9th Class Biology · Punjab Board · Complete learning guide
Chapter 5Tissues, Organs and Organ Systems
Every topic, every MCQ and every exercise question, explained step by step in simple language. Written for the Punjab Board new-syllabus Biology book, English medium.
Organisms are built on a pattern of increasing complexity. The levels of organization in multicellular organisms begin with the simplest and smallest level, the atom, and progress to the largest and most complex level, the organism.
Fig 5.1 (redrawn): levels of organization in an animal and a plant.
Level
Meaning (from the book)
Example
1. Atom
smallest unit of matter that keeps the property of an element
carbon, hydrogen, oxygen
2. Molecule
atoms combined; may have different properties
water, protein, nucleic acid
3. Organelle
molecules combined into a subcellular part with one job
mitochondria, ribosomes
4. Cell
organelles assembled; smallest unit with characteristics of life
unicellular or multicellular organisms
5. Tissue
group of similar cells working together for specific functions
epithelial, muscle; epidermal, vascular
6. Organ
related tissues working together for specific functions
heart, lungs; leaves, roots
7. Organ system
multiple organs working together for related functions
circulatory, digestive; root, shoot system
8. Organism
a living entity functioning independently through its organ systems
humans, trees
Tissue examples
In animals
In plants
Covering / protecting
epithelial tissue: covers body surfaces, lines cavities (skin)
epidermal tissue: protects underlying parts (leaf epidermis)
Working
muscle tissue: movement (cardiac muscle)
vascular tissue: transports water and nutrients (xylem, phloem)
Topic 2
Emergent properties
In organisms, the components at each level do not work solely. Instead, they interact. Due to their interactions, they create new functions called emergent properties: abilities present at a higher level of organization that are not possible from the individual components.
Did you know?
The Greek philosopher Aristotle said: "The whole is greater than the sum of its parts."
From → to
Emergent property (from the book)
Organelles → cell
cell division, protein synthesis, energy production
Cells → tissue
muscle cells form muscle tissue, which can contract and generate force
Tissues → organ
muscle, connective and epithelial tissues let the heart pump blood
Organs → organ system
mouth, oesophagus, stomach, intestines, liver together digest food and absorb nutrients
Organ systems → organism
consciousness, thinking, ability to respond to the environment
Topic 3
Organs and organ systems in plants
Organs are made of two or more types of tissues organized to serve a particular function. Organs which perform related functions work together and make an organ system.
Plant organ
Function (from the book)
Roots
anchor the plant, absorb water and minerals, store nutrients
Stems
support leaves, flowers and fruits; xylem and phloem move water, minerals and nutrients
Leaves
primary sites of photosynthesis and transpiration (water vapour lost through stomata)
Flower
reproductive part; key role in sexual reproduction
Leaf as an organ
In plants, a leaf is a complex organ made of several related tissues:
Epidermal tissue: outermost layer. The upper epidermis is covered by a waxy cuticle, which reduces water loss and protects. The lower epidermis has guard cells with a pore (stoma) between them; stomata control gas exchange and loss of water vapour.
Mesophyll tissue: between the two epidermises; cells rich in chloroplasts; the site of photosynthesis. Palisade mesophyll: just beneath the upper epidermis, tightly packed elongated cells. Spongy mesophyll: below it, loosely arranged cells with air spaces for diffusion of gases.
Vascular tissue: in the midrib and veins; a complex tissue of xylem and phloem. Xylem brings water and minerals from the stem; phloem carries sugars from leaf cells to the stem.
Fig 5.2 (redrawn): tissues which make the leaf organ.
Organ systems in plants
Plants are non-moving organisms, so their organ systems are less complex. They have two main organ systems: the root system and the shoot system. The root system anchors the plant, absorbs water and salts, and sometimes stores food. The shoot system (stems, branches, leaves, flowers and fruits) enables photosynthesis and reproduction.
Fig 5.3 (redrawn): organs and organ systems in plants.
