Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Evolution is the cumulative change in the heritable characteristics of a population over time. These changes are encoded in the DNA and passed from one generation to the next via alleles.
The fossil record provides evidence for evolution by revealing a sequence of organisms that matches the expected complexity. For example, the appearance of (a transitional fossil) shows the link between fish and tetrapods.
Selective breeding (artificial selection) of domesticated animals and crops shows that rapid evolutionary change can occur when specific heritable traits are selected for by humans, acting as a model for natural selection.
Homologous structures are anatomical features that are similar in structure but may perform different functions. They provide evidence for adaptive radiation and a common ancestor. The most prominent example is the pentadactyl limb found in amphibians, reptiles, birds, and mammals.
Speciation occurs when populations of a species become gradually more diverged due to different environmental pressures, eventually leading to reproductive isolation.
Continuous variation across the geographical range of related populations (clines) supports the concept of gradual divergence, as seen in the various species of gulls.
Industrial melanism in the peppered moth ( ) serves as an observable example of transient polymorphism and natural selection. Darker melanic forms () increased in frequency in polluted areas where tree bark was covered in soot, increasing their survival rate () compared to the light speckled form ().
📐Formulae
(Simpson's Diversity Index used to quantify biodiversity)
(Exponential growth model illustrating potential population pressure)
(Allele frequency representation in a population)
(Change in allele frequency over generations)
💡Examples
Problem 1:
Explain how the pentadactyl limb provides evidence for evolution and identify the type of evolution it represents.
Solution:
The pentadactyl limb is a homologous structure found in diverse taxa (). Despite different uses (e.g., wings for flight in bats, fins for swimming in whales, and hands for grasping in humans), the internal bone structure (humerus, radius, ulna, carpals, and digits) is fundamentally the same.
Explanation:
This represents divergent evolution through adaptive radiation. The similarity in structure implies a common ancestor, while the functional differences result from different selection pressures in various environments.
Problem 2:
Calculate the Simpson's Reciprocal Index for a forest where two species are found: Species A () and Species B (). Use the formula .
Solution:
Explanation:
A lower value for the Simpson's Reciprocal Index indicates lower diversity, as the community is heavily dominated by Species B.