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Chapter 5: Problem 1

What is natural selection? What conditions are necessary for natural selection to occur?

Short Answer

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Answer: Natural selection is the process by which organisms with certain advantageous traits are more likely to survive and reproduce than those without these traits, leading to a change in the population's genetic composition over time. The five primary conditions necessary for natural selection to occur are variation, inheritance, overproduction, differential survival and reproduction, and time.

Step by step solution

01

Definition of Natural Selection

Natural selection is the process by which organisms with certain advantageous traits are more likely to survive and reproduce than those without these traits. This, over time, leads to a change in the population's genetic composition, as more organisms with the advantageous traits pass on their genetic information to future generations.
02

Conditions Required for Natural Selection

There are five primary conditions necessary for natural selection to occur: 1.
03

Variation

For natural selection to take place, there must be variation in the traits or characteristics within a population. These variations may be physical, behavioral, or physiological and arise from genetic differences among individuals in the population. 2.
04

Inheritance

The variation must be heritable, meaning it can be passed down from parent to offspring through the genes. Only traits that have a genetic basis can be selected for or against through natural selection. 3.
05

Overproduction

In most species, more offspring are produced than can survive, leading to competition for limited resources. This overproduction of offspring creates a 'struggle for existence' among individuals, increasing the importance of advantageous traits to aid survival and reproduction. 4.
06

Differential Survival and Reproduction

Organisms with traits that are advantageous in a given environment are more likely to survive and reproduce than those without these traits. This is a core component of natural selection – the differential survival and reproduction of individuals based on their specific traits. 5.
07

Time

Natural selection does not happen overnight; it is a gradual process that occurs over multiple generations. As the advantageous traits are passed on and become more prevalent in a population, the overall genetic makeup of that population will change over time. By understanding the conditions necessary for natural selection to occur, we can gain a deeper comprehension of the mechanisms underlying the process of evolution and the development of life on Earth.

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Most popular questions from this chapter

How might genetic drift and inbreeding be important processes in the conservation of endangered species?

Why are small populations more prone to variations in allele frequency from generation to generation as a result of genetic drift than are large populations?

If the phenotype trait of an \(A a\) heterozygous individual is the same as that of an \(A A\) homozygous individual, which allele is recessive?

What is phenotypic plasticity?

David Reznick, an ecologist at the University of California at Riverside, studied the process of natural selection in populations of guppies (small freshwater fish) on the island of Trinidad. Reznick found that populations at lower elevations face the assault of predatory fish, whereas the populations at higher elevations live in peace because few predators can move upstream past the waterfalls. The average size of individuals in the higher-elevation waters is larger than the average size of guppies in the lower-elevation populations. Reznick hypothesized that the smaller size of individuals in the lower-elevation populations was a result of increased rates of predation on larger individuals; in effect, predation was selecting for smaller individuals in the population. To test this hypothesis, Reznick moved individuals from the lower elevations to unoccupied pools upstream, where predation was not a factor. Eleven years in these conditions produced a population of individuals that were on average larger than the individuals of the downstream populations. Is the study by Reznick an example of natural selection (does it meet the necessary conditions)? If so, what type of selection does it represent (directional, stabilizing, or disruptive)? Can you think of any alternative hypotheses to explain why the average size of individuals may have shifted through time as a result of moving the population to the upstream (higher-elevation) environment?
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