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💡 One cell, a true nucleus
Amoeba, Paramecium, Euglena — single cells that, unlike bacteria, carry a proper nucleus. They drift in ponds and puddles, some feeding, some making their own food.
Activity 12.5 — Let us make
In this Activity, we will make a hay infusion to observe living protists under the microscope.
Activity 12.5 - Hay Infusion
Step 1
Fill a bottle with grass and pond water
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Step 2
Cover it and keep for a week
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Step 3
Take a drop onto a slide
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Step 4
Observe protists under the microscope
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Amoeba, Paramecium and Euglena appear
- Collect mowed grass, straw or fodder and fill one-fourth of a small glass bottle with it.
- Fill the bottle with stagnant or pond water, mix, cover with muslin cloth and tie.
- Keep it undisturbed for a week (wear a lab coat, mask and gloves; the infusion may smell bad).
- Take a drop on a clean slide and observe it under a microscope; compare with Fig. 12.7.
What we observe
Moving single-celled organisms like
Amoeba, Paramecium and Euglena
appear — protists that live in water and moist places.
What is Kingdom Protista?
Protista
Single-celled eukaryotes with a true nucleus that live in water or moist places.
Example:
Amoeba, Paramecium, Euglena
- Protista includes single-celled eukaryotes without a cell wall, or with a cell wall of cellulose (Fig. 12.7).
- They are microscopic and highly diverse; some are autotrophic and others heterotrophic.
- They are an important link in aquatic food chains — some produce oxygen, some are food for small animals, and some act as decomposers.
NCERT Question 5 — You find an unlabelled slide
You find an unlabelled slide of a single-celled organism that has a well-defined nucleus and multiple cilia. Which group would it most likely belong to? Give reasons.
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NCERT Question 13 — A scientist discovers a new
A scientist discovers a new organism with the characteristic features of locomotion and autotrophic nutrition. Which character(s) would help the scientist identify the organism belonging to Protista according to the five kingdom classification?
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⏸▶ Pause and Ponder
2. How can a single-celled organism carry out all its life processes when billions of cells are needed in multicellular organisms like us? In a protist, that one cell performs every function — nutrition, movement, respiration and reproduction — with specialised structures inside it.
Important Definitions
- Protista — the kingdom of single-celled eukaryotes, with no cell wall or a cellulose cell wall, living in water or moist places.
- Hay infusion — a preparation of grass or straw kept in stagnant water for a week, used to grow and observe protists under a microscope.
