so that they are protected from the air while the tide is out, and from being battered by the waves when the tide comes in.

The fresh water: Lakes, rivers, streams and ponds are all fresh water environments. Plankton is found in lakes and ponds.

Fishes are different from those in the sea because they have to live in fresh, not salt, water.

Many land creatures spend their early stages in fresh water, like the nymphs of dragonflies.

The Land: Because of variations in the climate and soil, and therefore plants, the land provides many more kinds of habitat, or home, than the sea.

There are the extremes, such as cold polar regions, sandy barren deserts and dark caves.

In these places living things have interesting features to suit them to their environments, like the fleshy tissues of cactus leaves, specially for water storage.

An environment can be divided up into many smaller habitats where different animals and plants live.

There are many even in a garden, like the lawn with its worms, and leaves with their caterpillars.

Living Things: Some living things provide a home for other plants and animals.

For instance, certain fungi grow on the bark of trees.

Some animals and plants live on or in other plants or animals, like maggots in apples and tapeworms in the intestines of birds.

The tapeworm’s environment is dark and contains partly digested food, so it needs no eyes and no digestive organs.

Scientists believe that life began in the sea and that some forms of it came gradually on to the land.

During this change-over, living things underwent slow changes in structure and habit for life on land.

This means they adapted themselves to it.

Plants developed woody stems and seeds.

Backboned animals developed lungs to obtain oxygen from the air and changed the structure of their fin-like limbs to be able to walk, run, jump, burrow and fly.

The environment of past ages caused these changes and helped to make living things as they are today.

Environments are always changing and living things have to be able to survive these changes.

The factors which cause these changes can be grouped into two kinds, the living and the non-living.

Living things change all the time, by growing, reproducing, dying and decaying, so the organisms found in an environment change with time.

There is also succession of different kinds of communities, or groups, of living things, example; when a bare piece of ground is covered by moss, then by some grass and worms, which in turn make way for bigger plants and animals.

The non-living factors include water, carbon dioxide, oxygen, nitrogen and other elements like those in the soil and light and temperature.

All living things need water and so the presence or absence of water has much to do with presence or absence of life in any place.

Light and temperature are continually changing, and the climate brings drastic changes such as floods and droughts.

Seasonal changes are very important to living things.

In the spring new plants grow, while autumn causes many trees to shed their leaves and animals to migrate or hibernate.

Garden plants are sensitive to small changes in temperature and water supply, and sometimes respond by wilting.

Most animals have a well developed sense of organs which tell them what is happening around them.

Man reacts to heat by perspiring, to cold by shivering.

Man and his Environment and Diseases:

Man can enter many different environments for he can think out ways to protect himself and can make machines such as aircraft and submarines.

He is even able to adapt to outer space.

He adapts himself to cold and to regions where there is little air. He uses extra clothing and special food in polar regions and extra oxygen on high mountains.

Unlike other living things he has found ways of controlling the environment to his benefit.

In greenhouse he controls light, temperature and water, so that plants grow to their best advantage.

He controls the environment in his home so that germs cannot flourish.

But man's control over his environment to his benefit can also be abused.

The rapid increase in the human population since the 18th century has caused overcrowding in cities and made it very difficult to supply everyone with essentials of food, clothing shelter and employment.

The spread of vast and often congested cities, with their industrial areas and interlinked transport systems, is changing the Earth's natural environment and threatening human and other life forms.

Bad farming methods combined with weather erosion, have made deserts of once fertile regions.

The introduction of certain types of animal into areas where they were previously unknown has sometimes upset the natural balance and caused problems of pest control.

The irresponsible dumping of domestic and industrial waste into river and seas has caused severe pollution and destroyed many millions of water creatures.

The expulsion of poisonous gases from factory chimneys, motor car exhausts and aircraft engines has endangered the purity of the atmosphere.

Diseases are caused by air pollution, exposure to radiation, toxic external agents, cigarette smoking, iatrogenic drug injury, toxic metals, volatile organic solvents and vapors, pesticides, intake of oral contraceptives, alcohol, barbiturates and narcotics.

Environmental pathology is a subject that deals with diseases caused by exposure to these harmful external agents.

With the recognition that many of these causative agents are environmental contaminants, a component called "occupational disease" was added in the list.

In comparison to all other environmental hazards, the mortality and morbidity rate is extremely high in cases of voluntary intake of tobacco smoke, alcohol (ethanol, ethyl alcohol), and illicit psychoactive drugs.

Death and disease related  to lightning, hyperthermia, hypothermia, radiation, air pollution, industrial exposures, are relatively minor dangers compared to the problems that people willingly bring upon themselves.

I have updated a number of diseases caused by environmental factors and made a list of these lesions from my websites ; and  

This page will include links to various topics related to Environmental Pathology.



Lead - The Lethal Metal: Pathology of Lead Poisoning



Killer Heat - Pathology of Heatstroke: (Infographic)



Arsenic exposure: Major public health hazard.

Pathology of Arsenic Poisoning




Mercury: Keep away from Toxic Heavy Metal

Pathology of Mercury Poisoning




"Brr! It's so cold outside" - Human body responses to cold and hypothermia




Toast to your health this festive season?  Be careful !


Dangers of  "Holiday Heart Syndrome" and other complications of Chronic Alcoholism




Struck by Lightning - Pathology of Lightning Induced Injuries



Pathology of Cadmium Poisoning


Cadmium is a known Human Carcinogen




Adverse Effects of Smoking on Cardiovascular System




Pathology of Carbon Monoxide Poisoning - "A Silent Killer" 



Deadly Deep Sea Diving -

Pathology of Decompression Sickness (Caisson disease )



Beware Ladies! - Hazards of Oral Contraceptives











Coal Pneumoconiosis






"Environmental pollution is an incurable disease. It can only be prevented." - Barry Commoner



Dr Sampurna Roy  MD

Consultant  Histopathologist

(Kolkata - India)






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Pathology Quiz Online 


Paediatric Pathology Online


Pancreatic Pathology Online




Endocrine Pathology Online


Eye Pathology Online


Ear Pathology Online


Cardiac Path Online


Pulmonary Pathology Online


Lung Tumour Online




Nutritional Pathology Online


Environmental Pathology Online


Soft Tissue Tumour Online


GI Path Online-India


Gallbladder Pathology Online


E-book - History of Medicine  


Microscope - Seeing the Unseen





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