Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Adaptive features are inherited functional or structural features of an organism that increase its fitness ( ).
Xerophytes are plants adapted to survive in environments with limited liquid water. Key adaptations include a thick waxy cuticle to reduce evaporation, sunken stomata to trap moist air, and a reduced leaf surface area to volume ratio ().
Hydrophytes are plants adapted to live in aquatic environments. They often possess large air spaces called to allow and to diffuse to submerged parts and to provide buoyancy.
Natural Selection is the process by which individuals with favorable phenotypes are better suited to their environment, making them more likely to survive and pass on their alleles to the next generation.
Variation is the differences between individuals of the same species. It can be phenotypic (caused by both genes and environment) or genotypic (caused by mutations and meiosis).
Discontinuous variation results in a limited number of distinct phenotypes with no intermediates (e.g., blood groups), usually controlled by a single gene.
Continuous variation results in a range of phenotypes between two extremes (e.g., human height), often influenced by multiple genes () and environmental factors.
📐Formulae
💡Examples
Problem 1:
Calculate the surface area to volume ratio of a spherical cactus with a radius and compare it to a flat leaf of the same volume. Explain which is a better adaptation for a xerophyte.
Solution:
For the sphere: . . Ratio . A flat leaf has a much higher for the same .
Explanation:
A lower ratio reduces the area available for loss via transpiration, which is a vital adaptive feature for survival in arid climates.
Problem 2:
In a population of beetles, a mutation occurs in the sequence of a gene controlling shell color. If the environment changes to favor dark-colored beetles, how does the allele frequency change?
Solution:
The frequency of the dark-shell allele will increase over generations as dark beetles have higher fitness ().
Explanation:
Dark beetles are better camouflaged from predators, leading to differential survival. They survive to reproduce and pass the 'dark' allele to offspring, illustrating natural selection.