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UNIT I: DIVERSITY IN LIVING WORLD Topic 1:

What is ‘Living’?

It is extremely hard to characterize "living" and traditionally different qualities common to

every single living being are to be recognized. Some of them are recorded beneath:

(a) Cellular Association: Living things are composed of single cell (Unicellular Organisms) or

many cells (Multicellular Organisms) which associate with each other to perform vital

functions of the body.

(b) Response to Stimuli: All living things can respond and adapt themselves to any change in

the environment.

(c) Reproduction: Living things reproduce either sexually or asexually to produce offsprings of

their own kind.

(d) Growth: All living things grow, develop and eventually die.

(e) Metabolism: Living things need energy to carry out their vital life processes.

Biodiversity

The variability among living organisms from all sources including, inter alia, terrestrial,

marine and other aquatic ecosystems and the ecological complexes of which they are

part; this includes diversity within species, between species and of ecosystems.

Varieties of organism present on a particular region.

Includes all ecosystems—managed or unmanaged. Need For Classification

To study and include each organism along with its identification and habitat.

• To establish the relationship among different organisms and to know about their

evolution. Classification is needed for convenient study of living organisms. It is necessary for knowing the different varieties of organisms. It helps in the correct identification of various organisms. It helps to know the origin and evolution of organisms. It helps to determine the exact position of the organism in the classification. It helps to develop phylogenetic relationship between different groups of organisms. Objectives of Classification are quite similar to needs of biological classification. There are basically three types of Biological Classification which can be categorized as

artificial, natural and phylogenetic.

Three Domains of Life (Six Kingdom Classification) – 1990

Introduced by Carl Woese,

Divides cellular life forms into archaea, bacteria and eukarya domains.

Emphasizes the separation of prokaryotes into two groups, originally called eubacteria

(now bacteria) and archaebacteria (now archaea) because of their fundamental

differences

Woese argued that each of the two arose separately from an ancestor with poorly

developed genetic machinery, often called a progenote.

In fact the three-domain system is loosely based on the traditional five- kingdom

system but divides the monera into two ‘’domains’’, leaving the remaining eukaryotic

kingdoms in the third domain.

It is actually a six kingdom classification.

Archaea domain:

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The domain contains prokaryotic organisms which have a monolayercore of lipids in

the cell memebrane and distinct nucleotides in their 16S RNA. It contains a single

kingdom.

Kingdom archaebacteria

The kingdom contain early prokaryotes which live in extreme environments,

For Example:

(a) Methanogens- metabolize hydrogen and carbon dioxide into methane.

(b) Halophiles - live in salt.

(c) Thermoacidophiles – live in acid high temperatures (upto 110 degrees Celsius).

(2) Bacteria domain:

The domain contains prokaryotes which lack membrane covered cell organelles but do

have a sort of micro chambers for separating various activities. There is a single

kingdom.

Kingdom eubacteria:

The domain contains diverse type of bacteria having peptidoglycan cell wall, glycogen

as food reserve,naked DNA coiled to form nucleoid, absence of sap vacuoles and

presence of 70S ribosomes. Some common groupare bacteria, my-coplasma,

ctinomycetes, rickettsiae, spirochaetes, firmicutes, cyanobacteria.

(3) Eukarya domain.

The domain contains eukaryotic organisms which originated by endosymbiotic

association between some archaebacteria and eubacteria. It has four kingdoms- protista,

fungi, plantae and animalia.

Taxonomy

Taxis = orderly arrangement, nomos =law The term taxonomy was coined by A. P. de Candolle.

Carolus Linnaeus is called the father of taxonomy.

H. Santapau is called the father of Indian taxonomy

“Taxonomy is the study of principles and procedures of classification.”

Includes study of following 4 points

o Identification: Identification of living organisms

o Nomenclature: Nomenclature of living organisms

o Classification: Classification of living organisms in groups

o Affinities: Study of inter relationship between living organisms

Types:-

1. Alpha taxonomy-Only morphological characters are used for identification and

classification of plants.

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2. Beta taxonomy- Involves genetical, anatomical, cytological, palynological,

physiological and other characters.

3. Omega taxonomy- Analysis and synthesis of all information and typesof data to

develop classification system based on phylogenetic relationship.

4. Cytotaxonomy –The use of cytological characters of plants in classification or in

solving taxonomic problems is called cytotaxonomy.

