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 world because they rely on water for the transportation of male gametes, known as antherozoids, to reach the archegonium for fertilization. 

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:  As the flowering plant is diploid, so the number of chromosomes is 36, but in a haploid, it will be 2n = 36,
n= 18
And we know the number of chromosomes in the endosperm is 3n so it will be 3×18 = 54.

Q3. Does heterospory have some evolutionary significance in the plant kingdom?
Ans: Pteridophytes occupy an intermediary position between bryophytes and gymnosperms. The early pteridophytes are characterized by homospory, while more advanced pteridophytes exhibit heterospory. In contrast, bryophytes are homosporous, while gymnosperms are heterosporous.

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 Moses’s life cycle, which is haploid. Most of them resemble multicellular green algae in nature. 

Q5. Discuss the phylogenetic relationship of Cycas with any other group of plants.
Ans: Cycas is a perennial plant resembling a palm tree, sharing a phylogenetic connection with pteridophytes. Its evolutionary features encompass:

• Dispersal of seeds while the embryo is still undeveloped.
• 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 the mutually beneficial relationship between fungi and the roots of vascular plants. This mycorrhizal partnership can be observed in coniferous trees like Pinus and Cedrus. In Cycas, we find specialized structures called coralloid roots. These coralloid roots form clusters near the stem's base and extend above the ground. They have a greenish hue and exhibit a dichotomous branching pattern.

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’ reproductive structures of angiosperms.
Ans: 

The following reproductive part that is compared with the angiosperms are- 

1. Storbili/ cone – Flower
2. Microsporophyll – Stamen
3. Megasporophylls – Pistil/ Carpel
4. Microsporangium – Another
5. Megasporangium – Ovule

Q8. The heterosporous pteridophytes exhibit certain characteristics which are precursors to the seed habits in gymnosperms. Explain.
Ans: Heterospory involves the creation of two distinct types of spores: megaspores and microspores. Microspores give rise to male gametophytes that produce male gametes, while megaspores develop into female gametophytes responsible for generating archegonia and nourishing the embryo. Consequently, heterospory results in a reduction in the size of the gametophyte. This process in pteridophytes serves as the foundation for the development of seed-bearing characteristics in gymnosperms.

Q9.  What do you mean by double fertilisation and triple fusion?
Ans:  Double fertilisation is the fertilisation of two male gametes with their respective female gametes. In it, one male gamete fertilises with the female gamete egg and forms a diploid zygote. At the same time, the other male gamete fuses with the two polar nuclei found in the ovule to form a triploid zygote that further develops into an endosperm.
And when the three haploid gametes fuse to form an endosperm, this process is termed triple fusion.

Q10. When the fruit ripens, what are the changes that take place?
Ans: Three main changes take place when the fruit ripens. These changes are –

• The starch gets converted into sugar
• Breakdown of Chlorophyll takes place, resulting in the fruit’s colour change.
• There is a difference in taste, texture, and flavour due to the production of various organic substances.

Long Answer Type Questions

Q1. Explain the alternation of generation in bryophytes briefly.
Ans:  Bryophytes are non-vascular plants that require water for fertilisation. They show an alternation of generation between the independent gametophyte generation and the dependent sporophyte generation. The gametophyte stage is responsible for the production of sex organs like sperm and egg, while the sporophyte stage is responsible for the production of spores. So a developing relationship between the sporophytic and gametophytic stages is said to be the alternation of generation.
For example, Moss is a gametophytic plant. But the development of it is started by the spores. The spore grows and forms into a Protonema which is the juvenile stage. It further generates the male and female gametes. And the process of fertilisation takes place. This alternation of the gametophyte stage with the sporophyte stage is the alternation of generation.

Q2. How is gametophyte a dominant phase in the life cycle of bryophytes?
Ans: The gametophyte is a pivotal phase in the life cycle of bryophytes, where it serves as the prominent and recognizable stage. Within this gametophytic phase, specialized structures known as antheridia house the male reproductive organs, while archegonia function as the female reproductive organs. These reproductive structures play essential roles in the production of gametes: antherozoids, the male gametes, and egg cells, the female gametes.

The remarkable journey of the bryophyte life cycle begins with the fusion of an antherozoid and an egg cell, an event that gives rise to a zygote. This zygote, in turn, marks a critical transition in the life cycle as it initiates the development of a multicellular structure called the sporophyte. The sporophyte represents the subsequent stage in the bryophyte life cycle, where it matures and eventually releases spores, thus completing the intricate and fascinating life cycle of these non-vascular plants.

Q3. What are the different lifestyles shown by Angiosperms?
Ans: There are four major lifestyles shown by the Angiosperms that are Hydrophytic, Halophytes, Xerophytes and Insectivorous. These are described briefly – 

• Hydrophytic plants – These are the plants that live in water or marshy areas. They are further classified as submerged and free-floating plants. Examples of submerged plants are Hydrilla and Vallisneria. At the same time, Examples of free-floating plants are Pistia and Nymphea.
• Halophytes plants – They are classified as xerophytic plants but under marine conditions. These plants cannot survive in fresh or aquatic water. 
• Xerophytes plants – These plants survive under the scarcity of water. Example cactus. They don’t need water for their growth and development.
• Insectivorous plants – A few Angiosperms plants trap insects to overcome the shortage of nitrogen. They need it for photosynthesis, and these plants depend on insects for their food. Some examples of these types of plants are the Pitcher plant, sundew etc.

