01/04/2023
Monday
BIOLOGY
CHAPTER 1: the living world
TOPICS
• INTRODUCTION
• CHARACTERISTICS OF LIVING BEINGS
the living world
Characteristics of
living beings
 Growth
 Reproduction
 Metabolism
 Cellular
organisation
 Respond to
stimuli
(consciousness)
Diversity in
living world
 Biodiversity
 Binomial
nomenclature
 Classification
 Identification
 Taxonomy
 Systematics
Taxonomic
categories
 Taxa
 Taxonomic
hierarchy
 Species
Taxonomical aids
 Herbarium
 Botanical
gardens
 Family
 Museum
 Zoological
Parks
 Order
 Key
 Genus
 Class
 Phylum /
Division
 Kingdom
DARWIN OF THE 20TH CENTURY- Ernst Mayr
CONTRIBUTION:
 Proposed the Biological Species Concept.
 “A species is not just a group of morphologically
similar individuals, but a group that can breed only
among themselves, excluding all others.”
Ernst Mayr
(1904- 2004)
DEFINE LIFE:
 Both living and non living things are made of chemical compounds(matter).
 But only some matter has the property of life.
 So, what is life?
 Life is a unique, complex organization of molecules expressing itself through
chemical reactions which lead to growth, development, responsiveness, adaptation
and reproduction.
CHARACTERISTICS OF LIVING BEINGS
What is living ?
Living things typically show the following features:
 Growth
 Reproduction
 Metabolism
 Ability to sense environment and respond
 Self replicate, self organise and interact
a. GROWTH:

What is growth?
Increase in mass and number of individuals.
 What are the twin characteristics of growth?
Mass and number
 Why mass and number are called twin characteristics of growth?
Increase in body mass (by cell division) and increase in number of individuals by
reproduction are considered as twin characteristics of growth.
 How multicellular organism grow?
cell division (increase in mass)
Plants: cell division occurs throughout life span
Animals: grows only up to a certain age. But some tissues can replace damaged cells.
This is called regeneration.
 How unicellular organisms grow?
Cell division
INCREASE IN NUMBER OF INDIVIDUALS
bacterial colony on microscope
 In living organisms growth is from inside. Justify this statement.
If we consider increase in mass as a criterion for growth, then mass of non
living things also increases.
For instance, mountains, sand mounds also “grow.”
But this is simply the accumulation of materials on the surface.
However, in living organisms growth is from inside as the result of cell
division.
 Why growth cannot be taken as a defining property of living organisms?
Conditions have to be explained.
Thus, a dead organism does not grow.
b. REPRODUCTION:
REPRODUCTION IN MULTICELLULAR ORGANISM
 Sexual and asexual
 Modes of Asexual Reproduction
 Asexual spores- Fungi
 Budding- Yeast, Hydra
 True regeneration- Planaria
 Fragmentation- Filamentous algae, protonema of mosses
 Asexual spores of fungi
Budding in Hydra
Budding in Yeast
 True regeneration in Planaria
Fragmentation- Filamentous algae
Fragmentation- protonema of mosses
REPRODUCTION IN UNICELLULAR ORGANISM





Cell division- binary fission
Increase in number of cells= reproduction
Thus growth and reproduction are synonymous
E.g. bacteria, amoeba
Sometimes bacteria reproduce sexually
Binary fission in bacterium
Binary fission in amoeba
Why reproduction cannot be taken as a defining property of living organisms?
 Some organisms do not reproduce
 Mules, worker bees
 Non living objects replicate or reproduce by itself.
c. METABOLISM
 What is metabolism?
Sum total of all the chemical reactions occurring in
our body.
Anabolism + Catabolism = Metabolism
Anabolism- formation of biomolecules (glycogen)
Catabolism- breaking up of biomolecules
(TCA cycle)
Only living organisms perform metabolic reactions.
Non living things do not perform metabolic reactions.
If only living things can perform metabolic reactions then
how experiments can be conducted in in-vitro conditions?
In in vitro conditions metabolic reactions are carried out.
E.g.: PCR
Such reactions are carried out in cell free systems.
These isolated metabolic reactions outside body of organisms are neither living
nor non living but living reactions.
Metabolism is the defining feature of all living forms but, isolated metabolic
reactions are not living things but living reactions.
02/04/2023
Tuesday
BIOLOGY
CHAPTER 1: the living world
TOPICS
• CHARACTERISTICS OF LIVING BEINGS
• DIVERSITY IN LIVING WORLD
d. CELLULAR ORGANISATION
 Organisms are typically made up of cells.
