Solved Examples

How to Use This Section

This chapter carries no formulae and almost no mechanism. What it carries is precision - exact definitions, exact example organisms, exact rank order. So the questions here are built to test whether your recall is precise, not merely present.

The 32 questions are organised in three tiers:

1. Concept Checks - direct definition and recall, the kind that appear as straight NEET recall items.
2. Application and Scenarios - you are handed a name, an organism or a sequence and asked to act on it.
3. Analytical and Multi-Concept - reasoning that pulls two or three parts of the chapter together, which is where the harder NEET items live.

Work them with the answer covered. If you get a Tier 1 item wrong, the fix is a re-read, not more practice.

Coverage of the chapter-end exercises

Every chapter-end exercise is worked here, so this section is the one place to check that you have covered the textbook in full.

The Facts These Examples Draw On

A compressed reference so you can check yourself without flipping back.

• Described species: 1.7 - 1.8 million. Biodiversity = number and types of organisms present on earth.
• ICBN plants, ICZN animals.
• Binomial nomenclature, given by Carolus Linnaeus: Generic name + specific epithet; Latin, italics, separately underlined when handwritten, genus capitalised, epithet in small letters, author abbreviated at the end.
• Four processes basic to taxonomy: characterisation, identification, classification, nomenclature.
• Systematics from Latin systema; Linnaeus's Systema Naturae; accounts for evolutionary relationships.
• Hierarchy (ascending): species, genus, family, order, class, Phylum/Division, kingdom.
• Trend: species to kingdom - shared characteristics decrease, difficulty of determining relationships increases.
• Key groups: Panthera (leo, tigris, pardus) and Felis to Felidae; Felidae + Canidae to Carnivora; Primata + Carnivora to Mammalia; classes to Chordata (notochord + dorsal hollow neural system). Solanum, Petunia, Datura to Solanaceae; Solanaceae + Convolvulaceae to Polymoniales (floral characters).

Tier 1 - Concept Checks

Question 1

Q. What is meant by biodiversity in this chapter?

Answer. Biodiversity here means the number and types of organisms present on earth. The species known and described so far come to between 1.7 and 1.8 million.

Question 2

Q. Why is nomenclature necessary?

Answer. Because local names vary from place to place, even within a country. A standardised name makes sure one organism is known by the same name all over the world.

Question 3

Q. Which code governs plant names and which governs animal names?

Answer. ICBN - International Code for Botanical Nomenclature - for plants. ICZN - International Code of Zoological Nomenclature - for animals.

Question 4

Q. What are the two components of a binomial name called?

Answer. The generic name and the specific epithet.

Question 5

Q. Who is credited with the binomial system of nomenclature?

Answer. Carolus Linnaeus.

Question 6

Q. Define a taxon and give examples at different hierarchical levels.

Answer. A taxon is a unit of classification, a category standing for a rank in the taxonomic arrangement. Taxa sit at very different levels: 'plants', 'animals', 'mammals', 'dogs' and 'wheat' are all taxa, even though a dog is a mammal and mammals are animals. The same thing with formal ranks attached: Homo sapiens (species), Panthera (genus), Felidae (family), Carnivora (order), Mammalia (class), Chordata (phylum), Animalia (kingdom).

Takeaway: This one is set at the end of the chapter. Give both the definition and examples at more than one level. This is one of the chapter-end exercises.

Question 7

Q. Define classification.

Answer. Classification is sorting things into convenient categories on the basis of some easily observable characters.

Question 8

Q. Name the four processes basic to taxonomy.

Answer. Characterisation, identification, classification and nomenclature.

Question 9

Q. From which word is systematics derived and what was the title of Linnaeus's publication?

Answer. From the Latin systema, meaning systematic arrangement of organisms. Linnaeus's publication was titled Systema Naturae.

Question 10

Q. Define and understand the following terms: (i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus.

Answer.

• (i) Phylum - the category just above class in animals. It pulls together classes like fishes, amphibians, reptiles, birds and mammals. In plants the same thing is called a Division.
• (ii) Class - it holds related orders, so Mammalia takes in Primata and Carnivora.
• (iii) Family - a group of related genera, with still fewer similarities than you find inside a genus or a species. In plants, families are characterised on both vegetative and reproductive features.
• (iv) Order - an assemblage of families that show a few similar characters, like Carnivora and Polymoniales.
• (v) Genus - a group of related species sharing more characters than species of other genera do. Genera are aggregates of closely related species.

Takeaway: This is one of the chapter-end exercises, verbatim. One line each is enough.

Question 11

Q. Which is the lowest taxonomic category, and does it apply to plants as well as animals?

Answer. Species - and yes, all organisms, including those in the plant and animal kingdoms, have species as the lowest category.

