Unit 5: Adaptive Ecology and Biogeography

Adaptive ecology focuses on how plants adjust to environmental variations to ensure survival and reproduction.

Key Concepts

• Variations: Differences in traits among individuals of a species, which can be genetic or environmental.
• Adaptation: The process by which plants develop structural or functional features that enhance their fitness in a specific environment.

The Theory of Tolerance (Shelford's Law of Tolerance) suggests that an organism's success is based on a complex set of environmental conditions.

Each organism has a minimum, maximum, and optimum environmental factor limit or range of tolerance for survival.

• Stenotopic: Organisms with a narrow range of tolerance for a factor.
• Eurytopic: Organisms with a wide range of tolerance for a factor.

Continental drift describes the movement of Earth's continents relative to each other over geological time.

• Impact on Plant Distribution: As landmasses separated, plant populations became isolated, leading to divergent evolution and the current distribution of flora globally.

Endemism refers to species that are native to a single defined geographic location and are not found anywhere else.

• Paleoendemism: Species that were formerly widespread but are now restricted to a small area.
• Neoendemism: Species that have recently evolved and have not yet spread beyond their original area.

India is characterized by diverse biogeographical zones, each with distinct biomass and environmental conditions.

Major Zones Include:

• The Trans-Himalaya and The Himalayas.
• The Indian Desert and The Semi-Arid zones.
• The Western Ghats.
• The Deccan Peninsula.
• The Gangetic Plain.
• The Coasts and The Islands.
• North-East India.

Phytogeography deals with the geographical distribution of plant species. India is divided into several phytogeographical regions based on climate and vegetation.

Local Vegetation Focus: North-East India

North-East India is a biodiversity hotspot characterized by high rainfall and diverse topography, resulting in rich vegetation types ranging from tropical evergreen forests to alpine meadows.

7. Exam Focus: Tips and FAQs

Common Pitfalls

• Mistake: Confusing "Endemism" with "Native." Correction: Native species can be found in multiple regions; endemic species are found only in one specific location.
• Mistake: Overlooking the role of "Continental Drift" in modern plant science. Correction: It is the historical foundation of why similar plants are found on different continents (e.g., South America and Africa).

Frequently Asked Questions

Q: What is the difference between Eurytopic and Stenotopic organisms?
A: Eurytopic organisms have a wide tolerance range (e.g., can live in many temperatures), while Stenotopic organisms have a very narrow range and are easily affected by change.

Q: Why is North-East India significant phytogeographically?
A: It serves as a transition zone between the Indian, Indo-Malayan, and Indo-Chinese biogeographical regions, harboring high levels of endemism and species richness.