Plant Kingdom - Class 11 Medical Biology - Extra Questions

Red algae are usually present at the bottom or base of the oceans, they have pigments like phycoerythrins and phycobilins. These pigments absorb those lights that are penetrated deeper into the oceans such as violet light or blue light as they have a shorter wavelength. The light having longer wavelengths can be absorbed by the organisms that are present at the deeper region of the sea. These light have a high penetrating power than the ones like red light which have a shorter wavelength.

$$\textbf{Solution:}$$ 

$$\bullet$$ Unlike the bryophytes and pteridophytes, the gymnosperm has both male and female which are not free living.

$$\bullet$$ Both these gametophytes are within the sporangium which remains inside the sporophytes. 

$$\bullet$$ The female gametophyte remains inside the parent sporophyte for a variable period of time as it does not have a free existence.

Examples of algae which exhibits diplonatic alternation of life cycle are Cladophora glomerata, Acetabularia, etc.

In pteridophytes, asexual reproduction occurs by spore formation and sexual reproduction occurs by zygote formation.

In gymnosperms, ovaries are absent and thus seeds are present in the cones. The male and female gametophytes are present inside cones. These produce pollen and egg respectively. Through wind pollination, the pollen grains are transferred to the female cones. One of the two sperm cells produced in the pollen fuse with the egg to form the zygote. The other one degenerates. The zygote develops inside the female cone. Nourishment is provided by endosperm derived from the female gametophyte. So, the process of double fertilization is not observed in gymnosperms, though they are seeded plants.

Answer-

Angiosperms are the most abundant plants on this Earth and their greater rate of survival is often attributed to double fertilization. The reasons are as stated below:

1. Double fertilization results in two products - zygote and endosperm.
2. It increases the chances of polyembryony and this provides better survival opportunities to the plant.
3. Endosperm is responsible for nourishment of the developing embryo and thus ensures proper growth of the embryo.
4. Viability of seeds also increases as a result of double fertilization.

Cycus tree	Mango tree
It is a saprophytic plant body and appears like a small palm tree.	It is a tropical deciduous tree.
Grows up to a height of 8-15 feet.	Grows up to a height of 115-130 feet.
The presence of endophytic algae, make the roots look like swollen as coral.	It bears fruits in the hot climate.

Algae	Fungi
Contain chlorophyll (green in colour)	Do not contain chlorophyll (non-green)
Autotrophic nutrition	Heterotrophic nutrition

Algal bloom refers to the vigorous growth of algae or blue-green algae in the water, due to the enrichment of water body with mineral nutrients coming from fields, resulting in discoloration of the water body. This causes an increase in the biological oxygen demand (BOD), resulting in the death of fishes and other aquatic animals, due to suffocation.

Pteridophyta are vascular plants that do not have any flowers or seeds which means the reproduction is hidden. They reproduce by the formation of spores. They are also called cryptogams.

Agar-Agar or Agar is a jelly-like substance made from the mixture of agarose and agaropectin. It is extracted from red algae Gelidium or Gracilaria. Chemically it is a polymer made up of subunits of the sugar galactose. 

The word 'crypto' means 'hidden', cryptogams are the plants in which the reproductive organs are inconspicuous  So, thallophytes, bryophytes, and pteridophytes are cryptogams as their reproductive organs are not clearly visible or distinct. On the other hand, phanerogams include seed-producing angiosperms and gymnosperms, which have distinct and well-differentiated reproductive organs.

Euglena is a claimed to be a plant by botanists because it contains chloroplats and obtains its food through photosynthesis. On the other hand, zoologists consider it to be an animal as its body is covered by pellicle, it bears myonemes and reproduces by binary fission. Since Euglena possesses the features of both plants and animals, it is often, called as a plant - animal.

The three kinds of pigments found in algae are chlorophyll, caratenoids, phycobilins.

Macrocystis (40-100m)

Algae, the major food of fish (and thus indirectly of many other animals), are a keystone in the aquatic food chain of life; they are the primary producers of the food that provides the energy to power the whole system. They are also important to aquatic life in their capacity to supply oxygen through photosynthesis. Seaweeds, e.g., the kelps (kombu) and the red algae Porphyra (nori), have long been used as a source of food, especially in Asia. Both cultivated and naturally growing seaweeds have been harvested in the Pacific Basin for hundreds of years. Kelp are also much used as fertilizer, and kelp ash is used industrially for its potassium and sodium salts. Other useful algae products are agar and carrageen, which is used as a stabilizer in foods, cosmetics, and paints.

Eichhornia crassipes, commonly known as water hyacinth, is an aquatic plant native to the Amazon basin and is often considered a highly problematic invasive species outside its native range. The plant Eichhornia crassipes is nicknamed as the "Terror of Bengal" because it grows at an alarming rate and spreads on the surface of the water body. This cut out of the light and it also causes an increase in the oxygen demand which hampers the aquatic life.

