Sainavle, Author at WBBSE Solutions

Question 1. Differentiate between catabolism and anabolism.
Answer: Catabolism involves breaking down larger molecules into smaller ones, thereby releasing energy, while anabolism involves the formation of larger molecules, using smaller molecules, thereby utilizing energy. Respiration is a catabolic process, while photosynthesis is an anabolic process.

The Living World

Question 2. What is intussusception?
Answer: Overall growth of a body due to an increase in the dry weight of the protoplasm, is called intussusception.

Question 3. Which are the coordinators within the body of plants and animals?
Answer: In case of animals, hormones act as chemical coordinators, while nerves act as physical coordinators. In case of plants, only hormones are present, which act as coordinators. Due to their presence, different cells, tissues, organs and organ systems function in a coordinated fashion.

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Question 4. What is homeostasis?
Answer: Homeostasis is the ability of maintaining a stable internal environment of the body irrespective of the changes in the external environment. For example, normal body temperature is 98.6°F. When the body temperature rises above this, hypothalamus sends signals all over the body, through the motor neurons. As a result, sweat is released which lowers the temperature to normal.

Question 5. What is taxonomy?
Answer: The branch of biology, that deals with the classification of organisms and provide required information for classification such as nomenclature; rules of nomenclature, identification, is known as taxonomy.

Question 6. What is systematics?
Answer: The branch of biology, that reveals relationship j among different organisms with the help of identification, nomenclature, description, and classification is known as systematics.

Class 11 Biology WBCHSE

Question 7. What is the difference between taxonomy and systematics?
Answer: The science which deals with identification, classification and nomenclature of organisms is known as taxonomy. On the other hand systematics is the science, that studies diversification of organisms — both past and present and the relationship among them, over the course of time.

Question 8. What is binomial nomenclature?
Answer: The system of naming, that is done by using only genus and species name is known as binomial | nomenclature. For example, Pisum sativum.

Question 9. What are taxonomic category and taxonomic hierarchy?
Answer: The different levels of classification are known as categories or taxonomic categories.
When these categories of classification are arranged in a definite order, then it is known as hierarchy or taxonomic hierarchy.

Question 10. What are monotypic and polytypic genus?
Answer: The genus which includes only one species is known as monotypic genus. For example, sapiens is the only species present in the genus Homo. Hence, Homo is a monotypic genus. The genus which includes more than one species is known as polytypic genus. For example, tigris and leo, both these species come under the genus Panthera. Hence, Panthera is a polytypic genus.

Class 11 Biology WBCHSE The Living World Multiple Choice Question and Answers

Question 1. Joint Forest Management Concept was introduced in India during —

1970s

1980s
1990s
1960s

Answer: 2. 1980s

Question 2. Which is the National Aquatic animal of India?

River Dolphin

Blue whale
Sea-horse
Gangetic shark

Answer: 1. River Dolphin

Question 3. Red List contains data or information on—

All economically important plants

Plants whose products are in international trade
Threatened species
Marine vertebrates only

Answer: 3. Threatened species

Question 4. Nomenclature is governed by certain universal rules. Which one of the following is contrary to the rules of nomenclature?

The first word in a biological name represents the genus name and the second is a specific epithet

The names are written in Latin and are italicised
When written by hand, the names are to be underlined
Biological names can be written in any language

Answer: 4. Biological names can be written in any language

Question 5. Following are the two statements regarding the origin of life —

The earliest organisms that appeared on the earth were non-green and presumably anaerobes

The first autotrophic organisms were the chemoautotrophs that never released oxygen Of the above statements which one of the following options is correct?

2 is correct but i is false
Both 1 & 2 are correct

Both 1 & 2 are false
1 is correct but 2 is false

Answer: 2. Both 1 & 2 are correct

Question 6. Taxonomic categories showing correct hierarchical arrangement in ascending order is—

Kingdom→ Order → Division→ Class → Genus → Species
Species→ Genus→ Division → Class → Order → Kingdom

Kingdom → Division → Class → Order → Family → Genus → Species
Species→ Genus → Family → Order → Class → Division → Kingdom

Answer: 4. Species→ Genus → Family → Order → Class → Division → Kingdom

Question 7. Which one of the following shows the hierarchical arrangement of taxonomic categories of plants in descending order?

The Living World Taxonomic Categories Of Plants In Descending Order

Answer: 4. Kingdom→Division→Class→Order→Family→Genus→Species

Question 8. A taxonomic group of any rank is –

Taxon
Tribe

Race
Variety

Answer: 1. Taxon

Question 9. Which of the following is correctly sequenced?

Phylum, class, order, family
Phylum, order, class, genus

Phylum, class, family, order
Phylum, order, family, class

Answer: 1. Phylum, class, order, family

Question 10. Family is placed between—

Genus and species
Order and class

Class and genus
Order and genus

Answer: 4. Order and genus

Question 11. ICBN stands for

Indian Congress of Biological Names
International Code of Botanical Nomenclature

International Congress of Biological Names
Indian Code of Botanical Nomenclature

Answer: 2. International Code of Botanical Nomenclature

Class 11 Biology WBCHSE The Living World Very Short Question And Answers

Question 1. Name the bird whose beak structure and feeding habit were studied by Darwin, while studying evolution.
Answer: Finch

Question 2. Name the book written by Charles Darwin.
Answer: Origin of Species

Question 3. What is taxon?
Answer: According to international rule of classification, each unit of classification is known as taxon.

Question 4. In which journal did Linnaeus publish his modified classification system?
Answer: Systema Naturae.

Question 5. What is hierarchy?
Answer: The arrangement of taxonomic categories one above the other in a definite logical way is known as hierarchy.

Question 6. Expand the abbreviation ICNCP?
Answer: ICNCP stands for International Code of Nomenclature for cultivated Plants.

Question 7. What is genus?
Answer: The genus is a unit of classification which is formed by collection of species with similar | characteristics.

Question 8. What is meant by trinomial nomenclature?
Answer: The nomenclature that includes genus name, species name, and subspecies name is called: trinomial nomenclature.

Question 9. What is species?
Answer: Species is a group of living organisms hearing similar characteristic features and they are. capable of interbreeding.

Question 10. What is subspecies?
Answer: There are several differences among organisms belonging to same species due to differences in geographical location. These species are thus divided into smaller groups known as subspecies.

Question 11. What do you mean by polytypic genus?
Answer: The genus which contains more than one species is known as a polytypic genus. Example- Plasmodium is a polytypic genus. It has GO j species, some of which are, Plasmodium vivax, P. falciperum, P. malariae, etc.

Question 12. What is meant by couplets in identification key?
Answer: The pair of opposite characteristic features written in taxonomic key is known as couplet.

Question 13. What is identification key?
Answer: The identification key is a set of alternate characters arranged in such a fashion that by selection and elimination of them one can quickly identify the organism. It is an important tool for studying taxonomy It may be printed or computerised.

Class 11 Biology WBCHSE

Question 14. What is lead?
Answer: The different characteristics which are written as a couplet are known as lead.

Question 15. Name the popular key of taxonomy.
Answer: Indented key is the popular key of taxonomy.

Question 16. Given below is the scientific name of mango.

Identify the correctly written name.

Mangifera Indica
Mangifera indica

Answer: 2. Mangifera indica

Question 17. Linnaeus is considered as father of taxonomy. Name two other botanists known for their contribution to the field of taxonomy.
Answer: George Bentham and Sir J.D. Hooker.

Question 18. What does ICZN stand for?
Answer: ICZN stands for International Code of Zoological Nomenclature.

Question 19. What is a museum?
Answer: A museum is an institution that preserves objects of scientific, artistic, cultural or historical importance.

Question 20. Can you identify the correct sequence of Itaxonomical categories?

Species —> Order —> Phylum —> Kingdom
Genus —> Species —> Order —> Kingdom

Species→ Genus→ Order → Phylum

Answer: 3. Species→ Genus→ Order → Phylum

Question 21. Taxonomic key is one of the taxonomic tools in the identification and classification of plants and | animals. It is used in the preparation of—

Monographs
Flora
Both 1 and 2

None of these

Answer: 3. Both 1 and 2

Question 22. The term systematics refers to—

Identification and classification of plants and j animals
Nomenclature and identification of plants and ; animals
Diversity of kinds of organisms and their ; relationships

Different kinds of organism and their classification

Answer: Both 1 And 2

Question 23. Which is the largest botanical garden in the world? Name a few well known botanical gardens in India.