5. Chemotexonomy –The use of chemical compounds present in plants for

classification or in solving taxonomic problems is called chemotaxonomy or

chemical taxonomy.The basic chemical compounds used in chemotaxonomy are

alkaloids, carotenoids, tannins, polysaccharides, nucleic acids, fatty acids,

aromatic compounds etc.

6. Karyotaxonomy –Itis based on the characters of nucleus and chromosomes.

Pattern of chromosomal bands (dark bands and light bands) is most specific

character for classification of organisms.

Systematics

Proposed by Linnaeus in 1735.

Includes description of external morphological characters of plant or living

organisms. E.g., morphological characters of root, stem, leave, flowers.

New systematics or Neo systematics or Biosystematicsis a new branch. Its name

was given by Julian Huxley (1940).

Basis includes:

o Identification: Identification of living organisms

o Nomenclature: Nomenclature of living organisms

o Classification: Classification of living organisms in groups

o Affinities: Study of inter relationship between living organisms

Concept of species and taxonomical Hierarchy:

Speciesis the basic unit of biological classification and a taxonomic rank.

A species is often defined as the largest group of organisms in which two individuals can

producefertileoffspring, typically by sexual reproduction.

For example, with hybridisation, in a species complex of hundreds of similar microspecies,

or in a ring species, the boundaries between closely related species become unclear..

All species are given a two-part name, a "binomial".

The first part of a binomial is the genus to which the species belongs.

The second part is called the specific name (zoology) or the specific epithet (in botany, also

sometimes in zoology).

For example, Boa constrictor is one of four species of the Boa genus.

Species were seen from the time of Aristotle until the 18th century as fixed kinds that could

be arranged in a hierarchy, the great chain of being.

Taxonomical Hierarchy

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Binomial Nomenclature:

System of providing a name with 2 components.

2 Components- Generic name and Specific epithet.

Given by Carolus Linnaeus.

Example: Mango

Scientific name: Mangiferaindica ,Mangifera – Genus name, indica – species name

Universal rule :

1. Biological name gemerally in Latin and written in Italics.

2. First name is Genus , second name is species

3. When handwritten both the components are separately underlined. Printed in italics to

show its latin origin.

4. Denoting the genus starts with a capital letterwhile the specific epithet starts with a

small letter. It can beillustrated with the example of

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Mangiferaindica

Name of the author appears after the specific epithet, i.e., at the end ofthe biological

name and is written in an abbreviated form,

e.g., Mangiferaindica Linn. It indicates that this species was first described by

Linnaeus.

Tools for study of Taxonomy:

Biologists have established certain procedures and techniques to storeand preserve the

information as well as the specimens.

Some of these are

1. Herbarium

Store house of collected plant specimens that are dried, pressed and preserved

on sheets.

These sheets are arranged according to a universally accepted system of

classification.

These specimens, along with their descriptions on herbarium sheets, become a

store house or repository for future use.

The herbarium sheets also carry a label providing information about date and

place of collection, English, local and botanical names, family, collector’s

name, etc.

Serve as quick referral systems in taxonomical studies.

2. Botanical Gardens

Specialised gardens have collections of living plants for reference.

Plant species in these gardens are grown for identification purposes and each

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

The famous botanical gardens

Kew (England),

Indian BotanicalGarden, Howrah (India)

National Botanical Research Institute,Lucknow (India).

3. Museum

Set up in educational institutes suchas schools and colleges.

Have collections of preserved plantand animal specimens for study and

reference.

Specimens are preservedin the containers or jars in preservative solutions.

Plant and animalspecimens may also be preserved as dry specimens.

Insects are preservedin insect boxes after collecting, killing and pinning.

Larger animals likebirds and mammals are usually stuffed and preserved.

Oftenhave collections of skeletons of animals too.

4. Zoological Parks

These are the places where wild animals are kept in protected

environmentsunder human care and which enable us to learn about their food

habitsand behaviour.

All animals in a zoo are provided, as far as possible, theconditions similar to

their natural habitats. Children love visiting theseparks, commonly called Zoos

Topic 2: Five Kingdom Classification

Given by R. H. Whittaker (1969).

Based on 3 characters: Complexity of cell: Cell is prokaryote or eukaryote, on this basis, kingdom

Monera is formed. And all the prokaryotes are grouped into it.

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Complexity of organism: Organism is unicellular or multicellular, on this basis kingdom

Protista was formed, and all the unicellular eukaryotes are grouped into it.