Topic 4
Organs in the human body; the stomach
Organ
Function (from the book)
Heart
muscular organ that pumps blood; delivers oxygen and nutrients, removes wastes
Lungs
breathing; exchange of oxygen and carbon dioxide with the environment
Brain
control centre: coordination, thinking, decision-making
Liver
filtering blood, producing bile, storing glucose
Kidneys
filtering wastes from blood, producing urine
Stomach
muscular organ that breaks down food with digestive enzymes
Intestines
long tubes that digest food and absorb nutrients
Pancreas
digestive enzymes; hormones insulin and glucagon
Stomach as an organ
The stomach is an important organ of the digestive system, responsible for the partial digestion of proteins; it also stores food. It is composed of the following tissues:
Epithelial tissue: the inner wall; glandular; secretes mucus, which protects the wall from acid, and gastric juice containing pepsinogen (protein digestion) and hydrochloric acid (activates pepsinogen to pepsin).
Connective tissue: beneath the epithelium; structural support; contains blood vessels, nerves and lymphatics.
Muscle tissue: three layers of smooth muscle, outer longitudinal, middle circular, inner oblique; contract and relax to mix food with gastric juice.
Outer connective tissue: the outermost layer that encircles and supports the stomach.
Fig 5.4 (redrawn): tissues which make the stomach organ.
Topic 5
Organ systems in the human body
System
Organs (from the book)
Function
Skeletal
bones, cartilages, tendons
structure, support, protection; framework for muscles; stores minerals, makes blood cells
Digestive
mouth, oesophagus, stomach, small and large intestine
digestion and absorption of food
Respiratory
lungs, trachea (windpipe), bronchi
exchange of O₂ and CO₂ between body and environment
Muscular
skeletal muscles attached to bones
movement and locomotion
Nervous
brain, spinal cord, nerves
coordinates and controls body functions by nerve impulses
Fig 5.5 (redrawn): some organ systems of the human body.
Topic 6
Homeostasis
Definition
Homeostasis
The ability of an organism to maintain a stable internal environment of the body despite changes in the external environment. Examples: regulating temperature, blood pressure, blood sugar and pH levels.
Importance of homeostasis
Each cell works properly only when extracellular conditions (temperature, pH, salts, glucose, oxygen) are kept in the normal range.
Hot: when hard work raises body temperature, the temperature regulating centre in the brain sends a message to sweat glands; sweating cools the body back to 37 °C.
Cold: when body temperature falls, the centre sends a message to muscles; shivering generates heat.
Blood sugar: after drinking juice, blood glucose rises; the pancreas releases insulin, which lowers it to normal.
Exercise: muscles need more oxygen, so breathing rate and heartbeat increase to supply oxygen and food.
Fig 5.6 (redrawn): homeostasis of body temperature around 37 °C.
Organ systems working together for homeostasis
System
Role (from the book)
Nervous and endocrine
regulate and coordinate heart rate, respiration, metabolism; respond to environment
Respiratory
enough oxygen for respiration; expels excess CO₂
Cardiovascular
regulates body temperature and pH; delivers substances to all cells
Digestive
distributes nutrients for energy, growth and repair
Muscular and skeletal
posture, support and movement
Urinary
removes wastes; water and salt balance; blood volume, pressure and pH
Integumentary (skin)
barrier against external factors; temperature by sweating
The wording follows published solved exercises and every answer was re-checked by hand, so the wording or the order of options may differ slightly from your print.
Answered 0 of 24 · Correct 0
Set A: Textbook exercise 10 MCQs
The multiple-choice questions at the end of Chapter 5 in your book, in the book's option order.
Q5.1Emergent Properties
A higher level of organization exhibits emergent properties when:
Answer(d) Its parts interact to perform more functions.
Step by step
Interaction → new abilities not present in the parts.
Why the others are wrong
(a) independent parts give no new property.
(b) reversed: the whole is greater than the sum of its parts.
(c) Wrong.
Remember
Emerge = come out of teamwork.
Q5.2Levels of Organization
Which of the following demonstrates the levels of organization of the body, from simplest to most complex?
Answer(b) Organelle → Cell → Tissue → Organ → Organ system
Step by step
Organelles make cells, cells make tissues, tissues make organs.
Why the others are wrong
(a) tissue comes before organ.