Ans. Royal Botanical garden, ICew (London). Some well known botanical gardens in India are

Acharya Jagadish Chandra Bose Indian Botanic Garden, Shibpur, Howrah;
Lloyd Botanical Garden, Lucknow.

Question 24. Genus represents—

An individual plant or animal
A collection of plants or animals

A group of closely related species of plants or animals
None of these

Answer: 3. A group of closely related species of plants or animals

Class 11 Biology WBCHSE

Question 25. How is key helpful in identification of living organisms?
Answer: Key helps to identify various taxa such as genus, species, etc. It is a systemic representation of different identifying characters belonging to different taxa.

Question 26. How can you relate metabolism with growth?
Answer: Metabolism involves both catabolism and anabolism. Growth occurs when the rate of anabolism is greater than the rate of catabolism.

Question 27. How can you distinguish between human beings and other living organisms?
Answer: Human beings have ability to think about higher concepts that other animals cannot. This feature distinguishes human beings from other animals.

Question 28. Amoeba multiplies by mitotic cell division. Is this phenomenon growth or reproduction? Explain.
Answer: In unicellular organisms like Amoeba, cell division is the means of multiplication. So, it helps in reproduction. But it also helps in the growth of their colony. Thus, in unicellular organisms, mitosis helps in both growth and reproduction.

Archaebacteria Characteristics and Types Notes

April 16, 2024November 15, 2023 by Sainavle

Domain Archaea

Domain Archaea Characteristics:

They are the most primitive organisms.
Members of this domain have prokaryotic cells.

Cell membranes have branched hydrocarbon chains attached to glycerol by a type of linkage called ester linkage.
Certain chemical constituents of cell membrane help them to withstand extreme temperature and highly acidic environment.
Peptidoglycan is absent in cell wall.

Extreme halophiles (organisms thriving in highly saline environment) and hyperthermophiles (organisms thriving in extremely hot environment) are best examples of Archaea.

Domain Archaea

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Kingdoms included: Domain Archaea contains only one kingdom called Archaebacteria. This kingdom is further divided into three groups—methanogens, halophiles and thermoacidophiles. These groups have been discussed later in the chapter.

Domain Bacteria

Domain Bacteria Characteristics:

This group includes prokaryotic bacteria.
Cell membranes have unbranched fatty acid chains attached to glycerol by a type of linkage called ester linkage.
Peptidoglycan is present in cell wall.

Most of them are decomposers, some are autotrophic in nature.
Most of them cause diseases in higher organisms but some may be beneficial.

Kingdoms included: This group also has a single kingdom called Eubacteria. This kingdom is again subdivided into four groups— Proteobacteria (Rhizobium 1 sp.), Cyanobacteria (Nostoc sp.), Spirochaetes (Treponema sp.), Firmidicutes (Clostridium sp.) and Mycoplasmas. These groups too have been discussed later in the chapter.

Domain Eukarya

Domain Eukarya Characteristics:

The members of Eukarya have eukaryotic cells, which have cell membranes nearly similar to that of bacteria.

True nucleus and membranous cell organelles are present.
Some eukaryotes may have cell wall, but peptidoglycan is absent.

Kingdoms included: Domain Eukarya is further divided into Kingdom Protista (algae, protozoans, etc.), Kingdom Fungi (yeast, mould, etc.), Kingdom Plantae (flowering plants, ferns, etc.) and Kingdom Animalia (insects, vertebrates, etc.).

Biological Classification Comparison Among The Three Domains

Kingdom Monera

The Kingdom comprising of the simplest unicellular, prokaryotic living organisms, is known as Kingdom Monera.

Kingdom Monera Distribution: The members of kingdom Monera are present in all types of environment. Some of them are even present in extremes of environment (such as high temperature, saline, alkaline or acidic environment, etc.).

Kingdom Monera General features:

Cell nature: These organisms are prokaryotic. They are simple, unicellular and microscopic. They may form filament or thread-like structure.
Cell shape and size: Cell shape is generally characteristic of a given bacterial species. They are microscopic, with a volume of about 0.2-10.0pm3, length being 0.1-0.5pm.

Cell wall: Cell wall is present in some organisms. It is generally made up of peptidoglycans. In case of archaebacteria, the cell wall is made up of proteins. The cell wall is absent in case of mycoplasma.
Cytoplasm: The cytoplasm appears as colourless jelly. It contains nuclear material, non-membranous cell organelle and gas vacuoles. True cytoskeleton is absent but may contain primitive cytoskeleton.
Nuclear material: They do not possess a definite nucleus or a nuclear membrane. The nuclear material without the nuclear membrane and nucleus, is known as nucleoid.

Genetic material: The genetic material is constituted of naked double-stranded DNA, that remains without histone proteins. It is present within the cytoplasm. This type of DNA is known as prochromosomes.In some cases, plasmids (small DNA molecules that replicate independently) and episomes (small DNA molecules that can replicate independently as well as integrated within the chromosome) are present.
Cell organelles: Double membrane-bound cell organelles are absent.Chloroplast is absent. The pigment-containing, membranous thylakoids remain freely suspended in the cell. These are known as chromatophores. Mesosomes are cell organelles that carry respiratory enzymes. These organelles are present in the inner lining of the cell membrane.
Vacuoles: Gas vacuoles may be present.

Cellular appendages: Sometimes single-stranded flagella may be present. Some of the members may also contain pili and fimbrae.
Nutrition: Some of the members of this kingdom can synthesise their food (autotrophs), while some derive nutrition from others (heterotrophs).
Respiration: They perform both aerobic and anaerobic types of respiration.

Cell division: Cell division is mainly amitosis.
Reproduction: Reproduction is asexual in nature. This occurs by budding and binary fission.Genetic recombination (exchange of genetic material between chromosomes) is observed.
Nitrogen fixation: Some bacteria and blue-green algae have the capacity to fix atmospheric nitrogen as ammonia. They are called nitrogen fixing bacteria. Examples: Bacteria, mycoplasma, and blue-green algae.

Classification of kingdom Monera

The microorganisms in Kingdom Monera are considered the most ancient living forms on earth. The kingdom is divided into two groups—Archaebacteria and Eubacteria. These have been discussed under separate heads.

Biological Classification Monera

Subkingdom—Archaebacteria

Archaebacteria are small, primitive microbes that can survive in extreme and harsh environmental conditions. Hence, they are also known as extremophiles.

Subkingdom General features:

Cell wall: Cell wall is made up of polysaccharides (other than cellulose) and proteins. In particular, their cell wall lacks peptidoglycan. Thus they may be resistant to antimicrobial agents, interfering with peptidoglycan biosynthesis.

Cell membrane: Single-layered lipids are present in the cell membrane. Fatty acids are attached to the glycerol units by ether bond instead of ester bond.
Nucleotides: 16S rRNA nucleotide is different from that in other organisms. RNA polymerase is also structurally dissimilar in different organisms.
Respiration: Most of them are anaerobes in nature.

Effect of antibiotics: They do not get affected by These have bacterial antibiotics.
Classification of archaebacteria: Based on their habitats, the archaebacteria are classified as methanogens, halophiles and thermoacidophiles. They have been discussed under separate heads.

Methanogens

Methanogens Characteristics:

The members of this group are anaerobic organisms. They cannot survive under aerobic conditions.
They produce methane as a metabolic byproduct in anoxic conditions, using carbon dioxide and energy from decaying organisms.
They live in marshy areas, such as lakes, muddy puddles, etc; They also live within the guts of the ruminant animals.

They are responsible for the production of biogas from the dung of the above-mentioned animals.
They are autotrophic in nature.

Examples: Methanobacterium ruminantium, Methanobacterium bryantii, Methanobacterium formicicum and Methanococcus sp., etc.

Halophiles

Halophiles Characteristics:

The term halophile means salt loving in Greek. Therefore, as the name suggests, the members of this group live in extremely saline regions.
Halophiles include all microorganisms that are found in acid lakes, Dead Sea and oceans.

Their bodies contain a photoreceptor (light-sensitive) pigment called bacteriorhodopsin. This pigment helps to synthesise ATP, on absorbing light of a specific wavelength.
The osmotic concentration of fluids within their body is high. This, in turn, helps them to survive in saline environment.
They are aerobic in nature.

Example: Halobacterium sp., Halococcus sp., Nitzschia, diatoms, etc.

