Short & Long Question Answers with Solution: Plant Kingdom | Biology Class 11 - NEET PDF Download

 Short Answer Type Questions 

 Q.1. Why are bryophytes considered amphibians of the plant kingdom?
 Ans:  Bryophytes are often likened to amphibians in the plant kingdom because they require water for the movement of male gametes (antherozoids) to reach the archegonium for fertilisation. This reliance on water links bryophytes closely to aquatic environments, much like amphibians that live both in water and on land.

 Q2. If the diploid number of chromosomes of a flowering plant is 36 chromosomes, what would be the chromosome number in the endosperm of the flowering plant? 
 (a) 36
(b) 18
(c) 54
(d) 72 
Ans: (c)

Explanation: Since the flowering plant is diploid with 2n = 36 chromosomes, the haploid number n = 18. The endosperm is triploid (3n), so the chromosome number in the endosperm will be 3 × 18 = 54.

 Q3. Does heterospory have some evolutionary significance in the plant kingdom?
 Ans:  Pteridophytes occupy an intermediate evolutionary position between bryophytes and gymnosperms. Early pteridophytes are homosporous, but more advanced pteridophytes exhibit heterospory. Bryophytes are homosporous, whereas gymnosperms are heterosporous. The evolution of heterospory is significant as it provides a basis for seed habit development.

 Q4. Protonema is
 (a) Haploid and is found in mosses
 (b) Diploid and is found in liverworts
 (c) Diploid and is found in pteridophytes
 (d) Haploid and is found in pteridophytes
 Ans:  (a)
Explanation: Protonema is the juvenile stage in the life cycle of mosses, which is haploid. It often resembles multicellular green algae in appearance.

 Q5. Discuss the phylogenetic relationship of Cycas with any other group of plants.
 Ans:  Cycas is a perennial plant superficially resembling a palm tree, showing phylogenetic links with pteridophytes. Its evolutionary features include:

• Seed dispersal while the embryo is still undeveloped.
• Slow or gradual growth rate.
• Monocyclic wood structure.
• Limited secondary growth.
• Megasporophylls resembling leaves.
• Coiled young leaves (circinate vernation).
• Persistent leaf bases.
• Well-defined arrangement of microsporangia and archegonia.

 Q6. Mycorrhiza and coralloid roots are found in which plants? What do these terms mean? 
Ans: Mycorrhiza is a mutualistic association between fungi and the roots of vascular plants. Such mycorrhizal relationships are commonly found in coniferous trees like Pinus and Cedrus. Coralloid roots are specialized roots found in Cycas; these roots form coral-like clusters near the stem base, often growing above the ground. They have a greenish colour and display dichotomous branching. These roots harbour nitrogen-fixing cyanobacteria, aiding the plant’s nutrition.

 Q7. The respective male and female reproductive organs of several pteridophytes and gymnosperms are comparable to the floral structures of the angiosperms. Compare the various reproductive parts of pteridophytes and gymnosperms with the reproductive structures of angiosperms.
 Ans:  

The reproductive parts that correspond to angiosperm structures are:

1. Strobili/cone – Flower
2. Microsporophyll – Stamen
3. Megasporophyll – Pistil/Carpel
4. Microsporangium – Anther
5. Megasporangium – Ovule

 Q8. The heterosporous pteridophytes exhibit certain characteristics which are precursors to the seed habits in gymnosperms. Explain.
 Ans:  Heterospory is the production of two types of spores: megaspores and microspores. Microspores develop into male gametophytes producing male gametes, while megaspores develop into female gametophytes that produce archegonia to nourish the developing embryo. Heterospory leads to a reduction in the size of the gametophyte and the development of more specialised reproductive structures. This process in pteridophytes represents a key evolutionary step toward the seed habit seen in gymnosperms.

 Q9. What do you mean by double fertilisation and triple fusion?
 Ans:   Double fertilisation involves the fusion of two male gametes with two different female nuclei. One male gamete fuses with the egg cell to form a diploid zygote, while the other male gamete fuses with the two polar nuclei in the ovule to form a triploid cell, which develops into the endosperm. The fusion of the three haploid nuclei forming the triploid endosperm is called triple fusion.

 Q10. When the fruit ripens, what changes take place?
 Ans: Three key changes occur during fruit ripening:

• Conversion of starch into sugars, increasing sweetness.
• Breakdown of chlorophyll, leading to changes in the fruit’s colour.
• Changes in taste, texture, and flavour due to the production of various organic compounds.

 Long Answer Type Questions 

 Q1. Explain the alternation of generation in bryophytes briefly.
 Ans: Bryophytes are non-vascular plants requiring water for fertilisation. Their life cycle shows alternation of generations between an independent gametophyte and a dependent sporophyte. The gametophyte produces sexual organs (antheridia and archegonia) that form gametes, while the sporophyte produces spores. The alternation between these two stages is called the alternation of generation.
For example, in mosses, the spore germinates to form a protonema (juvenile stage), which then develops into the mature gametophyte producing male and female gametes. Fertilisation leads to the formation of the sporophyte, completing the cycle.

