Notes "Biological Classification"

 Notes "Biological Classification"

By: Nagraj Sir

Biological classification:- The process of grouping living organisms into convenient categories based on simple  characters is known as Biological classification.

 Two Kingdom Classification. (Linnaeus)

·        Plants. (autotrophs,cell wall, do not move)

·        Animals (heterotrophus, no cell wall, can move) 

Draw back of two kingdom classification

1.      Prokaryotes & Eukaryotes were grouped together.

2.      Heterotrophs & Autotrophs were together.

3.      No difference between unicellular and multicellular

4. Simple organisms were placed along with higher organism

Three Kingdom Classification System
Ernst Haeckel in 1866, classified living organisms into three kingdoms-Plantae, Protista and Animalia. The new kingdom-Protista included all those organisms, which lack the capability of tissue differentiation. These are algae, fungi and Protozoa.

I.   Five Kingdom Classification. (R.H Whittaker 1959) 

criteria for classification:

1.      cell structure (prokaryotes/ eukaryote )

2.      Body organization (unicellular/ multicellular)

3.      Mode of nutrition (autotrophic / heterotrophic/ holozoic)

4.      Reproduction

5.      Phylogenic relationships (revolutionary history)

 

Five kingdoms are

1.   Kingdom Monera (bacteria ) – prokaryotic unicellular

2.    Kingdom Protista ( amoeba ) – eukaryotic unicellular

3.    Kingdom Fungi - multicellular eukaryotic

4.      Kingdom Plantae - multicellular eukaryotic

5.    Kingdom Animalia – multicellular eukaryotic

1.Kingdom - Monera

• Unicellular, prokaryotes and contain the most primitive of living forms
• cell wall is generally present.
• Extremophilic (extreme environments conditions)
• Membrane bounded organelles are absent.
• Reproduction is asexual
• Flagella may be present and are of single stranded.
• Mode of nutrition – autotrophs and hetetrophs.

Based on shape, bacteria are 4 types: Coccus (Spherical),

Bacillus (Rod-shaped), Vibrium (Comma-shaped) &

Spirillum (Spiral).

I. Archaebacteria

• They are most primitive prokaryotes 
• which live under most hostile conditions like extreme salty area (halophiles), hot springs (thermoacidophiles) and marshy area (methanogens). 
• Methanogens are present in the gut of several ruminant animals like cows and buffalo, which is responsible for production of biogas (methane) from dung of these animals.

II. Eubacteria (‘true bacteria’)

• They have a rigid cell wall and a flagellum (ifmotile).
• They include Autotrophs (photosynthetic and chemosynthetic) and Heterotrophs.
• Cyanobacteria or blue-green algae photosynthetic bacteria. 
• They may be unicellular, colonial or filamentous, fresh water, marine or terrestrial. Some of them have specialized heterocyst cells to perform nitrogen fixation (Eg. Nostoc)
• Chemosynthetic bacteria oxidize inorganic substances like nitrate, nitrite, ammonia etc. to produce energy and help in recycling of nitrogen, phosphorous, sulphur etc.
• Heterotrophic bacteria – Decomposers – making curd from milk, antibiotics, nitrogen fixing (Rhizobium ) some are pathogenic ( cause diseases ) cholera, T.B, diarrhea. Reproduction by binary fission, spore / sexual reproduction

III. Mycoplasma – 

• Mycoplasmas are organisms without a cell wall. They are the
• smallest living cells. They can survive without oxygen.
• They cause disease in plants and animals.

2.Kingdom - Protista

• Unicellular
• Eukaryotic
• It is connecting link with plants, animals and fungi.
• Primarily  aquatic
• Flagella / cilia str.
• Reproduce sexually / asexually

a) Chrysophyta :

•  diatoms (planktons)  and golden algae ( desmids )

• Fresh water/ marine moist places

• photosynthetic Autotrophs

• In diatoms, cell wall is indestructible (silica )form diatomaceous earth

• Reproduction Binary fission
• Diatoms are the chief ‘producers’ in the oceans.

b)Dinoflagellates:

• mostly Marine photosynthetic
•  yellow, green, blue or red pigmented 
• Asexual 
• Rigid Coat Cell wall is cellulosic 
• Most of them have 2 flagella; one lies longitudinally and the other transversely in a furrow between the wall plates
• Red dinoflagellates (E.g. Gonyaulax) undergo rapid multiplication so that the sea appears red (red tides). They release toxins that kill marine animals like fishes.

c)Euglenoid 

• eg. Euglena
• Fresh water 
• longitudinal binary fission
• no cell wall (flexible protein layer is present,called pellicle) with flagella
• they are Mixotrophic, because Photosynthetic (in light) Heterotrophs (when no light).(Mixotrophs Means – Mixture of both autotrophs and heterotrophs.)

d)Slime moulds.