(c) organelle is simplest.
(d) reversed.
Remember
O-C-T-O-O: Organelle, Cell, Tissue, Organ, Organ system.
Q5.3Human Organ Systems
At which level of organization gas exchange occurs between body and environment?
Answer(d) Organ system level in the respiratory system
Step by step
Body ↔ environment exchange needs the whole system: airways + lungs.
Why the others are wrong
(a) mitochondria use O₂ inside cells.
(b) cells alone cannot exchange with the environment.
(c) a tissue alone is not enough.
Remember
Body-environment exchange = respiratory system.
Q5.4Human Organs and Stomach
The epithelial tissue in the stomach wall is responsible for producing:
Answer(d) All of these
Step by step
Mucus protects; HCl activates pepsinogen to pepsin.
Why the others are wrong
(a) not only mucus.
(b) not only pepsinogen.
(c) not only HCl.
Remember
Stomach epithelium makes all three.
Q5.5Human Organs and Stomach
In the wall of stomach, which tissue also contains blood vessels and nerves?
Set A: Textbook exercise short questions 8 questions
The short questions at the end of the chapter in your book.
Short Q 5.1
Enlist the levels of organization from cells to organ systems.
Answer
Cell → tissue → organ → organ system (the full list: atom, molecule, organelle, cell, tissue, organ, organ system, organism).
Levels of organization.
Short Q 5.2
What are the major roles of the epithelial tissue present in the stomach?
Answer
Secretes mucus, which lines and protects the inner wall from acid.
Secretes gastric juice with pepsinogen for protein digestion and hydrochloric acid to activate it into pepsin.
Short Q 5.3
How do the smooth muscles contribute to the stomach's function?
Answer
Three layers of smooth muscle (outer longitudinal, middle circular, inner oblique) contract and relax to churn the food and mix it with gastric juice, helping its breakdown, and push it on to the intestine.
Short Q 5.4
What is the function of the palisade mesophyll in the leaf?
Answer
Its tightly packed, elongated cells lie just beneath the upper epidermis and are rich in chloroplasts; it is the main site of photosynthesis, catching the most light.
Short Q 5.5
What is the role of the shoot system in plants?
Answer
The shoot system (stems, branches, leaves, flowers and fruits) supports the plant, carries out photosynthesis and reproduction, and transports materials between roots and leaves.
Short Q 5.6
What is homeostasis, and why is it important for organisms?
Answer
The ability of an organism to maintain a stable internal environment despite changes in the external environment. It is important because cells work properly only when temperature, pH and the levels of salts, glucose and oxygen stay in the normal range.
Short Q 5.7
How does the human body maintain a stable internal temperature?
Answer
The temperature regulating centre in the brain controls it around 37 °C. If temperature rises, it signals sweat glands; sweat evaporates and removes heat. If temperature falls, it signals muscles to shiver, generating heat.
Temperature homeostasis.
Short Q 5.8
Differentiate between: (i) tissue and organ, (ii) root system and shoot system, (iii) epidermal and mesophyll tissue, (iv) palisade and spongy mesophyll.
Answer
First
Second
(i)
Tissue: group of similar cells with a specific function (e.g. muscle tissue)
Organ: related tissues working together (e.g. heart, leaf)
(ii)
Root system: roots; anchor, absorb water and salts, store food
Shoot system: stems, leaves, flowers, fruits; photosynthesis and reproduction
Spongy: loosely arranged cells with air spaces for gas diffusion
Set B: More short questions 25 questions
The book's in-text exercises first, then short questions on every topic of the chapter (SLO-based), as asked in board papers.
In-text boxes
SQ 5.1
What did Aristotle say about the whole and its parts?
Answer
"The whole is greater than the sum of its parts." This describes emergent properties.
Levels and emergent properties
SQ 5.2
Define tissue with two plant and two animal examples.
Answer
A group of similar cells working together to perform specific functions. Animals: epithelial, muscle tissue; plants: epidermal, vascular (xylem, phloem) tissue.
SQ 5.3
Define organ and organ system with examples.
