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During breeding season, many female elk mate with males, but not all mated females become pregnant. Female elk having body fat less than 6% were found to have greatly reduced chances of becoming pregnant than female elk having body fat above 10%. Explain how natural selection was likely involved in establishing this trait in elk. (credit: USGS Northern Prairie Wildlife Research Center) a. Through natural selection, female elk that did not have the energy reserves to carry a pregnancy to term and did not become pregnant died whereas those which became pregnant anyway were favored. b. Natural selection favored the selection of traits preventing pregnancies in female elk with low fat reserves, so this trait has become predominant in natural elk herds observed today. c. Natural selection randomly changes the frequency of genes allowing traits preventing pregnancies in female elk with low fat reserves to be favored. d. Natural selection leads to a sudden inheritable change in the genome of the female elk, ensuring female elk with very high fat reserves to effectively carry out pregnancy.

Step by step solution

01

Understand the Problem

Identify how natural selection might influence the reproductive success of female elk based on their body fat percentage.

02

Identify Key Information

Females with less than 6% body fat have reduced chances of becoming pregnant. Females with more than 10% body fat have better chances of becoming pregnant.

03

Analyze the Choices

Review each answer choice to see which best explains natural selection's role in favoring traits related to body fat and pregnancy in female elk.

04

Eliminate Incorrect Options

a. Incorrect - It suggests that females who do not become pregnant died, which is not necessarily required for natural selection. d. Incorrect - It proposes a sudden genetic change, which is not characteristic of natural selection.

05

Compare Remaining Options

b. Correct - Natural selection favors traits that enhance reproductive success, so traits preventing pregnancies in females with low fat reserves would become predominant. c. Incorrect - Natural selection is not a random process; it involves differential survival and reproduction based on traits.

06

Conclusion

The best explanation is that natural selection favored traits that prevent pregnancies in female elk with low fat reserves, enhancing the overall fitness of the population.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

natural selection

Natural selection is a key mechanism of evolution. It explains how traits that increase an organism's chances of survival and reproduction become more common in a population over time. This process occurs because individuals with beneficial traits are more likely to survive, reproduce, and pass these traits to their offspring. Over generations, natural selection can lead to adaptations that fit organisms better to their environment. For the elk population, females with higher body fat percentage are more likely to thrive and reproduce, increasing the frequency of this trait in the herd.

body fat percentage

Body fat percentage is a measure of the fat content in an animal's body, expressed as a percentage of its total weight. In the context of elk reproduction, the body fat percentage is crucial. Female elk need sufficient energy reserves to support themselves during pregnancy and lactation. Females with less than 6% body fat struggle to get pregnant because they do not have enough reserves to sustain a pregnancy. Conversely, those with more than 10% body fat have better energy reserves, making pregnancy more likely. This difference in energy reserves directly affects their reproductive success and survival.

elk reproduction

Elk reproduction is highly influenced by the physical condition of the female elk, particularly their body fat percentage. During the breeding season, female elk mate with males, but not all females that mate become pregnant. The likelihood of pregnancy is greatly reduced for females with less than 6% body fat. This is because they lack the necessary energy reserves for pregnancy. On the other hand, females with more than 10% body fat have a better chance of becoming pregnant. This results in healthier offspring who inherit better fat reserve traits, ensuring the continuation of these favorable traits within the population.

evolutionary fitness

Evolutionary fitness refers to an organism's ability to survive and reproduce, passing on their genes to the next generation. It doesn't necessarily mean the strongest or fastest, but the most adaptable to their environment. In the case of elk, females with higher body fat percentages exhibit higher evolutionary fitness. They can sustain pregnancies, ensuring the birth and survival of their calves. This reproductive success allows their genes to spread in the population. Over generations, natural selection will favor these traits, leading to an increase in the average body fat percentage of females in the elk population, enhancing the herd’s overall fitness.