 Now, we talk about various factors that can affect an environment. There are different types of physical factors that affect an environment like air. The air currents as we know they can change or modify the temperature of an environment. Air in the form of wind, if it is a very strong wind, it can disturb the trees, the soil, it can move the soil from its place and move it to another part particularly in the soil in deserts or the sand in desert actually, is moved from one part to another part by the wind because wind is blowing so fast. The lightning is also very important factor because lightning can destroy the life at many places. It can destroy some habitats of different organisms. Then the water, water is also very important factor because water is critical for life. Different organisms need water and they have to obtain water from the environment. So water is also very important factor. Then comes the human interference itself. Humans also always interfere with the environment because they are progressing, they are going ahead. They have to, they have to make different things, they have to get different things from environment and they have to make their, the things of their need. The industrial growth has disastrously affected environment. Human beings are making different types of industries. These industries, when they produce some important things, they also produce many byproducts, waste products. These waste products have to be dumped somewhere and that dump is the environment because industries have to return those, their effluents, their byproducts, their waste products back to the environment. Actually these, these waste products are disastrous for the environment. Many of the waste products do have heavy metals in them which are heavily dangerous for the crops or the plants living in that area. These are also very dangerous for the, the, the birds and the animals. If they are, if they are added to the runoff waters and they go to the ponds or to the rivers, they may cause heavy loss of biodiversity. These industrial effluents or the waste products may be solid, may be liquid. In both cases, they are disastrous. They can damage the biodiversity of different ecosystems. We have solution for it, the wastewater plants. Industries by the rules of most of the governments have to install a treatment plant for their waste. Before they remove their waste and send it to the environment, they have to clean up that waste with the help of a treatment plant. The function of the treatment plant is actually to convert the toxic materials into very less toxic or non-toxic forms and then send it to the environment. So human beings, they create problems and they can solve them. But if they want to. So industrial effluents, they are our problems. They can cause contamination of waters, of lands, but these could be solved by human effort. Look at a diagram or look at a picture actually of a solid waste produced by an industry. A liquid waste, which is produced by an industry and is dumped into the soil. If some birds drinks this water, they may die. If this water is not cleaned up. If this water is cleaned up, then it may be okay, it may be all right. Then the deforestation. Deforestation is also a big problem for the ecological systems, the ecosystems. Say deforestation means cutting down the forest. As we know that human beings, they need wood for their different use. Wood is used in making furniture. It is used in making buildings. It is used in making our doors, our windows, the beautiful furniture. It is also used as the firewood. Human beings cut down the forest for wood. Cut down the trees, which is very disastrous for the ecosystem. Because these trees may be the habitat of various birds. If the trees are cut down, where will those birds go? Either they have to migrate or maybe they die because they cannot survive without it. There may be other birds, which eat upon those birds, they will die. And there are different types of insects on which these birds were feeding upon. For example, if a bird is feeding upon the grasshoppers and its habitat is destroyed and they die, then the grasshoppers will increase in very large quantities and maybe they eat up all our crops. So now remember the food chains and the food webs. If one organism is disturbed, it may disturb the whole of the food chain and even the whole of the food web. And this may result in a disaster or a problem for human being themselves. The other cause of deforestation is urbanization, urban spread. Human population is on increase everywhere and due to accommodate that population, they have to live somewhere, they need houses, they need hospitals, they need places. The forests are cut down for this purpose. This is also a major cause of deforestation. So deforestation could be controlled by number one, controlling the increase in human population, one thing. And secondly, if we are cutting down the trees, we can plant more trees. It is said that if you cut down one tree, you plant ten more. If you cut down one tree, then after some years those trees will grow up and they will compensate. So planning is required to handle this problem. The urban spread is one of the most important factors because the cities are expanding. The villages, we know that they can accommodate different types of habitats of birds and other animals and the plants. But for the cities, we have to make buildings, industries, schools, colleges, all of the buildings, which for which we have to cut down the trees and the plants. And when the human beings come there and they live there and they interact with the environment, all the natural populations, they are disturbed. There are different types of examples of that in the world. Then in Pakistan, now forests are reducing in their size because towns and cities, they are expanding. So urban spread is a threat to the environment, is a problem for the environment. Look at a picture which shows the urban spread towards an ecosystem. We can see that a lot many houses are formed, a road is going in between them. And on the other side, we can see an intact ecosystem which consists of, looks like a grassland and the mountains. But the urban areas or the town or the city is expanding towards that ecosystem. If this will expand just like this without planning, then that ecosystem after some time may be destroyed. The result again is the destruction of the ecosystem will result in the instability of the environment. If trees are, for example, cut down, there are fewer trees, temperature of the area may rise. If there are few