Answer
Organ: related tissues working together (heart, lungs, leaf, root). Organ system: multiple organs working together for related functions (circulatory, digestive; root and shoot systems).
SQ 5.4
What is a molecule? Give examples.
Answer
Atoms combine to form molecules, which can have different properties from their atoms: water, protein, nucleic acid.
SQ 5.5
Define organism.
Answer
A living entity that can function independently on behalf of the proper functioning of its organ systems, e.g. humans and trees.
SQ 5.6
What are emergent properties?
Answer
New functions created by the interaction of components, present at a higher level but not possible from the individual parts.
SQ 5.7
Give two examples of emergent properties.
Answer
Muscle cells together form muscle tissue that can contract and generate force; the tissues of the heart together pump blood.
Plant organs and systems
SQ 5.8
Write the functions of roots and stems.
Answer
Roots anchor the plant, absorb water and minerals and store food. Stems support leaves, flowers and fruits and carry water, minerals and food in xylem and phloem.
SQ 5.9
What is transpiration?
Answer
The loss of water vapour from leaves through small pores called stomata.
SQ 5.10
Name the tissues of a leaf.
Answer
Epidermal tissue, mesophyll tissue (palisade and spongy) and vascular tissue (xylem and phloem).
Leaf tissues.
SQ 5.11
What is the role of the cuticle and stomata?
Answer
The waxy cuticle reduces water loss and protects; stomata (between guard cells) control gas exchange and loss of water vapour.
SQ 5.12
Why is vascular tissue called a complex tissue?
Answer
Because it consists of two tissues: xylem and phloem.
SQ 5.13
Why are the organ systems of plants less complex than animals?
Answer
Plants are non-moving organisms; they need only the root and shoot systems.
Root and shoot systems.
Human organs and systems
SQ 5.14
Write the functions of the liver and kidneys.
Answer
Liver: filters blood, produces bile, stores glucose. Kidneys: filter wastes from blood and produce urine.
These test whether you really understand. Give a reason every time.
CRQ 5.1
(Inquisitive) How does the structure of epithelial tissue relate to its function in different parts of the body?
Answer
Epithelial tissue covers body surfaces and lines cavities; its structure matches each job:
Where
Structure
Function
Skin
many layers of tightly packed cells
protection against injury, germs and water loss
Stomach lining
glandular cells
secrete mucus (protection) and gastric juice (HCl, pepsinogen)
Lungs (alveoli)
single layer of thin, flat cells
fast diffusion of O₂ and CO₂
Small intestine
tall cells with folds and microvilli
large surface for absorption of food
Airways (trachea)
cells with cilia and mucus cells
trap and sweep out dust
Thin where things must pass through, thick where protection is needed, glandular where secretion is needed.
CRQ 5.2
(Inquisitive) 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 work together for homeostasis: the nervous and endocrine systems coordinate; respiratory supplies O₂; circulatory carries it; digestive supplies nutrients; urinary removes wastes.
Organelle: specialized subcellular part (mitochondria for respiration, ribosomes for protein synthesis).
Cell: organelles assembled; smallest unit of life; can reproduce.
Tissue: similar cells for a specific function (epithelial, muscle; epidermal, vascular).
Organ: related tissues working together (heart, lungs; leaves, roots).
Organ system: organs for related functions (circulatory, digestive; root, shoot).
Organism: independent living entity (humans, trees).
Contribution
Each level builds on the one below and adds emergent properties: cells divide and make proteins; tissues contract; the heart pumps; the digestive system digests; the organism thinks and responds. The organism functions only when all levels work together.
Long Q 5.2
What is a tissue level? Explain plant and animal tissues.
Answer
Definition
Tissue
A group of similar cells that work together to perform one or more specific functions.
Animal tissues
Epithelial tissue: covers body surfaces and lines cavities (skin, stomach lining).
Muscle tissue: enables movement (cardiac muscle in the heart; smooth muscle in the stomach).
Connective tissue: support; contains blood vessels and nerves.
Plant tissues
Epidermal tissue: protects underlying parts (leaf epidermis with cuticle and stomata).
Mesophyll tissue: photosynthesis (palisade and spongy).
