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In this article, we provide a solution of BBYCT 131 Biodiversity (Microbes, Algae, Fungi and Archegoniates). Read and make an assignment for your assessment.

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BBYCT 131 Solved Assignment 2024

Note: Attempt all questions. The marks for each question are indicated against it.

1. a) Differentiate between DNA viruses from RNA viruses with the help of suitable diagram.

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b) Discuss the mechanism of transformation in bacteria with appropriate example and diagram.

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2. a) Discuss the biological significance of heterospory in pteridophytes.

Ans: Heterospory is a reproductive strategy where a plant species produces two distinct types of spores: microspores (male) and megaspores (female). This phenomenon is particularly significant in the life cycle of pteridophytes, which include ferns and their relatives. The biological significance of heterospory in pteridophytes lies in several key aspects:

1. Evolutionary Advantage:

Heterospory represents an evolutionary advancement from the more primitive condition of homospory (producing only one type of spore). This specialization allows for greater reproductive efficiency and adaptability to various environments.

2. Increased Genetic Diversity:

By producing two different types of spores, heterospory promotes genetic diversity. Microspores and megaspores develop into separate male and female gametophytes, respectively. This separation of sexes enhances genetic variability, facilitating better adaptation to changing environmental conditions.

3. Efficient Reproduction:

Heterospory ensures more precise and efficient reproduction compared to homospory. Microspores develop into male gametophytes that produce sperm, while megaspores develop into female gametophytes that house the eggs. This separation of reproductive functions aids in successful fertilization, increasing the chances of successful reproduction.

4. Specialized Spore Production:

Microspores are typically smaller and lighter, facilitating dispersal by air, wind, or other means, ensuring broader distribution. Megaspores, being larger, have more stored nutrients, providing better resources for the development of the female gametophyte.

5. Life Cycle Complexity:

Heterospory adds complexity to the life cycle of pteridophytes. It involves alternation of generations between the sporophyte (the dominant phase in ferns) and the gametophyte. This alternation allows for different modes of reproduction and helps in ensuring the survival of the species in various environmental conditions.

Overall, heterospory in pteridophytes enhances reproductive success, genetic diversity, and adaptability to changing habitats. It marks an evolutionary advancement that contributes significantly to the survival and proliferation of these plants in diverse ecosystems.

b) Discuss why is the seed of gymnosperms considered having remarkable combination of two generation.

Ans: The seed of gymnosperms is considered a remarkable combination of two generations—the sporophyte and the gametophyte. This uniqueness lies in the way gymnosperms have evolved to protect and nourish their offspring, resulting in several key aspects:

1. Sporophyte Dominance:

Gymnosperms exhibit a dominant sporophyte phase in their life cycle. The seed itself represents the sporophyte generation, which is the larger, more prominent phase in the life cycle of these plants. This sporophyte phase develops from the fertilized ovule and contains the embryo, endosperm, and protective seed coat.

2. Integration of Both Generations:

Within the seed of gymnosperms, the embryo represents the young sporophyte generation, while the surrounding tissues (such as the endosperm) are remnants of the gametophyte generation. The endosperm serves as a nutrient-rich tissue that supports the developing embryo, providing essential nutrients for its growth.

3. Protective Structures:

The seed coat of gymnosperms acts as a protective layer, guarding the developing embryo against desiccation, physical damage, and microbial attack. This protective layer ensures the survival of the embryo in harsh environmental conditions.

4. Efficient Dispersal Mechanism:

Gymnosperm seeds have evolved various mechanisms for dispersal, ensuring the spread of their offspring. Some gymnosperms utilize wind, animals, or water to disperse their seeds over long distances, increasing the chances of successful colonization in new areas.

5. Adaptation to Diverse Environments:

The seed structure of gymnosperms has contributed to their ability to thrive in diverse environments, ranging from temperate forests to arid regions. The protective seed coat and the nutrient-rich endosperm facilitate the survival of the embryo in different conditions.

6. Evolutionary Advantage:

The development of seeds with these combined features of both generations—the sporophyte providing protection and the remnants of the gametophyte providing nutrients—has been a significant evolutionary advancement. This combination enhances the chances of successful reproduction and propagation of gymnosperms in various habitats.

