Railway Science (Biology – Miscellaneous) (Part-III)

A lot of water is lost by plants in the form of vapor through stomata during transpiration. It generates a force which pulls up water absorbed by the roots from the soil, to reach the stem and leaves. It also cools the plant.

Rhizoid - A structure in plants and fungi that functions like a root in support or absorption. They assist in the absorption of water and nutrients. It grows out of the base of the gametophyte.
Plants which consist of rhizoids are known as the bryophytes and include mosses, hornworts, and liverworts. In mosses, rhizoids are multicellular. In liverworts and hornworts they are unicellular.
Rhizoids are simpler in structure compared to true roots found in vascular plants.

There are seven main taxonomic ranks - kingdom, phylum or division, class, order, family, genus, and species.
Species - It is the basic unit of classification. Genus - A group of closely related species form a genus.
Family - It is a larger group of related genera. Order - An order is a group of closely related families.
Class - It is a group of related orders. Phylum/Division - It is a group of related classes.
Kingdom - It is the highest category in biological classification. Carl Linnaeus is known as the father of modern taxonomy.

Force generated by the muscles is used to carry out movement through joints, where the joint acts as a fulcrum. Joints are classified into 3 major structural forms, namely, fibrous, cartilaginous and synovial.

Regeneration: The ability of an organism to restore or replace its lost body part.

Smooth or unstriated muscles are present in the dermis of skin and in the wall of various hollow visceral organs like alimentary canal, urinary bladder. They are usually controlled by the autonomic nervous system. Their contraction process is slow and not under voluntary control and therefore they are also called involuntary muscles.

Holotropic organisms (holozoic organisms) take the food inside their body, break it down into smaller parts and then it gets digested and absorbed by the body to get energy. It involves the process of ingestion, digestion and egestion. Example - Human.
Other types of Heterotrophs : Parasitic - The Organism which lives on or in the body of other organisms called hosts. Example - Lice, tapeworms. Saprotrophic - Obtain their food from dead and decaying organisms. Example - Fungi.

Muscles are a tissue made of muscle cells, also called muscle fibers. Muscle fiber are made of thick and thin myofilaments made of myosin and actin protein molecules respectively. Muscles contract and relax to cause movement. Muscle contraction is explained by sliding filament theory of muscle contraction.

Tooth decay occurs when the pH of the mouth is lower than 5.5. At a pH below 5.5, the acids produced by bacteria in the mouth begin to demineralize the enamel, leading to tooth decay.

The two main types of contractile proteins are actin and myosin. Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments respectively. Hemp protein, basa or lipoprotein, and whey protein are types of dietary proteins.