Nutrition:Organism is autotrophic or heterotrophic, on this basis kingdom Fungi, Plantae

and Animalia were formed.

The five kingdoms classified by Whittaker are:

Kingdom Monera:

Salient features

Includes prokaryotes.

Typically unicellular organisms (but one group is mycelia).

Genetic material is naked circular DNA, not enclosed by nuclear envelop.

Ribosomes and simple chromatophores are the only subcellular organelles in the

cytoplasm. The ribosomes are 70S.

Sap vacuoles do not occur. Gas vacuole may be present.

The predominant mode of nutrition is absorpitive. But some groups are photosynthetic

and chemosynthetic.

The organisms are non-motile ior move by beating of simple gflagella or by gliding.

Flagella composed of many interwined chains of a protein flagellin.

Maoneran cells are moicroscopic.

Most organisms bear a rigid cell wall (peptidoglycan).

Reproduction is primarily asexual by binary fission or budding. Mitotic apparatus is not

formed during cell division.

Examples: bacteria, actinomycetes, mycoplasma and cyanobacteria.

Smallest and most abundant organism on Earth.

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Classification

I. Bacteria:

Bacteria are found in various shapes like:

a) Coccus (spherical)

b) Bacillus (rod-shaped)

c) Vibrio (comma shaped)

d) Spirillum (spiral shaped)

Bacteria found almost everywhere and can be Photosynthetic autotrophs,

Chemosynthetic autotrophs or Heterotrophs.

II. Archaebacteria:

Archaebacteria has different cell wall structure due to which they can live in most harsh

habitats.

a) Halophiles (salt-loving), e.g., halobacterium and halococcus

b) Thermoacidophiles (in hot springs), e.g., sulfobolus and thermoplasma

c) Methanogen (marshy area),e.g., Methanobacterium, Methanolinea

o Methanogens are also found in the guts of several ruminant animals such as cows and

buffalos and they are responsible for the production of methane (biogas) from the dung

of these animals.

III. Eubacteria:

These are also known as true bacteria.

They have a rigid cell wall.

They posses flagellum, if motile.

They also known as blue green algae or Cyanobacteria.

Cyanobacteria are photosynthetic autotrophs.

These are unicellular, colonial or filamentous algae.

Colonies are surrounded by gelatinous sheath.

Some of the eubacteria can fix atmospheric nitrogen by specialized cells,

e.g. Anabaena andNostoc. These special cells are called heterocyst.

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Chemosynthetic autotrophs:

Oxidize various inorganic substances such as nitrates, nitrites and ammonia

and use the released energy for their ATP production.

They play great role in recycling nutrients like nitrogen, phosphorous, iron and

sulphur.

IV. Heterotrophic bacteria:

Most abundant in nature

Most of them are decomposer

They are helpful in making curd from milk.

They are helpful in Production of antibiotics

Some are pathogen causing diseases like cholera, typhoid, and tetanus.

Bacteria reproduce mainly by fission, also produce spore in unfavorable

condition.

Reproduce sexually by transfer of DNA form one bacteria to other, the process

called conjugation.

V. Mycoplasma: Completely lack a cell wall.

Smallest living cells known.

Can survive even without oxygen.

Pathogenic in animals and plants

Kingdom Protista:

Salient features:

All are unicellular and eukaryotic

Primarily aquatic, can live in moist places.

Forms a link with the others dealing with plants, animals and fungi.

The cell body contains a well-defined nucleus and membrane bound organelles

Some have cilia or flagella.

Reproduce asexually and sexually by a process involving cell fusion and zygote formation.

Classification

i. Chrysophytes:

Includes diatoms and golden algae (desmids)

Photosynthetic.

They are found in freshwater as well as in marine environments

Mostly planktonic ( passive swimmer)

Cell walls overlap to fit together like a soap box

Cell wall contains silica hence indestructible.

Their accumulation forms ‘Diatomaceous Earth’.

Used in polishing, filtration of oils and syrups.

Diatoms are the chief ‘producers’ in the oceans.

ii. Dinoflagellates : Marine, photosynthetic.

Cell wall has stiff cellulose plates.

Appears yellow, green, brown, blue or red depending on the pigments.

Have two flagella − one longitudinal and other transversely in a furrow between

wall plates.

Red Dinoflagellates (Gonyaulax) form red tides.

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iii. Euglenoids

Majority of them are fresh water organisms found instagnant water.

Instead of a cell wall, they have a proteinrich layer called pellicle which makes their

body flexible.