The organism that is referred as 'Terror of Bengal' is water hyacinth or Eichhornia crassipes. It is a most prominent weed which invades the water and causes eutrophication. Due to the eutrophication, the oxygen content decreases which finally, hampers the aquatic life.

Organisms like fungi and algae switch to sexual mode just before the onset of adverse conditions because sexual reproduction would bring about variations into the organisms. This variation might help them to be able to survive in unfavorable conditions. 

Seaweeds are marine algae. They may be green, brown or red in colour. 

The bacterium is a prokaryote while diatom is a eukaryotic cell. When both the microorganism are observed under a microscope, the scattered genetic material can be seen in the cytoplasm without nuclear membrane in a bacterium while a dense region of genetic material with nuclear membrane is visible in a diatom.

The word 'crypto' means 'hidden', cryptogams are the plants in which the reproductive organs are inconspicuous  Thallophytes, bryophytes, and pteridophytes are cryptogams as their reproductive organs are not clearly visible or distinct. 

Sphagnum moss belong to the group of Bryophytes. They are used in nursery for growing new plants as they have many advantages. Sphagnum have high water retention capacity and porosity for sufficient aeration for the plants. They are sterile and do not contain any bacteria. The pH of the moss is arounf 3.5-6 and are suitable for acid loving plants like strawberries. 

Agar-agar also known as agar is a gelatinous substance produced by red algae. It is a polysaccharide that contains agarose and agaropectin. Agarose is responsible for the gelatinous properties. Agar is mainly used in electrophoresis process and Asian desserts and dissolves in boiling water.

$$\underline {Phycoerythrin}$$ is the red colored pigment found in algae.

Pathogenicity occurs due to a certain mode of nutrition followed by reproduction, wherein an organism acquires it food and then undergoes replication or reproduction by infecting the cells of another living organism, the host, however, this results in a diseased condition for the host. Since, algae are photosynthetic autotrophs they are capable of preparing their own food, unlike many fungi and bacteria that lack the necessary pigments for autotrophic mode of nutrition and hence are saprophytes or pathogens.

A juvenile autotrophic filamentous stage of mosses is called protonema.

Palmella stage is formed under desiccation conditions and in the presence of toxic salts.

Gametophyte	Sporophyte
It is haploid phase in life cycle.	It is diploid phase in life cycle.
It forms gametes.	It forms spores.
Gamete takes part in fertilization to form diploid zygote.	Diploid spore mother cell undergoes meiosis to form haploid meiospores.
Growth of zygote produces sporophyte.	Growth of meiospore produces gametophyte.

Megasporophyll	Microsporophyll
It bears megasporangia.	It bears microsporangia.
It bears one functional megaspore.	It contains numerous microspores.
In angiosperm, the megasporophyll is rolled to produce a carpel.	In angiosperms, the microsporophyll is modified into stamen.

Antheridia	Archeognia
Antheridia are round-shaped.	Archegonia are flask-shaped.
They are male organs of bryophytes and pteridophytes.	They are female organs of bryophytes, pteridophytes and gymnosperms.
It forms a large number of male gametes.	It encloses a single female gamete.

Liverworts	Mosses
Gametophytic plant body may be thallose or foliose.	Gametophytic plant body is differentiated into prostrate, protonema and gametophore.
Stomata and chlorophyll are absent.	Stomata and chlorophyll are present for exchange of gases.
Dehiscence of capsule is irregular.	Dehiscence of capsule is regular.
Example: Riccia.	Example: Funaria.

Green plants are called natural purifiers of the air.

Bryophytes	Pteridophytes
The dominant phase is the gametophyte	The dominant phase is the sporophyte.
The sporophyte is dependent on gametophyte.	The sporophyte is independent.
They are avascular.	They have xylem and phloem.
Rhizoids are present instead of roots.	True roots are present.

The degree of randomness or disorder in a system is called its entropy. Every energy transfer results in the conversion of some energy to an unusable form (such as heat), and since heat that does not do work goes to increase the randomness of the universe. 

rhizoids

In algae, sex organs are naked structures, whereas in bryophytes, they remain protected by jacket cells.

Angiosperms are flowering plants that bear seed enclosed within the fruit. They are the large division of plants that produce flowers and have seeds enclosed within an ovary(fruit). 

Green algae are photosynthetic organisms. They are able to synthesize their own food in presence of sunlight by the process of photosynthesis. They contain green pigment chlorophyll. All these are striking similarities to the plant world. Hence, green algae are considered similar to the plant world.

• Two useful algae are:- 1) Chorella (contains proteins therefore used in making protein supplements)  2) Gelidium (used in making agar)
• Two harmful algae:- 1)  Chaetoceros species (kill fishes), 2) Alexandrium tamarense ( produces a neurotoxin).

