Class 9 Biology Notes Chapter 5

CHAPTER 5: TISSUES, ORGANS, AND ORGAN SYSTEMS

EXERCISE SOLUTION

A. SELECT THE CORRECT ANSWERS FOR THE FOLLOWING QUESTIONS

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

(a) Its parts function independently.
(b) The sum of its parts is greater than the whole.
(c) The 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.

Note: Interactions among components generate novel properties and functions.

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

(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

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

(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.

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

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

Correct Answer: (d) All of these

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

(a) Epithelial
(b) Muscle
(c) Inner connective tissue
(d) Outer connective tissue

Correct Answer: (c) Inner connective tissue.

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

(a) Xylem
(b) Mesophyll
(c) Epidermis
(d) Phloem

Correct Answer: (b) Mesophyll

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

(a) To transport sugars to other parts
(b) To transport water to parts of the 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.

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

(a) Storing minerals and producing blood cells
(b) Removing carbon dioxide from blood
(c) Filtering blood to remove waste products
(d) Breaking down food for energy

Correct Answer: (a) Storing minerals and producing blood cells.

9. Which structures are responsible for the transport of food in the plant body?

(a) Xylem tissue
(b) Palisade mesophyll
(c) Phloem tissue
(d) Spongy mesophyll

Correct Answer: (c) Phloem tissue

10. In a plant, which of the following is the primary function of the flower?

(a) Transporting water and minerals
(b) Supporting leaf growth
(c) Facilitating reproduction through pollination
(d) Regulating gas exchange

Correct Answer: (c) Facilitating reproduction through pollination.

B. WRITE SHORT ANSWERS

1. Enlist the levels of organization from cells to organ systems.

Answer: Cell → Tissue → Organ → Organ System → Multicellular Organism.

2. What are the major roles of the epithelial tissue present in the stomach?

Answer: Epithelial tissue in the stomach secretes gastric juices, including hydrochloric acid, pepsinogen, and mucus, to aid digestion. It also protects the underlying stomach wall tissues from self-digestion and abrasion.

3. How do the smooth muscles contribute to the stomach’s function?

Answer: Smooth muscles in the stomach wall contract rhythmically to churn, mix, and mechanically break down ingested food with gastric juices. They also push the resulting chyme forward into the small intestine.

4. What is the function of the palisade mesophyll in the leaf?

Answer: Palisade mesophyll cells are densely packed with chloroplasts and serve as the primary site for capturing light energy to carry out photosynthesis.

5. What is the role of the shoot system in plants?

Answer: The shoot system consists of the above-ground parts of a plant, including stems, leaves, and flowers. It is responsible for photosynthesis, gas exchange, reproduction, transport of water and nutrients, and structural support.

6. What is homeostasis, and why is it important for organisms?

Answer: Homeostasis is the maintenance of a relatively stable internal environment within an organism despite external environmental changes. It is vital because cellular enzymes and metabolic processes require precise internal conditions, such as temperature, pH, and water balance, to function properly.

7. How does the human body maintain a stable internal temperature?

Answer: The human body maintains a stable internal temperature through negative feedback mechanisms coordinated by the hypothalamus. When body temperature rises, the body responds through vasodilation and sweating to cool down. When temperature drops, vasoconstriction and shivering help conserve and generate heat.

8. Differentiate between the following:

(i) Tissue and Organ

A tissue is a group of similar cells working together to perform a specific function, whereas an organ is a structure composed of multiple different tissues working in coordination to perform complex body functions.

(ii) Root System and Shoot System

The root system comprises underground structures (roots) responsible for water and mineral absorption and anchorage. The shoot system comprises above-ground structures, including stems, leaves, and flowers, responsible for photosynthesis, transport, and reproduction.

(iii) Epidermal and Mesophyll Tissue

Epidermal tissue forms the protective outer covering of a plant. Mesophyll tissue forms the inner photosynthetic layer between the upper and lower epidermis in leaves.

(iv) Palisade and Spongy Mesophyll

Palisade mesophyll consists of tightly packed, column-shaped cells specialized for maximum light absorption. Spongy mesophyll consists of loosely arranged cells with air spaces that facilitate gas exchange.

C. WRITE ANSWERS IN DETAIL

1. Explain the levels of organization in a multicellular organism. How does each level contribute to the overall functioning of an organism?

Answer:

Cell Level: The cell is the fundamental unit of life. It carries out basic metabolic and cellular functions.

Tissue Level: Groups of similar cells coordinate to perform shared, specialized tasks.

Organ Level: Different tissues combine to perform complex, specialized physiological tasks. For example, the heart pumps blood.

Organ System Level: Multiple organs work in coordination to manage major life processes, such as digestion and circulation.

Organism Level: All organ systems integrate to sustain the life, growth, and survival of the whole individual.

2. What is the tissue level? Explain plant and animal tissues.

Answer:

Tissue Level: The tissue level is a level of organization between cells and organs, where groups of similar cells specialize to perform a common function.

Plant Tissues: Plant tissues are divided into meristematic tissues, which contain actively dividing cells responsible for growth, and permanent tissues, which include epidermal, ground, and complex vascular tissues such as xylem and phloem.

