Biology Class Eleven  

Living Beings

Characteristics of Living Beings

Growth: Growth is an important feature of living beings. Growth can be seen in some non-living things; like a cloud. But the growth in non-living things happens because of accumulation of matter from outside. On the other hand, the growth in a living being happens because of internal processes, i.e. cell division. Most of the plants show indeterminate growth, while the growth in animals is definite.

Reproduction: All living beings produce their offspring through the process of reproduction. Reproduction is important for continuing the lineage of a species. There are two main types of reproduction, viz. sexual and asexual.

Metabolism: The chemicals within a living organism undergo a continuous change. This process is called metabolism. Metabolism is composed of two processes, viz. anabolism and catabolism.

  1. Anabolism: The process of synthesis of any substance is called anabolism, e.g. photosynthesis.
  2. Catabolism: The process of breaking up of a substance is called catabolism, e.g. respiration.

Response to External Stimuli: All living organisms respond to external stimuli. Light, heat, chemicals, other organisms, etc. are examples of external stimuli. Response to external stimuli is important for the survival of an organism.

Nomenclature and Identification:

An organism is known by different names in different languages. It would be impossible for any person to remember the names of an organism in all the languages. Hence, there is need for a uniform system of nomenclature of organisms. A uniform system of nomenclature and identification helps the scientists in systematic study of living beings. ICBN (International Code for Botanical Nomenclature) applies to the plants and ICZN (International Code for Zoological Nomenclature) applies to the animals.

General Rules for Nomenclature:

  • Biological names are usually written in Latin. They are written in italics.
  • A biological name usually contains two terms. The first term shows the genus, while the second term shows the species.
  • Biological name is underlined, when it is handwritten.
  • The first term of the biological name begins with a capital letter. The second and the subsequent terms begin with the small letter.
Taxonomic Categories

Various steps of the classification hierarchy are called taxonomic categories. Each category represents a particular rank and is usually called the taxon.

Species: A group of individuals in which the individuals can interbreed among themselves is called species. Members of a species have a large number of similar characters. For example; all the tigers are called Panthera tigris. Since all of them can interbreed hence, they are kept under one species.

Genus: A group of closely related species is called genus. Example; Lion (Panthera leo), leopard (Panthera pardus) and tiger (Panthera tigris) are members of the genus Panthera. Similarly, potato, tomato and brinjal belong to the genus Solanum.

Family: A group of closely related genera is called a family. For example; potato and chili belong the family Solanaceae. Similarly, the genus Panthera and the genus Felis belong to the family Felidae.

Order: A group of closely related families is called order. For example; Convolvulaceae and Solanaceae are plant families which belong to the order Polymoniales. Similarly, Felidae and Concidae belong the order Carnivora.

Class: The group of closely related orders is called class. For example; orders Primata and Carnivora belong to the class Mammalia.

Phylum: A group of closely related classes is called phylum. In the Plant Kingdom; the term phylum has been replaced with division. For example; pisces, amphibia, reptilia, aves and mammalia belong to the Phylum Chordata.

Kingdom: The group of all the related phyla is called the Kingdom. For example; all autotrophic organisms which are eukaryotic and contain chloroplast are kept under the Plant Kingdom. Similarly, all heterotrophic organisms which are eukaryotic and lack a cell wall are kept under Animal Kingdom.

Living Beings - Class eleven -Biology - NCERT Solution
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