• Algae is useful in fish culture- Scenedesmus is often exclusively used as a daily dose of fish meal for the culture T. mossambica.
  
• Algae is useful in sewage treatment plants-  Eugelina provides oxygen for decomposition of waste.
  
• The blue-green algae are responsible for the formation of extensive limestone deposits around hot springs and glaciers. 
  
• Kombu, a Japanese food is prepared from stipes of species of Laminaria.
  
• Rhodymenia palmata and Alaria esculenta, are favourable food of goats, cows, and sheep
  

• Chlorophyceae are one of the classes of green algae.
• They are usually green due to the dominance of pigments such as chlorophyll- a, chlorophyll- b and beta- carotene.
• Most of the members have one or more storage bodies called pyrenoids in the chloroplast.
• Pyrenoids contains proteins and starch.
• Some store food in the form of oil droplets.
• Eg- 1)Chlorella produces food rich in proteins, fats, vitamins and minerals.

      2) It also yields antibiotic chlorellin.

• Spirulina is a non- toxic, blue-green algae which are a rich source of protein.
• It is named as the world's first superfoods because of its multiple benefits.
• It contains 70% full protein by biomass.
• It is used as a protein supplement.
• It is also a source of vitamin B12.

• Holdfast is a root- like structure by which an aquatic sessile algae are attached to a substrate.
• Its primary function is to secure the organism to the sea floor, i.e anchorage.

The salient features of Bryophyta are: 

• Pteridophytes are vascular plants which are also known as cryptogams (i.e reproduction is hidden).
• It reproduces through dispersal of spores as they neither produce flowers nor seeds. 
• They include ferns, horsetails etc.
• They include four classes:-

1)  Psilopsida-  are the most primitive vascular plants in which roots are absent and rhizoids occur instead of roots. Leaves may be present or absent.

Red Algae	Brown Algae
The cell wall is made of cellulose. pectin and phycocolloids	The cell wall is made of cellulose and algin
Photosynthetic pigments are chlorophyll a, chlorophyll d and phycoerythrin	Photosynthetic pigments are chlorophyll a. chlorophyll c and fucoxanthin
Classified under the class Rhodophyceae	Classified under the class Phaeophyceae
Stored form of food in floridean starch	Stored form of food in laminarin or mannitol
Examples include Porphyridium, Chondrus	Examples include Fucus, Ectocarpus

Chlorophyceae are group of green algae. They are photosynthetic in nature. They contains chlorophyll a and b as photosynthetic pigments. Food reserves are stored in the form of starch. 

Cycas	Living fossils
Thuja	It is a tree and its leaves and leaves oil is used for medicinal purpose
Pinus	Resin and turpentine production
Araucaria	Ornamental plant

So, the correct answer is ' Thuja - Agar production. '

The general characteristics of pteridophytes are as follows:

Bryophytes are non-vascular plants with stem like, leaf like and root like structures. They are referred to as amphibians of plant kingdom.

Thallophyta is a group of non-mobile organisms which are often known as lower plants because they lack proper body differentiation.

In the paddy fields, cyanobacteria, for example, blue green growth settle climatic nitrogen to improve the nitrogen substance of soil. In this manner, the whole need of nitrogen to rice product can be provided by blue green growth, prompting increment in yield.

Both cycas and pinus may have branched stems. In cycas the stem may be branched or unbranched but pinus shows ex-current branching of stem. Cycas has large pinnate leaves and needle like leaves are only seen in pinus. Both cycas and pinus bear 2-3 archegonia. Cycas is dioecious while pinus is monoecious. Sulpher shower is a characteristic of pinus and is not seen in cycas. In pinus male gametophyte is reduced while in cycas it is large. 

• The botanical name and family of castor plant is 
• Botanical Name: Ricinus communis.
• Family: Euphorbiaceae.

Pteridophyta are vascular cryptogams. They do not produce flowers. Structures for sexual reproduction are inconspicuous. They have stems, roots and leaves. 

Bryophytes are found in moist places, fertilization occurs with the help of water. For example, Marchantia, Riccia, etc. Hence bryophytes are called amphibians of the plant kingdom. 

Wood from coniferous gymnosperm is called softwood which is more porous and less dense, while wood from Angiosperm is called hardwood which is less porous and more dense.

