biology notes

1. CLASSIFICATION SYSTEM IN
BIOLOGY

2. IMPORTANT TERMS RELATED TO CLASSIFICATION
1. Classification: it is the process of grouping animals and
plants into convenient categories on the basis of certain
traits.
2. Identification : it is determination of correct position of an
organism in the classification.
3. Nomenclature : it is the process of giving scientific name to
the organisms.
4. Systematic : this includes the classification, nomenclature and
identification of organisms based on various parameter.

3. HISTORY OF CLASSIFICATION
• Hippocrates : he classified animals into various groups like insects,
fishes and birds , etc.
• Aristotle : known as father of Zoology/biology. He had written
Historia animalium.
• Threophrastus : known as father of botany.
• A Swedish naturalist named Carolus Linnaeus is considered the
'Father of Taxonomy' because, in the 1700s, he developed a way to
name and organize species that we still use today. His two most
important contributions to taxonomy were:
1) A hierarchical classification system
2) The system of binomial nomenclature

4. ROLE OF NOMENCLATURE
• In binomial nomenclature each scientific name has 2 components :
i) Generic name (Genus)
ii) Specific name (Species)
• The generic name begins with capital letter, whereas the specific
name with small letter.
• Both the generic and specific names are separately underlined (if
handwritten), or given in italic (if printed) to indicate their Latin
origin.
• The first (generic) name is usually a noun, whereas the second
(species) is an adjective.

5. HISTORY AND TYPES OF CLASSIFICATION
1. Artificial system of classification
2. Natural system classification
3. Numerical taxonomy/Quantitative taxonomy
4. Phylogenetic classification
5. Karyo-taxonomy
6. Experimental taxonomy
7. Chemo-taxonomy
8. Biochemical taxonomy
9. New systematics

6. Basic concept of taxonomic hierarchy
• There are seven basic categories of hierarchy:
1. Kingdom
2. Phylum
3. Classes
4. Order
5. Families
6. Genus
7. Species

7. • Kingdoms - The most basic classification of living things is kingdoms.
Currently there are five kingdoms (Monera Kingdom, Protista Kingdom,
Fungi Kingdom, Plant Kingdom, and Animal Kingdom.). Living things are
placed into certain kingdoms based on how they obtain their food, the types
of cells that make up their body, and the number of cells they contain.
• Phylum - The phylum is the next level following kingdom in the
classification of living things. It is an attempt to find some kind of physical
similarities among organisms within a kingdom. These physical similarities
suggest that there is a common ancestry among those organisms in a
particular phylum.
• Classes - Classes are way to further divide organisms of a phylum. As you
could probably guess, organisms of a class have even more in common than
those in an entire phylum. Humans belong to the Mammal Class because we
drink milk as a baby.

8. • Order - Organisms in each class are further broken down into orders. A taxonomy
key is used to determine to which order an organism belongs.
• Families - Orders are divided into families. Organisms within a family have more
in common than with organisms in any classification level above it. Because they
share so much in common, organisms of a family are said to be related to each
other. Humans are in the Hominidae Family.
• Genus is a way to describe the generic name for an organism. The genus
classification is very specific so there are fewer organisms within each one. For this
reason there are a lot of different genera among both animals and plants. When
using taxonomy to name an organism, the genus is used to determine the first part
of its two-part name.
• Species are as specific as you can get. It is the lowest and most strict level of
classification of living things. The main criterion for an organism to be placed in a
particular species is the ability to breed with other organisms of that same species.
The species of an organism determines the second part of its two-part name.

9. Example of taxonomy of humans
• Common name : Human
• Biological name : Homo sapiens
• Domain :Eukarya
• Kingdom : Animilia
• Phylum : Chordate
• Class : Mammalia
• Order : Primates
• Family : Hominidae
• Genus : Homo
• Species : sapien

10. Kingdom: Animalia
Multicellular organisms; cells with a nucleus, with cell membranes
but lacking cell walls
Phylum: Chordata
Animals with a spinal cord
Class: Mammalia
Warm-blooded chordates that bear live young; females have
mammary glands that secrete milk to nourish young
Order: Primates
Mammals with collar bone; eyes face forward; grasping hands with
fingers; two types of teeth (incisors and molars)
Family: Hominidae
Primates with upright posture, large brain, stereoscopic vision, flat
face, different use of hands and feet
Genus: Homo
Hominids with S-curved spine, recognisable as human
Species: Homo sapiens
Humans with high forehead, well-developed chin, thin skull bones