trees, many animals and organisms cannot live in that area. Like different birds, many predator birds and those predator birds may eat up all those insects which can later on eat up our crops. So if we diminish the trees, we are raising up temperature. If we are diminishing the habitats of animals, this may result in increase of the grasshopper or other insects which later on will eat up our crops. And then we will face a food shortage. So disturbing the environment means disturbing human life themselves, by themselves. Another way of disturbing the environment is like construction of dams and the waterways. That is huge constructions. These huge constructions can also disturb the environment. The dams are built upon rivers and maybe they could be built upon canals. If they are built upon rivers, they will disturb the whole biodiversity of the rivers ecosystem because fish are living in that ecosystem, for example. They have to move from one place to another place in that ecosystem. That is they have to move from like this part of water to another part of water which is miles away. And if a dam is constructed in between, they cannot move from this place to another place. Maybe that is the place of their breeding. It means that by constructing these dams in the waterways, maybe this is possible that we are disturbing the biodiversity. But we also have some solution for it. We can make certain areas in our dams from which those fish can move. And we can make those fish adapt to that particular situation that they do not move through the whole of the river and they move from a waterway, from a side. If the fish, this particular fish is disturbed, maybe there are other fish which this fish is feeding upon. There are maybe in that particular water body, small invertebrates or phytozooplankton which that fish eat, which is disturbed. If the population of that fish is diminished, then those organisms will increase in their numbers because they are not eaten. And this may disturb the whole ecosystem of the river. So we can make a solution. That is, if we are making a dam, look at the biodiversity and find out ways in which we can conserve that biodiversity and we can make the dam. Remember that loss of biodiversity will result in the instability of the ecosystem. For example, if our river is full of phytoplankton and zooplankton, then if we collect that river in a water body, like a lake of a dam, this water may be not as suitable as it was previously for our agriculture or maybe for making electricity. So we are creating problem for ourselves. We have to solve it before time by planning. So look at a diagram which shows human impact on environment. Tourism, agriculture, runoff pollutants, maybe from agriculture industries, maybe from agricultural feeds, the urban development, the shipping, the fishing, the aqua culture, the coal mining and the processing, different types of mining, mining of different metals, maybe mining of coals and so on, everything actually in any way or the other affects the environment. But this could be handled with planning. Look at a picture, tourism, people are going to a very beautiful area but what they are throwing different types of plastic bags, maybe other wrappers here and there and these things are disturbing the environment. We are going to the environment, we are disturbing it by tourism. Agriculture, agriculture also affect the environment. When we grow crops of our own interest, then some crops may be exhaustive. For some crops we are adding different types of fertilizers. We have to keep in mind while doing agriculture, the natural balance of the ecosystem should be maintained. If this is not maintained then later on maybe the ecosystem is changed and we ourselves may not be able to grow our crops that well what we are doing today, maybe without precautions. Another picture, agriculture, there are the natural factors. There are a lot many natural factors which also affect the environment like the floods, the earthquakes, many of these factors lead towards total or partial habitat destruction. For example, if an earthquake comes or a flood comes, it may result in the destruction of lot many trees and those trees may be the habitat for different birds. If the trees are destroyed, the habitat of those birds is destroyed and they are homeless just like the people of that area. Sometimes these are so disastrous that they change the whole ecosystem of that particular area. Just remember the floods in just a few months back in the sin. Just remember a very big earthquake in the Khabar Pakhtunkha area just a few years back which actually changed the whole of the ecosystems of that particular area and those populations which were surviving there were no more able to survive and the people who are working on the ecology have to protect them. Another picture which shows a tree just fallen due to an earthquake, a natural disaster. If this tree is a habitat of different birds, may be some reptiles, may be squirrels, then all of those animals will become homeless, their habitat will be destroyed. If lot many trees are fallen like this, then this may result in the loss of habitat of all those birds, they may have to migrate or they may die. That is they become extinct from that particular area. Look at another picture of same kind by a flood. We can see that another habitat destruction, lot many trees are fallen. Now, importance of environment for the healthy living of an organism. Why environment is so important? Very simple. Organisms have to get food, shelter and other resources from the environment. We have to get our food, all the organisms have to get their food from the environment. Either they are producers or they are consumers or they are decomposers. If the environment is stable and healthy, then the organisms will be easily taking, getting their food from the environment and surviving. If the environment is disturbed or the balance of environment change, it may result in the loss of habitats for different organisms, which may lead towards extinction of different types of organisms from that area. And we know that if one organism is disturbed, a big food web will be disturbed by its absence because all the organisms who feed upon that organism or all those organisms which are eaten up by that organism all will be disturbed. So a balanced ecosystem is required for the healthy living of organisms. This was about the ecology, the environment, biotic and abiotic factors of an ecosystem and various factors which affect the ecosystem. I hope all of this is become clear to you.