Question 12

Q. On what basis were the earliest classifications made?

Answer. On the 'uses' of various organisms, because early human beings needed sources for their basic needs of food, clothing and shelter.

Tier 2 - Application and Scenarios

Question 13

Q. Identify the correctly written name: Mangifera Indica or Mangifera indica.

Answer. Mangifera indica. The specific epithet has to start with a small letter. This is one of the chapter-end exercises.

Question 14

Q. Rewrite musca DOMESTICA linnaeus correctly and list the corrections.

Answer. Correct form: Musca domestica Linn.

1. musca to Musca - the genus takes a capital letter.
2. DOMESTICA to domestica - the specific epithet takes a small letter, not capitals.
3. Both words must be italicised in print, or separately underlined when handwritten.
4. linnaeus to Linn. - the author's name is written in abbreviated form, capitalised, at the end, and is not italicised.

Question 15

Q. Given Panthera leo, Panthera pardus, Felis catus - group these by genus and then state the family.

Answer. **Genus *Panthera: P. leo, P. pardus. **Genus *Felis: F. catus. Both genera are placed in the family Felidae.

Question 16

Q. Arrange in ascending order: Family, kingdom, species, order, genus, class, phylum.

Answer. Species, genus, family, order, class, phylum, kingdom.

Question 17

Q. Can you identify the correct sequence of taxonomical categories? (a) Species - Order - Phylum - Kingdom (b) Genus - Species - Order - Kingdom (c) Species - Genus - Order - Phylum

Answer. (a) and (c) are correct. Both list ranks in ascending order, skipping some but never reversing any. (b) is incorrect because it puts genus before species.

Takeaway: This is one of the chapter-end exercises. A sequence with gaps is still correct; a sequence with an inversion is not.

Question 18

Q. A plant's classification reads: Family Poaceae, order Poales, class Monocotyledonae, division Angiospermae. Name the plant and its binomial.

Answer. Wheat, Triticum aestivum, genus Triticum.

Question 19

Q. An animal is placed in Muscidae, Diptera, Insecta, Arthropoda. Identify it and give its genus.

Answer. The housefly, Musca domestica, genus Musca.

Question 20

Q. What different criteria would you choose to classify people that you meet often?

Answer. There is no single right answer here, and that is the lesson. Any set of easily observable characters that gives you convenient categories will do. You could go by where you meet them (school, neighbourhood, family), how often you meet them, their occupation, their age group, their language, or shared interests. Each of these cuts the same set of people into different groups, so classification depends on the characters you pick and on what you want the classification for.

Takeaway: This one is set at the end of the chapter. Marks come from naming criteria and noting that different criteria yield different groupings. This is one of the chapter-end exercises.

Question 21

Q. Why are living organisms classified?

Answer. Because it is nearly impossible to study all the living organisms one by one - there are 1.7 to 1.8 million described species and the count keeps rising. Putting them into convenient categories based on easily observable characters makes the study possible, lets you read off a whole group's characters from the group name, and shows up the relationships between organisms.

Takeaway: This is one of the chapter-end exercises.

Question 22

Q. Why are classification systems changing every now and then?

Answer. Because the evidence base keeps growing and improving. New organisms are continuously being identified as we explore new areas and even old ones, so the groupings have to make room for them. Modern taxonomy also works from external and internal structure, cell structure, development process and ecological information, so as better information on each turns up, old placements get revised. And systematics takes evolutionary relationships into account, and our understanding of those keeps changing too.

Takeaway: This is one of the chapter-end exercises - a 3-mark answer needs the new-organisms point and the improved-evidence point.

Question 23

Q. What do we learn from the identification of individuals and populations?

Answer. Identification tells you what organism a name is attached to, and without that you cannot name it at all. Along the way you learn the organism's characters - external and internal structure, cell structure, development and ecology - so you know where it belongs in the taxonomic hierarchy. Across populations, identification brings out the similarities and dissimilarities among individuals of the same kind and of different kinds, and that is exactly what you need to put organisms into categories and to spot the relationships among them.

Takeaway: This one is set at the end of the chapter. This is one of the chapter-end exercises.

Question 24

Q. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

Answer.

Animal - man: species sapiens, genus Homo, family Hominidae, order Primata, class Mammalia, phylum Chordata, kingdom Animalia. Biological name Homo sapiens.

Plant - wheat: species aestivum, genus Triticum, family Poaceae, order Poales, class Monocotyledonae, division Angiospermae, kingdom Plantae. Biological name Triticum aestivum.

Notice that the animal gets a phylum while the plant gets a division at the same rank.

Takeaway: This is one of the chapter-end exercises. Give one plant and one animal, and go all the way to kingdom.

