IB Biology Topic A4.2.8: Evolutionarily Distinct and Globally Endangered Species in Conservation Prioritization Notes

EDGE Species: Evolutionarily Distinct and Globally Endangered Species Deserve Priority

1. EDGE species, Evolutionarily Distinct and Globally Endangered, represent some of the rarest and most valuable species on earth.

Evolutionary Distinctness: Some Species Sit Alone on Ancient Branches of the Tree of Life

1. Some species belong to large families with many close relatives, like cats, dogs, or rodents.
2. Others, however, stand alone on ancient evolutionary branches, having evolved independently for millions of years.

1. Key Features of Evolutionary Distinct Species
2. Unique Traits: EDGE species often have characteristics found nowhere else in the animal kingdom.
   1. For example, the axolotl can regenerate entire body parts, a trait with significant scientific value.
3. Rare Lineages: Some species represent the sole surviving members of ancient evolutionary branches.
   1. For instance, the Yangtze giant softshell turtle or the kakapo.
4. Vulnerability: Once lost, these lineages cannot be recovered, erasing a unique piece of evolutionary history forever.

Global Endangerment: Small Populations, Restricted Ranges, and Human Threats Push Species Toward Extinction

1. Global endangerment refers to the high risk of extinction a species faces.
2. Factors contributing to this status include:
   1. Small or Declining Populations: The vaquita porpoise has fewer than 10 individuals left, making it the most endangered marine mammal in the world.
   2. Restricted Ranges: The pygmy three-toed sloth exists only on one island in Panama, making it highly vulnerable to habitat destruction.