11. BROAD CONCEPT CLASSIFICATION
• There is a great diversity in structure, cellularity, habitat, mode
of nutrition of different organisms in ecosystem. To understand
these differences and similarities between different organisms,
we can classify various animals and plants on the basis of the
following parameters.
1. Cellularity
2. Ultra structure (Prokaryotes/Eukaryotes)
3. Energy and carbon utilization
4. Ammonia excretion
5. Habitat

12. 1) CELLULARITY
• A cell is the structural and functional unit of life. The total
number of cells present in an individual varies from one organism
to the other. Based on the number of cells, organisms are classified
into:
1. Unicellular Organisms
2. Multicellular Organisms

13. Unicellular Organisms
• They are simple, minute, single-celled organisms, made up of a single cell
which existed about 3.8 million years ago.
• Bacteria , amoeba, Paramecium archaea, protozoa, unicellular algae, and
unicellular fungi are the main groups of unicellular organisms.
• These unicellular organisms are mostly invisible to the naked eye. Most of
the unicellular organisms are prokaryotes.
• Unicellular entities fulfil their nutritional requirements through a process
known as phagocytosis.
• They reproduce through asexual means through the process of replication.
• Movement in unicellular entities is brought about through cilia,
pseudopodia, flagella, etc
• Examples : Amoeba, Paramecium , Plasmodium , Euglena etc.

15. Multicellular Organisms
• Organisms which are composed of multiple cells are called
multicellular organisms. These cells are attached to each other to form
tissue and after that procedure a multicellular organism (Cells→
Tissues → Organs → Organ Systems)
• Organisms including, animals, birds, plants, humans are the main
groups of a multicellular organism. Most of the multicellular organisms
are eukaryotes.
• Most of these cells are visible to the naked eye.
• Examples : Animal – Hydra , Plant – Spirogyra , Cyanobacteria
such as Chara (Multicellular prokaryotic organisms) , Species of
gymnosperms and angiosperm plants (Multicellular eukaryotic
organisms)

17. 2)Ultra structure (Prokaryotes/Eukaryotes)
• On the basis of internal structure of cell of an organisms, cells can
be divided into :
1. Prokaryotic cell -A prokaryote is a single-celled organism that
does not have a membrane-bound nucleus, mitochondria, or any
other membrane-bound organelle. Example – bacteria

18. 2. Eukaryotic cell - Eukaryotic cells are cells that contain a true
nucleus and membrane bound organelles, and are enclosed by a
plasma membrane. Example – animal, plants, fungus etc.

20. 3) Energy and carbon utilization
• On the basis of energy and carbon utilization, the
organism are divided into 3 types..
1. Autotrophs
2. Heterotrophs
3. Lithotrophs

21. Autotrophs
• An autotroph is also derived from the Greek word, where auto means ‘self‘
and trophe means ‘nourishing‘. Hence these types are considered as primary
producer, which are able to prepare their own food with the help of
sunlight, water, and air.
• The two major types of autotrophs are chemoautotrophs and
photoautotrophs.
• Photoautotroph mainly plants with green leaves like from the mosses to
long trees, algae, phytoplankton and some bacteria uses a process called
photosynthesis, where plants acquire energy from the sun and use them in
converting carbon dioxide from the air and water from the soil into a
nutrient called glucose.

22. • Chemoautotrophs derive energy for their life functions from
inorganic chemicals. They feed on chemicals that are good electron
donors, such as hydrogen sulfide, sulfur, or iron.
• Like all autotrophs, chemoautotrophs are able to “fix” carbon. They
take atoms of carbon from inorganic compounds, such as carbon
dioxide, and using it to make organic compounds such as sugars,
proteins, and lipids.
• Chemoautotrophs are commonly found in environments where
plants cannot survive, such as at the bottom of the ocean, or in
acidic hot springs.
• One type of chemoautotroph, Nitrosomonas, plays the crucially
important role of fixing nitrogen in the soil of some ecosystems..

