The history of the Earth has been divided by scientists into eras. Which geologic time scale shows the arrangement of these eras into the proper sequence from the oldest to the most recent? Cenozoic, Mesozoic, Paleozoic, Precambrian Precambrian, Paleozoic, Mesozoic, Cenozoic Paleozoic, Cenozoic, Precambrian, Mesozoic Precambrian, Mesozoic, Cenozoic, Paleozoic Question 36 1 pt Which of the following mechanisms will greatly affect changes in organisms with small populations? gene frequency sexual selection natural selection genetic drift gene flow
The Correct Answer and Explanation is:
- Geologic Time Scale Sequence:
The correct sequence for the geologic time scale, from the oldest to the most recent, is: Precambrian, Paleozoic, Mesozoic, Cenozoic.Explanation:
The Earth’s history is divided into four major eons, which are further subdivided into eras. The Precambrian, which is the oldest and longest era, makes up about 88% of Earth’s history. It is followed by three subsequent eras: the Paleozoic, Mesozoic, and Cenozoic.- Precambrian: This spans from the formation of the Earth (about 4.6 billion years ago) until approximately 541 million years ago. During this time, life began to form and evolve.
- Paleozoic: This era lasted from 541 million years ago to about 252 million years ago. It saw the development of many complex life forms, including the first fish, amphibians, and reptiles.
- Mesozoic: Known as the age of dinosaurs, it lasted from 252 million to 66 million years ago.
- Cenozoic: This era, which continues today, began about 66 million years ago and includes the rise of mammals and humans.
- Mechanism Affecting Small Populations:
The mechanism that will greatly affect changes in organisms with small populations is genetic drift. Explanation:
Genetic drift refers to the random changes in allele frequencies that occur in small populations due to chance events. This is especially significant in smaller populations because the genetic diversity is lower, and small events (like a natural disaster) can dramatically alter the gene pool.- Gene frequency refers to the proportion of different alleles in a population, but it is not a mechanism itself.
- Sexual selection is a form of natural selection where individuals with traits that are more attractive to mates are more likely to reproduce. It typically has a more substantial impact in larger populations.
- Natural selection acts on traits that increase an organism’s fitness, but its effect depends on environmental pressures and does not directly focus on population size.
- Genetic drift is more pronounced in small populations because each individual represents a larger proportion of the population’s gene pool. For instance, if a few individuals happen to die by chance, their alleles may be lost from the population entirely.
