Chapter Notes: The Living World - Class 11 Biology Notes
Topics in the Chapter
• Introduction
• What is ‘Living’?
• Diversity in the Living World
• Taxonomic Categories
• Taxonomical Aids
Revise These Term
1. Diversity : Large variety of anything.
2. Biodiversity : Large variety of organisms.
3. Nomenclature: Scientific naming of organisms.
4. Identification : Correct description of organism prior to nomenclature.
5. Classification : Grouping of organisms in to categories on the basis of similarities & differences.
6. Taxon : Concrete biological object or category of classification.
1. Taxonomy : Process of classification of organisms.
2. Systematics : branch of biology dealing with taxonomy along with evolutionary relationship between organisms.
3. Species : Group of Individual organisms with fundamental
similarities (with capacity if sexually reproducing).
What is Living?
The main characteristics of living are:
(i) Growth
(ii) Reproduction
(iii) Metabolism
(iv) Cellular organization
(v) Consciousness
→ Those characteristics which have no exception is called defining property of life.
→ Growth and Reproduction are not the defining property of life as well as metabolism, cellular organization, consciousness is the defining property of life.
(i) Growth
→ Overall increase in mass or size of tissue or organism or its parts is called growth.
→ Increase in mass and increase in number are the twin characteristics of growth. This is an irreversible permanent increase in size of the organ or its part or even of an individual cell.
→ Growth is of two types:
• Intrinsic growth: Growth from inside of the body of living organism. This is the defining property of life.
• Extrinsic growth: Growth from outside of the body of the organism. Like accumulation of material on any body surface . Non-living exhibits this type of growth.
→ Intrinsic Growth is of two types:
• Indeterminate growth\Unlimited growth: Growth which occurs continuously throughout their life span. It occurs only in plants.
• Determinate growth\ limited growth: Growth which occurs only up to certain age. It occurs only in animals. Cell division occurs only in certain tissues to replace lost cells.
(ii) Reproduction
→ Production of new individual or progeny is called as reproduction.
→ Reproduction in case of multicellular organism is production of progeny possessing features more or less similar to those of parents.
→ Reproduction in case of unicellular organism like bacteria, unicellular algae or amoeba is increaser in number of cell. Means in unicellular organism the growth and reproduction are synonyms or same.
→ Reproduction is not found in any nonliving object. There are many living organism which can\do not reproduce like mules, sterile human couples, worker bees. This is also not taken as defining property of life.
→ Reproduction is of two types:
• Asexual reproduction: Reproduction in which fertilization or gametic fusion and meiosis is not involved is called asexual reproduction.
(a) By Asexual spores: In algae and fungi.
(b) By Budding: In Yeast and Hydra.
(c) By Fragmentation: In filamentous Algae, Fungi and Protonema of moss plants.
(d) By True Regeneration: Fragmented organism regenerate the lost parts of its body and becomes a new organism i.e. Planaria.
→ Regeneration is a process in which only lost part of the body is repaired or regenerated. Ex: Star fish, Lizards.
• Sexual Reproduction: Reproduction in which gametes are formed by meiosis and fertilization takes place to form progeny is called as sexual reproduction.
(iii) Metabolism
→ The sum total of all the chemical reaction occurring in our body is metabolism.
-It is defining property of living beings.
→ All organism, both unicellular as well as multicellular exhibit metabolism. No nonliving objects show metabolism.
→ It is the defining property of life.
→ The isolated metabolic reaction outside the body of an organism, performed in a test tube (in vitro) is neither living nor living. These isolated reactions cannot be regarded as living things, but they are definitely living reactions because they are similar to the reaction performing in our body.
→ All plants, animals, fungi, and microbes exhibit metabolism.
(iv) Cellular organization
→ Cell is the basis unit of life. All organisms are composed of cells.
→ Some are composed of single cell and are called as unicellular organism while other are composed of many cells, are called multicellular organism.