• Saprophytic – body moves on decaying twigs and leaves
• moist Places.
• During fav. conditions form plasmodium(free living & Multinucleate) 
• Unfavourable conditions form spores and survive for many years.

e)Protozoans – 

• Heterotrophs – predators/ parasites
• diverse habitat

There are4 major groups;

i) Amoeboid protozoans. Fresh water, sea and moist soil -pseudopodia – marine forms have silica shells . Entamoeba (parasite) cause Amoebic dysentery

ii) Flagellated protozoans - free living / parasites have flagella – parasites cause diseases – Sleeping sickness(Trypanoroma)is a parasite of flagellated protozoans.

iii)Ciliated protozoans – aquatic cilia, cavity gullet eg. Paramoecium.

iv)Sporozoans – Spore stage in their life cycle. Plasmodium causes malarial fever.

3. Kingdom - Fungi:

• Multicellular – eukaryotic –cosmopolitan -grow in warm and humid places.

• Fungi are filamentous with long, slender thread like Hyphae and the net work of hyphae is known as Mycelium – They can be septate or non septate (aseptate)

• Multinucleated cytoplasm (coenocytic hyphae)

• Cell wall is chitin.

• heterotrophic - Saprophytic/Parasitic/ symbionts

• Symbionts of algae and fungi(Lichens) and Pine trees roots and fungi(Mycorrhizae)on roots to absorb water.

• Reproduction by fragmentation, fission, budding

• Asexual reproduction by oospores, ascospores, basidiospores.

• Sexual reproduction steps.

1. Plasmogamy

2. Karyogamy

1. Phycomycetes :

▪ Aquatic decaying wood mycelium is aseptate coenocytic

▪ asexual reproduction by zoospores (motile ) / aplanospores ( non motile )

Sexual reproduction: isogamous (similar in morphology)or oogamous (dissimilar).

▪ Eg. Rhizopus, mucor.

2. Ascomycetes :

▪ Multicellular (penicillium )/Unicellular ( yeast )

▪ Saprophytic – decomposers – parasitic

▪ Mycelium is branched and septate –asexual spores are called conidia

▪ Sexual spores are called ascospores.

▪ Eg. Aspergillus

3. Basidiomycetes : Eg. Agaricus (Mushroom)

▪ Grow in soil, logs, tree stumps,in plant bodies as parasitic (as rust and smuts)

▪ Mycelium is branched and septate

▪ Reproduction by fragmentation(Asexual)

▪ Sexual by somatic cell (somatogamy)

▪ Eg. Agaricus(mushroom)

4. Deuteromycetes :

▪ Imperfect fungi mycelium is septate and branched.

▪ Only asexual reproduction by conidial spores

▪ Saprophytes/ parasitic / decomposers

▪ Eg. Trichoderma, Alternaria

4.Kingdom - Plantae :

-eukaryotic chlorophyll-containing organisms with cellulosic cell wall.

- Some are partial heterotrophs (e.g. insectivorous plants or Venus flytrap) or parasites (e.g. Cuscuta). 

- Plantae includes algae, bryophytes, pteridophytes, gymnosperms and angiosperms. 

5.Kingdom Animalia :

-multicellular, heterotrophic, eukaryotic - They have a definite growth pattern 

-without cell wall. definite shape and size.

- They directly or indirectly depend on plants for food

- They digest their food in an internal cavity and store food

-capable of locomotion.

-Their mode of nutrition is holozoic (by ingestion of food).

- The sexual reproduction 

(viruses, viroids & prions) and lichens a

- non-cellular and not truly ‘living’. 

- inert crystalline structure outside the living cell.

- Viruses are obligate parasites.

- When they infect a cell, they take over the machinery of host cell to replicate 

-A virus is a nucleoprotein, i.e., it has a protein coat

(capsid) & genetic material (RNA or DNA).

-D.J. Ivanowsky (1892) discovered virus.

- No virus contains both RNA & DNA.

- Generally, plant viruses have single stranded RNA. Animal viruses have either single or double stranded RNA or double stranded DNA. 

-Bacteriophages (viruses that infect bacteria) usually have double stranded DNA.

- The capsid made of small subunits (capsomeres) protects nucleic acid. 

Viroid: It is an infectious agent with a free low molecular weight RNA and no protein coat. These are smaller than viruses. It is discovered by T.O. Diener (1971). He found

that it caused potato spindle tuber disease.

Prions: These are abnormally folded protein that cause some infectious neurological diseases. These are similar in size to viruses. They cause mad cow disease in cattle and

Cr-Jacob disease (CJD) in humans.

Lichens : symbiotic associations between algae & fungi.

-The algal component is called phycobiont (autotrophic) and fungal component is mycobiont (heterotrophic)

-Algae prepare food and fungi provide shelter and absorb nutrients and water 

-Lichens are very good pollution indicators. They do not grow in polluted areas.