9th class biology

Chapter 10 Reproduction: Solved Exercise for 9th Class

by

Looking for solved exercises for Chapter 10: Reproduction? Our comprehensive solutions are specifically designed for 9th Class students based on the updated 2025 syllabus. Simplified answers to key topics like binary fission, vegetative propagation, and the life cycle of flowering plants are included to make your preparation easier and more efficient.

MCQs with Solutions

1. Which of the following organisms commonly reproduce by binary fission?

  • Options:
    a) Yeast
    b) Bacteria
    c) Rhizopus
    d) Plants
  • Answer: b) Bacteria
  • Explanation: Binary fission is a simple asexual reproduction method where a single cell divides into two identical daughter cells. This process is typical in prokaryotic organisms like bacteria.
  • Tip/Trick: Remember that binary fission is exclusive to unicellular organisms like bacteria.

2. What is the primary method of reproduction in yeast?

  • Options:
    a) Binary fission
    b) Spore formation
    c) Budding
    d) Fragmentation
  • Answer: c) Budding
  • Explanation: Yeast, a unicellular fungus, reproduces primarily by budding, where a new cell forms as an outgrowth of the parent cell.
  • Tip/Trick: Associate yeast with budding since it involves a “bud” growing on the parent cell.

3. Which of the following statements is true about spore formation in fungi?

  • Options:
    a) They produce spores during sexual reproduction.
    b) They produce two kinds of spores.
    c) Spores can only grow into new fungi in dry environments.
    d) Spores are produced to withstand harsh conditions.
  • Answer: d) Spores are produced to withstand harsh conditions.
  • Explanation: Spores in fungi are designed to survive extreme environmental conditions, including dryness, heat, or lack of nutrients.
  • Tip/Trick: Focus on “harsh conditions” when considering the purpose of fungal spores.

4. What happens in some bacteria during harsh conditions?

  • Options:
    a) Creation of a bud that detaches from the cell.
    b) Formation of thick-walled endospores.
    c) Splitting the cell into two identical daughter cells.
    d) Fusion of two bacterial cells.
  • Answer: b) Formation of thick-walled endospores.
  • Explanation: Endospores are highly resistant structures formed by bacteria to protect their genetic material during unfavorable conditions.
  • Tip/Trick: Recall that endospores = bacterial survival strategy.

5. Which of the following is an example of vegetative propagation through runners?

  • Options:
    a) Potato
    b) Strawberry
    c) Onion
    d) Ginger
  • Answer: b) Strawberry
  • Explanation: Strawberries propagate vegetatively through runners, which are horizontal stems that grow along the soil’s surface and develop new plants.
  • Tip/Trick: Think of “running strawberries” for runners.

6. Which plant propagates through tubers?

  • Options:
    a) Onion
    b) Potato
    c) Ginger
    d) Garlic
  • Answer: b) Potato
  • Explanation: Tubers are thickened underground stems, such as potatoes, that store food and enable vegetative propagation.
  • Tip/Trick: Visualize a potato’s “eyes” as propagation points.

7. The horizontal aboveground stem, which produces leaves and roots at its nodes:

  • Options:
    a) Stolon
    b) Bulb
    c) Rhizome
    d) Corm
  • Answer: a) Stolon
  • Explanation: Stolons are horizontal stems that grow above the ground and help plants like strawberries propagate.
  • Tip/Trick: Stolons are “above-ground runners.”

8. Which of these does NOT help a plant in vegetative propagation?

  • Options:
    a) Rhizome
    b) Corm
    c) Runner
    d) Flower
  • Answer: d) Flower
  • Explanation: Flowers are reproductive structures for sexual reproduction, not vegetative propagation.
  • Tip/Trick: Vegetative propagation relies on structures like stems, roots, and leaves, not flowers.

9. Which part of the flower is responsible for producing pollen?

  • Options:
    a) Stigma
    b) Anther
    c) Ovary
    d) Petal
  • Answer: b) Anther
  • Explanation: The anther is a part of the stamen in flowers and is responsible for producing and releasing pollen grains.
  • Tip/Trick: Associate “anther” with “pollen production.”

10. Which of the following is NOT a part of the carpel?

  • Options:
    a) Filament
    b) Style
    c) Stigma
    d) Ovary
  • Answer: a) Filament
  • Explanation: The carpel (or pistil) is the female reproductive part of the flower and consists of the stigma, style, and ovary. The filament is a part of the stamen, the male reproductive structure.
  • Tip/Trick: Remember the carpel components as “SOS” — Stigma, Ovary, Style.