23. Heterotrophs
• Heterotrophs is an organism that cannot manufacture its own food by carbon
fixation and therefore derives its intake of nutrition from other sources of
organic carbon, mainly plant or animal matter. In the food chain, heterotrophs
are secondary and tertiary consumers. By consuming reduced carbon
compounds, heterotrophs are able to use all the energy that they consume for
growth, reproduction and other biological functions.
• There are two forms of heterotroph.
• Photo-heterotrophs use light for energy, although are unable to use carbon
dioxide as their sole carbon source and, therefore, use organic compounds
from their environment. Helio-bacteria and certain proteo--bacteria are photo-
heterotrophs.
• Chemo-heterotrophs obtain their energy from ingesting preformed organic
energy sources such as lipids, carbohydrates and proteins which have been
synthesized by other organisms. Example : human

24. Examples of Heterotroph
• Herbivores: Heterotrophs that eat plants(producers) to obtain
their nutrition are called herbivores, or primary consumers.
• Carnivores : eat only other consumers. The energy carnivores can
use as energy mainly comes from lipids (fats) that the herbivore
has stored within its body. Small amounts of glycogen is stored
within the liver and in the muscles and can be used for energy
intake by carnivores, although the supply is not abundant.
• Omnivores : eat both consumers and producers

25. • Lithotrophs are a diverse group of organisms
using inorganic substrate (usually of mineral origin) to
obtain reducing equivalents for use in biosynthesis (e.g., carbon
dioxide fixation) or energy conservation (i.e., ATP production)
via aerobic or anaerobic respiration.
• An example of this is chemolithotrophic bacteria in giant tube
worms or plastids, which are organelles within plant cells that may
have evolved from photolithotrophic cyanobacteria-like organisms.
• Lithotrophs belong to the domains Bacteria and Archaea.
• The term "lithotroph" was created from the Greek terms 'lithos'
(rock) and 'troph' (consumer), meaning "eaters of rock".
• Many but not all lithoautotrophs are extremophiles.

27. 4) Ammonia excretion
• Different animals expel different nitrogenous compounds. On the
basis of the type of nitrogenous end product. There are 3 modes of
excretion. They are:
• (a) Ammonotelism
• (b) Ureotelism
• (c) Uricotelism

28. a) Ammonotelism : It is the type of excretion in which ammonia is the main
nitrogenous waste material. Such animals are called ammonotelic.
• It is found in aquatic animal groups like sponges, coelentrates, crustaceans,
echinoderms, bony fish, tadpole larvae and salamander.
b) Ureotelism : It is a type of excretion where urea is the main nitrogenous waste
material. Animals showing ureotelism are called ureotelic animals.
• Generally found in land animals which can afford to excrete sufficient volume
of water or to concentrate urea in considerable quantity in the urine. It is
commonly found in man, whales, seals, desert mammals like kangaroo rats,
camels, toads, frogs, aquatic and semi aquatic reptiles like alligator, terrapins
and turtles.
c) Uricotelism : Elimination of uric acid as the main nitrogenous waste material
is called uricotelism. Animals showing uricotelism are called uricotelic animals.
• It is a common method seen in birds, land reptiles, insects, land snails and
some land crustaceans.

29. Habitat
• a habitat is the type of natural environment in which a particular
species of organism lives. It is characterized by both physical and
biological features. A species' habitat is those places where it can find
food, shelter, protection and mates for reproduction.
• Aquatic Habitats: The animals which live in water are called aquatic
animals. According to the nature of the water aquatic animals may be
marine or fresh-water.
• Marine Animals: About three fourths of the earth’s surface is covered
by the oceans. The salt water serves as the home for the marine
animals who can survive neither in fresh water nor on land.
• Fresh-Water Animals : :Fresh-water animals are found in ponds, pools,
rivers, lakes and swamps. Some prefer to live in stagnant water but
others choose the running stream.

30. • Terrestrial Habitats: Terrestrial animals are those who live on the
land. They may be simple surface dwellers or they may burrow
beneath the soil and thus become sub terrestrial. The surface
communities may choose to live on rocks, or plains, or desert or
damp forest. The aerial animals spend a part of their time in the
air, but they depend on the surface for rest. A number of animals
are arboreal, homing amongst the branches of the tree.