Biological Classification Sulpholobus And Halococcus

Thermoacidophiles

Thermoacidophiles Characteristics:

They live in highly acidic, sulphur-rich, extremely hot environments.
They prefer temperatures ranging between 70-80°C and pH between 2-3.
They live mostly in hot springs and/or within deep ocean hydrothermal vents (fissures on the floor of the sea, from which mineral-rich, hot water flows).

Thermoacidophiles are anaerobic in nature.
They show autotrophic mode of nutrition and synthesise food by chemosynthesis.

Examples: Thermoplasma sp., Sulpholobus sp., Picrophilus sp., and Thermococci sp., etc.

Subkingdom—Eubacteria

Eubacteria, known as ‘true bacteria’, are unicellular, prokaryotic organisms that have a rigid cell wall.

Classification of eubacteria: Eubacteria is further divided into 6 groups—bacteria, cyanobacteria, mycoplasma, actinomycetes, spirochaetes and rickettsia. All of them have been discussed under separate heads.

Bacteria

Bacteria Definition: Unicellular prokaryotic organisms, containing primitive nucleus, that can survive under all kinds of environment are known as bacteria.

Bacteria Distribution: Bacteria are the most abundant living organisms in nature. They are found in the land, water, air, i.e., everywhere around us.

Bacteria General features:

Bacteria are microscopic organisms containing non-organised nucleus.

Their cell wall contains peptidoglycan.
They contain a single, highly coiled, double-stranded DNA, that is not bound to histone proteins.
Some amount of plasmid DNA may be present.

Sometimes bacteria may contain cellular appendages such as flagella, pili or fimbrae.
Membranous cell organelles are absent. However, mesosome and 70S ribosomes are present.
Cellular respiration is carried out using mesosomes.

These bacteria may be aerobic or anaerobic.
They show autotrophic or heterotrophic mode of nutrition. Pigments like bacteriochlorophyll, bacterioviridin, etc., are present in autotrophic bacteria.
Cell division is amitosis.

Bacteria reproduce mainly by fission. Sometimes, under unfavourable conditions, they produce structures called spores. These spores germinate when conditions are favourable. They reproduce by sexual reproduction, which involves DNA transfer from one bacterium to the other.
The majority of bacteria are decomposers in nature.
Many of them have a significant impact on human life. They are helpful in making curd from milk, production of antibiotics, nitrogen fixation in legumes, etc. Some, however, are pathogens, causing damage to human beings, crops, farm animals and pets.

Biological Classification Bacterial Cell

Classification of Bacteria

According to shape: Bacteria may be classified into different types on the basis of their shape—cocci (spherical shaped), bacilli (rod-shaped), spirochaetes (spiral), etc. The table below shows the different types of bacteria according to their shapes.

Biological Classification Different types Of Bacteria Their Features Example And Shapes

Biological Classification Different types Of Bacteria Their Features Example And Shapes.

According to the staining behaviour: Bacteria may also be classified on the basis of their staining behaviour. A Based on Gram staining, bacteria may be classified into two types—Gram positive and gram negative.

Biological Classification Bacteria

Gram positive bacteria have a thicker peptidoglycan layer in their cell wall. This layer retains the crystal violet stain during the alcohol wash.
Hence, the bacteria show violet colouration. Gram negative bacteria, on the other hand, have a thinner peptidoglycan layer in the cell wall.

This layer does not retain the crystal violet stain but retains safranine (red-coloured counterstain). Hence after alcohol wash, the bacteria appears red instead of violet.

According to the nature of respiration: On the basis of the need of oxygen during respiration, bacteria are classified into two types— aerobes and anaerobes. Those bacteria that need oxygen are called aerobes.

Those that do not need oxygen are called anaerobes. Both aerobes and anaerobes can be obligate or facultative. The bacteria, that cannot grow in the absence of oxygen, are called obligate aerobes (E.g.,Nitrobacter spv Thiobacillus sp.).

The bacteria, that cannot grow in the presence of oxygen, are called obligate anaerobes (E.g., Clostridium acetobutylicum).
In some bacteria, respiration generally takes place in the presence of oxygen, but may also take place in its absence.
These are called facultative aerobes (E.g., Escherichia coli, Clostridium tetani). In some bacteria, respiration usually takes place in the absence of oxygen, but may also take place in its presence.

These are called facultative anaerobes (E.g.,Rhodobacter sp.). In some bacteria, anaerobic respiration takes place, even in presence of oxygen. These are called aerotolerant anaerobes (E.g.,Clostridium intestinale).

According to thermal sensitivity: On the basis of the temperature required for growth, bacteria can be classified into the following groups—

Psychrophiles (cold-loving) can grow at 0°C but optimum temperature for their growth is about 15°C.

Psychrotrophs can grow at 0°C also but optimum temperature for j their growth is 20 – 30°C. 0 Mesophiles (moderate temperature-loving) grow best at moderate temperature around 37°C.
Thermophiles (heat-loving) have an optimum growth at around 60°C.
Hyperthermophiles have optimum growth at 80°C or even higher temperature (as in case of archaea).

According to number and position of flagella: Flagella are fine hair-like, proteinaceous structures present in motile bacteria.There are also some bacteria like Corynebacterium diphtheriae that do not have flagella. Such bacteria are called atrichous. On the basis of the number of flagella, the bacteria are classified into four groups.These are—

Monotrichous bacteria having one flagellum at one end.E.g., Vibrio cholerae.
Lophotrichous bacteria having more than one flagella at one end. E.g., Pseudomonas sp.

Amphitrichous bacteria having one flagellum present on either end of the cell. E.g., Spirillum sp.
Peritrichous bacteria having flagella distributed all over the body. E.g., Salmonella typhi.

Biological Classification Classification Of Bacteria According To Number And Arrangement Of Flagella

According to the mode of nutrition: On the basis of the mode of nutrition, bacteria may be classified into different types. These have been depicted through a flowchart on the next page.

Reproduction in bacteria: Bacteria reproduce by vegetative, asexual and sexual means.

Vegetative reproduction

Binary fission: In this method, a single cell divides into two equal halves. Cells undergo division after every 20-30 minutes.
Budding: In case of budding, the bacterial cell develops a small swelling. This swelling is called the bud. It gradually increases in size. DNA in the mother cell produces daughter DNA. The nucleus undergoes division first, forming two daughter nuclei. One such daughter nucleus remains with the mother cell and the other, along with some cytoplasm, moves to the bud. The pinched off bud gets separated from the mother cell by the formation of partition wall in between them. Thus another bacterial cell is formed. Examples are hyphomicrobium vulgare, Rhodomicrobium vannielia, etc.

Biological Classification Binary Fission Of Bacteria

Asexual reproduction

Cyst formation: Cysts are formed by the deposition of additional wall or layer surrounding the mother cell wall. They survive the unfavourable conditions and germinate at the onset of favourable conditions. Example, many members of Azotobacter sp.
Endospore formation: Endospores are formed during unfavourable environmental conditions like desiccation and starvation. The nucleoid replicates to form endospores with cytoplasmic material.

On germination during favourable conditions, a spore gives rise to a normal bacterial cell. Example, Bacillus subtilis, Clostridium tetani, Escherichia coli, etc.

Sexual reproduction

Conjugation: It is the transfer of genetic material between two bacterial cells, through plasmid. This occurs by direct cell-to-cell contact or by a tubular connection between two cells. It was discovered in 1946 by Joshua Lederberg and Edward Tatum.

Transduction: It is the transfer of genetic material between bacterial cells by a virus (also known as vector). This virus is usually a bacteriophage. This was studied by Lederberg and Zinder in Salmonella sp. bacteria.

Classification of bacteria on the basis of mode of nutrition:

Biological Classification Classification Of Bacteria On The Basis Of Mode Of Nutrition

Transformation: It is the transfer of genetic material between bacterial cells by extraction or liberation of genes. Bacterial transformation was discovered by Griffith in Pneumococcus sp. (bacterial species causing pneumonia).

Classification System Of Living Organisms Notes

April 24, 2024November 15, 2023 by Sainavle

Sequential Development Of Classification System Of Living Organisms

Initially, biologists divided all living things into two large groups or kingdoms—the plant and the animal. However there were certain limitations, so this classification system was discarded. Gradually, three and four-kingdom classification systems were proposed.

But they too were discarded due to some reason. With time, five and six-kingdom classification systems were proposed. Today, most biologists favor the five-kingdom system of classification.