 Q2. How is gametophyte a dominant phase in the life cycle of bryophytes? 
Ans: In bryophytes, the gametophyte is the dominant and conspicuous phase of the life cycle. It possesses specialized structures: antheridia (male reproductive organs) that produce antherozoids, and archegonia (female reproductive organs) that produce egg cells. Fertilisation occurs when antherozoids swim to the eggs.
The zygote formed grows into the sporophyte, which remains attached and dependent on the gametophyte for nutrition. Sporophytes eventually produce spores, which disperse and grow into new gametophytes, thus completing the cycle.

 Q3. What are the different lifestyles shown by Angiosperms? 
Ans: Angiosperms demonstrate four major lifestyles:

• Hydrophytic plants. These grow in water or marshy areas. They are either submerged (e.g., Hydrilla, Vallisneria) or free-floating (e.g., Pistia, Nymphaea).
• Halophytes. These are xerophytes adapted to saline or marine environments and cannot survive in fresh water.
• Xerophytes. Adapted to survive water scarcity, such as cacti, they can thrive with minimal water.
• Insectivorous plants. These plants trap insects to supplement nitrogen deficiency, important for their nutrition. Examples include the pitcher plant and sundew.

 Q4. Describe the life cycle of a plant. 
Ans: The plant life cycle begins with seed formation. Under favourable conditions, the seed germinates into a young plant, which grows and produces flowers. Pollination and fertilisation lead to the development of fruits containing seeds.
As the plant completes its life cycle and dies, the seeds disperse and germinate under suitable conditions, giving rise to new plants. This cyclical process maintains the continuity of plant species.

 Q5. Describe the main features of pteridophytes. 
Ans: Pteridophytes are predominantly tropical and humid environment plants. They are small and have distinct roots, stems, and leaves. They are vascular plants with xylem and phloem but do not produce flowers or seeds; instead, they reproduce by spores.
Pteridophytes are multicellular and exist independently. Examples include ferns, horsetails, and clubmosses. They represent the first group of plants to develop vascular tissue allowing efficient water (via xylem) and food (via phloem) transport. Xylem conducts water unidirectionally (roots to leaves), whereas phloem can transport food bidirectionally.

 Q6. What are parasitic algae? 
Ans: Parasitic algae are plant pathogens that commonly occur in warm, humid climates. They infect plants with leathery leaves such as litchi, hollies, magnolias, and viburnums, causing foliar diseases. An example is the red rust disease of tea leaves caused by the parasitic green alga Cephaleuros. These algae can adversely affect plant health and productivity, making their control important in agriculture and horticulture.

 Q7. What is heterospory? Briefly comment on its significance. Give two examples. 

Ans: Heterospory is the production of two distinct types of spores by a single plant: microspores and megaspores. Microspores are smaller and develop into male gametophytes that produce male gametes. Megaspores are larger and develop into female gametophytes that produce female gametes.
Megaspores develop within megasporangia, aiding proper development of the zygote after fertilisation. Fertilisation between microgametes and megagametes forms the zygote. Heterospory marks an evolutionary advancement and was first noted in plants such as Selaginella and Salvinia.

 Q8. What are angiosperms? Give their characteristic features. 
Ans:

The characteristic features of angiosperms include:

• The ovules are enclosed within the ovary, which protects them. After fertilisation, ovules develop into seeds.
• Male gametes (pollen grains) are produced in large numbers to increase the chances of fertilisation.
• During pollination, pollen grains land on the stigma and enter the ovary through the style (correct term is “style,” instead of “Onicrophy”).
• The pollen grain is a three-celled structure at maturity.
• The embryo sac contains eight nuclei (cells) before fertilisation and seven after fertilisation.
• Both double fertilisation and triple fusion occur: one male gamete fuses with the egg nucleus to form a diploid zygote, while the other fuses with the two polar nuclei to form a triploid endosperm.

 Q9. What do you mean by double fertilization and triple fusion? 
Ans: Double fertilisation is a process in flowering plants where one male gamete fertilises the egg cell producing a diploid zygote, while the other male gamete fuses with two polar nuclei to form a triploid cell (endosperm). This involves two fusion events: the formation of the zygote and the endosperm.
The fusion of the three haploid nuclei forming the triploid endosperm is called triple fusion. This process provides nourishment to the developing embryo and is critical for seed development.

 Q10. Write a note on the economic importance of algae and gymnosperms.  
Ans: 
Economic Importance of Algae –
Algae are a diverse group of aquatic and marine autotrophic organisms. Green algae such as Ulva and Chlorella perform photosynthesis and contribute to oxygen production. Algae like Caulerpa are used in the production of antibiotics.
Certain algae, such as Chlamydomonas, produce methane gas used in sewage oxidation tanks, promoting waste treatment.
Economic Importance of Gymnosperms –
The seeds of Pinus are edible and consumed after roasting.

• The softwood of gymnosperms is widely used in construction, furniture, plywood, packing cases, matchsticks, railway sleepers, etc.
• Wood from Picea species is used in paper manufacturing.
• Pine needles, derived from gymnosperms, are utilised to make fibreboards.
• The drug Ephedrine, used to treat respiratory ailments such as asthma, is extracted from the gymnosperm plant Ephedra.