CBSE Class 12 Biology Notes Chapter 15 Biodiversity and Conservation

Causes of Biodiversity Losses

The accelerated rates of species extinctions are primarily attributed to human activities, often referred to as "The Evil Quartet." These four major causes significantly impact biodiversity:

1. Habitat Loss and Fragmentation

Habitat loss and fragmentation are considered the most critical causes of extinction for both animals and plants. Large habitats, such as the Amazon rainforest, often called the "lungs of the planet," are being cut down and cleared for agricultural purposes, like cultivating soybeans or converting forests into grasslands. This fragmentation disrupts the natural habitats, making it challenging for animals, especially mammals and birds that require large territories, to migrate and thrive.

2. Over-Exploitation

Over-exploitation occurs when humans excessively harvest natural resources, leading to degradation and potential extinction. Examples include the extinction of the Steller’s sea cow and the passenger pigeon . Many marine fish populations face overharvesting, which threatens the survival of essential species and disrupts marine ecosystems.

3. Alien Species Invasions

The introduction of alien species—whether intentional or accidental can lead to declines or extinctions of indigenous species. Invasive species, such as the Nile perch introduced into Lake Victoria, have caused the extinction of over 200 unique cichlid fish species. Additionally, invasive weeds like parthenium , Lantana and water hyacinth threaten the survival of native species by outcompeting them for resources.

4. Co-Extinctions

Co-extinction occurs when one species becomes extinct, leading to the extinction of other species that are closely associated with it. For instance, if a host fish species disappears, its specific parasites and symbiotic organisms may also become extinct disrupting the balance of the ecosystem.

Biodiversity Conservation

Conserving biodiversity is essential for various reasons:

I. The Narrowly Utilitarian

Humans derive numerous direct economic benefits from nature, including food, firewood, fibers, construction materials, medicinal plants, and industrial products. By investing in bio-prospecting the exploration of biodiversity for new resources countries rich in biodiversity can anticipate significant economic gains.

II. The Broadly Utilitarian

Biodiversity is crucial for the ecosystem services that nature provides. These include oxygen production during photosynthesis, natural pollination and the overall enjoyment of nature. Such services are invaluable and contribute to the well-being of all life on Earth.

III. Ethical Considerations

Conserving biodiversity also involves ethical responsibilities. We owe it to the millions of plants, animals, and microorganisms with whom we share the planet to protect their existence. Each species has intrinsic value, regardless of its current economic worth. It is our moral obligation to care for their well-being and ensure that we pass on our biological legacy in a healthy state to future generations.

How Do We Conserve Biodiversity?

Conserving biodiversity is vital for maintaining healthy ecosystems and ensuring the survival of various species. There are two primary methods for biodiversity conservation:

1. In Situ (On-Site) Conservation

In situ conservation focuses on protecting ecosystems and their biodiversity in their natural habitats. Conservationists have identified certain regions known as biodiversity hotspots , which are characterized by high levels of species richness and endemism species that are found only in those specific areas. There are 34 recognized biodiversity hotspots globally, many of which are also facing accelerated habitat loss. In India, several measures have been implemented for in situ conservation, including:

• Biosphere Reserves : India has 14 biosphere reserves aimed at conserving both biodiversity and the cultural heritage of the area.
• National Parks : There are 90 national parks that protect various ecosystems and the species within them.
• Wildlife Sanctuaries : India has 448 wildlife sanctuaries that provide safe habitats for threatened and endangered species.

2. Ex Situ (Off-Site) Conservation

Ex situ conservation involves the removal of threatened species from their natural habitats and placing them in controlled environments where they can receive protection and care. This method allows for the preservation of genetic diversity and helps ensure the survival of species at risk of extinction. Some common ex situ conservation methods include:

• Zoological Parks : Zoos house animals in safe environments and contribute to breeding programs for endangered species.
• Botanical Gardens : These gardens conserve plant species, particularly those that are rare or threatened.
• Wildlife Safari Parks : These parks provide larger, more natural habitats for animals, allowing for more natural behaviors.

Advanced techniques, such as cryopreservation , are also used to preserve gametes (sperm and eggs) of threatened species in viable and fertile conditions for extended periods. In vitro fertilization and tissue culture methods are employed for propagating plants and ensuring their survival.

Global Commitments to Biodiversity Conservation

Significant international efforts have been made to promote biodiversity conservation. The historic Convention on Biological Diversity , known as The Earth Summit , was held in Rio de Janeiro in 1992. It called upon nations to implement measures for conserving biodiversity. At the World Summit on Sustainable Development in 2002, representatives from 190 countries pledged their commitment to achieving a significant reduction in biodiversity loss by 2010 at global, regional, and local levels.

Benefits of CBSE Class 12 Biology Notes Chapter 15 Biodiversity and Conservation

• Comprehensive Understanding : The notes provide a thorough overview of biodiversity and conservation, helping students grasp the key concepts, definitions and importance of biodiversity in ecosystems.
• Structured Learning : The notes are organized into clear sections, making it easier for students to follow the information and locate specific topics quickly such as types of biodiversity, patterns and conservation methods.
• Critical for Exams : Understanding the principles of biodiversity and conservation is important for CBSE Class 12 Biology exams, as it often includes questions related to these topics. The notes help students prepare effectively.
• Real-World Relevance : The content connects theoretical knowledge to real-world issues, emphasizing the significance of biodiversity for environmental health and human well-being, which can inspire students to care for the environment.
• Simplified Language : The notes use simple and clear language, making complex biological concepts more accessible to students enhancing their comprehension and retention of information.
• Preparation for Future Studies : A solid understanding of biodiversity and conservation lays the groundwork for students interested in pursuing further studies in environmental science, ecology or related fields.