NCERT Class 9 Science Exploration Chapter 12 Patterns in Life Diversity and Classification PDF Download

Chapter 12: Patterns in Life: Diversity and Classification

Have you ever wondered why some plants can survive long droughts while others cannot? Or, how certain insects protect crops while others damage them?

The Earth is home to an enormous variety of life forms. From microscopic organisms invisible to the naked eye to giant trees, from glowing jellyfish to soaring eagles, life exists in countless forms and habitats - from the snow-clad Himalayas to the coral reefs of the Andaman Sea. This immense variety of living organisms is known as biodiversity. Biodiversity is essential for life on the Earth. Every organism plays a role in keeping nature stable and functioning. Microscopic algae in the oceans release most of the oxygen we breathe. Fungi and bacteria decompose fallen leaves, and convert waste into manure, making the soil fertile. Birds, bees and bats pollinate flowers, while plants capture sunlight to prepare food that support nearly all life on the planet. These interconnections help sustain ecosystems and make the Earth suitable for living organisms.

Humans, too, depend on biodiversity for food, shelter, medicines and livelihoods. For centuries, farmers relied on their practical knowledge to conserve diverse crop varieties with useful characteristics, such as drought tolerance, pest resistance and their ability to grow in nutrient poor soils. They realised that diversity reduces the risk of crop failure and strengthens food security.

In such a vast diversity, organisms share certain similarities while also showing many differences. To study diversity systematically, scientists group and classify organisms based on their shared characteristics and evolutionary relationships. Classification helps us understand how organisms are related, how they function and how we can use this knowledge in activities, such as ecosystem management, biodiversity conservation, sustainable farming, and so on.

12.1 India as a Biodiversity Hotspot

The natural landscape of our country is diverse - with mountains in the north, desert in the west, rainforests in the North East India, plateaus in the south, and long coastlines along the Arabian Sea and the Bay of Bengal. Each of these regions has distinct soil types and different climatic conditions like temperature and rainfall. These diverse habitats together support a wide variety of species. Some of these species are restricted to particular regions of the world and are not found naturally anywhere else. Such species are called endemic species. For example, Nilgiri tahr (Fig. 12.1a), Lion-tailed macaque (Fig. 12.1b), Indian variety of the pitcher plant - Nepenthes khasiana (Fig. 12.1c) and Neelakurinji (Fig. 12.1d) are found only in India.

[Figure 12.1: (a) Nilgiri tahr, (b) Lion-tailed macaque, (c) Nepenthes khasiana, and (d) Neelakurinji, See in your textbook]

Regions that support a large number of endemic species and have undergone significant habitat loss are known as biodiversity hotspots. These areas are particularly important for biodiversity conservation. Regions, such as the Western Ghats, Indo-Burma (including North East India), the Himalayas, Sundaland (including the Nicobar Islands), are some examples of global biodiversity hotspots. These areas are especially rich in number and in the diversity of organisms. Protecting these regions is equally important, as they support food webs and help ecosystems remain healthy.

Teacher's Note

When you read about biodiversity hotspots, remember that they are hotspots because they have both many endemic species and significant habitat loss. A place with only endemic species but no habitat loss is not a hotspot for conservation purposes. The hotspot concept tells us where conservation efforts matter most.

12.2 How has the Biodiversity Evolved?

The biodiversity that we see today on the Earth was not always the same. Small differences among individuals affected their chances of survival and reproduction by helping them adapt to changed conditions. These differences accumulated over many generations and gave rise to new forms of life.

The diversity we see today is therefore, an outcome of continuous changes occurring over a vast span of time, shaped by interactions between organisms and their surroundings. The study of this biological diversity is possible through a systematic framework that is provided by classification.

India's Scientific Contributions

Some ancient Indian traditions, such as the Sangam Tinai classification of landscapes and the protection of sacred groves, demonstrate a sophisticated literary and cultural understanding of landscapes, and their biota. These customs effectively preserved locally diverse habitats, aligning with contemporary ecological principles, even if it is not articulated as a formal ecological theory.

12.3 How to Classify Organisms?

Activity 12.1: Let us compare and classify

Fig. 12.2 shows the diversity of animals in an ecosystem. Observe the image carefully. Can you guess how the organisms are grouped in the image?

[Figure 12.2: Day and night view of an ecosystem, See in your textbook]

1. Ponder on the questions given below:
   • Which animals can you identify in the given picture?
   • Where are they seen?
   • Which animals in the picture seem active:
     1. during the day?
     2. during the night?
     3. both during the day and the night?
2. Record your observations in Table 12.1.

Teacher's Note

When classifying organisms, you can use different bases - behavior (like day or night activity), physical features (like legs or wings), or habitat. The same organism can belong to different groups depending on which characteristic you choose. In exams, always state clearly which basis you are using to classify.

Key Points

• Biodiversity refers to the enormous variety of life forms on Earth, from microscopic organisms to giant trees, and is essential for maintaining stable and functioning ecosystems.
• Endemic species are organisms found only in particular regions of the world and nowhere else naturally; regions with many endemic species and significant habitat loss are called biodiversity hotspots.
• The biodiversity we see today evolved over vast spans of time through small differences among individuals that helped them adapt to changing conditions, and these differences accumulated over generations.
• Classification is a systematic framework that helps us group and organize organisms based on their shared characteristics and evolutionary relationships, making it easier to understand and study diversity.

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