Two kingdom classification:

The two-kingdom system of classification was proposed by Carolus Linnaeus. As mentioned before, it has two large groups— Plant Kingdom and Animal Kingdom. This classification system was developed based on locomotion and food habits seen in organisms. A.L. de Jussieu gave the major subdivisions of Kingdom Plantae. The major phyla of Kingdom Animalia were given by G.L.Cuvier.

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Classification System Of Living Organisms Notes

Drawbacks: This system included all plants and animals, without discriminating the eukaryotes and prokaryotes, unicellular and multicellular, autotrophic and heterotrophic organisms.

This system also failed to classify organisms that did not fall under either of these two groups. However, this two-kingdom system of classification was used for a long time but was eventually replaced by a three kingdom system.

Biological Classification Two kingdom classification

Three kingdom classification:

With the progressive development of the microscope, several microscopic organisms were discovered. These microorganisms were neither plants nor animals and so needed to be placed in another group. Hence, German; Scientist Ernst Haeckel (1866) introduced another kingdom called Protista. Haeckel included bacteria and cyanobacteria in this group. This modified classification system came to be known as the kingdom classification system.

Biological Classification Living Organisms 2

Biological Classification Three kingdom classification

Drawbacks: This system failed to distinguish between prokaryotic and eukaryotic organisms. Unicellular and multicellular organisms were still placed in the same group under this system.

Four kingdom classification:

With the discovery of electron microscope, the microorganisms could be observed better. As a result, prokaryotic and eukaryotic cells could be distinguished clearly. Based on this, Herbert F. Copeland proposed the four-kingdom classification system in 1938. He separated prokaryotic bacteria and blue-green algae from kingdom Protista and placed them under another kingdom called Monera.

Biological-Classification-Living-Organisms-3-1

Towards the beginning of 1960s, Stanier and Van Niel introduced another category (also called rank) above the Kingdom in the classification system. This category or rank came to be known as the Superkingdom or Empire. The living world was divided into two Superkingdoms— prokaryota and eukaryota.

Biological Classification Living Organisms 4

Biological Classification Four kingdom classification

Five kingdom classification

In 1969, R.H. Whittaker introduced the five-kingdom system of classification. According to Whittaker, all protists must be unicellular. He divided this kingdom Protista into two parts called subkingdoms.
One subkingdom included all uninucleated (eukaryotic) organisms—protozoans, diatoms, euglenoids, and many other microscopic organisms. Non-nucleated (prokaryotic) organisms, on the other hand, were included in the other subkingdom.
This group included both the true bacteria and the cyanobacteria. Cyanobacteria is an important group of prokaryotes that carry out oxygenic photosynthesis. They are often referred to as blue-green algae.

Whittaker excluded all of the fungi, marine algae, and other multicellular organisms from kingdom Protista and placed them in separate groups. This system of classification is called the Five Kingdom classification.

Basis of five kingdom classification: The previous classification systems (two, three and four kingdoms) had certain drawbacks. Many of such issues were resolved through Five kingdom classification system. The basis of classification under this system is as follows—

Complexity in body structure,

Complexity in cellular organization,
Mode of nutrition,
Variation in ecosystem,

Phylogenetic relationship.

Biological Classification Living Organisms 5

Biological Classification Five kingdom classification

On the basis of the above-mentioned features, living organisms were arranged hierarchically into three levels—

Prokaryotic organisms (placed under kingdom IVlonera);
Eukaryotic, unicellular organisms (placed under kingdom Protista); and

Eukaryotic, multicellular organisms (placed under kingdoms Fungi, Plantae and Animalia).

Comparison between the Five Kingdoms:

Biological Classification Comparison Between The Five Kingdoms.

Biological Classification Comparison Between The Five Kingdoms..

Merits and demerits of five kingdom classification

The five kingdom system of classification system has both merits and demerits.

Merits:

Monera has been placed as a separate kingdom. This is correct, as the members of Monera have characteristic features different from other unicellular organisms.
Bacteria, fungi and some algae were eliminated from Kingdom Plantae. This has led to proper study of the evolution of plants, in particular.

The group protozoa has been separated from Kingdom Animalia, which makes kingdom Animalia more homogeneous. Now the kingdom contains more organisms with similar features.
The groups of fungi and slime mould have been placed in a Kingdom. This is justified because they are totally different from other primitive prokaryotes like algae and protozoans.
The kingdom Plantae and Animalia are now more homogeneous groups than they were in the previous classification systems. This is due to the fact that now they contain only plants and animals, respectively.

The five kingdom classification puts stress on cellular organisation and modes of nutrition, both of which are basic characteristics of life.
It is the most accepted system of classification. This is mainly because the different groups of organisms have been placed according to their phylogenetic nature.

Demerits: The five kingdom classification has certain demerits as well, particularly with reference to j the lower forms of life. These are—

Biological Classification Primitive Microorganism

Different types of algae have been introduced under three separate; kingdoms, which is wrong. For example, cyanobacteria has been included under Monera, while bacillariophyceae and dinophyceae under Protista, and red algae, brown algae and green algae under Plantae. This is not acceptable as all of these belong to the same group—algae. Hence, these should not be placed in different kingdoms.
Kingdom Protista is made up of different types of organisms. This makes the kingdom more heterogeneous, hence complicates the relation between the organisms.

Chlamydomonas sp., inspite of being unicellular, has not been included under Protista as it closely resembles other members of green algae.
Red algae and brown algae, though placed under Kingdom Plantae, are quite different from the other members of the kingdom.
Viruses have not been placed under any kingdom in this system of classification.

Six kingdom classification

Cavalier Smith was first to propound the six kingdom classification in 1998. This system includes six kingdoms—bacteria, protozoa, chromista, plants, fungi and animals. The table below depicts different systems of classification as propounded by different scientists.

Biological Classification Classification Of Organisms Based On Evolution

Three domain classification: Towards the mid 1970s, scientists began classification of living organisms according to their genetic constitution. They placed organisms, that originated from the same ancestor, within the same group.
This led to the introduction of three domain classification system. It was put forth by American microbiologist, Carl Woese in 1990. In this system, the living world is divided into three groups or domains— Archaea, Bacteria and Eukarya.
Basis of classification: While searching for new unicellular organisms, Carl Woese discovered certain microorganisms. These organisms could survive under extreme conditions such as acid lakes, hot water springs, etc.

He named these as archaebacteria. Analysis of their DNA structure showed similarities with that of the eukaryotes but dissimilarities with prokaryotes. Later he named this domain as Archaea.
Classification: Basically, it is a system of classification of living organisms into three domains based on the differences in their 16S rRNA genes. According to Carl Woese, all organisms have evolved from a primitive organism or a progenote.
According to the genetic differences, he classified the kingdom Monera into eubacteria (mainly bacteria) and archaebacteria (presently archaea). The rest of the eukaryotic organisms were placed under the domain Eukarya. Each domain is further divided into several kingdoms.

Biological Classification Three Domain Classification

Biological Classification Question And Answers

April 15, 2024November 15, 2023 by Sainavle

Biological Classification Questions And Answers

Question 1. What is a domain?
Answer. The category above kingdom is the domain. In 1977, Carl Woese first used the term domain.

Biological Classification

Question 2. In how many domains is the living world classified and what are they?
Answer. Carl Woese classified the living world into three domains. These are—archaea, eukarya and bacteria.

Question 3. What are thermoacidophiles?
Answer. The obligate anaerobic bacteria or archaebacteria that thrive at places with high temperatures (110°C) and low pH (pH 2.0) are called thermoacidophiles.

Question 4. What are aerotolerant microorganisms?
Answer. The bacteria that can carry out anaerobic respiration at low concentrations of oxygen are called aerotolerant microorganisms. E.g., Lactic acid fermenting bacteria.

Question 5. What are the dissimilarities found between bacteria and archaebacteria?
Answer. Archaebacteria and bacteria differ in genetic constitution and biochemical constituents. The cell wall of bacteria possesses peptidoglycan but the cell wall of archaebacteria lacks peptidoglycan.

Read and Learn More WBCHSE Solutions For Class 11 Biology

Question 6. What are photoautotrophic organisms?
Answer. The microorganisms (bacteria) that contain photosynthetic pigment (such as bacteriochlorophyll, bacteriophaeophytin) and can prepare their food in the presence of sunlight, are called photoautotrophic organisms: E.g., Chlorobium sp.

