Tiêu đề BIOLOGY CRASH COURSE.pdf ✅

SOME IMPORTANT PROPERTIES OF LIVING BEINGS Growth F All living organisms grow. Increase in mass and increase in number of individuals are twin characteristics of growth. F In plants growth by cell division occurs continuously throughout their life span. In animals growth is seen only upto certain age. However, cell division occurs in certain tissue to replace lost cells. Reproduction F It refers to the production of progeny possessing features more or less similar to those of parents. Reproduction is of two types—asexual and sexual. F Asexual reproduction is uniparental that can occur by binary fission, spore formation, fragmentation, vegetative propagation etc. F In higher developed organisms like plants and animals, sexual reproduction is common which involves formation of gametes to form zygote which develops into new organism. Metabolism F The sum total of all the chemical reactions occurring in an organism is called metabolism (anabolism + catabolism). Cellular organisation F Cellular orgnisation of the body is the defining feature of all life forms. Consciousness F The most important and technically complicated feature of all living organisms is the ability to sense their surrounding and respond to stimuli which could be physical, chemical or biological. F All organisms, from prokaryotes to the most complex eukaryotes can sense and respond to stimuli, which represents consciousness. F Human being is the only organism who is aware of himself/herself, i.e., self conscious (can plan future, think of past, aware of existing world). DIVERSITY IN THE LIVING WORLD Biodiversity refers to the number and types of organisms present on earth. About 1.7 million species have been scientifically named and classified. These include 1.2 million animals and about 0.5 million plant species. Amongst animals, insects form the largest group, i.e., over 10,25,000 species. TAXONOMY AND SYSTEMATICS Taxonomy : The term taxonomy was given by A.P. de Candolle. Linnaeus is considered as the father of taxonomy. The basic elements of taxonomy are as follows : F Characterisation and identification : It is the determination of the similarities of an organism with an already known organism. F Nomenclature : It is the determination of correct name of an organism according to established rules. F Classification : It is grouping of organisms into convenient categories on the basis of easily observable characters. Systematics : The term systematics was first used by Carolus Linnaeus. “Systematics” is derived from Latin word Systema which means systematic arrangement. Systematics = Taxonomy + Phylogeny The Living World 1 THE LIVING WORLD 1 CHAPTER
NOMENCLATURE This system of providing a name with two components is called Binomial Nomenclature and was given by Carolus Linnaeus. He is the author of books like Systema Naturae and Species Plantarum. Rules for Binomial Nomenclature F Biological names are generally taken from Latin language irrespective of their origin (or are latinised). F Each organism is given only one name consisting of two components—generic name and specific epithet. F The scientific name is printed in italics or underlined separately when handwritten to indicate their latin origin. F The first word denoting genus starts with a capital letter, while the specific epithet starts with a small letter. F The name of the author or discoverer is written after specific epithet in abbreviation. Example : Mangifera indica Linn., Homo sapiens Linn. F Principle of priority : It is the most important of all rules. If the first name given to the organism is valid in terms of rules, it will be considered as the first preference. Any other valid name given after that will be considered as synonym. Trinomial Nomenclature : It is consist of three components—Generic name + Specific epithet + Subspecies (for animal)/ Variety (for plants). International Code of Nomenclature Scientific names have been standardised by the sets of rules and recommendations like. F ICBN : International Code of Botanical Nomenclature (1961). F ICZN : International Code of Zoological Nomen- clature (1964). F ICNB : International Code of Nomenclature of Bacteria. F ICNCP : International Code of Nomenclature for Cultivated Plants. F ICTV : International Committee for the Taxonomy of Viruses. F ICVCN : International Code of Virus Classification and Nomenclature. TAXON ( )pl : taxa Each category, referred to as a unit of classification, in fact, represents a rank and is termed as taxon. e.g., Animals (Kingdom-Animalia) mammals (Class- Mammalia) and Dog (Species—Canis familiaris) represents taxa at different levels. TAXONOMIC HIERARCHY It is the arrangement of different categories either in ascending or descending order. The taxonomic groups/categories are distinct biological entities and not merely morphological aggregates. We have seven obligate categories-Species, Genus, Family, Order, Class, Phylum (w.r.t animals)/Division (w.r.t plants) and kingdom. Species F Taxonomic studies consider a group of individual organisms with fundamental similarities as a species. It is the basic/lowest category of classification (w.r.t seven obligate categories). The term ‘species’ was given by John Ray. F One should be able to distinguish one species from the other closely related species based on the distinct morphological differences. Let us consider Mangifera indica, Solanum tuberosum (potato) and Panthera leo (lion). All the three names, indica, tuberosum and leo, represent the specific epithets, while the first words Mangifera, Solanum and Panthera are genera and represents another higher level of taxon or category. F Biological Concept of Species (a) Given by Ernst Mayr, “The Darwin of 20 th century”. (b) According to him, species is a group of organisms which: (i) are closely related—structurally and functionally. (ii) shares a common gene pool. (iii) can interbreed freely in nature and produce fertile offsprings. (iv) are reproductively isolated from other species. 2 Crash Course Biology for NEET Kingdom Phylum/Division Class Order Family Genus Species 1. Number of similar character decreases i.e., specificity decreases 2. Species diversity increases 1. Number of similar character increases i.e., specificity increases 2. Species diversity decreases
Genus It is a group of related species. Example : Potato, brinjal and makoi belong to the same genus Solanum. Family It is a group of related genera. Example : Genera Solanum, Artopa, Petunia, Datura belong to the family Solanaceae. Order It is a group of related families. Example : Families Convolvulaceae and Solanaceae belong to order Polymoniales. Class It is a group of related orders. Example : Orders like Sapindales and Polymoniales are included under class Dicotyledonae. Division (for Plants) or Phylum (for Animals) It is a group of related classes. Example : The classes Dicotyledonae and Monocotyledonae belong to the division Magnoliophyta (Angiospermae). Kingdom It is the highest category in taxonomical hierarchy with related divisions/phyla. Example : All plants belong to the plant kingdom (Plantae). All animals belong to the animal kingdom (Animalia). The Living World 3