11. Which structure forms the female gametophyte in flowering plants?

  • Options:
    a) Pollen grain
    b) Ovule
    c) Anther
    d) Sepal
  • Answer: b) Ovule
  • Explanation: The ovule in flowering plants develops into the female gametophyte, which contains the egg cell and is involved in reproduction.
  • Tip/Trick: The ovule = female gametophyte, while pollen grain = male gametophyte.

12. The male gametophyte in flowering plants is known as:

  • Options:
    a) Pollen grain
    b) Embryo sac
    c) Ovary
    d) Carpel
  • Answer: a) Pollen grain
  • Explanation: The pollen grain is the male gametophyte, carrying the male reproductive cells (sperm). It fertilizes the ovule during pollination.
  • Tip/Trick: Associate “pollen” with “male” and “grain” with small particles.

13. In the life cycle of flowering plants, which structure is triploid (3n)?

  • Options:
    a) Egg
    b) Fusion nucleus
    c) Endosperm nucleus
    d) Sperm
  • Answer: c) Endosperm nucleus
  • Explanation: The endosperm nucleus is triploid (3n) as it forms after the fusion of one sperm with two polar nuclei during double fertilization.
  • Tip/Trick: Triploid = three sets of chromosomes, found in endosperm for nutrient storage.

14. Embryo sac is formed inside:

  • Options:
    a) Filament
    b) Anther
    c) Style
    d) Ovule
  • Answer: d) Ovule
  • Explanation: The embryo sac is the female gametophyte and is located inside the ovule of flowering plants.
  • Tip/Trick: Embryo sac = female gametophyte = ovule.

15. Double fertilization involves:

  • Options:
    a) Fertilization of the egg by two male gametes.
    b) Fertilization of two eggs in the same embryo sac by two sperms.
    c) Fertilization of the egg and the fusion nucleus by two sperms.
    d) Fertilization of the egg and the tube cell by two sperms.
  • Answer: c) Fertilization of the egg and the fusion nucleus by two sperms.
  • Explanation: In double fertilization, one sperm fertilizes the egg to form a zygote (2n), while the other sperm fuses with two polar nuclei to form the endosperm nucleus (3n).
  • Tip/Trick: Think “double duty” — one sperm for the egg, the other for the polar nuclei.

Short Questions with Detailed Answers

1. Write a short note on budding in yeast.

  • Answer: Budding in yeast is a form of asexual reproduction. A small bud grows on the parent cell, enlarges, and eventually detaches to form a new yeast cell. This process ensures rapid multiplication under favorable conditions.

2. Write a short note on spore formation in fungi.

  • Answer: Spore formation in fungi is an asexual reproduction method where spores are produced inside a sporangium. These spores are resistant to harsh environmental conditions and germinate to form new fungi when conditions are favorable.

3. What are the advantages of spore formation in fungi and bacteria?

  • Answer:
    • Advantages:
      1. Allows survival in unfavorable conditions due to spore resistance.
      2. Enables rapid reproduction and dispersal over large areas.
      3. Requires minimal resources for reproduction.

4. Describe how vegetative propagation occurs through runners.

  • Answer: Runners are horizontal stems that grow above the ground. Nodes on these stems produce roots and shoots, which develop into new plants. This is commonly seen in plants like strawberries.

5. State how potatoes reproduce through tubers.

  • Answer: Potatoes reproduce vegetatively through tubers, which are swollen underground stems. “Eyes” on the tubers sprout into new shoots and roots, growing into new potato plants.

6. Describe the advantages and disadvantages of vegetative propagation.

  • Answer:
    • Advantages:
      1. Produces genetically identical offspring.
      2. Quick and efficient reproduction.
      3. No need for seeds or pollination.
    • Disadvantages:
      1. No genetic diversity, making plants susceptible to diseases.
      2. Overcrowding can occur, leading to competition for resources.

7. Name the four whorls present in a flower and their components.

  • Answer:
    1. Calyx: Made of sepals, protects the flower bud.
    2. Corolla: Made of petals, attracts pollinators.
    3. Androecium: Made of stamens, produces pollen.
    4. Gynoecium: Made of carpels, contains ovules.

