A4.2.1—Biodiversity as the variety of life in all its forms, levels and combinations

Biodiversity: The Tapestry of Life

Biodiversity, the variety of life on Earth, is a marvel of nature. It exists at multiple levels, from the genetic diversity within species to the rich tapestry of ecosystems. Ecosystem diversity encompasses the varied combinations of species living together in communities, shaped by diverse environments and geographical ranges. Species diversity reflects the evolutionary tree of life, with countless species exhibiting unique body plans, internal structures, life cycles, and nutritional modes. Genetic diversity within species, both between populations and within populations, is essential for adaptation and survival. Species with limited genetic diversity face increased vulnerability to threats like inbreeding and environmental change.

The preservation of biodiversity is crucial for our planet’s health and well-being. It provides us with essential ecosystem services, such as clean air and water, fertile soil, and climate regulation. Protecting biodiversity means safeguarding the intricate web of life that supports all living things, including ourselves.

Additional Interesting Facts:

• Over 8 million species may exist on Earth, although only about 2 million have been identified.
• Tropical rainforests are biodiversity hotspots, home to a significant portion of the world’s species.
• Human activities, such as habitat destruction and climate change, are major threats to biodiversity.

A4.2.2—Comparisons between current number of species on Earth and past levels of biodiversity

Earth’s history is marked by periods of flourishing biodiversity interspersed with mass extinctions. While millions of species exist today, many remain undiscovered. Fossil records reveal five major extinction events, with the most recent one wiping out the non-avian dinosaurs 66 million years ago. Between these catastrophic events, biodiversity generally increases gradually. Currently, we’re experiencing a period of high biodiversity, but human activities threaten to trigger a sixth mass extinction.

A4.2.3—Causes of anthropogenic species extinction

Anthropogenic means caused by humans or originating from human activity.

Human activities have significantly accelerated the rate of species extinction. Primary causes contribute to this alarming trend:

1. Overexploitation:

• Excessive harvesting of plants and animals for food, medicine, or other resources.
• Overfishing, particularly of large predatory fish, has depleted marine ecosystems.
• Illegal hunting and poaching threaten numerous species, including elephants, rhinos, and tigers.

2. Habitat Destruction:

• Deforestation, agriculture, and urbanization destroy natural habitats, fragmenting populations and reducing biodiversity.
• Conversion of forests and grasslands into agricultural land leads to habitat loss and fragmentation.