3. a) Explain the role of bryophytes in prevention of soil erosion/and as pioneers of vegetation.

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b) Enumerate the unifying characteristics of archegoniates.

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4. Differentiate between the following pairs of terms:

i) Flagella and Pili

Ans: Flagella and pili are both structures found in various types of cells, but they serve different functions and have distinct characteristics:

Flagella:

1. Function: Flagella are whip-like appendages used primarily for cellular movement. They propel the cell through its environment by their rotation or waving motion.
2. Composition: Flagella are long, thread-like structures made up of protein filaments, arranged in a helical pattern.
3. Location: Typically, cells possess a few flagella, often located at one end of the cell or distributed around the cell surface.
4. Occurrence: Flagella are found in various organisms, including bacteria, archaea, and some eukaryotic cells (such as sperm cells in animals or algae).
5. Movement Mechanism: Flagella move in a wave-like motion, either by rotating like a propeller (as in bacteria) or by undulating back and forth (as in eukaryotic cells).

Pili (Pilus – singular):

1. Function: Pili are hair-like appendages that serve various functions, including attachment to surfaces, transfer of genetic material (conjugation), and sometimes facilitating motility.
2. Composition: Pili are shorter and thinner than flagella, consisting mainly of protein subunits arranged in a helical or linear manner.
3. Location: Pili are often present in large numbers on the surface of bacterial cells, extending outwards from the cell wall.
4. Occurrence: Pili are predominantly found in bacteria. Some bacteria possess different types of pili that serve specific functions, such as adherence to host tissues or conjugation for genetic exchange.
5. Role in Conjugation: One of the critical functions of pili is their involvement in bacterial conjugation, where they facilitate the transfer of genetic material (plasmids) from one bacterium to another.

ii) Transduction and conjugation

Ans: Transduction and conjugation are two distinct mechanisms through which genetic material is transferred between bacteria, but they differ in their processes and the agents involved:

Transduction:

• Definition: Transduction is a process of horizontal gene transfer in bacteria where genetic material is transferred from one bacterium to another by a bacteriophage (a virus that infects bacteria).
• Mechanism: During a viral infection of a bacterium, the bacteriophage mistakenly packages fragments of bacterial DNA instead of its own genetic material. When this phage particle infects another bacterium, it injects the packaged bacterial DNA, which can then be integrated into the recipient bacterium’s genome.
• Nature of Transfer: Transduction involves the transfer of genetic material mediated by a virus (bacteriophage) and occurs without direct contact between donor and recipient bacteria.
• Types: Transduction can be either generalized, where any bacterial DNA can be transferred, or specialized, where only specific bacterial genes are transferred due to errors in phage DNA packaging.

Conjugation:

• Definition: Conjugation is a process of bacterial mating in which genetic material (usually plasmids) is transferred directly from one bacterium (donor) to another (recipient) through a specialized structure called a pilus or conjugation tube.
• Mechanism: The donor bacterium possesses a plasmid containing the genetic information to be transferred. A pilus extends from the donor bacterium and establishes contact with the recipient. The plasmid is then transferred through this pilus into the recipient bacterium.
• Nature of Transfer: Conjugation involves direct physical contact between the donor and recipient bacteria via a conjugation bridge formed by the pilus.
• Types: Conjugation often involves the transfer of plasmids carrying antibiotic resistance genes or other beneficial traits. It can also occur between different bacterial species, contributing to the spread of genetic material.

iii) Lysogenic and lytic cycle of bacteriophages

Ans: The differences between the lysogenic and lytic cycles of bacteriophages represent two distinct phases in the life cycle of these viruses when infecting bacterial cells:

Lysogenic Cycle:

1. Integration into Host DNA: In the lysogenic cycle, upon infecting a bacterial cell, the viral DNA (or sometimes RNA) integrates into the host bacterium’s chromosome. It becomes a prophage and replicates along with the bacterial DNA.
2. Dormancy: The integrated phage remains dormant within the host cell, not actively producing new phages or causing lysis immediately after infection.
3. Replication with Host: During bacterial cell division, the prophage DNA replicates along with the bacterial DNA. This replication is passive and doesn’t harm the host cell.
4. Conditions Triggering Switch: Under certain conditions (e.g., stress, UV radiation), the prophage can switch to the lytic cycle, initiating the production of new phages and eventual lysis of the host cell.