Have two flagella, a short and a long one.

They are photosynthetic in the presence of sunlight, whendeprived of sunlight they

behave like heterotrophs bypredating on other smaller organisms.

Thepigments of euglenoids are identical to those present inhigher plants.

iv. Slime Mould

Saprophytic protists.

The body movesalong decaying twigs and leaves engulfing organicmaterial.

Under suitable conditions, they form an aggregation called plasmodium which may grow

and spread over several feet.

During unfavourable conditions, the plasmodium differentiates and forms fruiting

bodies bearing spores at their tips.

The spores possess true walls.

They are extremely resistant and survive for many years,even under adverse conditions.

The spores are dispersedby air currents.

v. Protozoans

Heterotrophs and live as predators orparasites.

They are believed to be primitive relatives ofanimals.

There are four major groups of protozoans. Amoeboid protozoans:

These organisms live in fresh water, sea water or moist soil. They move and capture

their prey by putting out pseudopodia (false feet) as in Amoeba

Marine forms have silica shells on their surface. Some of them such as Entamoeba are

parasites.

Flagellated protozoans:

The members of this group are either free-livingor parasitic.

They have flagella. The parasitic forms cause diaseases suchas sleeping sickness.

Example: Trypanosoma

Ciliated protozoans:

These are aquatic, actively moving organisms becauseof the presence of thousands of

cilia.

They have a cavity (gullet) that opensto the outside of the cell surface. The coordinated

movement of rows ofcilia causes the water laden with food to be steered into the gullet.

Example:Paramoecium

Sporozoans:

Includes diverse organisms that have an infectious spore-like stage in their life cycle.

The most notorious is Plasmodium(malarial parasite) which causes malaria which has a

staggering effect onhuman population.

Kingdom Fungi Salient features:

Eukaryotic organisms.

They are non-vascular.

Reproduce by means of spores called conidia or sporangiospores or

zoospores.

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Depending on the species and conditions both sexual and asexual spores may be

produced.

Non-motile.

Exhibit the phenomenon of alteration of generation.

The vegetative body of the fungi may be unicellular or composed of

microscopic threads called hyphae. The network of hyphae is known as

mycelium.

The structure of cell wall is similar to plants but chemically the fungi cell wall is

composed of chitin.

Heterotrophic organisms.

They digest the food first and then ingest the food and in order to accomplish

this fungi produce exoenzymes.

Store their food as starch.

Biosynthesis of chitin occurs in fungi.

The nucleus of the fungi is very small.

During mitosis the nuclear envelope is not dissolved.

Nutrition in fungi is saprophytic, or parasitic or symbiotic.

Reproduction in fungi is both by sexual and asexual means. Sexual state is

referred to as teleomorph, asexual state is referred to as anamorph.

Classification:

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Lichens

Lichens are symbiotic associations i.e. mutually useful associations, between algae and

fungi.

The algal component -phycobiont , autotrophic

Fungal component - mycobiont, heterotrophic

Algae prepare food for fungi

Fungi provide shelter and absorb mineral nutrients and water for its partner.

Lichens are very good pollution indicators – they do not grow in polluted areas.

Viruses

No place in classification as not true living.

Non cellular organism, have inert crystalline structure outside the cell wall.

Infects the cell, Take over the host machinery by killing it and start to replicate.

Pasteur: Virus means venom or poisonous fluid.

D.J. Ivanowsky (1892): Identified causal agent of mosaic disease in tobacco. Smaller in

size than bacteria.

M.W.Beijerinek (1898): Fluid extracted from infected tobacco plant infected the

healthy plant and named the fluid as contagiumvivumfluidum. (infectous living fluid)

Obligate parasites

Contains DNA or RNA as genetic material along with protein.

Nucleoprotein and infectious genetic material.

Plant infecting viruses have single stranded RNA

Animal infecting viruses have either single or double stranded DNA or RNA.

Ex: Bacteriophages- Virus infecting bacteria. Double stranded DNA

Protein coat capsid made of capsomere (helical or polyhedral geometric), protects the

nucleic acid.

Disease in human : mumps, small pox, herpes, influenza, AIDS

Disease in plants: mosaic formation, leaf rolling and curling, yellowing and vein

clearing, dwarfing, stunted growth.

Viroids

They are the smallest self-replicating particles which were discovered by Diener

(1971).

They are obligate parasites.

Molecular weight of a viroid is low.

The RNA is tightly folded to form circular or linear structure.