Q4. Describe the life cycle of a plant.
Ans: The life cycle of a plant commences with the formation of a seed. This seed, under favorable conditions, undergoes germination, giving rise to a young plant. As this plant continues to grow and mature, it eventually develops flowers, which play a pivotal role in reproduction. Through pollination and subsequent fertilization, these flowers transform into fruits containing seeds.

The plant's life journey, however, is finite, and it eventually reaches the end of its life cycle. Upon the plant's death, it leaves behind the seeds it had produced during its reproductive phase. These seeds, when exposed to suitable environmental conditions, germinate, initiating the formation of a new plant. This cyclical process perpetuates the life cycle of the plant, ensuring its continuity and the spread of its genetic legacy.

Q5. Describe the main features of pteridophytes.
Ans: Pteridophytes are primarily found in tropical and humid environments. They are relatively small in size and can be divided into distinct parts: roots, stems, and leaves. These vascular plants do not produce flowers or seeds; instead, their primary function is the dispersal of spores. They consist of multiple cells and exist as independent organisms. Examples of pteridophytes include ferns, horsetails, and clubmosses. Notably, pteridophytes represent the initial group of plants to develop vascular tissue containing xylem and phloem. The xylem is responsible for transporting water, while the phloem facilitates the movement of food and nutrients. Xylem functions in a unidirectional manner, from the roots to the leaves, whereas phloem is bidirectional, allowing for the transport of substances both from leaves to roots and vice versa. 

Q6. What are parasitic algae?
Ans: Parasitic algae, often known as common plant pathogens, thrive in warm, humid climates and typically infest leathery-leafed plants like litchi, hollies, magnolias, and viburnums. They are notorious for causing foliar diseases, with the red rust disease of tea leaves being a prominent example. Cephaleuros serves as a representative parasitic green algae. These organisms pose significant challenges in plant cultivation, particularly in regions where they are prevalent, impacting both aesthetics and plant health. Understanding their ecology and behavior is crucial for effective management strategies.

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

Ans: Heterospory refers to the generation of two types of spores by a single plant. These spores are different in size and structure; one is called a Microspore, while the other is called a Megaspore. The microspore is smaller and gives rise to the male gamete after germination. 

On the other hand, Megaspores are larger and give rise to the female gamete after germination. The megaspore is enclosed within megasporangia, ensuring the zygote’s proper development. A zygote is formed after the process of fertilisation of the microgamete and the megagamete. Heterospory was first observed in plants like Selaginella and Salvinia. 

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

The characteristics features of Angiosperms are- 

• The ovules are well protected and enclosed within the ovary; after fertilisation, the ovules develop into seeds.
• The male gamete, i.e., the pollen grain, is generated at a huge amount to ensure fertilisation.
• During pollination, in the male gametes, pollen grain falls on the stigma and enters the ovary through Onicrophy. 
• The pollen grain is a three-cell structure when dehisced. 
• The embryo sac is an eight-cell structure that becomes seven after fertilisation.
• Both double fertilisation and triple fusion occur in the Angiosperms, where one male gamete fuses with the egg nucleus to form a zygote, and another male gamete fuses with the secondary nucleus to form a triploid endosperm. And when the three haploid gametes fuse to form an endosperm, this process is termed triple fusion. 

Q9. What do you mean by double fertilization and triple fusion?
Ans: In this biological process, one of the male gametes combines with the egg cell, resulting in the formation of a diploid zygote. Simultaneously, the other male gametes unite with two polar nuclei, giving rise to a triploid zygote, which subsequently develops into the endosperm. This intricate mechanism is aptly termed "double fertilization" because it involves two distinct fusion events: the first yielding the zygote and the second leading to the formation of the endosperm.

The fusion of the three haploid nuclei, which forms the endosperm, is referred to as "triple fusion." This process plays a vital role in plant reproduction and development, as it ensures the proper nourishment and support for the growing embryo within the seed. Double fertilization and triple fusion are essential components of the reproductive strategies employed by many flowering plants, contributing to their successful propagation and survival.

Q10. Write a note on the economic importance of algae and gymnosperm. 
Ans: 
Economic Importance of Algae – 
Algae is a diverse group that contains aquatic and marine organisms ranging from autotrophic to eukaryotic. Green algae like Ulva and Chlorella are used for the process of photosynthesis through which food is generated.
Algae like Caulerpa are used to form and obtain antibiotics.
The algae Chlamydomonas produce methane gas used in sewage oxidation tanks.
Economic Importance of Gymnosperm-
The seeds of Pinus are roasted and eaten in nature. 

• The softwood of gymnosperms is also used in constructing furniture, plywood, packing cases, match sticks, railway sleepers etc.
•  The wood from Picea is used in the manufacture of paper.
•  Pine needles, a derivent of gymnosperm, are used to make fibre boards.
• A drug called Ephedrine is extracted from the plant Ephedra, which is classified under gymnosperm. This drug, Ephedrine, is useful for respiratory ailments such as asthma.