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Biological Classification

Biological Classification

Biological Classification

Introduction:

A close analysis of Botany Chapter ‘Biological Classification‘ based on previous 22 years exam questions ( between 2000-2021) suggests that overall weight of this chapter in the NEET Exam is 10% which means on an average 5-7 questions are asked from this chapter each year.

The high priority topics of the chapter ‘Biological Classification‘ from which there is greater chance of occurrence in the NEET Exam are listed below.

1.Kingdom Monera | 2.Kingdom: Plantae | 3.Kingdom Fungi | 4.Viruses, Viroids And Lichens

The students are advised to practice at least 200-300 questions from the high priority topics mentioned above.

Noteworthy Points of the Chapter :

1. Aristotle was the earliest scientist to attempt a more scientific basis for classification. He used simple morphological characters to classify plants into trees, shrubs and herbs.

2. Linnaeus proposed Two Kingdom system of classification. He placed all the organisms into kingdoms Plantae and Animalia.

3. The Five Kingdom classification system proposed by Whittaker is based on criterias like cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships.

4. He proposed five kingdoms Monera, Protista, Fungi, Plantae and Animalia.

5. Monera includes all prokaryotes.

6. Protista includes unicellular eukaryotes.

7. Fungi includes organism with multicellular, loose tissue organisation and chitinuous cell wall.

8. Monera later on divided into two kingdoms Archaebacteria and Eubacteria.

9. The three-domain system has also been proposed that divides monera into two domains and placed all eukaryotes in single domain.

10. Archaebacteria live in extreme conditions such as salty area (halophiles) hot springs (thermoacidophiles) and marshy area (methanogens).

11. Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane from the dung of these animals.

12. In Nostoc, the site of nitrogen fixation is heterocysts.

13. Cholera, tetanus, and citrus canker are well known diseases caused by different bacteria.

14. Bacteria asexually reproduce mainly by fission. Sexual reproduction includes primitive type of DNA transfer. Exampraxis.com

15. Mycoplasma are organisms that completely lack a cell wall. They are smallest living cells known and can survive without oxygen.

16. Chrysophytes, euglenoids, slime moulds and protozoans belong to the kingdom Protista.

17. Chrysophytes include diatoms and desmids. 18. In diatoms, the cell wall forms two thin overlapping shells, that fit together as in a soap box.

19. Diatoms left behind large amount of cell wall (impregnated with silica) deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’.

20. Diatoms are the chief ‘producers’ in the oceans.

21. Dinoflagellates are mostly marine and photosynthetic. Red dinoflagellate (Gonyaulax) makes the sea appear red.

22. Euglenoids are fresh water organisms found in stagnant water. Instead of cell wall, they have a protein rich layer called pellicle which makes their body flexible. They are photosynthetic but in absence of sunlight behave as heterotroph.

23. Slime moulds are saprophytic protists.

24. Under suitable conditions, slime moulds form an aggregation called plasmodium which may grow and spread over several feet.

25. There are four major groups of protozoans like amoeboid, flagellated, ciliated and sporozoans.

26. Sleeping sickness is caused by a flagellated protozoan called Trypanosoma.

27 Fungal body is made up of thread like hyphae (coenocytic or septate/uninucleate).

28. Fungi can live as symbionts- in association with algae as lichens and with roots of higher plants as mycorrhiza.

29. Fungi growing on cattle dung are called coprophilous.

30. Fungi asexually reproduce through zoospores, conidia, sporangiospores, oidia and chlamydospores.

31. Fungi produce sexual spores or meiospores like ascospores and basidiospores. 

32. Mycelium is aseptate and coenocytic in phycomycetes.

33. Fusion of protoplasm between two motile or non-motile gametes is called plasmogamy.

34. In phycomycetes, asexual reproduction takes place by zoospores and aplanospores.

35. Albugo (parasite on mustard) and Mucor belong to the phycomycetes group of fungi.

36. Ascomycetes are commonly known as sac-fungi.

37. Asexual spores, conidia are produced in ascomycetes.

38 Ascospores are endogenously produced.

39. Neurospora, yeast, morels, truffles and Claviceps belong to the class ascomycetes.

40. In basidiomycetes, asexual spores are generally not found, but vegetative reproduction by fragmentation is common.

41. In basidiomycetes, sex organs are absent but plasmogamy is brought about by fusion of two vegetative or somatic cells of different strains or genotypes.

42. The basidiospores are exogenously produced on the basidium.

43 Puccinia, Agaricus and Ustilago belongs to basidiomycetes.

44. Deuteromycetes are commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known.

45. The deuteromycetes reproduce by asexual spores known as conidia.

46. Alternaria, Colletotrichum and Trichoderma belongs to class deuteromycetes.

47. Bladderwort and Venus fly trap are examples of insectivorous plants and Cuscuta is a parasite.

48. The viruses are non-cellular and are characterized by having an inert crystalline structure outside the living cell.

49. The name virus that means venom or poisonous fluid was given by Pasteur. W.M.Stanley showed that viruses could be crystallized and crystals consist largely of protein.

50. Viruses are obligate parasites.

51. In general, viruses that infect plants have single stranded RNA like TMV and viruses that infect animals have either single or double stranded RNA or double stranded DNA.

52. Bacterial viruses or bactriophages are usually double stranded DNA viruses. Exampraxis.com

53. Viroids are smaller than viruses, contains only RNA and cause potato spindle tuber disease.

54. Prions are abnormally folded proteins, smaller than viruses and causal agent of some neurological diseases like Cr-Jacob, bovine spongiform encephalopathy (BSE) and mad cow.

55. In lichens, the algal component is known as phycobiont and fungal component as mycobiont.

56. In five kingdom classification of Whittaker there is no mention of lichens and viruses, viroids and prions