Lacks the protein coat which is present in virus.

Viroid are known to cause diseases (some 20) in plants only, e,g,. potato spindle tuber,

chrysanthemum stunt.

Animal or human infection is not known.

Can multiply by both RNA development and DNA dependent replication

Topic 3: Salient features and classification of plants

Plant Classification

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Algae / thallophyta

Chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (both fresh water and

marine) organisms.

The microscopic unicellular forms – Chlamydomonas, Colonial forms – VolvoxFilamentous

forms – UlothrixandMarine and massive plant bodies – kelps.

Reproduction :

Vegetative reproduction – by fragmentation, each fragment develops into a thallus.

Asexual reproduction – by the production of different types of spores like zoospores.They are

flagellated (motile) and on germination gives rise to new plants.

Sexual reproduction – through fusion of two gametes.

Isogamous – If gametes are flagellated and similar in size – Chlamydomonas.

If gametes are non-flagellated and similar in size – Spirogyra.

Anisogamous – If gametes are dissimilar in size. e.g., some species

of Chlamydomonas.

Oogamous – Fusion between one large, non-motile female gamete and a smaller, motile

male gamete is termed oogamous, e.g., Volvox, Fucus.

The algae are divided into three main classes.

Classes Common

Name

Major

Pigments Stored Food Cell Wall

Flagellar

Number and

Position of

Insertions

Habitat

Chlorophyceae Green algae

Chlorophyll a, b Starch Cellulose 2-8, equal,

apical Fresh water,

brackish water,

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salt water

Phaeophyceae Brown algae Chlorophyll a,

c,fucoxanthin

Mannitol,

laminarin

Cellulose

and algin

2, unequal,

lateral

Fresh water (rare)

brackish water,

salt water

Rhodophyceae Red algae Chlorophyll a,

d,phycoerythrin

Floridean

starch Cellulose Absent

Fresh water

(some), brackish

water, salt water

(most)

Bryophytes (amphibians of the plant kingdom)

Include the various mosses and liverworts that are found commonly growing in moist

shaded areas in the hills.

Called amphibians of the plant kingdom because these plants can live in soil but are

dependent on water for sexual reproduction.

They play an important role in plant succession on bare rocks/soil.

It is thallus-like and prostrate or erect, and attached to the substratum by unicellular or

multicellular rhizoids (root like structure).

They lack true roots, stem or leaves. They may possess root-like, leaf-like or stem-like

structures.

The main plant body of the bryophyte is haploid.

It produces gametes, hence is called a gametophyte.

The sex organs in bryophytes are multicellular. The male sex organ – antheridium -

produce biflagellate antherozoids.The female sex organ - archegoniumis flask-shaped and

produces a single egg.

The bryophytes are divided into liverworts and mosses.

Liverworts

o The plant body of a liverwort is thalloid.

o The thallus is dorsiventral and closely appressed to the substrate.

o The leafy members have tiny leaf-like appendages in two rows on the stem-like

structures.

o Asexual reproduction – by fragmentation of thalli, or by the formation of

specialised structures called gemmae.

o Sexual reproduction – male and female sex organs are produced either on the

same or on different thalli.

o e.g., Marchantia

Mosses

Life cycle of a moss is the gametophyte which consists of two stages.

Protonemastage, which develops directly from a spore. It is a creeping, green,

branched and frequently filamentous stage

Leafy stage, which develops from the secondary protonema as a lateral bud. It

has upright, slender axes bearing spirally arranged leaves. This stage bears the

sex organs.

Vegetative reproduction – by fragmentation and budding in the secondary

protonema.

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Sexual reproduction – by the sex organs antheridia and archegonia, which are

produced at the apex of the leafy shoots.

After fertilization – the zygote develops into a sporophyte, consisting of a foot,

seta and capsule. The sporophyte in mosses is more elaborate than that in

liverworts. The capsule contains spores, which are formed after meiosis.

The mosses have an elaborate mechanism of spore dispersal.

e.g., Funaria, Polytrichumand Sphagnum.

Pteridophytes

The Pteridophytes include horsetails and ferns.

They are the first terrestrial plants to possess vascular tissues – xylem and phloem.

Found in cool, damp, shady places though some may flourish well in sandy-soil conditions.

The main plant body is a sporophyte which is differentiated into true root, stem and leaves.

The leaves in pteridophyta are small (microphylls) – Selaginellaor large (macrophylls) – ferns.