 They also follow an organization of cells followed by
tissues which form organs and in turn again combine
to form the organ system.
 Organ systems together form an organism.
 This kind of cellular organization is absent in
nonliving beings.
 A few examples are nerve cells, muscles, tissue, etc.
 Hence, cellular organisation is the defining feature of
life forms
e. ABILITY TO SENSE ENVIRONMENT AND RESPOND
 All living organisms sense their environment
 They respond to stimuli
 Plants: light, water, temperature, pollutants, pests.
 Photoperiodism affects reproduction in seasonal breeders.
 Animals: sense organs.
 All organisms are aware of their surroundings.
 Human has self consciousness “aware of themselves.”
 Thus consciousness becomes the defining property of living organisms.
 What about coma patients?
They have no self consciousness. They are brain dead
f. SELF REPLICATE, SELF ORGANISE AND INTERACT
 Living phenomena are due to underlying interactions.
 All living organism are self replicating, evolving, self regulating interactive
systems capable of responding to external stimuli.
DIVERSITY IN LIVING WORLD
Diversity- വൈൈിധ്യം
BIODIVERSITY- number and types of organisms present on earth.
1.8 million organisms are identified and described so far.
Why scientific names are required?
Each species has different names around the world e.g.; papaya.
Therefore a standard name must be given for an organism.
Scientific name ensures that each organism has only one name.
NOMENCLATURE:
The system of providing organisms with appropriate and distinct
names is called nomenclature.
IDENTIFICATION:
The process of determining that a particular (organism) belongs to a
recognized taxon. In order to name an organism it has to be identified
first.
There are certain rules and procedures in naming organisms:
a. ICBN (International Code of Botanical Nomenclature)- plants
b. ICZN (International Code of Zoological Nomenclature)- animals
BINOMIAL NOMENCLATURE
 Developed by Carolus Linnaeus
 Each name has two components- generic name and specific epithet
 Universal rules of nomenclature:
 Handwritten- underline separately.
 Print- italics
 First word represent genus name, first letter capital remaining small
 Second word represent species name, all letters small.
 Name of author appears after specific epithet in abbreviated form
 Scientific name of mango- Mangifera indica Linn.
NEET 2016
CLASSIFICATION
 Grouping organisms into some categories based on observable characters.
TAXONOMY
 It is the science of naming, describing and classifying organisms and
includes all plants, animals and microorganisms of the world.
 Taxonomy– “taxis” (arrangement or division) and “nomos” (method).
 It includes classification, identification and nomenclature.
SYSTEMATICS
 The branch of study of organism concerned with the evolution of organisms'
relationships.
 Systema- systematic arrangement of organisms.
Criteria
Definition
Function
Taxonomy
Systematics
Taxonomy is the study of identification,
Systematics is the study of diversity
description, naming and classification of
and evolutionary relationships of
organisms.
organisms through time.
It helps in the naming and identification
of an organism.
It gives evolutionary relationships,
classifications, cladistics and
phylogeny of an organism.
Evolutionary History
Environmental Conditions
Change with Time
Importance
Evolutionary history of the organism is
not studied.
Evolutionary history of the
organism is studied.
Environmental conditions do not directly
affect taxonomic studies.
Environmental conditions directly
affect the study of systematics.
It can change with time.
It does not change with time.
It helps in easy identification of a species
and thus facilitates easy communication
of biological information.
it provides a layout for all
taxonomic functions.
03/04/2023
Wednesday
BIOLOGY
CHAPTER 1: the living world
TOPICS
• Taxonomic categories
• Taxonomical aids
TAXONOMIC CATEGORIES
 TAXA
 A taxon (plural taxa) is a unit of classification.
 Any unit used in the science of biological classification, or taxonomy.
 The examples of taxa at different hierarchical levels are species, followed by
genus, family, order, class, phylum (in animals) or division (in plants), and
kingdom, in ascending order.
 Taxa are arranged in a hierarchy from kingdom to subspecies.
 TAXONOMIC HIERARCHY
 Is the process of arranging various
organisms into successive levels of the
biological classification either in a
decreasing or an increasing order from
kingdom to species and vice versa.
 Each of this level of the hierarchy is
called the taxonomic category or rank.
Following are the important taxonomic hierarchies in which different organisms are
classified.
 SPECIES
• It is the lowest level of taxonomic hierarchy.
• It refers to a group of organisms that are similar in shape, form, reproductive
features.
• Mangifera indica, Solanum tuberosum, Panthera leo, Homo sapiens sapiens
• Species can be further divided into sub-species.
