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A body is built step by step. Cells join to make tissues, tissues make organs, organs make organ systems, and these make a full organism.
Tissue
- Cells in a body work together.
- Similar cells group up.
- Such a group is a tissue.
- Muscle tissue is grouped muscle cells.
Example 1 — Muscle Tissue
- Many muscle cells join together.
- They all help in movement.
- Together they form muscle tissue.
Example 2 — Cells Working in Groups
- Single cells cannot do a big job alone.
- Similar cells team up for one task.
- So a tissue gets the job done better.
Important Points
- The cells in a tissue are similar in shape and work.
- Blood and bone are also tissues in the body.
- Trap: a tissue has similar cells; an organ has different tissues.
Definition — Tissue
A group of similar cells which work together to do a particular job.
Organ and Organ System
- Different tissues join into an organ.
- An organ does a particular job.
- Organs together form an organ system.
- Systems together make an organism.
Example 1 — The Heart as an Organ
- The heart is made of different tissues.
- Its job is to pump blood around the body.
- So the heart is an organ.
Example 2 — A Plant's Organs
- Roots, stem, leaves, flowers and fruit are plant organs.
- Roots take in water; leaves make food.
- Together they keep the plant alive.
Important Points
- Plant organs are roots, stem, leaves, flowers and fruit.
- The digestive system is an example of an organ system.
- Trap: an organ has many tissues; a system has many organs.
Definition — Organ System
A group of interconnected organs that work together to do a big job for the organism.
Levels of Organisation
Cells
→
Tissues
→
Organs
→
Organ systems
→
Organism
Objective Type Questions Q2(d) - Page 34 Lakhmir Singh
Question
Fill in the blank: Tissues make up ______.
Show answer
Organs.
Explanation
- Different tissues join to form an organ.
- So tissues make up organs.
Objective Type Questions Q3(a) - Page 34 Lakhmir Singh
Question
State whether true or false: Unicellular organisms have one-celled body.
Show answer
True.
Explanation
- Unicellular means made of one cell.
- So its body has just one cell.
Objective Type Questions Q3(f) - Page 34 Lakhmir Singh
Question
State whether true or false: The basic living unit of an organism is organ.
Show answer
False.
Explanation
- The basic living unit is the cell.
- An organ is made of many tissues of cells.
Subjective Type Questions - Short Answer Q1 - Page 34 Lakhmir Singh
Question
What is an organ system? Which of the following are plant organs and which are the animal organs? Brain, Leaf, Lungs, Roots, Stem, Kidneys, Flower, Heart.
Show answer
An organ system is a group of organs working together. Plant organs: leaf, roots, stem, flower. Animal organs: brain, lungs, kidneys, heart.
Explanation
- Several organs work together to do a big job, forming a system.
- Leaf, roots, stem and flower belong to plants.
- Brain, lungs, kidneys and heart belong to animals.
Subjective Type Questions - Long Answer Q1(b) - Page 35 Lakhmir Singh
Question
What are multicellular organisms? Name two multicellular organisms.
Show answer
Multicellular organisms are made of many cells, such as a human and a plant.
Explanation
- Multicellular means a body made of many cells.
- The cells do special jobs and cooperate.
- Humans and plants are examples.
Multiple Choice Questions Q12 - Page 37 Lakhmir Singh
Question
A group of similar cells which work together forms a/an: (a) organ (b) tissue (c) cell (d) organism
Show answer
(b) tissue.
Explanation
- A group of similar cells working together is a tissue.
