There are many diseases that fall into each of the four categories, if not one category, perhaps two or more.• The infectious category refers to an infectious disease caused by a biological agent such as a virus, a bacterium or a parasite. Infectious diseases are the invasion of a host organism by a foreign replicator, usually microorganisms, often called microbes. Disease-causing microbes are also known as pathogens. The most common pathogens are various bacteria and viruses. An infectious disease is said to be contagious if it is easily transmitted from one person to another. An organism infected by a microbe is known as the host of that microbe. In the human host, a microorganism causes disease by interrupting a vital body process or by stimulating the immune system to mount a defensive reaction. • A hereditary disease is very different from an infectious disease, as hereditary diseases are likely to be passed on to descendants. Each cell in the body contains 23 pairs of chromosomes. One chromosome from each pair is inherited from your mother and the other from your father. Chromosomes contain the genes you inherit from your parents. Different forms of the same gene can exist. There may be a faulty version of a gene that causes a medical condition and a normal version that may not cause health problems. Depending on which gene is the dominant gene depends on whether a disease is inherited or not. • Physical illnesses usually involve the 'physical' appearance of a person, this could be a permanent or temporary element. Physical illnesses are illnesses of the body, not of the mind. Many things, including bacteria, viruses, and genes, can cause physical disease. Physical illnesses can be divided into acute and chronic. And...... middle of the paper......occurs due to exposure to a fungus when there is a weakness in the body. This weakness may result from a compromised immune system or from an individual providing a warm, moist environment in which fungi can grow. Fungi usually reproduce sexually or asexually, but asexual reproduction is the most common type of reproduction in most fungi. In sexual reproduction, male and female cells fuse to produce spores within a fruiting body. In asexual reproduction they simply reproduce by making small copies of themselves. Protists are single-celled eukaryotic organisms capable of reproducing asexually and sexually. During sexual reproduction, two protists come together and exchange genetic material in the nucleus. Prostists make people sick when they become human parasites that infect through puncture wounds and through consumption of contaminated food or water.