Adaptations

Overview

Adaptations are the fascinating characteristics that allow organisms to survive and thrive in their specific environments, from the freezing poles to scorching deserts. This topic, 7.5 in the OCR specification, is a cornerstone of biology, linking directly to evolution, ecology, and genetics. Examiners frequently test this area using application-based questions (AO2), often presenting candidates with unfamiliar organisms and asking them to predict their adaptations. A solid grasp of the three core types of adaptation—structural, behavioural, and functional—is essential. Furthermore, this topic introduces a key mathematical skill: calculating and interpreting the surface area to volume ratio (SA:V), which is crucial for explaining how animals regulate heat. Mastering this guide will equip you to deconstruct complex questions, apply your knowledge confidently, and use the precise scientific language required to earn maximum credit.

Key Concepts

Concept 1: The Three Types of Adaptation

Examiners require you to classify adaptations into three distinct categories. Getting this right is often worth the first mark in a longer question.

• Structural Adaptations: These are physical features of an organism's body. Think of them as the 'hardware' of the animal or plant. For example, a polar bear's thick white fur provides both camouflage and insulation.
• Behavioural Adaptations: These are the actions or activities an organism performs to increase its chance of survival. For instance, meerkats huddle together for warmth, and many desert animals are nocturnal, only coming out at night to avoid the daytime heat.
• Functional Adaptations: These are internal processes related to how an organism's body works (its metabolism or biochemistry). A key example is the production of antifreeze proteins in the blood of some arctic fish, which prevents ice crystals from forming in their cells. This is a common point of confusion; remember, if it's a process happening inside the body, it's functional.

Concept 2: Surface Area to Volume Ratio (SA:V)

This is a fundamental concept that explains how an organism's size affects its ability to retain or lose heat. The rate of heat transfer is proportional to the surface area, while the amount of heat generated is proportional to the volume. Therefore, the ratio between these two values is critical.

• High SA:V Ratio: Small organisms have a large surface area compared to their volume. This means they lose heat to their surroundings very quickly. A mouse, for example, must eat constantly to fuel its high metabolic rate to stay warm.
• Low SA:V Ratio: Large organisms have a small surface area compared to their volume. This makes them very efficient at retaining heat. An elephant in a hot climate faces the opposite problem: it can overheat easily. Adaptations like its large, thin ears increase its surface area to help it radiate heat away.

Mathematical/Scientific Relationships

Surface Area to Volume Ratio Calculation (Must Memorise)

For a simple cube, the formulas are:

• Surface Area (SA) = 6 x (side length)^2
• Volume (V) = (side length)^3
• Ratio = SA : V (simplified to n:1)

Example Calculation:
For a cube with a side length of 2 cm:

• SA = 6 x (2)^2 = 24 cm^2
• V = (2)^3 = 8 cm^3
• Ratio = 24:8. To simplify, divide both sides by the volume (8), giving a final ratio of 3:1.

Candidates must show their working for SA and V separately and then present the simplified ratio to be awarded full marks.

Practical Applications

Extremophiles

Extremophiles are organisms adapted to survive in extreme conditions, such as high temperatures (thermophiles), high pressures (piezophiles), or high salt concentrations (halophiles). OCR might present you with a question about a newly discovered bacterium living in a volcanic vent.

How to approach this: Apply your knowledge. A thermophile might have functional adaptations like heat-stable enzymes that don't denature at 100°C. A halophile living in a salty lake might have functional adaptations to actively pump salt out of its cells to prevent water loss by osmosis. These are perfect examples of applying the core principles to an unfamiliar context.