Science Exploration Notes Class 9 English Medium 2026-27

Science Exploration Chapter 12. Patterns in Life: Diversity and Classification

CBSE Notes New Syllabus: Class 9

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Chapter 12. Patterns in Life: Diversity and Classification

This section explains Kingdom Protista, the second kingdom in the Five Kingdom Classification. Protists are mostly unicellular eukaryotic organisms that live in aquatic or moist environments. They exhibit diverse modes of nutrition and play an important role in aquatic ecosystems and nutrient cycling. :contentReference[oaicite:0]{index=0}

Kingdom Protista – Unicellular Eukaryotes

Introduction

Kingdom Protista includes mostly unicellular eukaryotic organisms. Unlike Monera, protists possess a true nucleus enclosed by a nuclear membrane. They are highly diverse and are commonly found in water bodies and other moist habitats. 

Characteristics of Kingdom Protista

• Mostly unicellular organisms.
• Cells are eukaryotic with a true nucleus.
• May or may not possess a cell wall.
• Found mainly in aquatic and moist environments.
• Some are autotrophic while others are heterotrophic.
• Many are capable of movement.
• Show great diversity in structure and nutrition.

Habitat

• Freshwater ponds
• Lakes and rivers
• Marine water
• Moist soil
• Damp environments

Cell Structure

Mode of Nutrition

• Autotrophic Protists prepare their own food through photosynthesis.
• Heterotrophic Protists obtain food from other organisms.
• Some protists can switch between autotrophic and heterotrophic nutrition depending on environmental conditions.

Movement in Protists

Many protists are capable of movement using specialised structures.

Examples of Kingdom Protista

• Amoeba
• Paramecium
• Euglena
• Chlamydomonas

Importance of Kingdom Protista

• Form an important link in aquatic food chains.
• Many photosynthetic protists release oxygen.
• Serve as food for several aquatic organisms.
• Some protists function as decomposers.
• Help in nutrient cycling within aquatic ecosystems.

Ecological Role of Protists

Summary of Kingdom Protista

ATP Education Concept Builder

Protists are considered a bridge between simple prokaryotic organisms and complex multicellular organisms. Their true nucleus, diverse nutrition and ecological roles make them an important group in the study of evolution and biological classification. 

ATP Education Exam Booster

• Remember that Protista consists of mostly unicellular eukaryotic organisms.
• Learn the examples of Amoeba, Paramecium, Euglena and Chlamydomonas.
• Understand the difference between autotrophic and heterotrophic protists.
• Remember the locomotory structures of common protists.
• Know the ecological importance of protists in aquatic food chains.
• CBSE competency-based questions may ask students to compare Monera and Protista based on cell structure, nucleus and mode of nutrition.