13.4.1 CONCEPTS

The miracle of the human body is more startling when seen in its interaction with the environment. The interaction between the internal and external environments is purposive and is not a product of chance. The nervous and endocrine system ensure that the human body can adjust to rapidly changing circumstances of the external environment. This even includes changes on anticipation of external changes. The interaction between humans and their external and internal environments is part of Allah’s grand design and is not by mistake. This implies that this interaction has to be harmonious and follows the laws of Allah sunan llah fi al kawn. The human body is programmed to interact with the environment in the most efficient way. However humans because of their free will can behave in ways that produce unhealthy interactions. There are some phenomena like disease or drought that may bring adversity to humans. These are part of the grand design to ensure that there are checks and balances in the eco-system that ensure equilibrium. The adversities are therefore not created for punishment of humans. The universe was placed under the humans (taskhir). They control and change it as they want. However this control is sometimes not proper resulting into imbalances and problems. The crucial question is to determine what changes are bad because they derange the permanent fixed laws of nature, al sunan. A decision must also be made on what changes must be made for purposes of building a civilization.

13.4.2 THE PHYSICAL ENVIRONMENT

The human body is able to adapt to all types of physical environments. Human eucaryotic cells are less dependent on the external chemical environment that pro-karyotic cells. They have in a way created their own environment in their internal environment. Human can change environment. Some of the changes are for the good of the eco-system while some others are definitely harmful. Humans can sustain injury from the environment.

13.4.3 THE BIOLOGICAL ENVIRONMENT

The biological environment consists of parasites, animals, and plants. Humans and parasites have evolved a mutual adaptation. This takes several forms: symbiosis, commensalism, and parasitism. Parasites undergo antigenic change to avoid host immune defences. Plants are a source of food. They are involved in the oxygen, carbon dioxide, and nitrogen cycles that are necessary for human comfort. Human are able to eat some plants or parts of plants for which they have the appropriate digestive enzymes. Plants or parts of plants indigestable by humans still provide human food by being eaten by herbivorous. Under the concept of taskhiir, the earth and its contents were put at the disposal of humans. Taskhiir has its limitations based on the need to establish balance and equilibrium in the eco-system and protect humans from harm. Animals and plants are a source of food. Humans are at the top of the food chain and all food webs.

13.4.4 MICROBIOLOGICAL ENVIRONMENT

Micro organisms are viruses, prokaryotes, and eukaryotes. Viruses are the smallest infective agents and are obligate intracellular parasites that depend on the host for survival. In prokaryotes DNA is not bound in a membrane and there is no separation between the nucleus and the cytoplasm. Bacteria, spirochetes, mycoplasmas, and rickettsieaie are prokaryotes. Eukaryotes have their DNA separated from the cytoplasm. Protozoa, fungi, helminthes, arthropods are eukaryotes. There are 3 basic types of host-parasite relations: symbiosis, parasitism, and commensalism. Vectors transport parasites in disease causation. Parasites have to overcome overcome host resistance and barriers before disease causation. There is a balance sheet between the benefits and harm of microorganisms. There are many Islamic teachings about avoiding infections.

13.4.5 CHEMICAL ENVIRONMENT

Water is 45-75% of body weight. Tissues consist of inorganic substances, carbohydrates, lipids, and proteins. Elements higher concentration in humans than earth are H, C, and I. Elements the same concentration in humans and human body and the earth are P, S, Cl, K, and Ca. Humans take elements from the earth as food, drink and through respiration. C is the basis of organic compounds. Humans do not release dangerous chemicals into the environment eg ammonia is detoxified and turned into urea. Humans have complicated the simple chemical environment bequeathed to them by producing new chemicals.