8. Briefly describe the formation of the egg cell and polar nuclei within the embryo sac of a flower.

  • Answer: The embryo sac forms inside the ovule during megasporogenesis. One megaspore divides to form eight nuclei, which organize into cells, including the egg cell (near the micropylar end) and two polar nuclei (in the center of the sac).

9. Differentiate between:

  • i. Asexual and sexual reproduction:
    • Asexual: Single parent, no gametes, offspring identical.
    • Sexual: Two parents, gametes involved, offspring genetically diverse.
  • ii. Binary fission in bacteria and amoeba:
    • Bacteria: Simple splitting without a nucleus.
    • Amoeba: Nucleus divides first, followed by cytoplasm.
  • iii. Stolon and rhizome:
    • Stolon: Horizontal above-ground stem.
    • Rhizome: Horizontal underground stem.
  • iv. Bulb and corm:
    • Bulb: Modified stem with fleshy leaves (e.g., onion).
    • Corm: Solid, fleshy underground stem (e.g., taro).

C. Write answers in detail

1. Explain the process of binary fission in bacteria and describe how it leads to the formation of two daughter bacteria.
Binary fission is the process by which bacteria reproduce. In this process:

  • The bacterial cell grows and its DNA (genetic material) is copied.
  • The cell divides into two parts, with each part getting one copy of the DNA.
  • This results in two identical daughter bacteria.

2. What do you mean by vegetative propagation? Differentiate among different plant structures modified for vegetative propagation.
Vegetative propagation is a way plants reproduce without seeds. New plants grow from parts like roots, stems, or leaves of the parent plant.

  • Modified roots: Examples are sweet potato and carrot.
  • Modified stems: Examples are potato (tuber) and ginger (rhizome).
  • Modified leaves: An example is Bryophyllum, where buds grow on leaves.

3. Describe the ways by which humans can grow new plants by using the vegetative parts of the parent plants.
Humans grow new plants using methods like:

  • Cutting: A part of a plant like a stem or leaf is cut and planted to grow into a new plant. Example: rose.
  • Grafting: Two plants are joined together so they grow as one. Example: mango.
  • Layering: A branch of a plant is bent to the ground and covered with soil. It grows roots and becomes a new plant. Example: jasmine.

4. Define sporophyte and gametophyte. State their roles in the life cycle of plants.

  • Sporophyte: The part of the plant that produces spores. It is usually larger, like the main body of a plant.
  • Gametophyte: The part that produces gametes (sperm and egg cells). It is smaller and often hidden.
    These two alternate in the life cycle of plants. Spores from the sporophyte grow into gametophytes, and gametophytes create gametes that form a new sporophyte.

5. Explain the life cycle of flowering plants, focusing on the alternation between the gametophyte and sporophyte generations.
The life cycle of flowering plants has two stages:

  • Sporophyte stage: The main plant that produces flowers and seeds. It creates spores.
  • Gametophyte stage: The spores grow into tiny structures inside the flower, which produce male and female gametes.
    When the gametes fuse (fertilization), a seed forms, and the cycle starts again.

6. Describe how the female gametophyte (embryo sac) develops within the ovule of a flower.

  • Inside the ovule of a flower, a cell divides to form a structure with 8 nuclei.
  • This structure becomes the embryo sac, which is the female gametophyte.
  • The embryo sac has one egg cell, which combines with sperm during fertilization to form a seed.

Chapter 5: Tissues, Organs, and Organ Systems – Solved Exercise

by

MCQs with Answers, Explanations, and Tips

1. A higher level of organization exhibits emergent properties when:

Options:
a) Its parts function independently.
b) The sum of its parts is greater than the whole.
c) Its individual parts are more important than the whole.
d) Its parts interact to perform more functions.

Correct Answer: d) Its parts interact to perform more functions.

Explanation:
Emergent properties arise when individual components of a system interact to create functions or characteristics that are not present in the individual parts alone.

Tip:
Think of “emergence” as something greater than the sum of its parts, like teamwork in a system.

2. Which of the following demonstrates the levels of organization of the body, from simplest to most complex?

Options:
a) Cell → Organ → Tissue → Organelle → Organ system
b) Organelle → Cell → Tissue → Organ → Organ system
c) Tissue → Cell → Organelle → Organ → Organ system
d) Organ system → Tissue → Cell → Organelle → Organ

Correct Answer: b) Organelle → Cell → Tissue → Organ → Organ system

Explanation:
The correct order of organization in the body progresses from the smallest functional unit (organelle) to the largest (organ system).

