Adaptive features

An adaptive feature is an inherited characteristic that helps an organism survive or reproduce in its environment. It may help the organism deal with a particular condition or make use of a resource it needs.

Whether a feature is adaptive depends on the conditions the organism faces. For example, thick fur can help a polar bear survive in a cold environment by reducing heat loss. The explanation connects the feature to a condition and then to a benefit for survival; simply saying that the bear has thick fur does not explain why the feature is adaptive.

Identifying an adaptive feature

An image or other information about a species can suggest a possible adaptive feature. To describe it as adaptive, identify the feature, the relevant environmental condition, and how the feature helps the organism survive or reproduce there.

An image may show a characteristic, but it does not by itself establish that the characteristic is inherited or that it is beneficial. Other information may be needed to support those claims.

Hydrophyte adaptations

Hydrophytes are plants adapted to living in water or in waterlogged conditions. Water is readily available to them, so preventing water loss is often less of a challenge than obtaining gases and functioning while submerged.

Air spaces within a hydrophyte’s tissues can help it float by providing buoyancy. They also provide pathways through which gases can move to submerged parts of the plant.

Floating leaves may have stomata on their upper surfaces. These small pores are exposed to the air, allowing gases to pass between the leaf and the air. Stomata on the lower surface would be in contact with water rather than air.

Submerged parts may have a thin waxy cuticle or no cuticle. This leaves less of a barrier across the surface, allowing gases to diffuse between the water and the plant.

These features are adaptations because they help hydrophytes survive and reproduce in aquatic conditions.

Xerophyte adaptations

Xerophytes are plants adapted to environments where water is scarce. Their features help them conserve water, take it up from the soil or keep it available for later use.

Reducing water loss

Water evaporates from leaves and is lost mainly through tiny pores called stomata. This loss of water is called transpiration. Xerophytes can reduce water loss in several ways:

• A thick waxy cuticle forms a barrier over the leaf surface, reducing evaporation from that surface.
• Reduced leaf area provides less surface through which water can be lost.
• Sunken stomata lie in pits in the leaf surface. Water vapour can collect in the pits, so the air around the stomata remains humid. This reduces the rate at which water vapour diffuses out of the leaf.

Obtaining and storing water

An extensive root system reaches through a large volume of soil, helping the plant take up available water. Some xerophytes also store water in fleshy tissues, such as those in their stems or leaves. This stored water remains available when water in the environment is scarce.

Together, these adaptations help a xerophyte maintain a water supply in dry conditions, supporting its survival and reproduction.