Question 7. What are myxamoeba, plasmodium and pseudoplasmodium of slime moulds?
Answer. The unicellular vegetative body of slime mould is called myxamoeba. Plasmodium is its naked protoplasm containing many nuclei. When myxamoeba fuse, the structure formed is called pseudoplasmodium.

Question 8. What is the basis of the five-kingdom classification?
Answer. The basis of the five kingdom classification is—

Complexity in the body system,
Complexity in cellular organisation,

Mode of nutrition,
Variations in the ecosystem,
Phylogenetic relationship.

Question 9. What are lichenology and mycology?
Answer. The study of lichens is called lichenology and the study of fungi is called mycology.

Question 10. Why are lichens called indicators of air pollution?
Answer. Lichens cannot survive in increased concentrations of air pollutants, mainly in high sulphur dioxide concentrations. So, the death rate of lichens is considered an indicator of air pollution.

Question 11. What is known as virion?
Answer. The nucleic acid containing and protein encapsulated pathogenic virus or its single unit is called a virion.

Question 12. What are prions?
Answer. The smallest infectious pathogen that lacks nucleic acid and is composed of only proteins is called prions. It is responsible for some diseases of the nervous system.

Question 13. What are dinoflagellates?
Answer. The unicellular, photosynthetic, golden brown protists, that possess two flagella are called dinoflagellates. E.g., Gonyaulaxs p., Gymnodinium sp.

Question 14. Write two differences between animal viruses and plant viruses.
Answer. Differences between animal and plant viruses are as follows—

Biological Classification Differences Between Animal And Plant Viruses

Biological Classification Very Short Answer Type Questions

Question 1. Who propounded the five-kingdom classification?
Answer: R.H. Whittaker propounded the five-kingdom classification of organisms.

Question 2. Name the five kingdoms of organisms.
Answer: The five kingdoms are—Monera, Protista, Fungi, Plantae and Animalia.

Question 3. Name the kingdoms whose organisms possess cell walls.
Answer: The cells of organisms of the kingdom Monera, Fungi and Plantae possess cell walls.

Question 4. Name the protein present in the flagella of bacteria.
Answer: Flagellin

Question 5. What is the full form of PPLO? What is its other name?
Answer: The full form of PPLO is Pleuro Pneumonia Organisms. It is also called mycoplasma.

Question 6. Which component is found in the cell wall of fungus?
Answer: Fungal cell walls have fungal cellulose or chitin. Besides, it also has polysaccharides, proteins, lipids, etc.

Question 7. Name the smallest free-living microorganism.
Answer: The smallest free-living microorganism is Mycoplasma.

Question 8. Which class of fungi is called club fungi?
Answer: Fungi of class Basidiomycetes are called club fungi.

Question 9. Which class of fungi is called sac fungi?
Answer: Fungi of the class Ascomycetes are called sac fungi.

Question 10. What type of stored food is found in fungi?
Answer: Glycogen is present as stored food in fungi.

Question 11. Name two symbiotic relations of fungi.
Answer: Two symbiotic relations of fungi are—lichen (fungi and algae) and mycorrhiza (fungi and roots of advanced plants).

Question 12. Which group of bacteria is known as ray fungi?
Answer: Bacteria belonging to the group Actinomycetes are called ray fungi.

Question 13. Name the chemical component present in the cell wall of bacteria.
Answer: The chemical component present in the cell wall of bacteria is peptidoglycan or murein.

Question 14. Name the causative agent of ‘black rust disease1 of wheat.
Answer: The causative agent of black rust disease of wheat is Puccinia graminis vartritici.

Question 15. Name the protozoa that cause malaria.
Answer: The causative agent of malaria is Plasmodium.

Question 16. Which phylum of Protista shows a resemblance with animals and fungi.
Answer: The phylum euglenophyta of the kingdom Protista shows a resemblance with animals and fungi.

Question 17. Why are some fungi classified as fungi imperfect?
Answer: Some fungi are classified as fungi imperfecti because they lack a sexual reproductive stage or perfect stage in their life cycle.

Question 18. Name one organism having a eukaryotic nucleus and lacking chlorophyll.
Answer: Fungi have eukaryotic nuclei but lack chlorophyll.

Question 19. Who first crystallised the virus?
Answer: The virus was first crystallised by W. M. Stanley.

Question 20. Who coined the term virus?
Answer: The name virus was coined by M.Beijernick.

Question 21. What genetic component is present in TMV?
Answer: The genetic component of TMV is RNA.

Question 22. Name one RNA molecule that shows features of a virus.
Answer: Viroids are RNA molecules showing features like viruses.

Question 23. Name the causative agent of AIDS.
Answer: The causative agent of AIDS is HIV (Human Immunodeficiency Virus).

Biological Classification Multiple Choice Question and Answers

November 20, 2023November 15, 2023 by Sainavle

Biological Classification Multiple Choice Questions

Question 1. Viroids differ from viruses in having—

DNA molecules without protein coat
RNA molecules with protein coat

RNA molecules without protein coat
DNA molecules with protein coat

Answer: 3. RNA molecules without protein coat

Question 2. Which of the following are found in extreme saline conditions?

Eubacteria
Cyanobacteria

Mycobacteria
Archaebacteria

Answer: 4. Archaebacteria

Read and Learn More WBCHSE Multiple Choice Question and Answers for Class 11 Biology

Question 3. Which among the following are the smallest living cells, known without a definite cell wall, pathogenic to plants as well as animals and can survive without oxygen?

Pseudomonas

Mycoplasma
Nostoc
Bacillus

Answer: 2. Nostoc

Question 4. The primary producers of the deep-sea hydrothermal vent ecosystem are—

Blue-green algae

Coral reefs
Green algae
Chemosynthetic bacteria

Answer: 4. Chemosynthetic bacteria

Question 5. The primary prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the—

Thermoacidophiles

Methanogens
Eubacteria
Halophiles

Answer: 2. Methanogens

Question 6. Which one of the following is wrong for fungi?

They are heterotrophic

They are both unicellular and multicellular
They are eukaryotic
All fungi possess a purely cellulosic cell wall

Answer: 4. All fungi possess a purely cellulosic cell wall

Question 7. Methanogens belong to—

Dinoflagellates

Slime moulds
Eubacteria
Archaebacteria

Answer: 4. Archaebacteria

Question 8. Select the wrong statement.

Diatoms are chief producers in the oceans

Diatoms are microscopic and float passively in water
The walls of diatoms are easily destructible
Diatomaceous earth is formed by the cell walls of diatoms.

Answer: 3. The walls of diatoms are easily destructible

Question 9. Select the mismatch.

Protists- Eukaryotes

Methanogens- Prokaryotes
Gas vacuoles- Green bacteria
Large central vacuoles- Animal cells

Answer: 4. Large central vacuoles- Animal cells

Question 10. Select the wrong statement.

Cyanobacteria lack flagellated cells

Mycoplasma is a wall-less microorganism
Bacterial cell wall is made up of peptidoglycan
Pili and fimbriae are mainly involved in motility of bacterial cells

Answer: 4. Pili and fimbriae are mainly involved in motility of bacterial cells

Question 11. Which of the following statements is wrong for Viroids?

They are smaller than viruses

They cause infections
Their RNA is of high molecular weight
They lack a protein coat

Answer: 1. They are smaller than viruses

Question 12. One of the major components of cell wall of most fungi is-

Chitin

Peptidoglycan
Cellulose
Hemicellulose

Answer: 1. Chitin

Question 13. Which of the following is not a feature of the plasmids?

Circular structure

Transferable
Single-stranded
Independent replication

Answer: 4. Independent replication

Question 14. Which of the following would appear as the pioneer organisms on bare rocks?

Lichens

Liverworts
Mosses
Green algae

Answer: 1. Lichens

Question 15. Chrysophytes, Euglenoids, Dinoflagellates and Slime moulds are included in the kingdom —

Monera

Protista
Fungi
Animalia

Answer: 2. Protista

Question 16. Choose the wrong statement—

Yeast is unicellular and useful in fermentation

Penicillium is multicellular and produces antibiotics
Neurospora is used in the study of biochemical genetics
Morels and truffles are poisonous mushrooms

Answer: 4. Morels and truffles are poisonous mushrooms

Question 17. Cell wall is absent in—

Nostoc

Aspergillus
Fun aria
Mycoplasma

Answer: 4. Mycoplasma

Question 18. In which group of organisms the cells walls form two thin overlapping shells which fit together?