Tip:
Memorize the hierarchy: “Organelle → Cell → Tissue → Organ → Organ System → Organism.”

3. At which level of organization does gas exchange occur between body and environment?

Options:
a) Organelle level in mitochondria
b) Cellular level in alveolar cells
c) Tissue level in epithelial tissues
d) Organ system level in the respiratory system

Correct Answer: d) Organ system level in the respiratory system

Explanation:
Gas exchange involves the respiratory system, particularly the lungs and alveoli, which function at the organ system level.

Tip:
Gas exchange is a system-wide process involving specialized organs like lungs.

4. The epithelial tissue in the stomach wall is responsible for producing:

Options:
a) Mucus
b) Pepsinogen
c) Hydrochloric acid
d) All of these

Correct Answer: d) All of these

Explanation:
The epithelial tissue of the stomach secretes mucus (protective layer), pepsinogen (enzyme precursor), and hydrochloric acid (to aid digestion).

Tip:
Remember that epithelial tissues in the stomach are multifunctional and secrete various substances critical for digestion.

5. In the wall of the stomach, which tissue also contains blood vessels and nerves?

Options:
a) Epithelial
b) Muscle
c) Inner connective
d) Outer connective

Correct Answer: c) Inner connective

Explanation:
Connective tissue in the stomach wall supports blood vessels and nerves, providing structural integrity and communication.

Tip:
Connective tissue “connects” and supports other tissues, including blood vessels and nerves.

6. In a leaf, which tissue is primarily responsible for photosynthesis?

Options:
a) Xylem
b) Phloem
c) Mesophyll
d) Epidermis

Correct Answer: c) Mesophyll

Explanation:
The mesophyll tissue contains chloroplasts, which carry out photosynthesis in plant leaves.

Tip:
Think of “meso” (middle) as the layer in the leaf where most photosynthesis occurs.

7. What is the primary function of the xylem tissue in a leaf?

Options:
a) To transport sugars to other parts
b) To transport water to parts of leaf
c) To synthesize chlorophyll
d) To control the opening and closing of stomata

Correct Answer: b) To transport water to parts of the leaf

Explanation:
Xylem is responsible for conducting water and dissolved nutrients from the roots to the leaves.

Tip:
Xylem = Water transport, while phloem = Food transport.

8. Which of these is a function of the human skeletal system?

Options:
a) Storing minerals and producing blood cells
b) Protecting internal organs
c) Filtering blood to remove waste products
d) Both a and b

Correct Answer: d) Both a and b

Explanation:
The skeletal system protects internal organs, stores minerals (like calcium), and produces blood cells in the bone marrow.

Tip:
Think of the skeletal system as a “protector” and a “reservoir” for minerals and blood production.

Question 9:

Statement: Which structures are responsible for the transport of food in plant bodies?
Options:
a) Xylem tissue
b) Palisade mesophyll
c) Phloem tissue
d) Spongy mesophyll

Answer: c) Phloem tissue

Explanation: Phloem tissue is responsible for the transport of food (in the form of sugars) produced during photosynthesis from the leaves to other parts of the plant. Xylem, on the other hand, is involved in transporting water and minerals.

Tips and Tricks:

  • Xylem transports “water.” Think of ‘X’ for “Xtra hydration.”
  • Phloem transports “food.” Think of ‘P’ for “Photosynthetic Products.”

Question 10:

Statement: In a plant, which of the following is the primary function of the flower?
Options:
a) Transporting water and minerals
b) Supporting leaf growth
c) Facilitating reproduction through pollination
d) Regulating gas exchange

Answer: c) Facilitating reproduction through pollination

Explanation: The flower’s main role is reproduction. It produces gametes, facilitates pollination, and forms seeds and fruits for the propagation of plants.

Tips and Tricks:

  • Remember: Flowers = Reproduction. They are like the “factories” of new plants.
  • Other processes like water transport, leaf support, and gas exchange are not related to flowers.

