Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Adaptive Radiation is the process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats).
It is a classic example of divergent evolution, where a common ancestor gives rise to multiple forms to exploit different ecological niches.
Darwin's Finches: On the Galapagos Islands, Darwin observed that the original seed-eating finches evolved into various forms such as insectivorous and vegetarian finches, with beaks modified for different food sources.
Australian Marsupials: A diverse range of marsupials evolved from a single ancestral stock within the Australian continent, including the Kangaroo, Sugar Glider, and Marsupial Mole.
Convergent Evolution: When more than one adaptive radiation occurs in isolated geographical areas (representing similar habitats), different groups of organisms may evolve similar features. Example: Placental mammals in North America and Marsupial mammals in Australia (e.g., Placental Wolf and Tasmanian Wolf).
The survival of certain traits during radiation is often influenced by natural selection, which acts upon the phenotypic variations within a population.
📐Formulae
💡Examples
Problem 1:
Explain why the beaks of Darwin's finches are considered a prime example of adaptive radiation.
Solution:
The beaks represent morphological adaptations to different feeding habits.
Explanation:
From an original seed-eating ancestor, various species evolved with beak shapes specialized for eating seeds, insects, or cactus fruit. This radiation from a single point to fill multiple ecological niches on the Galapagos Islands is the definition of adaptive radiation.
Problem 2:
In a population of finches, the frequency of a recessive allele for a small beak () is . According to the Hardy-Weinberg principle, what is the frequency of the homozygous dominant genotype ()?
Solution:
Explanation:
Since , we find . The frequency of the homozygous dominant genotype is .
Problem 3:
The Marsupial Mole and the Placental Mole are not closely related but look similar. Name the evolutionary phenomenon and explain its cause.
Solution:
Convergent Evolution.
Explanation:
Both organisms independently underwent adaptive radiation in similar ecological niches (burrowing/subterranean) in different geographical locations (Australia vs. other continents). This led to the selection of similar adaptive traits, despite different ancestral lineages.