Adaptive Colouration and its Functions | Biology for JAMB PDF Download

Objective

By the end of this note, candidates should be able to categorize countershading in fish, toads, and snakes, as well as understand the concept of warning colouration in mushrooms, with suitable examples.

Introduction

Adaptive colouration is a fascinating phenomenon observed in various organisms, enabling them to blend into their surroundings or communicate important messages. In this note, we will explore two types of adaptive colouration: countershading and warning colouration, focusing on fish, toads, snakes, and mushrooms.

Countershading in Fish, Toads, and Snakes

Countershading is a form of camouflage where an organism exhibits a darker coloration on its dorsal (upper) side and a lighter coloration on its ventral (lower) side. This adaptation helps organisms to blend into their environment and provides protection against predators.

• Fish:The Atlantic herring is a classic example of countershading. Its dark-colored back helps it blend with the dark ocean depths when viewed from above, while its lighter belly matches the brightness of sunlight when viewed from below.
• Toads: Many species of toads exhibit countershading. For instance, the American toad has a darker upper body, which helps it blend into the surrounding leaf litter or vegetation, while its lighter underside matches the brightness of the sky when viewed from below.
• Snakes: Countershading is also observed in certain snake species. The green tree python showcases this adaptation with its darker green dorsal scales that blend with the foliage, while its lighter ventral scales match the brightness of the sky.

Warning Colouration in Mushrooms

Warning colouration, also known as aposematism, is a defensive strategy where organisms display bright or striking colours to signal potential danger or toxicity to predators. This adaptation warns predators that they are unpalatable or harmful, thus discouraging attacks.

Example: Mushrooms - Many mushrooms exhibit warning colouration. The Fly Agaric (Amanita muscaria), with its iconic red cap and white spots, serves as a prominent example. This striking colouration warns animals that it contains toxic compounds, deterring them from consuming it.

Conclusion

Adaptive colouration plays a crucial role in the survival and success of organisms. Countershading helps fish, toads, and snakes blend into their surroundings, providing camouflage and protection from predators. On the other hand, warning colouration in mushrooms serves as a visual signal to predators, indicating potential toxicity. Understanding these adaptive colouration mechanisms expands our knowledge of the fascinating strategies organisms employ in their struggle for survival in diverse environments.