Short Questions with Answers:

  1. Enlist the levels of organization from cells to organ systems.
    Answer:
    • Cells → Tissues → Organs → Organ Systems → Organism
  2. What are the major roles of the epithelial tissue present in the stomach?
    Answer:
    • Protection: Lines the stomach to prevent damage from digestive acids.
    • Secretion: Produces mucus, enzymes, and hydrochloric acid.
    • Absorption: Assists in absorbing nutrients from food.
  3. How do the smooth muscles contribute to the stomach’s function?
    Answer:
    • Smooth muscles help in churning and mixing food with digestive enzymes and acids through peristaltic movements, aiding in digestion.
  4. What is the function of the palisade mesophyll in the leaf?
    Answer:
    • The palisade mesophyll is the primary site for photosynthesis due to the abundance of chloroplasts that capture sunlight.
  5. What is the role of the shoot system in plants?
    Answer:
    • The shoot system is responsible for supporting the plant, transporting water and nutrients, photosynthesis (leaves), and reproduction (flowers).
  6. What is homeostasis, and why is it important for organisms?
    Answer:
    • Homeostasis is the process by which organisms maintain a stable internal environment (e.g., temperature, pH, water balance). It is essential for optimal functioning of cells and survival.
  7. How does the human body maintain a stable internal temperature?
    Answer:
    • The body maintains temperature through mechanisms like sweating (to cool down), shivering (to generate heat), and blood flow regulation (vasodilation or vasoconstriction).
  8. Differentiate between the following:
    • Tissue and organ:
      Tissue: A group of similar cells performing a specific function.
      Organ: A structure made up of different tissues working together to perform a specific function.
    • Root system and shoot system:
      Root system: Underground part of the plant, absorbs water and nutrients.
      Shoot system: Above-ground part of the plant, supports photosynthesis and reproduction.
    • Epidermal and mesophyll tissue:
      Epidermal tissue: Outer protective layer of the leaf.
      Mesophyll tissue: Inner tissue responsible for photosynthesis.
    • Palisade and spongy mesophyll:
      Palisade mesophyll: Tightly packed cells for maximum light absorption during photosynthesis.
      Spongy mesophyll: Loosely packed cells for gas exchange.

Long Questions with Answers:

  1. Explain the levels of organization in multicellular organisms. How does each level contribute to the overall functioning of an organism?
    Answer:
    • Cells: Basic structural and functional units of life. E.g., nerve cells transmit signals.
    • Tissues: Groups of similar cells working together. E.g., muscle tissue contracts for movement.
    • Organs: Structures made of tissues performing specific tasks. E.g., the heart pumps blood.
    • Organ systems: Groups of organs working together. E.g., the digestive system processes food.
    • Organism: The entire living being, a sum of all systems working in harmony.
  2. What is a tissue level? Explain plant and animal tissues.
    Answer:
    • Tissue level: The organization where cells perform a common function.
    • Plant tissues:
      • Meristematic tissues: Growth tissues.
      • Permanent tissues: For transport (xylem, phloem), protection (epidermis), and storage (parenchyma).
    • Animal tissues:
      • Epithelial: Protection and secretion.
      • Muscle: Movement.
      • Connective: Support and binding.
      • Nervous: Signal transmission.
  3. Describe the tissue composition of the stomach. How does each tissue contribute to the digestive function of the stomach?
    Answer:
    • Epithelial tissue: Lines the stomach, secretes mucus, enzymes, and acids.
    • Muscle tissue: Smooth muscles churn food for digestion.
    • Connective tissue: Supports and binds stomach layers.
    • Nervous tissue: Regulates secretion and movement.
  4. Describe the tissue composition of the leaf. How does each tissue contribute to the functions of the leaf?
    Answer:
    • Epidermal tissue: Protects the leaf and controls water loss through stomata.
    • Mesophyll tissue: Palisade mesophyll for photosynthesis, spongy mesophyll for gas exchange.
    • Vascular tissue: Xylem transports water; phloem transports food.
  5. How do organ systems come together to form the human body?
    Answer:
    Organ systems are interdependent:
    • The digestive system provides nutrients.
    • The respiratory system supplies oxygen.
    • The circulatory system transports oxygen and nutrients.
    • The nervous system coordinates actions.
      Together, they maintain homeostasis and ensure survival.
  6. Explain the roles of the digestive system and the excretory system in maintaining homeostasis.
    Answer:
    • Digestive system: Breaks down food to provide nutrients and energy for cells.
    • Excretory system: Removes waste products like urea and excess water to prevent toxicity.
      Together, they regulate the internal environment, maintaining balance.
  7. Define homeostasis and explain its importance. Discuss how different organ systems work together to maintain homeostasis.
    Answer:
    • Homeostasis: The maintenance of a stable internal environment.
    • Importance: Ensures optimal conditions for cellular function.
    • Examples of systems working together:
      • Nervous and endocrine systems: Regulate temperature and glucose levels.
      • Respiratory and circulatory systems: Maintain oxygen and carbon dioxide balance.
      • Excretory and integumentary systems: Regulate water and salt balance.