There are two types of sporophytes in pteridophytes –

o Homosporous – all spores are of similar kinds, e.g., In majority of the pteridophytes.

o Heterosporous – 2 types of spores are produced, (a) small, male microspores, and (b)

large, female megaspores. e.g., Selaginellaand

The pteridophytes are further classified into four classes

1. Psilopsida – e.g.,Psilotum.

2. Lycopsida – e.g., Selaginella, Lycopodium.

3. Sphenopsida – e.g., Equisetum.

4. Pteropsida – e.g., Dryopteris, Pteris, Adiantum.

Gymnosperms o Plants in which the ovules are not enclosed by any ovary wall and remain exposed, both before

and after fertilisation.

o The seeds that develop post-fertilisation, are not covered (naked).

o Include medium-sized trees or tall trees and shrubs. The giant redwood tree Sequoia is one of

the tallest tree species.

o Roots –

The roots are generally tap roots.

Roots in Pinus have fungal association in the form of

In Cycassmall specialized roots called coralloid roots are associated with N2- fixing

cyanobacteria.

o Stem – The stems are unbranched (Cycas) or branched (Pinus, Cedrus).

o Leaves – o The leaves may be simple or compound, well-adapted to withstand extremes of

temperature, humidity and wind.

o In conifers, the needle-like leaves reduce the surface area. Their thick cuticle and

sunken stomata also help to reduce water loss.

o Spores are produced within sporangia that are borne on sporophylls, which are arranged

spirally along an axis to form lax or compact strobili or cones.

Angiosperms (Flowering plants)

In the angiosperms pollen grains and ovules are developed in specialized structures called

flowers.

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In angiosperms, the seeds are enclosed by fruits.

The angiosperms are present in wide range of habitat.

Smallest angiosperm – Wolfia; tallest angiosperm – Eucalyptus.

They provide us with food, fodder, fuel, medicines and several other commercially important

products.

They are divided into two classes : the dicotyledonsand the monocotyledons.

The dicotyledons are characterised by having two cotyledons in their seeds while the

monocolyledons have only one.

The male sex organs in a flower is the stamen. Each stamen consists of a slender filament with

an anther at the tip. The anthers, following meiosis, produce pollen grains.

The female sex organs in a flower is the pistil or the carpel. Pistil consists of an ovary

enclosing one to many ovules. Within ovules highly reduced female gametophytes

(embryosacs) are present. The embryo-sac formation is preceded by meiosis. Hence, each of

the cells of an embryo-sac is haploid.

Angiosperm Classification up to class level

o Belongs to kingdom Plantae

o Phylum: Anthophyta

o Has 2 sub division or classes namely Monocots and Dicots.

o Characteristic of Leaf:

o Characteristic of root:

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o Characteristic of stem:

Examples of Monocots:

Garlic, onions, corn, wheat, rice, asparagus, sugarcane, lilies, orchids and grass

Examples of dicots

Tomatoes, peppers, potatoes, cauliflower, broccoli, beans, peas, clovers, apples and pears

Topic 4: Salient features and classification of animal

o Animals belonging from phylum Porifera to phylum Echinodermata are categorized as non-

chordates.

o Non-chordates are animals without a notochord.

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Phylum Porifera

Members of this phylum are known as sponges.

Primitive, multicellular, asymmetrical, marine animals with cellular level of

organisation.

Sycon, Spongilla and Euplectella are some common examples of sponges.

Phylum Coelenterates (Cnidaria)

Members of this phylum are aquatic,

Marine, sessile or free-swimming, radially symmetrical,

Diploblastic animals with tissue level oforganisation.

Some coelenterates, like corals, have a skeletal structure made of calcium

carbonate.

Coelenterates have cnidoblasts on their tentacles and body, and hence, this

phylum is also known as Cnidaria

Cnidoblasts are used for anchorage, defence and to capture prey. Some common

Coelenterates are Physalia, Pennatula, Gorgonia and Meandrina.

Phylum Ctenophora.

Commonly known as sea walnuts or comb jellies.

Animals are marine, radially symmetrical,

Diploblastic with tissue level of organisation.

Bioluminescence

Have eight external rows of ciliated comb plates, which help in locomotion.

Pleurobrachia and Ctenoplana are some common ctenophores.

Phylum Platyhelminthes.

Bilaterally symmetrical, triploblastic, acoelomate animals with organ level of

organisation.

Flatworms are mostly endoparasites found in the digestive system of animals,

including humans.