→ Unicellular organism is capable of independent existence and performing essential functions of life. Anything less than a complete structure of a cell, does not ensure independent living.
→ Cell is the fundamental structure and functional structural and functional unit of all living organism. This is the defining property of life.
Consciousness
Ability to sense the surrounding environment and respond to these environment stimuli is called as consciousness. This is the most obvious and technically complicated features of all living organism. We sense these physical, chemical or biological stimuli through our sense organs. Plants also sense and respond to external factors like light, water, temperature, other organism, pollutants etc. All organisms from the prokaryotes to complex eukaryote show consciousness to environmental clues. Some common examples of consciousness can be seen in organism, like plants performs flowing in a particular seasons (photoperiodism), Some animals perform breeding in a particular season only (seasonal breeders), and all organism handle the chemicals entering their bodies etc. When human is concerned a very well developed nervous system and supreme level of skill of communication which is called as self-consciousness. Human is very fast to respond towards the external stimuli and even it can think or predict about possible changes of surrounding so it can prepare itself according to the surrounding situations. Further human can even change its surrounding situation up to a limit so this topmost or climax level of consciousness is regarded as self-consciousness, which cannot be seen elsewhere. Self –consciousness is thought to be present only in human. The brain dead coma patient who is supported who is supported by machines which replace heart and lungs also has consciousness so it is living but it does not has self-consciousness because it has lost the co-ordination of organs of different body parts. Means all the living phenomena are due to underlying interactions between different component of an individual or organ or tissue or cell. Living organism is self-replicating and self-regulating interactive system capable of responding to external stimuli. Adaptations and homeostasis are also very important characters of living.
DIVERSITY IN THE IVING WORLD:
Earth provides the physical base for living beings. There are millions of varieties of living organisms in the world around us. There are also many organisms that we cannot see with our naked eye around us. They are found in varied habitats like mountains, oceans, forests, lakes, deserts and even hot water springs. Number of species identified and studied is 1.7-1.8 million.
All organisms which live on earth together make up the natural diversity of life in the world. This natural diversity of life on earth is generally called biological diversity or biodiversity.
Taxonomy: The systematic arrangement of organisms that includes characterization, identification, nomenclature, and classification of organisms is called taxonomy. Systematics is a branch of science that deals with identification, nomenclature, classification and evolutionary history of an organism. Thus systematics includes evolutionary history along with taxonomic characteristics of an organism. Systematics is as old as human civilization. The term taxonomy was first introduced by A.P de Candolle in 1813.
Systematics (Latin ‘systema’) means systematic arrangement of organisms.
Systema Naturae is the book written by Linnaeus.
Neosystematics is a concept of systematics that considers a species to be the product of evolution. This concept was developed by Julia Huxley in 1940.It takes into consideration all the known characteristics of organisms and all the known evidences from different fields of biology.
Identification: is to determine the exact place or position of an organism in the set plan of classification. It is carried out with the help of taxonomic keys.
Classification: It is the placing of an organism or a group of organisms in category according to a particular system and in conformity with a nomenclature system.
Characterization: The understanding of characters of organisms like external and internal structure (morphology and anatomy), the structure of the cell (cytology), developmental process (embryology) and ecological information (ecology) of organism.
Nomenclature (naming): The naming of living organisms is called nomenclature. The names are of two
types-vernacular (common names) and scientific names.
Local names-Locally used names are called as local names. Local names are in local languages or common language. Local names are easy to use by local people, but these local names cannot be used by biologists due to the following draw backs.
- 1. A single local name is often used for many species.
- 2. The local names sometimes lead incorrect meaning about the organism.
- 3. Different local names are used to recognize an organism in different regions of country or world. These
local names also vary with the language.
Scientific names: These are the names given to the organisms by biologists based on agreed principle and
criteria. These are acceptable all over the world. To accomplish this, certain international codes have been
established.