9th Class Biology Chapter 3: The Cell – New Syllabus

by

1. The process of cellular respiration occurs in:

  • Options:
    a) Nucleus
    b) Mitochondria
    c) Ribosomes
    d) Golgi apparatus
  • Answer: b) Mitochondria
  • Explanation: Mitochondria are known as the “powerhouse of the cell” because they produce energy (ATP) through cellular respiration.
  • Tip: Associate “mitochondria” with “energy production.”

2. The smooth endoplasmic reticulum (SER) is primarily involved in the synthesis of:

  • Options:
    a) Proteins
    b) Lipids
    c) Carbohydrates
    d) Nucleic acids
  • Answer: b) Lipids
  • Explanation: The SER is specialized in lipid synthesis and detoxification of harmful substances in cells.
  • Tip: Think of “smooth” as “soft,” linked to fats (lipids).

3. Ribosomes are composed of:

  • Options:
    a) RNA and protein
    b) DNA and protein
    c) Carbohydrates and lipids
    d) RNA and carbohydrates
  • Answer: a) RNA and protein
  • Explanation: Ribosomes are made up of rRNA (ribosomal RNA) and proteins, enabling them to synthesize proteins.
  • Tip: Remember “R” in ribosomes for “RNA.”

4. What is the primary function of ribosomes?

  • Options:
    a) Energy production
    b) Protein synthesis
    c) Lipid synthesis
    d) DNA synthesis
  • Answer: b) Protein synthesis
  • Explanation: Ribosomes assemble amino acids into proteins.
  • Tip: Ribosomes are like “factories” for making proteins.

5. Which cell organelle is involved in packaging and modifying proteins?

  • Options:
    a) Nucleus
    b) Mitochondria
    c) Golgi apparatus
    d) Endoplasmic reticulum
  • Answer: c) Golgi apparatus
  • Explanation: The Golgi apparatus processes, modifies, and packages proteins for transport.
  • Tip: Link “Golgi” with “gift wrap” for packaging.

6. Which cell organelle is responsible for breaking down waste materials?

  • Options:
    a) Golgi apparatus
    b) Nucleus
    c) Mitochondria
    d) Lysosome
  • Answer: d) Lysosome
  • Explanation: Lysosomes contain digestive enzymes to break down cellular waste and debris.
  • Tip: Think “lyso-” as in “lysis” (breaking down).

7. Which of the following cell structures is involved in maintaining cell shape?

  • Options:
    a) Cytoskeleton
    b) Centrioles
    c) Nucleus
    d) Lysosome
  • Answer: a) Cytoskeleton
  • Explanation: The cytoskeleton provides structural support and maintains the shape of the cell.
  • Tip: “Skeleton” in cytoskeleton helps recall “support.”

8. What is the main function of the smooth endoplasmic reticulum in a cell?

  • Options:
    a) Synthesis of proteins
    b) Synthesis of lipids
    c) Digestion of cellular waste
    d) Storage of genetic material
  • Answer: b) Synthesis of lipids
  • Explanation: The smooth ER specializes in lipid and steroid hormone synthesis.
  • Tip: Recall that smooth ER handles “fats” (lipids), unlike rough ER, which synthesizes proteins.

9. Which specialized region of the nucleus is responsible for ribosome assembly?

  • Options:
    a) Nucleoplasm
    b) Nucleolus
    c) Chromatin
    d) Chromatid
  • Answer: b) Nucleolus
  • Explanation: The nucleolus is the site where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins.
  • Tip: Think “nucleolus” for “ribosome production hub.”

10. What is the main function of the nuclear pores?

  • Options:
    a) Regulation of cell division
    b) Control of pH of the cell
    c) Protein synthesis
    d) Control of transport of molecules
  • Answer: d) Control of transport of molecules
  • Explanation: Nuclear pores allow selective transport of molecules (e.g., RNA and proteins) between the nucleus and cytoplasm.
  • Tip: “Pores” indicate passage or transport.

