Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Adaptive features are inherited functional, structural, or behavioral traits of an organism that increase its fitness.
Fitness is defined as the probability of an organism surviving and reproducing in the environment in which it is found.
Xerophytes are plants adapted to survive in habitats where is scarce. Their adaptations include thick waxy cuticles, sunken stomata, and leaf rolling to reduce the water potential gradient () and minimize transpiration.
Hydrophytes are plants adapted to live in aquatic environments. They often lack a thick cuticle and possess large air spaces, known as aerenchyma, to facilitate the diffusion of and and provide buoyancy.
Natural selection acts on variations within a population. Individuals with adaptive features (advantageous alleles) have a higher selective advantage, leading to the inheritance of these traits in the and generations.
Structural adaptations involve physical body parts (e.g., the humps of a camel storing fat), while behavioral adaptations involve actions (e.g., desert animals being nocturnal to avoid heat).
📐Formulae
💡Examples
Problem 1:
A species of plant lives in an arid environment with high temperatures and low rainfall (). Describe two structural adaptations this plant might possess to survive.
Solution:
- Sunken stomata located in pits. 2. A thick, waxy cuticle on the leaf epidermis.
Explanation:
Sunken stomata trap a layer of moist air (high humidity) outside the pore, which reduces the concentration gradient between the leaf and the atmosphere. The thick waxy cuticle acts as a barrier to non-stomatal transpiration, as lipids are hydrophobic.
Problem 2:
Explain why hydrophytes like the water lily () have stomata only on the upper surface of their leaves.
Solution:
The lower surface of the leaf is in direct contact with , which would prevent gas exchange. Placing stomata on the upper surface allows for the uptake of and release of into the atmosphere.
Explanation:
Gas exchange via diffusion is much faster in air than in water. Since the lower epidermis is submerged, stomata there would be ineffective for the exchange of required for photosynthesis.
Problem 3:
In a population of beetles, some individuals are green and others are brown. Birds easily spot and eat the green beetles on the brown forest floor. Over time, the frequency of the brown allele increases. What process is occurring?
Solution:
Natural Selection.
Explanation:
The brown color is an adaptive feature providing camouflage. Beetles with the brown phenotype have higher fitness, meaning they survive longer and produce more offspring, passing the 'brown' alleles to the next generation.