These codes are
- ICBN-International Code of Botanical Nomenclature
- ICZN-International Code of Zoological Nomenclature
- ICVN-International Code of Viral Nomenclature
ICBN/ICNB-International Code for Bacteriological Nomenclature or Nomenclature of Bacteria
BINOMIAL NOMENCLATURE:
Carolus Linnaeus used this nomenclature system for the first time and proposed scientific name of all the plants and animals. He is the founder of binomial system.
Linnaeus proposed scientific name of plants in his book” Species plantarum”
In binomial nomenclature, each scientific name has two components-generic name (genus) and specific name (species) E.g., Mangifera indica Linn. Mangifera is the genus name and indica is the species name. Linn indicates that this species was first described by Linnaeus
Who can give scientific names: Any one can study, describe, identify and give name to an organism provided certain universal rules are followed.
Rules:
- A scientific name generally has two components (words) in Latin or derived from Latin irrespective of their origin.
- First word of the biological name denotes the genus name where as the second one denotes for species.
- Names are printed in italics or when hand written they are separately underlined to indicate their Latin origin.
- Genus name starts with capital letter and specific name starts with small letter.
- The name of the author is written in an abbreviated form after the species name and it is printed in Roman.
- Each taxonomic group can have only one correct name.
- The name should be short, precise and easy to pronounce.
Eg: Mangifera indica- Mangifera is the genus name and indica is the species name.
Taxonomic categories :
-Each rank or category of classification is termed as taxonomic category.
-Arrangement of categories in sequence is termed as Taxonomic Hierarchy.
Species: Group of organisms with fundamental similarities. eg. Mangiferaindica
In this species is indica.
Genus: Group of realated specieswith common characters.
eg. Panthera is a genus which includes lion(Pantheraleo),leopard(Pantherapardus) & Tiger (Pantheratigris).
Family: Group of realated genera .
eg. Genus Solanum,Petunia&Datura belong to one family Solanaceae.
Order : Group of related families.
eg. FamaliesConvolvulaceae,Solanaceae belong to one order- Polymoniales.
Class : Group of related orders.
eg. Order Primata&Carnivora belong to one class Mammalia.
Phylum: Group of related classes.
eg. Class Mammalia, Pisces,Amphibia,Reptilia belong to one phylum -Chordata.
Kingdom: Group of all related Phyla.
eg. Kingdom Animalia-includes all animals.
Taxonomical Aids
-Articles helpful in correct identification & classification of organisms are called taxonomical aids.
1-Herbarium:
1.Store house of collected plant specimens that are dried, pressed & preserved on sheets.
-Sheets are arranged according to universally accepted classification system.
-used as ready reference in scientific studies.
2. Botanical Gardens :
Collection of various living plant species in form of gardenfor identification purpose
-Used for identification of plants.
-Example: Royal Botanical Garden at Kew, England, Indian Botanical Garden Howrah, National Botanical Research Institute Lucknow etc.
3-Museum :
-Collection of preserved plant &animal specimens.
-Specimens may be preserved in preservative solutions viz.Formalin (40%).
-Specimens may also be preserved as dry specimenseg. Insects and stuffed large animals.
-Skeleton of animals may be also as museum specimen.
-Used as actual material for study and identification.
Zoological Parks:
Place where wild animals are kept in protected environment under human care . eg. Alipur zoo, Kolkata, West Bengal
National Zoological Park of New Delhi
1. Used as aid to learn about food habits and behaviour, Life cycle.
Key :
Taxonomical aid based on contrasting characters called as couplet
1. Couplet has two opposite statements, each called lead.
2. Separate keys for separate taxonomic categories needed.
3. Used to classify organism.
Flora :
Actual account of habitat & distribution of plant species in an area.
Manual :
•Have description of species in an area.
• Used for getting information foridentification of names.
Monograph :
1. Has information of any one taxon.
2. Used for classification purpose.
Biology Class 11th Chapter ~1 The Living World Question and Answers
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