Slime moulds

Chrysophytes
Euglenoids
Dinoflagellates

Answer: 2. Chrysophytes

Question 19. Select the wrong statement—

Mosaic disease in tobacco and AIDS in human being are caused by viruses

The viroids we discovered by D.J. Ivanowski
W.M. Stanley showed that viruses could be crystallized
The term contagium vivum fluidum was coined by M.W. Beijerinek

Answer: 2. The viroids we discovered by D.J. Ivanowski

Question 20. The structures that help some bacteria to attach to rocks and/or host tissues are

Holdfast

Rhizoids
Fimbriae
Mesosomes

Answer: 3. Fimbriae

Question 21. The imperfect fungi which are decomposers of litter and help in mineral cycling belong to—

Ascomycetes

Deuteromycetes
Basidiomycetes
Phycomycetes

Answer: 2. Deuteromycetes

Question 22. Which the following are most suitable indicator of S02 pollution in the environment?

Fungi

Lichens
Conifers
Algae

Answer: 2. Lichens

Question 23. Pick up the wrong statement—

Nuclear membrane is present in Monera

Cell wall is absent in Animalia
Protista have photosynthetic an heterotrophic modes of nutrition
Some fungi are edible

Answer: 1. Nuclear membrane is present in Monera

Question 24. Five kingdom system of classification suggested by RH Whittaker is not based on

Presence or absence of a well defined nucleus

Mode of reproduction
Mode of nutrition
Complexity of body organisation

Answer: 1. Presence or absence of a well defined nucleus

Question 25. Archaebacteria differ from eubacteria in—

Cell membrane structure

Mode of nutrition
Cell shape
Mode of reproduction

Answer: 1. Cell membrane structure

Question 26. Which of the following shows coiled RNA strand and capsomeres?

Polio virus

Tobacco mosaic virus
Measles virus
Retrovirus

Answer: 2. Tobacco mosaic virus

Question 27. Viruses have—

DNA enclosed in a protein coat
Prokaryotic nucleus
Single chromosome
Both DNA and RNA

Answer: Both DNA and RNA

Question 28. Identify the correct sequence of events in the viral replication process.

Eclipse
Maturation
Adsorption
Assembly
Penetration
Lysis

(1), (2), (3), (4), (5), (6)

(2), (1), (3), (4), (5), (6)

(3), (5),(1), (2), (4), (6)

(3), (5), (6), (4), (2), (1)

Answer: 3. Adsorption

Question 29. As per Whittaker’s classification, an organism possessing eukaryotic cell structure, multicellular organisation, with a cell wall and nuclear membrane showing heterotrophic nutrition can be placed under the kingdom—

Monera
Protista
Plantae
Fungi
Animalia

Answer: 4. Animalia

Question 30. Which of the following does not apply to Ascomycetes?

Mycelium coenocytic and aseptate
Commonly known as sac fungi
Asexual spores called conidia are produced exogenously
Sexual spores called ascospores are produced endogenously
They are saprophytic, decomposers, parasitic or coprophilous

Answer: 1. Mycelium coenocytic and aseptate

Question 31. Which of the following groups of organisms have a protein rich layer called pellicle?

Chrysophytes
Euglenoids
Dinoflagellates
Slime moulds
Protozoans

Answer: 2. Euglenoids

Question 32. Identify the correct pairs of combination

Viroid — Bovine spongiform encephalitis.

Prion — Creutzfeldt-Jakob disease.

Measles virus — Glycoprotein projections.

Rabies virus Polyhedral symmetry.

(3) and (4)
(1) and (3)
(1) and (2)
(2) and (3)

Answer: 4. (2) and (3)

Question 33. The protozoan with heliopodia as locomotory structures

Actinophryx
Entamoeba
Entamoeba
Euglypha

Answer: 1. Actinophryx

Question 34. The type of syngamy seen in Trichonympha is—

Hologamy
Anisogamy
Isogamy
Conjugation

Answer: 1. Hologamy

Question 35. Protists obtain their food as—

Photosynthesisers
Chemosynthesisers
Heterotrophs
Both 1 and 2

Answer: 4. Both 1 and 2

Question 36. Which of the following does not belong to kingdom—Protista?

Chrysophytes
Euglenoids
Ascomycetes
Dinoflagellates
Protozoans

Answer: 3. Dinoflagellates

Question 37. Bacteria differ from plants in that they do not have—

DNA
RNA
Cell wall
A well defined nucleus

Answer: 4. A well defined nucleus

Characteristics And Classification Of Gymnosperms

November 20, 2023November 15, 2023 by Sainavle

Gymnosperms

Gymnosperms Definition: Gymnosperms are plants in which seeds are not enclosed in an ovule.

The gymnosperms are seed-forming plants that include conifers, cycads, Ginkgo, and members of the order Gnetales. The term ‘gymnosperm’ comes from the Greek words gymnos (=naked) and sperma (=seed), meaning ‘naked seeds’. The naked condition of their seeds is due to the fact that the carpels do not fuse, enclosing the ovules, to form an ovary.

It is considered that gymnosperms have developed from a type of plant species, called progymnosperms They are intermediate to the pteridophyta and angiosperms. About 900 species of gymnosperms have been discovered so far.

Gymnosperms Distribution: Gymnosperms are present all over the world, but they are found more in the temperate zone, than the equatorial zone.

Read and Learn More: WBCHSE Notes for Class 11 Biology

Gymnosperms General features:

1. Most of the gymnosperms are perennial and evergreen in nature, with long, hard and woody stems. Some of them are shrub-like.

2. The main plant body is sporophytic (2n). It is independent, with the body being differentiated into true roots, stems, leaves, flowers and seeds.

3. Plants have a tap root system, that generally persists for a long time. Some adventitious roots also develop along with the primary root. In some cases, blue-green algae and fungi are found in roots in symbiotic association with the roots.

4. The stem is erect and woody. It may be branched (Pinus sp.) or unbranched (Cycas sp., Zamia sp.). Stem branches are of two types—long shoots and dwarf shoots.

5. Long shoots have unlimited growth while dwarf shoots show regulated and limited growth.

6. Vascular bundles in stems are of two types—open and collateral.

7. In roots, radially arranged xylem is made up of tracheids, parenchyma and xylem fibre. Vessels or trachea are only present in the xylem of Gnetum sp. and Ephedra sp. Phloem consists of sieve cells, phloem parenchyma and phloem fibre. The companion cells are absent.

8. Leaves are of two types—brown scale leaves and green foliage leaves. Long shoots bear scale leaves, while dwarf shoots bear both scale and foliage leaves

9. Venation in leaves may be reticulate (Gnetum sp.) parallel (Pinus wallichiana) or dichotomous (Gingko sp.).

10. The leaves are covered with thick cuticles, sometimes with a wax layer. Stomata are present on the lower surface of the leaves. Mesophyll may (Cycas sp.) or may not be (Pinus sp.) divided into palisade and spongy parenchyma.

11. Secondary growth is present in all members, where the mature metaxylem shows bordered pits (In Stangeria sp. and Zamia sp., the metaxylem shows scalariform thickening).

12. Flowers are monoecious, naked and devoid of accessories whor|s.

13. Male flowers are formed of microsporophylls, and female flowers are formed of megasporophylls, called carpels.

14. Microsporophylls and megasporophylls remain arranged and condensed on an axis to produce male and female cones respectively.

Plant Kingdom A male cone and a microsporophyll bearing tivo microsporangia

15. Microsporangia are present on the ventral side of the microsporophylls and megasporangia are present on the dorsal side of the megasporophylls.

16. Ovules or megaspores are exposed on the megasporophylls. Each megasporophyll may bear two or more ovules.

17. Inside microsporangia, numerous microspores (pollen grains) are produced.

18. Microspores produce male gametophytes. Male gametes are either ciliated or non-ciliated.

19. Megaspores in megasporangia produce female gametophytes. Egg cells are produced in one or more archegonia within female gametophytes.

20. Pollination occurs mainly by wind. Male gametes come in direct contact with the ovule (siphonogamy).

21. Sometimes more than one embryo may develop from a zygote (polyembryony).

22. Endosperm is haploid (n) and produced within female gametophytes before fertilisation.

23. Ovule (seed) consists of a single jacket or integument (unitegmic). Cotyledon may be one or two (Cycas sp.) or many (Pinus sp.).

