PCAT Biological Processes – Natural Selection
- Dec 18, 2017
- PCAT Question of the Day
The Modern Synthesis in evolutionary biology reflects the current consensus about how evolution proceeds. According to the Modern Synthesis, which of the following is a correct characterization of a principle of natural selection?
A) Most mutations that occur in a species that is well-adapted to its niche are likely to be harmful.
B) Those individuals within a species that reproduce in the greatest numbers are fittest.
C) Genetic drift has no impact on the overall gene distribution in a population.
D) Ecosystems across all niches can only support a finite population of each organism.
Click for Explanation
One of the basic assumptions of natural selection is that organisms produce more offspring than the environment is capable of supporting. Then, some of those individuals survive to reproduce and others don’t – which survive are controlled by natural selection through environmental forces. That best matches choice (D).
A) False. Most mutations are silent or neutral as they occur in “junk DNA” or non-coding regions of the genome.
B) Tempting, but not technically true. Fitness is determined by the number of fertile offspring that survive to reproduce, not simply the total number of offspring.
C) Genetic drift is a form of random change in the gene distribution.
Search the Blog
Free ConsultationSchedule Now
MCAT Blog How to Review MCAT Full-Lengths
Free MCAT Practice AccountNeed great MCAT practice?
Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.Learn More