 GENUS
• A group of similar species forms a genus.
• Some genera have only one species and is known as
monotypic, whereas, some have more than one species and is
known as polytypic.
• For eg., lion and tiger are placed under the genus Panthera.
• Potato and brinjal belong to genus Solanum
 FAMILY
• This category of taxonomic hierarchy
includes various genera that share a
few similarities.
• For eg., the Felidae (cat, lion, tiger).
 ORDER
• Order is a more specific rank than class.
The order constitutes one or more than
one similar families.
• There are around 26 orders in class
Mammalia such as primates, carnivora,
etc.
• Largest order is Coleoptera of class
Insecta.
CLASS
• Related orders
• Order primata monkey,
(gorilla, gibbon, modern
man), order Rodentia etc.
in class Mammalia.
PHYLUM/ DIVISION
• This is the next higher level of classification and is more specific than the
kingdom.
• Related classes
• There are 35 phyla in kingdom Animalia.
• For Example – Porifera, Chordata, Arthropoda, etc.
KINGDOM
• The kingdom is the highest level of classification.
• Different phyla give rise to kingdom.
• There are 5 kingdoms in which the living organisms are classified, namely,
Animalia, Plantae, Fungi, Protista, and Monera.
Common
name
Biological
name
Genus
Family
Order
Class
Phylum/
division
Man
Homo sapiens
Homo
Hominidae
Primata
Mammalia
Chordata
Housefly
Musca domestica Musca
Muscidae
Diptera
Insecta
Arthropoda
Mango
Mangifera
indica
Mangifera
Anacardiaceae
Sapindales
Dicotyledonae
Angiospermae
Wheat
Triticum
aestivum
Triticum
Poaceae
Poales
Monocotyledonae
Angiospermae
TAXONOMICAL AIDS
 Collections of samples or preserved organisms which help in extensive research
for the identification of various taxonomical hierarchy.
 Some taxonomical aids which provide specimens for such intensive studies are:
HERBARIUM
 It is a store that houses a collection of preserved
plant species.
 Plant specimens are preserved in forms of
herbarium sheets which are prepared by drying,
pressing and preserving the samples on sheets.
 These sheets are then arranged in their order of
classification in the taxonomic hierarchy.
 These herbarium sheets carry all the information
about the respective specimen.
BOTANICAL GARDEN
 These are gardens in which specific plants are grown and are labelled according
to their taxonomy.
 Thus, the labels carry their scientific names and family.
 The main purpose of botanical gardens is to identify the plant species under
consideration.
 Live plant species
 Grown for identification
 National Botanical Research Institute, Lucknow
 Indian Botanical Garden, Howrah
MUSEUM
 Biological museums are found in schools and colleges; like the biology laboratory
that we find in our schools.
 In these museums, plants and animal species are preserved in jars and containers with
the help of appropriate preservatives.
 They may also be dried and preserved.
 Birds and larger animals are usually stuffed before preserving and insects are killed
and pinned in the insect boxes.
 We sometimes find skeletons of various animals too.
ZOOLOGICAL PARK
 Zoological park is a place where various living animals are kept within
enclosures, displayed to public and may be used for study.
 Enable us to learn about their food habits and behavior.
 For example, Alipore zoological gardens, Kolkata.
 KEY
 This is a taxonomical aid where plants and animals are recognized based on
contrasting characteristics known as keys.
 Couplet- Two contrasting keys are generally kept as a pair, thus leading to
acceptance of one and rejection of another.
 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.
 Analytical in nature.
FLORA, MANUALS, MONOGRAPHS AND CATALOGUES
 Means of recording descriptions.
 Helps in identification.
 Flora: habitat and distribution of plants of a given area
 Manuals: information for identifying names of species.
 Monographs: information on any one taxon.
 Catalogues: booklets or registers that include a list of all species found in a
specific location or area (organized in a specific order, usually alphabetically)
FLORA
MANUAL
MONOGRAPH
CATALOGUE
LET US REVISE
Characteristics of
living beings
 Growth
 Reproduction
 Metabolism
 Cellular
organisation
 Respond to
stimuli
(consciousness)
the living world
Diversity in
living world
 Biodiversity
 Binomial
nomenclature
 Classification
 Identification
 Taxonomy
 Systematics
Taxonomic
categories
 Taxa
 Taxonomic
hierarchy
 Species
 Genus
 Family
 Order
 Class
 Phylum /
Division
 Kingdom
Taxonomical aids
 Herbarium
 Botanical
gardens
 Museum
 Zoological
Parks
 Key
 Flora,
Manuals,
Monographs
Catalogues