24. The alternation of generations observed in gymnosperms is heteromorphic.

Plant Kingdom Alteration ofgenerations in the life cycle ofa typical gymnosperm

Plant Kingdom Cones ofgymnosperm

Some common examples of gymnosperms are— Cycas sp., Pinus sp., Ginkgo sp., Gnetum sp., etc.

Commercial importance of gymnosperms: Gymnosperms are of great economic importance. The commercial uses of gymnosperms are as follows—

Timber: The coniferous wood may be very light or hard, strong or soft, coarse or grained and durable with distinct annual rings.

Pinus sp., Cedrus sp., Abies sp., etc., yield good quality timber that is used for making furniture, plywood, matchsticks, pencils, etc.

Resin source: Resin exudates from coniferous plants. Resin is a nitrogenous waste produced by plants which is soluble only in organic solvents. The resin is used in varnishes, plasters, enamels, medicine, printing ink, laundry soap, oil, etc.

Resins are of different types like—rosin (solid, obtaining Pinus sp. mainly), copals (hard, with essential oils, in Agathis sp.), sandarac (translucent, pale yellow or orange-coloured, in Tetraclinis articulate), Canada balsam (transparent, non-crystalline, in Abies balsamea)

Source of essential oils and gums: Almost all conifers yield volatile essential oils along with resins. Spruce oil is obtained from Picea abies which is used in room sprays, bath salts and deodorant.

The Siberian fir needle oil, obtained from Abies sibirica is also used in deodorant, toilet and shaving soaps, etc. Cedar oil is obtained from Cedrus deodara and Juniperus virginiana and is used in perfumery as well as in microscopic studies.

Source of paper: Conifers yield good quality timbers which are used for making paper pulp, used in the newsprint industry. Writing and printing papers are manufactured from the wood of Picea sp., Abies sp., Larix sp. and Tsuga sp., whereas craft papers are produced from Pinus sp. and Cryptomeria sp.

Production of medicines: Ephedra sp. is an important source of alkaloid, ephedrine. This is used as a bronchodilator in cough mixture used for the treatment of bronchial asthma. The leaves of Ginkgo biloba are an important source of the ginkgolide compound.

This compound is used to antagonize platelet-activating factor (PAF) in vertebrate blood. Another compound bilobalide obtained from Ginkgo leaves used in the treatment of neural disorders like Alzheimer’s disease. Extracts of these leaves are also used in the treatment of muscular disorders, cerebral insufficiency, vertigo, etc.

Taxus brevifolia is an important source of an anticancer drug, taxol. The leaves of Taxus baccata are useful in the treatment of asthma, bronchitis, hiccups, epilepsy and indigestion. The seeds of Cycas sp., are used as an herbal drug for curing boils, wounds and sores.

Source of tannins: The bark of Tsuga canadensis, Picea alba, Sequoia, etc., yields tannins which are used for different purposes.

As ornamental plants: Several varieties of Cycas sp., Pinussp., Cedrus sp., etc., are widely planted as ornamental plants in gardens, parks temples etc., for their beautiful appearance, symmetrical growth and evergreen nature Their branches and leaves are used as decorations.

Source of food: Spongy pith of Cycas, Zamia, and Macrozamia contain large amounts of starch which is used to prepare sago. It is used as a food. The seeds of Pinus sp., are used in cooking and are eaten raw.

Seeds of Juniperus sp., are used as condiments in cooking. The young unfolded succulent leaves and tender shoots of many species of Cycas sp., are taken as cooked food.

Classification of gymnosperms: The living gymnosperms plants are grouped into four main types—

Cycadopsida,

Ginkgopsida,
Coniferopsida
Gnetopsida. These groups have been discussed under separate heads.

Bryophyta -Definition and Characteristics Notes

April 19, 2024November 15, 2023 by Sainavle

Bryophyta

The term ‘bryophyta’ came from two Greek words bryon (moss) and phyton (plant).

Bryophyta Definition: Bryophytes are the simplest and most primitive, non-flowering, embryophytes, that do not contain vascular tissues.

Bryophyta Distribution: Bryophyta is the first group of plants to inhabit the land. They generally occur in moist and shady places. They are found at higher altitudes, on moist soil, stones, trunks and branches of trees. Though they are terrestrial, they require water to complete their life cycle, specifically during fertilisation. Therefore, they are considered as ‘the amphibians of plant kingdom’.

Bryophyta Size and shape: The size of bryophytes may range from very small (1-3 mm) to large (60 cm). Generally, they grow within a height of 15 cm and are herbaceous in nature. They grow closely packed as mats or cushions on rocks, and soil, as epiphytes on the trunks and leaves or as free-floating in water. Most of the bryophytes show dichotomous branching. They are either thalloid or foliose.

Read and Learn More: WBCHSE Notes for Class 11 Biology

Bryophyta General features:

The important characteristics of bryophytes are as follows—

The life cycle of bryophytes is divided into gametophytic and sporophytic phases (i.e., heteromorphic).
The gametophytic phase is predominant and ecologically persistent, i.e., green, independent and long-lived.

The sporophytic phase is very short-lived and completely dependent upon the gametophyte for nutrition and growth.

Plant Kingdom Riccia thallus

Characteristics of gametophytes: The characteristics of gametophytes have been discussed below.

Structure:

Gametophytes show the following structural features—

The gametophytic plant body is either thalloid or differentiated into the root-like rhizoid, stem-like erect caulid and leaf-like phyllid.

Roots are absent in bryophytes. Instead, structures called rhizoids, are present, and those perform the function of roots. They may be branched or unbranched, unicellular or multicellular. They are of two types smooth-walled (inner wall smooth) or tuberculated (inner wall with peg-like projections).
The thread-like body structure, produced during the germination of spores to produce immature gametophytes is called protonema.
The stem-like structure of bryophytes, above the ground is called caulid. These bear leaf-like structures are called phyllids.

Multicellular, coloured scales, are present at the ventral side of the thallus. They protect the cells from friction with the substratum.
Xylem and phloem are absent in these plants. They may have special lignin-containing, conducting tissue in sporophytes. Otherwise, the plant body is made up of parenchyma cells only.
Air pores present in the thallus and stomata present in the capsule in moss, allow gaseous exchange with the environment.

Bryophyta Reproduction: They reproduce by vegetative and sexual means. Asexual reproduction is completely absent in bryophytes.

Vegetative propagation takes place by fragmentation or some special, structures, like gemmae, tubers, protonema, adventitious branches, persistent apices, etc.
Sexual reproduction is of monogamous type. They have large, multicellular gametangia (sex organs), covered with a jacket of sterile cells.

Bryophytes are unisexual, either homothallic (monoecious) or heterothallic (dioecious),
The male sex organs, called antheridia, are multicellular, stalked, globose or ovoid structures. They have a single-layered thick jacket surrounding androgenic mother cells.
Biflagellate sperms or antherozoids (male gametes) are produced from these cells,

The female sex organs, called archegonia, are multicellular, vase-shaped or round-bottom flask-shaped structures,
They have a swollen base, called a venter, containing a ventral canal cell and an egg, and the upper elongated neck containing neck canal cells.
Both the venter and neck are surrounded by the single-layered jacket, made of sterile cells.

The sperms are motile and swim through the water to reach the archegonia. Hence, water is required for sperm dispersal and subsequent fertilisation.
The zygote does not pass through any resting phase. The diploid zygote or oospore develops into the embryo.
Embryonic growth of the sporophyte begins within the venter of the archegonium, soon after fertilisation.

Plant Kingdom Differences between rhizoids and scales

Exoscopic mode of development

The embryo follows an endoscopic mode of development. In this development, the zygote first divides transversely to form an outer epibasal cell and an inner hypobasal cell. The embryo develops from the epibasal cell. Thus, the shoot-forming apical cell is directed outwards, i.e., towards the neck of the archegonium.

Characteristics of Sporophytes:

The sporophytes are diploid.they remain attached to the gametophytic plants for nutrition.
They have bulbous feet, an unbranched stalk-like seta and a single terminal sporangium called a capsule. Sometimes the sporophyte is represented only by a capsule (Riccia sp.).

The capsule has a protective covering called calyptra, which is a part of the gametophyte.
Bryophytes are homosporous (spores are morphologically and physiologically identical). Spores are produced from the sporogenous cells of the capsule through meiotic division.
The haploid (n) spore after germination either produces a filamentous germ tube that gives rise to a young gametophyte (for example Riccia spv Marchantia sp.) or produces a juvenile plant or protonema that ultimately gives rise to an adult gametophytic plant.