Vascular tissue: xylem (water, minerals) and phloem (food); a complex tissue.
Plant tissues in a leaf.
Long Q 5.3
Describe the tissue composition of the stomach. How does each tissue contribute to the digestive function of the stomach?
Answer
Tissues of the stomach.
The stomach partly digests proteins and stores food. Its wall has four tissue layers:
1. Epithelial tissue
Inner glandular wall; secretes mucus (protects the wall from acid) and gastric juice: pepsinogen for protein digestion and HCl to activate it to pepsin.
2. Connective tissue
Beneath the epithelium; structural support; carries blood vessels, nerves and lymphatics (supply and control).
3. Muscle tissue
Outer longitudinal, middle circular and inner oblique smooth muscle; contract and relax to mix food with gastric juice.
4. Outer connective tissue
Encircles and supports the stomach.
Long Q 5.4
Describe the tissue composition of the leaf. How does each tissue contribute to the function of the leaf?
Answer
Tissues of a leaf.
Epidermal tissue
Upper epidermis with waxy cuticle reduces water loss and protects. Lower epidermis has guard cells and stomata that control gas exchange and loss of water vapour.
Mesophyll tissue
Cells rich in chloroplasts; site of photosynthesis. Palisade mesophyll: tightly packed elongated cells beneath the upper epidermis. Spongy mesophyll: loose cells with air spaces for diffusion of gases.
Vascular tissue
In midrib and veins; xylem brings water and minerals from the stem; phloem carries sugars to the stem.
Together they let the leaf make food (photosynthesis) and lose water vapour (transpiration).
Long Q 5.5
How do the organ systems come together to form the human body?
Answer
Human organ systems.
System
Organs
Function
Skeletal
bones, cartilages, tendons
support, protection, movement framework, minerals, blood cells
Muscular
skeletal muscles
movement and locomotion
Digestive
mouth, oesophagus, stomach, intestines
digestion and absorption
Respiratory
lungs, trachea, bronchi
gas exchange
Circulatory
heart, vessels, blood
transport
Nervous
brain, spinal cord, nerves
control and coordination
The systems are linked: digestive and respiratory systems take in food and oxygen, the circulatory system carries them to cells, the nervous system coordinates all, and their interaction gives emergent properties like thinking and responding to the environment.
Long Q 5.6
Describe the role of the digestive system and the excretory system in homeostasis.
Answer
Digestive system
It works for proper distribution of nutrients to cells for energy, growth and repair. The pancreas releases insulin when blood glucose rises (e.g. after juice), lowering it to normal; the liver stores glucose. So blood sugar stays stable.
Excretory (urinary) system
It eliminates waste materials from the body and regulates water and salt balance in body tissues; in this way it maintains blood volume, blood pressure and pH levels. The kidneys filter wastes from blood and produce urine.
Long Q 5.7
Explain the functions of various plant organs.
Answer
Roots: anchor the plant, absorb water and essential minerals, store nutrients.
Stems: support leaves, flowers and fruits; xylem and phloem move water, minerals and nutrients.
Leaves: primary sites of photosynthesis and transpiration.
Flowers: reproductive part; sexual reproduction (pollination, seeds and fruits).
Plant organs and systems.
Long Q 5.8
Describe the structure and function of the plant root system.
Answer
Structure
The root system consists of roots, usually underground: a main root with branches and fine root hairs (extensions of epidermal cells) that increase surface area; vascular tissue (xylem and phloem) runs through them.
Functions
Anchors the plant in the soil.
Absorbs water and salts (minerals) from the soil.
Stores food in some plants (carrot, radish).
Passes water up to the shoot through xylem.
Root and shoot systems.
Long Q 5.9
Define homeostasis and explain its importance. Discuss how different organ systems work together to maintain homeostasis.
Answer
Definition
Homeostasis
The ability of an organism to maintain a stable internal environment despite changes in the external environment.
Importance
Cells work properly only when temperature, pH, salts, glucose and oxygen stay in the normal range. Examples: sweating and shivering keep 37 °C; insulin lowers blood sugar; faster breathing during exercise.