31. MOLECULAR BASIS OF
CLASSIFICATION OF ORGANISMS

32. 3 Domains and 6 Kingdoms of Classification
• Carl Woese et al. classified organisms into 3 domain
classification based sequence of ribosomal RNA genes and
formed the molecular basis of dividing all organisms into 6
kingdoms.
1. Domain Bacteria
A. Kingdom Eubacteria : Unicellular and prokaryotic with
peptidoglycan.
2. Domain Archaea
A. Kingdom Archaea : Unicellular and prokaryotic without
peptidoglycan.

33. 3. Domain Eukarya :
C. Kingdom Protista : Unicellular/ Multi cellular and
eukaryotic.
D. Kingdom fungi : Unicellular/ multi cellular, eukaryotic
and decomposers.
E. Kingdom plantae : Multicellular, eukaryotic and
autotrophic.
F. Kingdom Animalia : Multi cellular, eukaryotic and
heterotrophic.

34. Model organisms
• A model organism is a species that has been widely studied ,
usually because it is easy to maintain and breed in a laboratory
setting has particular experimental advantages.
• These organisms have properties that made them excellent
research subject.

35. The characteristics of model organisms
1. Relatively easy to grow and maintain in a
restricted space.
2. Relatively short generation time.
3. Relatively well understood growth and
development.
4. Relatively easy to provide necessary
nutrients for growth
5. Closely resemble other organisms or system.

36. Different types of model organisms
Genetic model
organisms
Experimental
organisms
Genomic model
organisms
Good candidates for
genetic analysis.
Good candidates for
research in
developmental
biology.
Good candidate for
genome research.
Breed in large numbers
. Have short generation
time, hence large scale
crosses can be
followed over
generations.
Produce robust
embryos that can be
easily manipulated and
studied.
Easy to manage
genomes . genome is
similar to human.
Example : Drosophila Example : Frog Example : Rat

37. 3 types of model
1. Mammalian models :
• Mouse (Mus musculus)
2. Non – mammalian models
• Bacterium (Escherichia coli)
• Baker’s yeast (Saccharomyces cerevisiae)
• Nematode (Caenorhabditis elegans)
• Fruit fly (Drosophila melanogaster)
3. Plant model
• Arabidopsis thalania

38. E.coli
• It is a natural mammalian gut bacteria used as model
organism because..
1. E.coli is a singled cell organism so its simple to study.
2. Its life cycle is short.
3. It easily grow on nutrient medium.
4. It can be easily genetically manipulated.

39. Mouse (Mus musculus)
• It is a premier mammalian model organism because..
1. It has close genetic and physiological similarities to
human.
2. These are small, maintained easily and have a short life
span.
3. All new drugs , treatments are tried on mice.

40. Fruit fly (Drosophila melanogaster)
• It is a versatile model organism that has been used in
biomedical research over a century because..
1. Relationship between human genes and fruit fly genes is
close.
2. 75% of genes that cause human diseases are found in
fruit fly.
3. They have a short life span
4. These are inexpensive to maintain
5. It is easy to manipulate genes in fruit fly.

41. Yeast (saccharomyces cerevisiae)
• Yeast is one of the simplest eukaryotic organisms but
many essential cellular processes are the same in yeast
and human.
• Baker’s or budding yeast model has long popular model
organisms for basic biological research because…
1. It is easy to manipulate in lab
2. Yeast shows cell division in a similar way to our cells. In
1996, it was the first eukaryotic organisms to have its genome
sequence.
3. 20% of genes causing diseases are found in yeast.
4. Many drugs are tested on yeast which have functional
equivalent of mutated human genes to reverse the disease.

42. Nematode (caenorhabditis elegans)
• At approximately 1mm in length and transparent. It
is used as model organisms because…
1. It can easily grow in labs on nutrient medium
2. It produces over thousands egg each day
3. Worm is transparent so its cells can be easily studied.
4. Its genes can be easily mutated.

43. A. thalania
• It is a small flowering plant, used as model
organisms in plant biology.
• Arabidopsis is a member of the mustard family, it is
used as a model organism because..
1. It has a short life span
2. It can be easily cultivated
3. Mutations can be easily produced in this plants.