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Plant Kingdom

Biology · Class 11NCERT pp. 23–342 sets × 25 questionsFree

Key facts and formulas for Plant Kingdom, three worked sample questions, and two full practice sets. Every question has a hint, a reason for every option and a step-by-step solution, with a calculator or animation where one helps. English and Hinglish.

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Key facts for this chapter

IdeaRule or fact
Algal pigmentsGreen: chlorophyll a, b. Brown: a, c with fucoxanthin. Red: a, d with phycoerythrin.
Algal food and wallsGreen: starch, cellulose inside and pectose outside. Brown: laminarin or mannitol, cellulose with algin. Red: floridean starch.
HydrocolloidsAlgin from brown algae, carrageen from red algae, agar from Gelidium and Gracilaria.
Sexual reproduction in algaeUlothrix and Spirogyra isogamous, Eudorina anisogamous, Volvox and Fucus oogamous. Chlamydomonas varies by species.
BryophytesDominant haploid gametophyte, sporophyte of foot, seta and capsule; water needed for fertilisation; gemmae for asexual reproduction.
PteridophytesFirst vascular land plants; dominant sporophyte; free-living prothallus; Psilotum, Selaginella, Equisetum, Adiantum.
GymnospermsNaked seeds, heterosporous, wind pollination, pollen tube, tracheids but no vessels, haploid endosperm. Cycas coralloid roots, Pinus mycorrhiza.
Life cyclesHaplontic: Chlamydomonas. Diplontic: Fucus, seed plants. Haplodiplontic: Ectocarpus, bryophytes, pteridophytes.
SexualityMonoecious: Chara, Pinus. Dioecious: Cycas, Marchantia, papaya.
AngiospermsFlowers and fruits; Wolffia smallest, Eucalyptus over 100 m; Sequoia is a gymnosperm.

Three sample questions

Q1. Linnaeus based his classification of plants chiefly on
  1. evolutionary relationships
  2. vegetative characters or the structure of the androecium
  3. chromosome number
  4. chemical constituents
Hint and solution

Hint: Linnaeus gave an early, artificial scheme. Think of what could be seen easily without a microscope, such as the male reproductive whorl.

  1. Linnaeus = artificial system — The question asks the basis of Linnaeus's plant classification. His scheme is an early artificial system.
  2. Artificial = few easy characters — Artificial systems use a few external features, not the whole organism or its ancestry.
  3. Linnaeus: vegetative + androecium — So evolutionary, chromosomal and chemical bases are ruled out.
  4. Answer: vegetative characters and androecium — The correct basis is vegetative characters or the structure of the androecium. Option B.
Answer: B. Such schemes are called artificial.
Q2. Consider artificial systems of classification.
I. They used only a few characters.
II. Vegetative and sexual characters were given equal weight.
III. Close relatives could be placed in different groups.
Which are correct?
  1. I and II only
  2. II and III only
  3. I and III only
  4. I, II and III
Hint and solution

Hint: Recall the main flaws of artificial systems: few characters, equal weight to all, and unrelated or related plants wrongly grouped.

  1. I: few characters used — Artificial systems used only a few characters, so statement I is true.
  2. II: equal weight to all — They gave equal importance to vegetative and sexual characters, although vegetative ones change with environment. II is true.
  3. III: relatives separated — Because of this, closely related plants could land in different groups. III is true.
  4. Answer: I, II and III — All three are correct, so the answer is I, II and III. Option D.
Answer: D. All three were weaknesses; vegetative features are easily modified by the environment.
Q3. Natural classification uses internal evidence such as
  1. ultrastructure, anatomy, embryology and phytochemistry
  2. only leaf shape
  3. only flower colour
  4. only habit
Hint and solution

Hint: Natural systems go beyond outer form. Which option lists inside-the-organism features?

  1. Natural = many characters — Natural systems use the natural affinities among organisms, based on many characters.
  2. Internal evidence = inside features — Internal evidence means ultrastructure, anatomy, embryology and phytochemistry.
  3. Single external traits = artificial — Leaf shape, flower colour or habit alone are external, so they fail.
  4. Answer: first option — The internal evidence is ultrastructure, anatomy, embryology and phytochemistry. Option A.
Answer: A. Natural systems look beyond external form.

How to use this chapter

Read the NCERT pages first, then attempt Set 1 without the hints. Note every wrong answer in a mistake list, read the reason for each option, and retry Set 2 two days later. A topic is solid when you can say why each wrong option is wrong.

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