Temperature control.
Systems working together
Nervous and endocrine: regulate heart rate, respiration, metabolism.
Respiratory: oxygen in, CO₂ out.
Cardiovascular: temperature, pH, delivery to cells.
Digestive: nutrients.
Muscular and skeletal: posture and movement.
Urinary: wastes, water and salts, blood pressure.
Integumentary: barrier, sweating.
Long Q 5.10
Describe how the respiratory and circulatory systems work together to maintain homeostasis of oxygen and carbon dioxide levels in the body.
Answer
Respiratory system
The lungs, trachea and bronchi exchange oxygen and carbon dioxide between the body and the environment: oxygen enters the blood and CO₂ leaves it in the lungs.
Circulatory system
The heart pumps blood through vessels; blood carries oxygen from the lungs to every cell and brings CO₂ from cells back to the lungs.
Working together
During hard exercise, muscles need more oxygen and produce more CO₂; the nervous system increases the breathing rate and heartbeat, so more oxygen is supplied and extra CO₂ is removed. When activity stops, both rates fall. In this way O₂ and CO₂ (and blood pH) stay in the normal range.
Set B: More important long questions 3 questions
Long questions often set in board papers from this chapter, answered in the same full style.
Imp. LQ 1
What are emergent properties? Explain them with examples at each level of organization.
Answer
Components at each level interact and create new functions called emergent properties: abilities present at a higher level that are not possible from individual components. Aristotle: "The whole is greater than the sum of its parts."
Organelles → cell: cell division, protein synthesis, energy production.
Cells → tissue: muscle tissue contracts and generates force.
Tissues → organ: the heart pumps blood.
Organs → organ system: the digestive system digests and absorbs food.
Organ systems → organism: consciousness, thinking, responding to the environment.
Imp. LQ 2
Write a note on the human organs and their functions.
Answer
Organ
Function
Heart
pumps blood
Lungs
gas exchange
Brain
control, thinking, decisions
Liver
filters blood, bile, stores glucose
Kidneys
filter wastes, urine
Stomach
breaks down food
Intestines
digestion and absorption
Pancreas
enzymes; insulin and glucagon
Imp. LQ 3
Describe the homeostasis of body temperature.
Answer
Body temperature around 37 °C.
When temperature rises
During hard work muscles produce heat; the temperature regulating centre in the brain sends a message to sweat glands; sweat evaporates and heat is lost; temperature falls to 37 °C.
When temperature falls
The centre sends a message to muscles; shivering generates heat; temperature rises to 37 °C.
The skin (integumentary system) and blood flow (cardiovascular system) also help.
The ability of an organism to maintain a stable internal environment of the body despite changes in the external environment. Examples: regulating temperature, blood pressure, blood sugar and pH levels.
Common mistakes to avoid
Calling a leaf a tissue (it is an organ).
Writing "sum of parts greater than the whole" (it is the reverse).
Saying xylem carries food (phloem does).
Saying the outer connective tissue carries blood vessels (the inner one does).
Mixing up palisade (packed) and spongy (air spaces) mesophyll.
Saying insulin raises blood sugar.
Extra practice tap a question to see its answer
Emergent properties appear when?Show answer
Parts interact to perform more functions
Simplest to complex?Show answer
Organelle → cell → tissue → organ → organ system
Gas exchange with environment — level?Show answer
Organ system (respiratory system)
Stomach epithelium makes?Show answer
Mucus, pepsinogen and HCl
Stomach tissue with vessels and nerves?Show answer
Inner connective tissue
Photosynthesis tissue of leaf?Show answer
Mesophyll
Xylem in a leaf?Show answer
Transports water
Skeletal system also?Show answer
Stores minerals, makes blood cells
Food transport in plants?Show answer
Phloem
Function of flower?Show answer
Reproduction
Cooling mechanism?Show answer
Sweating
Hormone lowering glucose?Show answer
Insulin
Final self-test
Final self-test: all 24 MCQs, no answers
Give yourself 25 minutes. Pick one option for each question, then submit to see your score and which questions to revise. Any question you get wrong tells you which topic to read again.