11. Which of the following cellular structures is found in animal cells and helps in cell division?

  • Options:
    a) Cell membrane
    b) Plasmodesma
    c) Centriole
    d) Vacuole
  • Answer: c) Centriole
  • Explanation: Centrioles play a key role in the organization of spindle fibers during mitosis and meiosis in animal cells.
  • Tip: Centrioles are specific to animal cells for cell division.

12. Which sub-cellular organelle plays a crucial role in energy production within the cell?

  • Options:
    a) Endoplasmic reticulum
    b) Golgi apparatus
    c) Mitochondria
    d) Lysosomes
  • Answer: c) Mitochondria
  • Explanation: Mitochondria are the site of ATP production via cellular respiration.
  • Tip: Recall “powerhouse of the cell.”

13. In a multicellular plant, which cell type is responsible for the production of glucose?

  • Options:
    a) Xylem
    b) Phloem
    c) Epidermal
    d) Mesophyll
  • Answer: d) Mesophyll
  • Explanation: Mesophyll cells contain chloroplasts, where photosynthesis occurs to produce glucose.
  • Tip: Link “mesophyll” with “middle” (the leaf tissue performing photosynthesis).

14. Which organelle can double its number by itself?

  • Options:
    a) Ribosomes
    b) Lysosomes
    c) Mitochondria
    d) Golgi apparatus
  • Answer: c) Mitochondria
  • Explanation: Mitochondria have their own DNA and replicate independently through binary fission.
  • Tip: Mitochondria behave like “semi-autonomous” organelles.

15. Which of these are present on the surface of rough endoplasmic reticulum?

  • Options:
    a) Ribosomes
    b) Lysosomes
    c) Mitochondria
    d) Vacuoles
  • Answer: a) Ribosomes
  • Explanation: Ribosomes attached to the rough ER synthesize proteins, giving it a “rough” appearance.
  • Tip: Remember “Rough ER” is rough due to ribosomes.

Section B: Short Answers

1. What are the main functions of the cell membrane?

  • Answer:
    • Regulates the entry and exit of substances (selective permeability).
    • Protects the cell by providing structural support.
    • Facilitates communication and signaling between cells.

2. What key role does the Golgi apparatus play in eukaryotic cells?

  • Answer:
    • Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
    • Forms lysosomes and transports cellular materials.

3. How do lysosomes contribute to the cell’s functioning?

  • Answer:
    • Break down cellular waste and debris using digestive enzymes.
    • Play a role in recycling cellular components (autophagy).

4. Which organelle detoxifies harmful substances and breaks down lipids?

  • Answer: Smooth Endoplasmic Reticulum (SER).
  • Explanation: SER is involved in lipid synthesis, detoxification of drugs, and storage of calcium ions.

5. What is the smooth endoplasmic reticulum responsible for?

  • Answer:
    • Synthesis of lipids and steroid hormones.
    • Detoxification of harmful substances.
    • Storage and release of calcium ions in muscle cells.

6. How do the vacuoles in plant cells differ from vacuoles in animal cells?

  • Answer:
    • Plant cells have large central vacuoles for storage of water, nutrients, and waste.
    • Animal cells have smaller, temporary vacuoles, mainly for storage and transport.

7. What could happen if lysosomal enzymes stop working properly?

  • Answer:
    • Accumulation of waste materials and toxins within the cell.
    • Possible cell death due to impaired autophagy and digestion.

8. Why are the cristae important for cellular respiration?

  • Answer:
    • Cristae increase the surface area of the inner mitochondrial membrane, allowing more space for the enzymes and proteins involved in ATP production during cellular respiration.

Here’s the detailed solution to the questions in the uploaded image:

Section B: Short Answers

9. How are chromatin and chromosomes related?

  • Answer:
    Chromatin is the uncoiled and relaxed form of DNA, combined with proteins (histones), found in the nucleus during interphase. During cell division, chromatin condenses and organizes into tightly coiled structures called chromosomes.

10. Which type of cell is responsible for sending nerve signals?

  • Answer:
    Neurons (nerve cells) are specialized cells that transmit electrical and chemical signals throughout the body.

