Living World {Class 11th Biology}

Chapter: Living World
Unit: Diversity in Living Organisms

Class: 11th Biology

Presented By: Dr. Priyanka Patade

What is Living?

Characteristics of living organisms

⏩ Growth ⏪

⏩ Reproduction, Self-replication and self-organization ⏪

⏩ Response to stimuli or external environment ⏪

⏩ Show Homeostasis ⏪

(Regulation of the internal environment to maintain a constant state)

⏩ Cellular Organization ⏪

(all organisms are made of one or more cells- the basic unit of life)

⏩ Metabolism ⏪

(Sum total of all chemical reactions within a living cell)

⏩ Interactions with other cells and living organisms ⏪

⏩ Heredity ⏪

⏩ Show Adaptation ⏪

⏩ Evolve ⏪

Characteristics of life

According to one definition, living organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve.

The main characteristics of living are

⏩ Growth ⏪

⏩ Reproduction ⏪

⏩ Metabolism ⏪

⏩ Cellular organization ⏪

⏩ Consciousness ⏪

Growth

Overall increase in mass or size of tissue or organism or its parts is called 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

1) Intrinsic Growth: Growth from inside of the body of living organism. This is the defining property of life.

2) Extrinsic Growth: Growth from outside of the body of the organism. Like accumulation of mass on any body surface . Non-living exhibits this type of growth.

Reproduction

It is the ability to produce new individual organisms of same kind.

Non-living things do not have the property of replicating or reproducing themselves.

Occurs either sexually or asexually.

Asexual reproduction is a feature of lower organisms.

Sexual reproduction is commonly observed in higher plants and animals.

Many organisms, however, do not reproduce. For example, mules, sterile worker bees, infertile human couples, etc.

Therefore, reproduction is a characteristic of living organisms, but this cannot be taken as a defining property of living organisms.

Metabolism

Metabolism is defined as the sum total of all the chemical reactions occurring in an organism.

Two types: anabolism and catabolism.

Non-living objects never exhibit metabolism.

Metabolic reactions, however, can be carried out in vitro in cell-free systems in a laboratory (a metabolic reaction carried out in a test tube is neither living nor non-living, it’s just a reaction).

Metabolism is a defining feature of all living organisms.

Cellular Organization

All living organisms are made of CELLS.

A cell is the smallest basic unit of life, which can perform life processes independently.

No such organization is seen in non-living objects.

Therefore, cellular organization is also considered a defining characteristic of living organism.

Consciousness

It is the ability to sense their surroundings or environment and respond to these environmental stimuli (physical, chemical or biological).

Also known as sensitivity.

All organisms, therefore, are conscious, i.e., ‘aware’ of their surroundings.

Human beings (Homo sapiens) is the only species aware of itself (self- consciousness).

Consciousness is the defining property of living organisms.

Patients lying in coma in hospitals: no self-consciousness, not non-living as many organs or parts are showing all features of being living.

“Living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli. - All living organisms (present, past and future) are linked to each other through a common genetic material.”

Questions

1. Define biology. Which are the different branches of Biology?

2. What are the different characteristics of living organisms?

3. How will you define living organisms? Which are the defining properties of living organisms?

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Diversity in The Living World

Biodiversity refers to the number and variety of organisms (plants, animals, fungi, protists and monerans) on the planet earth.

According to IUCN (International Union of Conservation of Nature and Natural Resources), till now, 1.7-1.8 million species of different organisms have been described. Yet millions of unknown organisms are to be identified.

These organisms are distributed over a wide range of habitat including dense forest, thermal vents, dry deserts, hot springs, frost, etc.

The number of organisms are higher in dense forests.

Different plants and animals are known by their local names, which vary from place to place.

Hence, a need was realized for naming organisms by the same name all over the world.

Biodiversity - The diverse form of organisms present on earth is called biodiversity.

Nomenclature – It is a system of naming of organisms.

There are millions of plants and animals in the world.

Plants and animals are known in the local area by their local names.

These local names are vary from place to place, region to region and within a country also.

So, it is 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.

Identification - Identification is the process of assigning a pre-existing taxon name to an individual organism.

ICBN - International Code for Botanical Nomenclature.

ICZN - International Code for Zoological Nomenclature.

Classification – It is the process of grouping of organisms into categories based on easily observable characters.

Taxon - The scientific term for any unit used in the science of biological classification is called taxon.

Taxonomy - Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups.

Carolus Linnaeus is regarded as the father of taxonomy.

Bionomial Nomenclature

Bionomial nomenclature is a system of naming species by giving each a name composed of two components, generic name and species name.

Carolous Linnaeus invented the modern system of binomial nomenclature.

Carolous Linnaeus

Rules of Nomenclature

1. Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin.

2. The first word in a biological name represents the genus while the second component denotes the specific epithet.

3. Both the words in a biological name, when handwritten, are separately underlined, or printed in italics to indicate their Latin origin.

4. The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter. It can be illustrated with the example of Mangifera indica.

Name of the author appears after the specific epithet, i.e., at the end of the biological name and is written in an abbreviated form, e.g., Mangifera indica Linn. It indicates that this species was first described by Linnaeus.

Taxonomy

All living organisms can be classified into different taxa. The process is known as taxonomy (process of classification of organisms based on their characteristics).

Basis of modern taxonomy: internal and external structure, cell structure, development, and ecological information of organism.