The parasitic members possess hooks and suckers, and some of them use the

surface of their body to absorb nutrients directly from the host.

Taenia and Fasciola are some common flatworms.

Phylum Aschelminthes.

Have a circular body when seen in cross-section, and hence, are called

roundworms.

They may be aquatic or terrestrial, free-living or parasitic in plants and animals.

Bilaterally symmetrical, triploblastic, pseudocoelomate animals with organ-

system level of body organisation.

Ascaris and Wuchereria are common members of this phylum.

Phylum Annelida.

May be aquatic or terrestrial, free-living or sometimes parasitic.

Triploblastic, bilaterally symmetrical, coelomate animals with organ-system

level of body organisation.

Body segments as segments or metameres.

Pheretima and Hirudinaria are some common annelids.

Phylum Arthropoda:

Largest phylum of Animalia.

Bilaterally symmetrical, triploblastic, segmented, coelomate animals with

organ-system level of organisation.

Body is divided into the head, the thorax and the abdomen. These animals are

characterised by the presence of jointed appendages and a chitinous

exoskeleton.

Excretion through malphigian tubes.

Some common arthropods are Apis, Bombyx, Locusta and Heterometrus.

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Phylum Mollusca:

Second largest phylum of Animalia.

Terrestrial or aquatic animals.

Bilaterally symmetrical, triploblastic, coelomate animals with organ-system

level of organisation.

The body has a distinct head, a muscular foot and a visceral hump, and is

covered by a calcareous shell.

Radula is present in mouth

Pila, Pinctada, Sepia, Loligo and Octopus are some common molluscs.

Phylum Echinodermata:

Last phylum under non-chordates is Echinodermata.

Have an endoskeleton made up of calcareous ossicles.

Marine, triploblastic, coelomate animals with organ-system level of

organisation.

Adult echinoderms are radially symmetrical, but the larvae are bilaterally

symmetrical.

Posess water vascular system.

Phylum – Chordata

Animals belonging to phylum Chordata are fundamentally characterised by the

presence of a notochord, a dorsal hollow nerve cord and paired pharyngeal

[relating to the pharynx] gill slits.

They are bilaterally symmetrical, triploblastic, coelomate with organ-system

level of organisation.

Phylum Chordata is divided into three subphyla: Urochordata or Tunicata,

Cephalochordata and Vertebrata.

Subphyla Urochordata and Cephalochordata are often referred to as

protochordates and are exclusively marine.

In Urochordata, notochord is present only in larval tail, while in

Cephalochordata, it extends from head to tail region and is persistent throughout

their life.

Examples: Urochordata – Ascidia, Salpa, Doliolum; Cephalochordata –

Amphioxus or Lancelet.

Comparison of Chordates and Non-chordates

S.No. Chordates Non-chordates

1. Notochord present. Notochord absent.

2. Central nervous system is dorsal, hollow and

single.

Central nervous system is ventral, solid and

double.

3. Pharynx perforated by gill slits. Gill slits are absent.

4. Heart is ventral. Heart is dorsal (if present).

5. A post-anal part (tail) is present. Post-anal tail is absent.

Class – Cyclostomata

All living members of the class Cyclostomata are ectoparasitesLives on the outside of its

host] on some fishes.

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They have an elongated body bearing 6-15 pairs of gill slits for respiration.

Cyclostomes have a sucking and circular mouth without jaws.

Their body is devoid of scales and paired fins.

Cranium and vertebral column are cartilaginous.

Circulation is of closed type.

Cyclostomes are marine but migrate for spawning [release or deposit eggs] to fresh water.

After spawning, within a few days, they die. Their larvae, after metamorphosis

[transformation from an immature form to an adult form in two or more distinct stages.

Example: Larvae → Tadpole → Frog], return to the ocean.

Examples: Petromyzon (Lamprey) and Myxine (Hagfish).

Class Chondrichthyes

They are marine animals with streamlined body and have cartilaginous endoskeleton.

Mouth is located ventrally.

Notochord is persistent throughout life.

Gill slits are separate and without operculum (gill cover).

The skin is tough, containing minute placoid scales.

Teeth are modified placoid scales which are backwardly directed.

Their jaws are very powerful.

These animals are predaceous [shark].

Due to the absence of air bladder, they have to swim constantly to avoid sinking.

Heart is two-chambered (one auricle and one ventricle).