Tier 3 - Analytical and Multi-Concept

Question 25

Q. Two organisms share a family. A third shares only a class with them. Rank the three pairings by number of shared characters and justify.

Answer. The two family-mates share the most, and either of them paired with the third shares fewer. That comes straight from the central trend - the lower the taxon, the more characteristics its members share - and family sits below class. Two organisms that agree all the way down to family have also agreed at order, class, phylum and kingdom on the way there. Two that agree only at class split earlier, so they share less.

Question 26

Q. Explain why a cat and a dog are separated at one rank and united at the next one up.

Answer. A family groups related genera on a fairly tight set of shared characters, and cat and dog differ enough to fall into two of them - Felidae and Canidae. An order, though, is an assemblage of families exhibiting only a few similar characters, which is a looser test, so at that rank both families go into Carnivora. There is no real contradiction - the test relaxes as you climb, so groups that were separate below end up united above.

Question 27

Q. Distinguish between taxonomy and systematics, and state which is broader.

Answer. Taxonomy is the process of classification - sorting organisms into taxa by their characters, working from external and internal structure, cell structure, development process and ecological information. Systematics started as the study of the relationships among organisms, and its scope was later enlarged to include identification, nomenclature and classification. It also takes evolutionary relationships into account. So Systematics is the broader term.

Question 28

Q. "Higher the category, greater is the difficulty of determining the relationship to other taxa at the same level." Explain the causal chain.

Answer. As you climb the hierarchy, each rank holds more organisms but its members share fewer common characteristics. You judge relationships between taxa from shared characters, so with fewer of them you have less evidence for deciding whether two taxa at the same level belong together. On top of that, higher categories are picked out from aggregates of characters rather than from a few decisive ones, so the call becomes more of a judgement. That is why the problem of classification becomes more complex.

Question 29

Q. A taxonomist has a specimen and wants to give it a valid scientific name. Set out the complete procedure, naming the process at each step.

Answer.

1. Characterisation - record the specimen's external and internal structure, cell structure, development and ecology.
2. Identification - work out correctly what organism this is, and whether it matches an already-described species.
3. Classification - place it in the hierarchy: Species, genus, family, order, class, phylum or division, kingdom.
4. Nomenclature - give it a binomial under the ICBN if it is a plant or the ICZN if it is an animal. Check that the name has not been used for any other known organism, capitalise the genus, keep the epithet in small letters, italicise both, and put the author's abbreviation at the end.

These four are exactly the processes basic to taxonomy.

Question 30

Q. From Table 1.1, which two of man, housefly, mango and wheat are the most distantly related, and how do you know from the table alone?

Answer. Man and housefly, or man and either plant. Within the animals, man and housefly are as far apart as the table lets them be. They share no category at all in it, differing at phylum (Chordata vs Arthropoda), class (Mammalia vs Insecta), order (Primata vs Diptera), family (Hominidae vs Muscidae) and genus. Mango and wheat at least share the division Angiospermae. The table on its own settles this, because agreement at the highest rank listed is the strongest relationship it can record.

Question 31

Q. Try to collect all the currently accepted meanings for the word 'species'. Discuss the meaning of species in higher plants and animals on one hand, and bacteria on the other.

Answer. In this chapter a species is a group of individual organisms with fundamental similarities, kept apart from closely related species by distinct morphological differences. That is the morphological criterion. For higher plants and animals you usually add the biological sense on top: members of a species can interbreed among themselves and are reproductively separated from other such groups. Ernst Mayr pioneered that definition, which is why he is introduced on the unit-opening page. For bacteria neither test works cleanly. Bacteria are morphologically simple, so there are few distinct morphological differences to go on, and they reproduce asexually, so interbreeding cannot be the test. Bacterial species are marked off by other evidence instead - biochemical, physiological and genetic similarity.

Takeaway: This one is set at the end of the chapter. It is an open-ended discussion question; the marks are in recognising that one definition does not fit all groups. This is one of the chapter-end exercises.

Question 32

Q. A student argues: "Since Panthera leo and Panthera tigris share a genus, and a genus is an aggregate of closely related species, the two must be able to be treated as one species." Dismantle this.

Answer. The premise is right but the conclusion does not follow. A genus really is an aggregate of closely related species - and the word doing the work there is species, plural. The definition itself requires that one species be distinguishable from another closely related species on the basis of distinct morphological differences, and lion and tiger clearly are. Sharing a genus only means sharing more characters in comparison to species of other genera, not sharing all of them. Merging the two would also wreck the point of the binomial system, where the second word exists precisely to separate species inside one genus - leo, tigris, pardus.

Takeaway: Questions that push a correct definition one step too far are common at the hard end of NEET. The defence is always to re-read the definition and find the word being overrun.