Animal Tissues: Animal tissues are categorized into four primary types:

1. Epithelial Tissue: Provides lining and protection.

2. Connective Tissue: Provides support and transport, as seen in bone and blood.

3. Muscle Tissue: Produces movement.

4. Nervous Tissue: Transmits electrical impulses.

3. Describe the tissue composition of the stomach. How does each tissue contribute to the digestive function of the stomach?

Answer:

Epithelial Tissue: It lines the inner stomach cavity, secretes gastric juices, including hydrochloric acid and digestive enzymes, and produces protective mucus.

Muscle Tissue (Smooth Muscle): It contracts rhythmically to churn and mix food with digestive juices.

Connective Tissue: It binds other tissues together and contains blood vessels that supply nutrients and oxygen, as well as nerves that help regulate contractions and secretions.

Nervous Tissue: It coordinates glandular secretions and muscular contractions in response to stimuli.

4. Describe the tissue composition of the leaf. How does each tissue contribute to the functions of the leaf?

Answer:

Epidermal Tissue: It covers the upper and lower surfaces of the leaf, secretes a protective cuticle, and regulates gas exchange through guard cells and stomata.

Mesophyll Tissue (Palisade and Spongy): It contains chloroplasts for photosynthesis and facilitates internal gas circulation.

Vascular Tissue (Xylem and Phloem): Xylem transports water and minerals to leaf cells, while phloem transports synthesized sugars away from the leaf to other parts of the plant.

5. How do the organ systems come together to form the human body?

Answer: The human body consists of multiple interdependent organ systems, such as the circulatory, respiratory, digestive, nervous, and excretory systems, which work collectively. No single system functions in isolation. For example, the digestive system provides nutrients, the respiratory system takes in oxygen, and the circulatory system distributes them to all body tissues. Meanwhile, the nervous system coordinates activities, ensuring the survival of the organism.

6. Describe the roles of the digestive system and the excretory system in homeostasis.

Answer:

Digestive System: It maintains homeostasis by taking in food, breaking it down enzymatically, and absorbing essential nutrients and water into the bloodstream to support cellular metabolism.

Excretory System: It maintains homeostasis by filtering metabolic wastes, such as urea, excess salts, and water, from the blood and eliminating them from the body. It also helps regulate blood volume, pH, and ion concentrations.

7. Explain the functions of various plant organs.

Answer:

Roots: They anchor the plant firmly in the soil, absorb water and dissolved mineral ions, and store food reserves.

Stems: They support leaves, flowers, and fruits. They also transport water and minerals upward and sugars to other parts of the plant through vascular tissues.

Leaves: They serve as the primary sites of photosynthesis and regulate transpiration and gas exchange.

Flowers: They facilitate sexual reproduction through pollination and the production of seeds and fruits.

8. Describe the structure and function of the plant root system.

Answer:

Structure: The root system comprises primary roots, lateral root branches, and root hairs, which are fine extensions of epidermal cells. Root tips are protected by a root cap.

Function: The root system anchors the plant securely in the ground. Root hairs provide a large surface area for absorbing water and mineral salts from the soil through osmosis and active transport.

9. Define homeostasis and explain its importance. Discuss how different organ systems work together to maintain homeostasis.

Answer:

Definition: Homeostasis is the ability of an organism to maintain a stable internal environment despite changes in external conditions.

Importance: It is essential because optimal enzyme activity, cell membrane stability, and metabolic reactions require carefully regulated internal conditions.

Coordination Among Systems: The nervous and endocrine systems detect imbalances and issue regulatory signals. The respiratory and circulatory systems regulate gas exchange and nutrient distribution. The urinary system removes metabolic wastes and controls water balance, while the integumentary and muscular systems help regulate body temperature.

10. Describe how the respiratory and circulatory systems work together to maintain homeostasis of oxygen and carbon dioxide levels in the body.

Answer: The respiratory system brings air into the lungs, where oxygen diffuses across the alveolar membranes into the blood and carbon dioxide diffuses out to be exhaled. The circulatory system pumps oxygen-rich blood through arteries to body tissues and organs. It also collects carbon dioxide produced by cells and transports it back to the lungs for elimination. Together, these systems maintain the balance of oxygen and carbon dioxide in the body.

D. INQUISITIVE QUESTIONS

1. How does the structure of epithelial tissue relate to its function in different parts of the body?

Answer: The structure of epithelial tissue varies according to its function.

Simple Squamous Epithelium: It consists of a single, very thin layer of flat cells, making it suitable for rapid diffusion and filtration, as found in lung alveoli and capillary walls.

Stratified Squamous Epithelium: It consists of multiple layers of cells and provides protection against mechanical wear and abrasion, as found in the outer layer of the skin.

Simple Columnar Epithelium: It consists of tall cells specialized for secretion and absorption, such as those lining the stomach and intestines.

2. Evaluate the importance of organ systems working in harmony and predict the consequences of a failure in one system on the others.

Answer: Organ systems operate in an integrated network of physiological interdependence. If one system fails, it can trigger a chain reaction affecting the entire body.

For example, if the respiratory system fails, oxygen delivery to the blood and tissues becomes inadequate. This deprives the circulatory and nervous systems, along with other organs, of the oxygen needed for normal functioning. Severe oxygen deprivation can lead to cellular energy failure, organ damage, heart failure, and ultimately death.

Therefore, coordination among organ systems is essential for sustaining life.

Notes by Sir Dilawar

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