Lytic Cycle:

1. Attachment and Entry: In the lytic cycle, the bacteriophage attaches to the host bacterium’s cell wall and injects its genetic material (DNA or RNA) into the cell.
2. Replication and Transcription: The viral genome takes control of the host cell’s machinery, forcing it to produce viral components—new phage DNA, proteins, and sometimes an enzyme to break the bacterial cell wall.
3. Assembly and Lysis: New phages are assembled within the host cell, and eventually, the cell lyses (bursts open), releasing multiple new phages to infect neighboring cells.
4. Continuous Infection: The lytic cycle leads to the immediate death of the host cell and the rapid propagation of the virus.

iv) Root of Cycas and Pinus

Ans: The root structures of Cycas and Pinus exhibit some differences based on their anatomy, origin, and function:

Root of Cycas:

• Structure: Cycas roots are characterized by having a well-defined taproot system with numerous lateral roots branching off from the main taproot. They possess a primary root that grows vertically downward, giving rise to smaller lateral roots.
• Origin: These roots originate from the radicle of the embryo, which is the primary embryonic root. The radicle elongates to form the primary taproot, which further develops lateral roots.
• Function: Cycas roots primarily serve for anchorage and absorption of water and nutrients from the soil. They anchor the plant firmly into the ground and aid in the uptake of water and essential minerals necessary for the plant’s growth and development.

Root of Pinus:

• Structure: Pinus roots consist of a fibrous and shallow root system. They lack a distinct taproot. Instead, numerous thin lateral roots spread out horizontally from the base of the stem.
• Origin: These roots originate from the radicle of the embryo, similar to Cycas. However, as the plant grows, the primary root does not develop into a prominent taproot but instead forms a network of fine lateral roots.

Function: The root system of Pinus contributes to stability by spreading wide and relatively shallow. They efficiently absorb water and nutrients from the upper soil layers and help in the uptake of these resources from a broader area.

5. Prepare clear and well labelled diagrams of any four of the following:

i) Formation of palmella stage in Chchlamydomonas

Ans: Chlamydomonas is a genus of green algae, and it undergoes various life cycle stages, including the palmella stage. The palmella stage is a non-motile, coccoid (spherical) stage in the life cycle of certain algae, including Chlamydomonas. It typically occurs under unfavorable conditions, such as nutrient depletion or other environmental stressors.

The formation of the palmella stage in Chlamydomonas is often a response to adverse environmental conditions that make the motile flagellated cells less viable. When faced with stress, Chlamydomonas cells can undergo a process called palmelloid transformation, leading to the formation of palmella cells. Here’s a general outline of the process:

1. Environmental Stress: Unfavorable conditions, such as nutrient scarcity or changes in light intensity, trigger stress responses in Chlamydomonas.
2. Cellular Changes: The motile, biflagellate cells of Chlamydomonas undergo morphological and physiological changes in response to stress. The cells lose their flagella and aggregate to form spherical, non-motile palmella cells.
3. Cell Wall Modifications: The cell wall of Chlamydomonas may undergo modifications during the transition to the palmella stage. The cells become surrounded by a protective layer, providing resistance against external stress factors.
4. Storage Products: Palmella cells often accumulate storage products such as lipids or starch, allowing the cells to withstand the unfavorable conditions by utilizing these reserves.
5. Resistance to Desiccation: The palmella stage is often more resistant to desiccation (drying out) compared to the motile stage, allowing the algae to survive in harsh environments.