The characterization, identification, classification and nomenclature are the processes that are basic to taxonomy.

In modern times, relationships between organisms are also studied in addition to their diversity and individual studies.

This is referred as systematics: deals with characterization, identification, classification and nomenclature of organisms based on their diversities and evolutionary relationships among themselves.

Systematics

The word systematics is derived from the Latin word ‘systema’ means systematic arrangement of organisms.

Systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time.

Linnaeus used Systema Naturae as the title of his publication.

TAXONOMIC CATEGORY

Classification involves hierarchy of steps where each step represents a rank or category.

Various steps of the classification hierarchy are called taxonomic categories.

Each level in the hierarchy represents an increase in organisational complexity.

SPECIES

Species are a group of similar organisms which can interbreed freely among themselves to produce fertile offspring.

Share common characteristics.

Two closely related species have distinct morphological difference.

Examples, Mangifera indica, Solanum tuberosum (potato) and Panthera leo (lion).

Indica, tuberosum and leo are specific epithets.

⏫

GENUS

A group of related species which has more characters in common in comparison to species of other genera.

Aggregates of closely related species, e.g., potato, tomato and brinjal are three different species (tuberosum, lycopersicum, melongena respectively) but all belong to the genus Solanum.

Lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) with several common features, are all species of the genus Panthera.

Panthera genus differs from Felis including cats.

⏫

FAMILY

A group of related genera with considerable number of similarities but lesser than the genus and species.

In plants, families are characterised on the basis of both vegetative and reproductive features, for example, three different genera Solanum, Petunia and Datura are placed in the family Solanaceae.

Among animals for example, genus Panthera, comprising lion, tiger, leopard is put along with genus, Felis (cats) in the family Felidae.

⏫

ORDER

Order is an assemblage of families which exhibit a few similar characters.

The similar characters, however, are less in number as compared to different genera included in a family.

Plant families like Convolvulaceae, Solanaceae are included in the order Polymoniales mainly based on the floral characters.

The animal order, Carnivora, includes families like Felidae and Cancidae.

⏫

CLASS

This category includes related orders.

For example, order Primata comprising monkey, gorilla and gibbon is placed in class Mammalia along with order Carnivora that includes animals like tiger, cat and dog.

Class Dicotyledonae includes order polymoniales and sapindales (mango).

⏫

PHYLUM

This category includes classes with few similarities.

Phylum Chordata includes classes fish, amphibia, reptilia, aves and mammalia (because of common feature: presence of notochord and dorsal hollow neural system).

Division Angiospermae includes class dicotyledonae and monocotyledonae.

⏫

KINGDOM

Highest category of taxonomy.

Animals in kingdom Animalia.

Plants in kingdom Plantae.

Lower the taxa, more are the characteristics that the members within the taxon share. (the number of similar characters decreases as we go higher from species to kingdom taxa).

Higher the category, greater is the difficulty of determining the relationship to other taxa at the same level.

Taxonomical aids

HERBARIUM

It’s is a store house of collected plant specimens that are dried, pressed and preserved on sheets (or collection of preserved plant specimens and associated data used for scientific study).

Label at the base on the sheet for providing information about: date and place of collection, English, local and botanical names, family, collector’s name, etc.

Specimens are mounted on sheets of standard size herbarium paper 42 cm x 29 cm.

Important Herbaria of the World*

Royal Botanical Garden, Kew (England)

British Museum of natural History (BM)

Central National Herbarium, Calcutta (CAL)

Herbarium of forest Research Institute, Dehradun (DD)

Herbarium of NBRI, Lucknow

Click HERE for expanded image

BOTANICAL GARDENS

Specialized gardens, where living plants are grown for scientific studies (taxonomic) or reference.

Each plant is well-labelled indicating its botanical/scientific name and its family.

Famous Botanical Gardens*

Royal Botanical Garden, Kew (England)

Indian Botanical Garden, Howrah (India)

National Botanical Research Institute, Lucknow (India)

Lloyd Botanical Garden, Darjeeling (India)

ZOOLOGICAL PARKS

Specialized places where living animals are kept in protected environments under human care. Example: National Zoological Park (Delhi).

All animals in a zoo are provided, as far as possible, the conditions similar to their natural habitats.

MUSEUMS

Set up for educational purposes primarily.

Have collections of preserved plant and animal specimens for study and reference.

Specimens are preserved in the containers or jars in preservative solutions.

Dry specimens of plants and animals are also preserved.

Insects are preserved in insect boxes after collecting, killing and pinning.

Larger animals like birds and mammals are usually stuffed and then preserved.

Skeletons of animals are also reserved.

Information as labels are provided along with all specimens in the museums.

Example: National Museum of Natural History (NMNH) in Delhi.

KEY

Key is another taxonomical aid used for identification of plants and animals based on the similarities and dissimilarities (or a device used by biologists for identifying unknown organisms).

Keys are generally analytical in nature. They are based on the contrasting characters generally in a pair called couplet: two opposite options from which a choice is made. Thus one is accepted and the other is rejected.

Each statement in the key is called a lead.

Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes.

OTHER TAXONOMICAL AIDS

Flora, manuals, monographs and catalogues:

Flora is the account (habitat and distribution) of plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life.

Manual contains listing and description of the plant species found in an area. This is not necessarily exhaustive and is usually user defined.

Monograph contains systematic study of a particular taxonomic group (one taxon).

Catalogue is simply a listing of all species organized alphabetically.