Growth is defined as an increase in mass and an increase in the number of individuals.
Types of Growth:
Intrinsic Growth (Growth from inside):
This type of growth is characteristic of living organisms. It is protoplasmic growth, meaning growth occurs from within the body.
This is considered a defining character of living organisms.
Extrinsic Growth (Growth from outside):
This occurs in non-living things due to the accumulation of material on their surface. Examples include mountains and boulders growing in size due to the deposition of sand or snow.
Since non-living things can also grow by extrinsic means, growth cannot be considered a defining characteristic of living organisms if only extrinsic growth is considered.
Twin Characters of Growth:
Increase in Number (Cell Division):
In Maize root tip cells, they divide to form 17,500 cells per hour.
Increase in Mass (Size):
A cell of a watermelon increases 3,50,000 times its initial size during growth.
Indirect Ways to Measure Protoplasmic Growth:
Number (e.g., Maize: 17,500 cells per hour)
Mass (Size) (e.g., Watermelon cell)
Length (e.g., Pollen tube growth)
Area (e.g., Surface area of a leaf)
These are all measurable aspects of growth.
2. Reproduction
No non-living thing can reproduce.
When we talk about reproduction, we are generally referring to "Sexual Reproduction."
However, a few organisms do not reproduce, such as mules, infertile human couples, or drones (male bees).
Despite not being able to reproduce, these organisms are still considered living.
Therefore, reproduction cannot be considered a defining property of living organisms, as there are exceptions.
Growth and Reproduction in Organisms:
In Unicellular Organisms (Prokaryotes): Growth and Reproduction are mutually inclusive.
This means that in unicellular organisms, the terms 'growth' and 'reproduction' can be used synonymously or interchangeably because growth (increase in cell mass/size) directly leads to reproduction (cell division resulting in new individuals).
In Multicellular Organisms: Growth and Reproduction are mutually exclusive.
This means that growth (increase in body mass/size) and reproduction (producing offspring) are distinct processes and do not necessarily occur simultaneously or depend on each other in the same way as in unicellular organisms.
In Eukaryotes (e.g., Plants): Growth and Reproduction are related but still exclusive.
In plants, vegetative growth (increase in size, leaves, stems) leads to reproductive growth (flowering, seed formation). Reproduction is a step or part of growth, but they do not show the same meaning; both are "exclusive" in the sense that they are distinct biological processes.
Examples of Reproduction (Vegetative or Asexual Reproduction):
Generally, NCERT considers vegetative and asexual reproduction interchangeably, but they still have differences.
Plant body breaks, detaches, and forms a new organism (e.g., Fragmentation in Spirogyra, an algae).
Budding in yeast and Hydra.
Asexual Spores in Fungi.
High power of Regeneration in Planaria (Flatworms).
3. Metabolism
Metabolism is the sum of all chemical reactions occurring in the cells/body of an organism.
This is a Defining Character of Living organisms.
Chemical Reactions in Cell-Free Systems (in vitro):
Chemical reactions may occur in cell-free systems or in vitro (e.g., in a test tube).
Are these chemical reactions in a test tube living? No, they are neither living nor non-living.
They are considered "living reactions" but not "living beings."
For a reaction to be considered a living reaction within a living being, it must occur within a cellular boundary.
Therefore, Cellular Organization is a Defining Property of living organisms because metabolic reactions, to be considered part of a living system, must occur within the organized structure of a cell.
4. Consciousness
Consciousness is the ability of an organism to sense and respond to external stimuli.
An External Stimulus leads to a Response by the living organism. This interaction between the external environment and the organism results in consciousness.
All living creatures are conscious.
Self-Consciousness:
Humans are also "Self-Conscious."
This means humans are conscious of themselves and know that "we are conscious."
A patient in a coma, lying on a bed, is conscious (their organs are interacting with each other and responding to some stimuli, albeit minimally) but not self-conscious.
Consciousness is a defining property of living organisms, and self-consciousness is a unique defining property of humans.
5. Interaction
Cells interact with each other and show "emergent properties" as a Tissue.
Emergent properties are characteristics that arise from the interaction of simpler components and are not present in the individual components themselves. For example, a tissue has properties that individual cells do not possess.
6. Self-Evolution
Living organisms are self-replicating, evolving, and growing systems that interact and respond to external stimuli.
Mind Mapping: Diversity of Living World (Biodiversity)
Biodiversity refers to the number and variety of life forms on Earth.
There are approximately 1.7 to 1.8 million described species.
To study organisms, we need:
Characterization
Identification
Nomenclature
Classification
These are the prerequisites for studying the diversity of life.
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Characterization
→
Identification
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Nomenclature
Taxonomy
Taxonomy is the classification of organisms based on their external structure, internal structure, cell structure, ecological role, and developmental process.
Basic of Taxonomy:
Characterization, Identification, Classification, and Nomenclature are the fundamental basis of Taxonomy.
Systematics
The word "Systematics" originated from "Systema."
It means the systematic arrangement of organisms.
Systematics includes everything from Taxonomy (Characterization, Identification, Classification, and Nomenclature) along with evolutionary relationships of organisms.
Taxonomical Categories
There are 7 basic taxonomical categories in ascending order:
Species
Genus
Family
Order
Class
Phylum/Division (Phylum for animals, Division for plants)
Kingdom
As we move towards the upper rank of the category (from species to kingdom), the common characters among the discussed members are going to decrease.
Binomial Nomenclature
Binomial Nomenclature is a system of naming organisms with two parts.
Species Plantarum (Publishing date: May 1, 1753) - Considered as the starting point of Botanical Nomenclature.
Genera Plantarum
The publishing year of the 10th edition of Systema Naturae (1758) is considered the starting point of Zoological Nomenclature.
Rules of Binomial Nomenclature:
Species name is Binomial: It is made up of two words:
[A] Generic Name (Genus)
[B] Specific Epithet (Species)
Example: Mango's botanical name is Mangifera indica.
Generic Name: Mangifera
Specific Epithet: indica
Name should be in Latin: Latin is a dead language, or it should be Latinized.
For example, Sandalwood is white. So in Latin, "white" is "album." The botanical name is Santalum album.
First letter of Generic name should be Capital.
Specific epithet should be in small letters.
Both names should be underlined separately when handwritten.
When printed, they should be in Italics to show their Latin origin.
Name of the Scientist who described that organism is written at the end.
Example: Mangifera indica Linn, Rosa indica Linn.
Nomenclature Systems:
Presently, the Botanical Nomenclature System is governed by the Rules of ICBN (International Code of Botanical Nomenclature).
Zoological Nomenclature is governed by ICZN (International Code of Zoological Nomenclature).
Trinomial System:
In Botanical Nomenclature, the Trinomial System (three parts: genus, species, sub-species/variety) should be avoided.
In Zoological Nomenclature, the Trinomial System can be accepted.
Example: Homo sapiens sapiens (Cabbage - Sub Species, acceptable in Zoology).
Botanical examples like Brassica oleracea var. capitata (Cabbage) and Brassica oleracea var. botrytis (Cauliflower) are generally not acceptable in Botany for formal binomial naming conventions, though they are used to denote varieties.
Tautonyms:
Tautonyms are names where the generic name and specific epithet are the same.
Tautonyms are not acceptable in Botany.
Tautonyms are agreed upon in Zoological Nomenclature.