Algae are photosynthetic organisms. They have chlorophyll to perform photosynthesis. 

	source of	Algae
1	Food	Chlorella, Laminaria, Sargassum etc
2	Agar-agar, used in preparing culturing media, in cosmetics,  paper industry etc	Gracillaria, Gelidium etc
3	Diatomaceous earth - used in filteration, insulation etc	Diatoms
4	Carrageenan - used in preparation of toothpaste, paint, blood coagulant etc	Chondrus crispus
5	Alginates - ice creams, paints,  flame proof fabrics	Laminaria, Ascophyllum etc
6	Fodder	Laminaria, Ascophyllum, Sargassum, Fucus
7	Fertilizer	Lithophyllum, Chara
8	Chlorellin - antibiotic against Gram- negative and Gram - positive bacteria.	Chlorella
9	Chlamydomonas	Sewage treatment, pollution indicators
	Fungi
1	In baking and brewing industry	Saccharomyces cerevisiae
2	Food sources	Agaricus sps, Morchella esculenta
3	medicines - Antibiotics, Penicillin	Penicillium notatum
4	Asbiofertilizers in the form of symbiotic association, with roots, Mycorrhizae. As biopesticides against nematodes	From basidiomycetes and Ascomycetes group. Pleurotus sps

Bryophytes need water for at least one stage of their life cycle as like amphibians which also need water to lay their eggs and their tadpoles develop in water. So, bryophytes are called the amphibians of the plant kingdom.

The reproductive organs in Pteridophytes are  inconspicuous. They reproduce by formation of spores .The plants belonging to this group are, therefore, called 'Cryptogams'. 

Cycas is considered a 'living fossil' because it is the only living species in the family Cycadaceae. All other species of this family are now extinct. This plant is often considered as the plant of the Old World; which means it is found only at those places which can be associated with some of the oldest rocks in the world. Due to these reasons; it is called the 'relic of the past'. Moreover, the Cycas plant shows more resemblance to Pteridophytes than Gymnosperms. This shows the phylogenetic relationship between Pteridophytes and Gymnosperms.
Some of the characters of Cycas which indicate this are as follows :

• Seeds are shed when the embryo is still mature. In other gymnosperms; seeds are shed only when the embryo is mature.
• The megasporophylls appear like leaves.
• In spite of the presence of pollen tubes, male gametes are flagellate.
• The leaf base is persistent.
• It shows circinate ptyxis venation like the pteridophytes.

The differentiating characteristic of Angiosperm is the presence of flower as reproductive structure, and seeds enclosed within the fruit.

Mannitol is the reserve food material in Phaeophyceae or Brown Algae.

Cyanobacteria are very important organism for the health and growth of many plants. They are one of many few organism that convert inert atmospheric nitrogen into organic form such as nitrate or ammonia. It is these fixed form of nitrogen which helps the plants to grow and they must obtain this from soil.

Bryophyta	Pteridophyta
They consist of a leafy or thalloid body.	The Pteridophyte body is differentiated into roots, stem and leaves.
Absence of vascular tissues such as xylem and phloem	Presence of vasculatures such as xylem and phloem
Antheridium is present on a stalk.	Antheridium is attached directly to the plant.
The dominating part of the life cycle is the gametophyte.	The dominating stage is the sporophyte.
They mostly have a haploid body having an “n” number of chromosomes.	A diploid body is observed here having a “2n” number of chromosomes.
Examples include mosses, liverworts, hornworts, etc.	They include spikemoss, clubmoss, ferns, etc.

B - Girdle shaped - Ulothrix (1)
C - Stellate - Zygnema (4)

Answer-

Liverworts	Moss
They have unicellular rhizoids.	They have multicellular rhizoids.
Scales are present very often.	Scales are absent.
They are generally thalloid, with dichotomous branching.	They are foliage, with lateral branching.
Gemma cups are present.	Gemma cups are absent.
Sporophyte has very little photosynthetic tissue.	Sporophyte has abundant photosynthetic tissue.

 (iii)

Homosporous	Heterosporous
They bear spores that are of the same type.	They bear two kinds of spores – microspores and megaspores, differing in size.
They produce bisexual gametophytes.	They produce unisexual gametophytes.

 (iv)

Syngamy	Triple fusion
It is the process of fusion of the male gamete with the egg in an angiosperm.	It is the process of fusion of the male gamete with the diploid secondary nucleus in an angiosperm.
A diploid zygote is formed as a result of syngamy.	A triploid primary endosperm is formed as a result of triple fusion.

(a) Holdfast

(a) Photic region is the surface layer of the ocean that receives sunlight. It is also called as euphotic zone. It is the uppermost 260 feet of the ocean. In this region, photosynthesis by phytoplankton and plants takes place.

Cycas resembles with ferns in having circinate tyxis or vernation

R. H. Whittaker has given the five kingdom classification. According to five kingdom classification organisms are divided into Bacteria, Algae, Fungi, Animalia, Plantae. In five kingdom classification, there was no place of the acellular organism like viruses, viroids and lichens.

The coralloid roots contain symbiotic cyanobacteria (blue-green algae), which fix nitrogen and, its association with root tissues, produce such beneficial amino acids as asparagine and citrulline.