11. What do mesophyll cells do in plant leaves?

  • Answer:
    Mesophyll cells in plant leaves perform photosynthesis. They contain chloroplasts that use sunlight, carbon dioxide, and water to produce glucose and oxygen.

12. How would you define a stem cell?

  • Answer:
    A stem cell is an undifferentiated cell capable of dividing and differentiating into specialized cell types. Stem cells also have the ability to self-renew.

13. Name the chemical compounds that make up:

  • a) Cell membrane: Phospholipids, proteins, carbohydrates, and cholesterol.
  • b) Fungal cell wall: Chitin and glucans.
  • c) Plant cell wall: Cellulose, hemicellulose, and pectin.
  • d) Bacterial cell wall: Peptidoglycan (murein).
  • e) Ribosomes: rRNA (ribosomal RNA) and proteins.
  • f) Chromosomes: DNA and proteins (histones).

14. Label the parts of these cell diagrams.

For the provided cell diagrams, the labels typically represent major cell organelles. Based on general diagrams:

  • A: Nucleus
  • B: Mitochondria
  • C: Endoplasmic reticulum
  • D: Golgi apparatus
  • E: Cell membrane
  • F: Lysosome
  • G: Ribosome

Section C: Detailed Answers

1. Explain the fluid mosaic model of the cell membrane.

  • The cell membrane is a phospholipid bilayer with embedded proteins.
  • The “fluid” aspect refers to the flexible and dynamic nature of the bilayer, allowing lateral movement of lipids and proteins.
  • The “mosaic” aspect describes the patchwork of proteins interspersed within the bilayer, performing various functions such as transport, signaling, and enzymatic activity.

2. Describe the structure and functions of the cell wall.

  • Structure:
    • Found in plants, fungi, and bacteria.
    • Composed of cellulose (plants), chitin (fungi), or peptidoglycan (bacteria).
  • Functions:
    • Provides structural support and protection.
    • Maintains cell shape.
    • Prevents excessive water uptake (osmotic regulation).

3. Discuss the components of the nucleus.

  • Nuclear envelope: Double membrane with pores for transport.
  • Nucleoplasm: Fluid containing ions, enzymes, and nucleotides.
  • Nucleolus: Site of ribosome assembly.
  • Chromatin: DNA and protein that form chromosomes during cell division.

4. Describe the structure and function of lysosomes and the endoplasmic reticulum.

  • Lysosomes:
    • Membrane-bound organelles containing digestive enzymes.
    • Function: Breakdown of waste materials, cellular debris, and pathogens.
  • Endoplasmic Reticulum (ER):
    • Rough ER: Ribosomes on its surface; synthesizes proteins.
    • Smooth ER: Synthesizes lipids and detoxifies harmful substances.

5. Describe the formation and function of the Golgi apparatus.

  • Formation: Derived from vesicles from the ER.
  • Function: Modifies, sorts, and packages proteins and lipids for secretion or delivery within the cell.

6. Describe the structure and functions of the chloroplast.

  • Structure:
    • Double membrane.
    • Contains thylakoids stacked into grana, surrounded by stroma.
    • Contains chlorophyll for capturing light energy.
  • Function: Photosynthesis to convert light energy into glucose and oxygen.

7. How does turgor pressure develop in a plant cell?

  • Turgor pressure develops due to water entering the cell via osmosis. The vacuole swells, pressing the plasma membrane against the cell wall, providing rigidity to the plant.

8. Write any four differences between a plant cell and an animal cell.

FeaturePlant CellAnimal Cell
Cell wallPresent (cellulose)Absent
ChloroplastsPresent (photosynthesis)Absent
VacuolesLarge central vacuoleSmall, temporary vacuoles
CentriolesAbsentPresent

9. Describe the concept of division of labor and how it applies in multicellular organisms.

  • Concept: Division of labor refers to specialization of cells, tissues, or organs to perform specific functions.
  • Examples:
    • Red blood cells transport oxygen.
    • Neurons transmit nerve signals.
    • Muscle cells contract to enable movement.

10. Write a note on cell specialization.

  • Cell specialization is the process where generic cells develop into specific cell types to perform unique functions. For example:
    • Muscle cells specialize in contraction.
    • Xylem cells specialize in water transport.
    • Specialized cells increase efficiency and allow multicellular organisms to perform complex tasks.

©2024. Everexams.com. All Rights Reserved.