Some of them have electric organs (e.g., Torpedo) and some possess poison sting (e.g.,

Trygon).

They are cold-blooded (poikilothermous) animals, i.e., they lack the capacity to regulate

their body temperature.

Sexes are separate. In males pelvic fins bear claspers.

They have internal fertilisation and many of them are viviparous [give birth to young

ones].

Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carchaiodon (Great white shark),

Trygon (Sting ray).

Class Osteichthyes

It includes both marine and fresh water fishes with bony endoskeleton.

Their body is streamlined. Mouth is mostly terminal.

They have four pairs of gills which are covered by an operculum on each side.

Skin is covered with cycloid/ctenoid scales.

Air bladder is present which regulates buoyancy.

Heart is two- chambered (one auricle and one ventricle).

They are cold-blooded

Sexes are separate.

Fertilisation is usually external.

They are mostly oviparous and development is direct.

Examples: Flying fish, Sea horse, Fighting fish, Angel fish etc.

Class – Amphibia

As the name indicates (Gr., Amphi : dual, bios, life), amphibians can live in aquatic as well

as terrestrial habitats.

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The amphibian skin is moist without scales [mucus glands in the skin]. The eyes have

eyelids. A tympanum represents the ear.

Alimentary canal, urinary and reproductive tracts open into a common chamber called

cloaca which opens to the exterior.

They have a three-chambered heart (two auricles and one ventricle). These are cold-

blooded

Respiration is through gills, lungs and through

Respiration is by gills, lungs and through skin.

Sexes are separate. Fertilisation is external.

They are oviparous and development is indirect.

Examples: Toad, Frog), Tree frog, Salamander, Limbless amphibia.

Class – Reptilia

The class name refers to their creeping or crawling mode of locomotion (Latin, repere or

reptum, to creep or crawl).

They are mostly terrestrial animals and their body is covered by dry and cornified skin,

epidermal scales or scutes. Snakes and lizards shed their scales as skin cast.

They do not have external ear openings. Tympanum represents ear. Limbs, when present,

are two pairs.

Heart is usually three-chambered, but four-chambered in crocodiles.

Reptiles are poikilotherms [cold-blooded animals].

They lay eggs with tough coverings and do not need to lay their eggs in water, unlike

amphibians.

Sexes are separate.

Fertilisation is internal.

They are oviparous and development is direct.

Examples: Turtle), Tortoise, Chameleon (Tree lizard), Garden lizard, Crocodile, Alligator,

Wall lizard, Poisonous snakes – Naja (Cobra), Bangarus (Krait), Vipera (Viper).

Class – Aves

They have a four-chambered heart. They breathe through lungs. All birds fall in this

category.

The characteristic features of Aves (birds) are the presence of feathers and most of them

can fly except flightless birds (e.g., Ostrich). The forelimbs are modified into wings.

The hind limbs generally have scales and are modified for walking, swimming or clasping

the tree branches.

Skin is dry without glands except the oil gland at the base of the tail.

Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities

(pneumatic).

The digestive tract of birds has additional chambers, the crop and gizzard.

They are warm-blooded (homoiothermous) animals, i.e., they are able to maintain a

constant body temperature.

Respiration is by lungs. Air sacs connected to lungs supplement respiration.

Sexes are separate. Fertilisation is internal. They are oviparous and development is direct.

Examples : Crow, Pigeon, Ostrich), Neophron (Vulture) etc..

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Class – Mammalia

Mammals are warm-blooded animals with four-chambered hearts.

Most mammals familiar to us produce live young ones. However, a few of them, like the

Platypus and the Echidna lay eggs, and some, like kangaroos give birth to very poorly

developed young ones.

They are found in a variety of habitats – polar ice caps, deserts, mountains, forests,

grasslands and dark caves. Some of them have adapted to fly or live in water.

The most unique mammalian characteristic is the presence of milk producing glands

(mammary glands) by which the young ones are nourished.

They have two pairs of limbs, adapted for walking, running, climbing, burrowing,

swimming or flying.

The skin of mammals is unique in possessing hair. External ears or pinnae are present.

Different types of teeth are present in the jaw.

Heart is four-chambered. They are homoiothermous[warm-blooded]. Respiration is by

lungs.

Sexes are separate and fertilisation is internal.

They are viviparous with few exceptions and development is direct.

Examples: Oviparous – Platypus; Viviparous – Kangaroo, Flying fox), Delphinus

(Common dolphin), Balaenoptera (Blue whale), etc.