Sporophytes Alternation of generations: The alternation of generations is of a heteromorphic nature. The main plant body is gametophytic and bears haploid germ cells. After fertilisation, a diploid zygote is produced.

This undergoes division and differentiation to form a diploid sporophytic (2n) plant. Haploid spores are produced within the spore mother cells of the sporangia in sporophytic plants by the process of meiosis.

These spores germinate to produce haploid gametophytic(n) generation. The alternation of generations In a typical bryophyte has been depicted In.

Some common examples of Bryophytes are—Riccia sp., Marchantia sp., Anthoceros sp., Pellia sp., Pogonatum sp., etc.

The commercial importance of Bryophyta: There are various commercial applications of bryophytes These have been discussed as follows—

Indicator Species: Both liverworts and mosses are often good indicators of environmental conditions. In Finland, terrestrial bryophytes are used to characterise forest types. Bryophytes are used as indicators for mineral concentration. Copper mosses grow almost exclusively in areas with high concentrations of copper, particularly copper sulphate. Thus they serve as good metal indicators.

Soil erosion control: Cultivation of bryophytes on bare land by spreading spores or vegetative fragments or propagules of bryophytes could help to prevent soil erosion. The protonemata, which develop from both fragments and spores, form mat-like structures that cover and bind exposed soil particles.

Sphagnum sp. has a high water holding capacity. They control the water content of the soil during spring runoff in the Arctic. also responsible for soil formation and storing water It is during floods. They are used as nursery beds, for proper conservation of the plants.

Barometer

In Japan, H. Taoda (1976) developed a bryometer, a bag of mosses that respond in predictable ways to various levels of air pollution. By exposing a variety of mosses to various levels of SO₂, he determined that most species are injured by 10-40 hours of exposure to 0.8 ppm SO₂. Since that time, the use of the barometer has spread around the world.

Nitrogen fixation: Nitrogen is often a limiting nutrient for plant growth, especially in agriculture. Bryophyte crusts, endowed with nitrogen-fixing cyanobacteria, can contribute considerable nitrogen, particularly to dry soils.

Nostoc sp., a cyanobacterium living symbiotically with Anthoceros sp., is able to fix atmospheric nitrogen as an ammonium salt. Hence, it can be used as fertiliser.

pH regulation of soil: Sphagnum sp., helps to maintain the acidity of the soil. Hence, acid-loving plants or oxylophytes are known to grow in such soil.

Food sources: Bryophytes are very rarely consumed by the animals. They may be the source of specific needs of animals at a time when fresh food is scarce. These are used as food in snow-capped mountain regions.

Medicines: Bryophytes (especially liverworts) are used as herbal medicine. Numerous compounds, including oligosaccharides, polysaccharides, sugar alcohols, amino acids, fatty acids, and aliphatic compounds occur in bryophytes.

Bryophytes such as Sphagnum sp. are used to treat skin diseases, and Marchantia polymorpha is used to treat liver ailments. Rhodobryum giganteum and R. roseum are used to treat cardiovascular diseases and nervous prostration.

Polytrichum commune reduces inflammation and fever. It is also used as a diuretic laxative and hemostatic agent. Haplocladium microphyllum is used to treat cystitis, bronchitis, etc.

Plant Kingdom Alteration ofgenerations in the life cycle ofa typical Bryophyte

Classification of Bryophyta: Rothmaler (1951) classified bryophytes into three classes—Hepaticopsida, Anthoceropsida and Bryopsida. In accordance with the International Code of Botanical Nomenclature. Proskauer (1957) modified the classification of Rothmaler by changing the class name Anthoceropsida to Anthocerotopsida.

Plant Kingdom Bryophyta

Class: Liverworts or Hepaticopsida

Liverworts General features:

Gametophytes are dorsoventrally flattened, and thalloid in nature. Thallus dichotomously branched (apical growing point divided into two growing parts producing two branches in a forked manner). Each lobe of the thallus has a dorsal groove and an apical notch.
The thallus structure has multicellular scales and unicellular rhizoids.

The thallus has chloroplasts but is devoid of pyrenoids.
Multicellular sex organs, i.e., antheridia and archegonia, are present on the dorsal side of the thallus. In some species (Marchantia sp.) sex organs are bore on specified structures called antheridiophores and archegoniophores.
Male antheridia are stalked, globose or ovoid. Each antheridium has several antherozoid mother cells which produce biflagellate,comma-shaped antherozoids or sperms.

Female archegonia is flask-shaped. Its lower part is called the venter and its upper slender part is called the neck. Inside the venter single egg is present.
A sporophyte is devoid of foot and seta. Capsules are globose or ellipsoid, brown or black in colour. Setae are small delicate stalks. [Exception: Foot and seta are absent in the sporophyte of Marchantia sp.]
The capsule wall is made up of a single-cell layer. The capsule contains haploid spores developed from spore mother cells through meiosis. Some species (for example Marchantia sp.) have haploid, needle-like elaters. These elaters help in the dehiscence of the capsule.

Some examples of Hepaticopsida are: Riccia sp., Marchantia sp.

Plant Kingdom Some common members ofHepaticopsida

Class: Hornworts or Anthocerotopsida

Hornworts General features:

Gametophytes are thalloid, with the structure being dorsoventrally flattened and irregularly lobed.
The thallus is not differentiated into stems and leaves and is always homogeneous. Each cell has a chloroplast with centrally placed pyrenoids.

Air cavities and scales may be absent, but smooth and septate rhizoids are present.
The reproductive organs are present on the dorsal side of the thalamus.
In some species, the thallus sometimes contains mucilage cavities which are inhabited by Nostoc, a cyanobacterium.

The mature sporophyte shows a bulbous foot and a slender cylindrical capsule standing out like a bristle from the thallus. The meristematic zone is present at the basal part of the capsule. Seta is absent.
Capsules have a central column of sterile cells called columella (Exception: In Notothylas, columella is absent). The spore mother cells remain surrounding the columella.
The spore mother cells generate haploid spores through meiosis. The capsule also contains numerous unicellular structures resembling elaters, called pseudoelaters. Some examples of Anthocerotopsida are— Anthoceros sp., Notothylus sp., Ceratophyllum sp., etc.

Plant Kingdom Some members ofAnthocerotopsida

Class: Moss or Bryopsida

Moss or Bryopsida General features:

Matured gametophytes, originating from branched protonema, are erect plants with a stem-like axis (caulid).
The axis is covered with spirally arranged leaf-like phyllids.
Phyllids are flattened leaf lamina-like structures, light green in colour with serrated margins. The midrib is prominent.

Multicellular and branched rhizoids are present instead of roots. Caulids possess a cylinder of primitive conducting tissue, made up of thick-walled cells. A central, parenchymatous pith-like structure is also seen.
Multicellular sex organs are present at the top of the branches of caulids. The sex organs develop at the axils of leafy structures called perichaetial leaves.
Antheridia are small, stalked and dumbbell-shaped, while the archegonia are distinct and flask-shaped.

Sporophyte is dependent on gametophytic plants. It is differentiated into foot, seta and capsule.
The foot is bulbous and acts like a haustorium. Capsules may be green, brown, yellow or red in colour, with a short green, yellow or translucent seta.
The capsule contains a dome-shaped spore sac containing sporogenous tissue, overarching a centrally located columella and single cell-layered thick ribbon-like trabeculae.

At the top of the capsule, there is a cap-like structure called an operculum. Below the operculum one or more ring or teeth-like structures (peristome teeth) are present. These help in the opening of the capsule and the release of spores.
The mature capsule is protected by a covering called calyptra. The diploid sporogenous tissues in the spore sac can produce haploid spores through meiosis. These spores germinate to form haploid protonema.

Some examples of Bryopsida are: Sphagnum sp., Funaria hygrometrica, Pogonatum sp., etc.

Plant Kingdom Some members ofMoss

Similarities between algae and Bryophyta

Both are non-flowering, autotrophic, without any vascular tissue.

Both do not have roots. Generally, both of them have a thallus body structure.
Both require water for their fertilisation. The male gametes are flagellate and hence, they are motile in nature.
Both have cellulose in the cell wall.

Protonema of mosses resembles the thread-like algae.
Both have similar photosynthetic pigments.
Gametophyte is the main plant body in both.

Plant Kingdom Comparison among Hepaticopsida, Anthocerotopsida and Bryopsida

Plant Kingdom Differences between algae and bryophyta