It’s important to note that the formation of the palmella stage is a survival strategy for Chlamydomonas, enabling the organism to endure challenging conditions until more favorable conditions return. Once environmental conditions improve, Chlamydomonas can revert to its motile, flagellated form and resume its typical life cycle.

ii) L.S. of male cone of Pinus

Ans: A longitudinal section (L.S.) of a male cone of Pinus, commonly known as a pine cone, would reveal its internal structures related to the production and release of pollen. The male cones of Pinus are smaller and typically located on lower branches, and their main function is to produce and release pollen grains. Here are the main features you might observe in a longitudinal section of a male cone of Pinus:

1. Microsporophylls (Sporophylls): These are modified leaves that bear microsporangia, where pollen grains (microspores) are produced. In a longitudinal section, you would see these structures arranged spirally or in a whorl on the cone axis.
2. Microsporangia: The microsporangia are located on the lower surface of the microsporophylls. They are small structures containing cells that undergo meiosis to produce haploid microspores, which will develop into pollen grains.
3. Pollen Sac: This is a structure within the microsporangium where the actual process of meiosis takes place, resulting in the formation of microspores. Each pollen sac typically contains a number of developing microspores.
4. Pollen Grains: These are the mature male gametophytes produced by the microspores. In a longitudinal section, you might observe these pollen grains within the microsporangia or released into the surrounding environment.
5. Cone Scales: While the primary focus of the male cone is on the microsporophylls and microsporangia, you may also see the overall structure of the cone scales. The scales protect the developing microsporangia and are arranged in a way that facilitates pollen dispersal.

Remember that the male cones of Pinus and other conifers are adapted for wind pollination. The release of large quantities of lightweight pollen allows for efficient dispersal by the wind, increasing the chances of reaching female cones for fertilization.

It’s worth noting that the structure of the male cone can vary between different species of Pinus, but the general features described above are common to the reproductive structures of most conifers.

iii) Life Cycle of Fucus

Ans: Fucus is a genus of brown algae commonly known as rockweeds. The life cycle of Fucus involves alternation of generations, with a multicellular diploid (2n) sporophyte generation and a multicellular haploid (n) gametophyte generation. Fucus exhibits a type of life cycle known as the heteromorphic alternation of generations. Here is an overview of the life cycle of Fucus:

1. Diploid Sporophyte Generation:
2. Sporophyte Development: The life cycle begins with the release of diploid (2n) spores from mature sporangia located on the sporophyte (2n) individual.
3. Spore Dispersal: These spores are dispersed in the water and can settle on a suitable substrate (rock or other surfaces).
4. Haploid Gametophyte Generation:
5. Germination of Spores: When a spore settles and finds a suitable substrate, it germinates to give rise to a multicellular haploid (n) gametophyte.
6. Gametangia Formation: The gametophyte produces gametangia, which are specialized structures that house the gametes.
7. Gamete Formation and Release:
8. Male Gametophytes: Some gametophytes produce male gametes (sperm cells) in male gametangia.
9. Female Gametophytes: Other gametophytes produce female gametes (egg cells) in female gametangia.
10. Gamete Release: Both male and female gametes are released into the water.
11. Fertilization:
12. Fusion of Gametes: The sperm cells swim toward the eggs, and fertilization occurs in the water. This results in the formation of a diploid zygote.
13. Diploid Zygote and Sporophyte Development:
14. Zygote Attachment: The zygote attaches to a substrate and develops into a multicellular diploid sporophyte.
15. Sporophyte Growth: The sporophyte grows and matures, producing structures such as blades and air bladders.
16. Sporangia Formation and Spore Release:
17. Sporangia Development: Mature sporophytes develop sporangia, which contain diploid spores.
18. Spore Release: Sporangia release diploid spores into the water, restarting the cycle.

This alternation of generations in Fucus involves a clear distinction between the multicellular diploid sporophyte and the multicellular haploid gametophyte, each giving rise to the other through a series of reproductive processes. The life cycle ensures genetic variation and adaptation to changing environmental conditions.

iv) Sexual reproduction in Marchantia

Marchantia is a genus of liverworts, which are a group of non-vascular plants. Liverworts like Marchantia exhibit a unique mode of sexual reproduction that involves specialized structures and cells. Here is an overview of sexual reproduction in Marchantia:

1. Gametophyte Stage:
2. Dominant Gametophyte: In the life cycle of Marchantia, the dominant and long-lived stage is the gametophyte. It is a flat, thallus-like structure that grows on the surface of the soil or on other substrates.
3. Archegoniophores and Antheridiophores: The gametophyte produces two types of structures for sexual reproduction: archegoniophores (female reproductive structures) and antheridiophores (male reproductive structures).
4. Archegoniophores (Female Structures):
5. Archegonia Formation: Archegoniophores bear flask-shaped structures called archegonia, each containing a single multicellular egg (n).
6. Egg Maturation: The egg matures within the archegonium.
7. Antheridiophores (Male Structures):
8. Antheridia Formation: Antheridiophores bear umbrella-like structures called antheridia, which produce multicellular sperm cells (n).
9. Sperm Release: Sperm are released into the environment, often assisted by water.
10. Fertilization:
11. Archegonium Reception: Water helps in the transfer of sperm to the archegonia. The sperm swims to the archegonium where fertilization occurs.
12. Zygote Formation: Fertilization results in the formation of a diploid zygote (2n) within the archegonium.
13. Zygote Development:
14. Embryo Formation: The zygote develops into a multicellular embryo within the archegonium.
15. Spore Capsule Formation:
16. Sporophyte Development: The developing embryo eventually gives rise to a small, short-lived sporophyte.
17. Sporangium Formation: The sporophyte produces a capsule (sporangium) that contains haploid (n) spores through the process of meiosis.
18. Spore Dispersal:
19. Sporangium Opening: The capsule opens, and spores are released into the environment.
20. Spore Dispersal: Spores are dispersed by air, water, or other means.
21. Germination of Spores:
22. Germination: A spore germinates to give rise to a new gametophyte, restarting the life cycle.

The alternation of generations in Marchantia involves a multicellular haploid gametophyte generation and a short-lived multicellular diploid sporophyte generation. This complex life cycle helps ensure genetic diversity and adaptability in changing environments.

6. Compare the characteristics of liverworts, hornworts and mosses in a tabular form with appropriate diagrams.

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7. a) With the help of suitable diagram depict different types of chaloroplast structures in algae

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b) Explain vegetative reproduction in fungi with examples and diagram.

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8. Discuss the application of Lichens in food, medicine and dyes.

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9. Describe the internal and external structure of a typical bacterium. Differentiate a bacterial cell from an archaeal cell.

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10. Write notes on the following:

i) Telome Theory

Ans: The Telome Theory, proposed by Eduard Strasburger in the late 19th century, was an early botanical hypothesis regarding the evolution of leaves in land plants. Strasburger suggested that leaves, as well as other lateral organs like stems, originated from the fusion of telomes. Telomes were envisioned as structures similar to the sporangia found in primitive plants like liverworts.

The Telome Theory proposed that leaves were formed through the fusion of these telomes, which were thought to be originally independent, sporangium-like structures. According to Strasburger, the fusion of these telomes led to the development of the flattened, leaf-like structures seen in higher plants.

While the Telome Theory had an influential role in early botanical thought, especially during a time when the understanding of plant morphology was evolving, it was later superseded by other theories. Modern molecular and genetic research has provided more detailed insights into the evolution and development of plant structures, shedding light on the genetic regulation and evolutionary processes involved.

ii) Economic importance of Gymnosperms as medicine

Ans: Gymnosperms, including species like pine, fir, and spruce, have economic importance in medicine. Their extracts are utilized for traditional remedies and pharmaceuticals. Compounds like taxol from Taxus species are employed in cancer treatments, showcasing the medicinal value of gymnosperms in the pharmaceutical industry.

iii) Economic importance of mycorrhiza

Ans: Mycorrhizal associations between fungi and plant roots enhance nutrient absorption, improve plant growth, and increase resistance to environmental stress. This symbiosis has significant economic importance in agriculture, forestry, and horticulture, reducing the need for fertilizers, promoting crop yield, and contributing to sustainable land management practices.

iv) Gemma cups

Ans: Gemma cups are reproductive structures found in liverworts, specifically in the genus Marchantia. These cup-like structures produce gemmae—small, asexual reproductive units. Gemma cups are typically found on the upper surface of the thallus and aid in the dispersal and propagation of liverwort plants in favorable conditions.

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