HS-LS4-4. Construct an explanation based on evidence for how natural selection leads to adaptation of populations.

Natural selection is a key mechanism of evolution that drives the adaptation of populations to their environments. This review sheet will explore how natural selection leads to changes in gene frequencies within populations and how these changes result in adaptation. We will focus on using data to understand how biotic and abiotic factors contribute to these evolutionary changes.

Main Concepts

Natural Selection: Natural selection is the process where individuals with advantageous traits are more likely to survive and reproduce. Over time, these traits become more common in the population. This process is driven by the differential survival and reproduction of organisms based on their traits.

Adaptation: Adaptation is the process by which a population becomes better suited to its environment. It results from the accumulation of advantageous traits over generations, which enhance the organisms' ability to survive and reproduce in specific environmental conditions.

Biotic and Abiotic Factors:

• Biotic Factors: These include interactions with other organisms such as competition, predation, and symbiosis. Changes in these interactions can influence which traits are advantageous.
• Abiotic Factors: These include non-living environmental factors such as temperature, climate, acidity, light, and geographic barriers. Variations in these factors can affect which traits provide survival advantages.

Change in Gene Frequency: Natural selection leads to changes in gene frequencies within a population. Over time, alleles that contribute to advantageous traits increase in frequency, while those associated with less favorable traits decrease.

Evidence for Adaptation: Data supporting adaptation can include observations of changes in trait distributions, survival rates, and reproductive success related to specific environmental factors. Statistical analysis and graphical representations help illustrate these changes and their impact on gene frequencies.

NGSS Aligned Testing Question

One potential source of stress on coral reefs is atmospheric carbon dioxide, which dissolves in the seawater forming carbonic acid. When excess carbon dioxide is present, it changes the acidity of ocean water and the availability of calcium carbonate for organisms to build and maintain their shells, skeletons, and other calcium carbonate-based structures. Research shows that another stressor is the current trend of the large-scale temperature change in oceans. This causes the zooxanthellae to either leave or be ejected from the coral polyps. The graphs below show changes in ocean conditions over the past century.

Some species of zooxanthellae and coral have traits that make them more tolerant of changes to the temperature of the water in which they live. Scientists are experimenting with selective breeding of these species of coral and zooxanthellae to produce a coral that would be more likely to survive changing ocean temperatures.

	Identify the explanation that best describes how the coral and zooxanthellae populations would be expected to change if the current trend in water temperatures were to continue over several generations within the coral reef.
1	The proportion of coral and zooxanthellae that can tolerate higher water temperatures will increase because they will survive at a higher rate than those that are sensitive to temperature changes.
2	The coral will eject zooxanthellae that are sensitive to cold water temperatures so that less sensitive algae may take their place.
3	The proportion of coral and zooxanthellae that are cold water tolerant will increase because they will have greater access to calcium carbonate to build stronger outer skeletons.
4	The coral will take in zooxanthellae that are sensitive to high water temperatures so that there is less of a chance that they will develop deformed outer shells.

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Review Questions and Answers

1. What is natural selection and how does it lead to adaptation?

Natural selection is the process where individuals with advantageous traits are more likely to survive and reproduce. Over time, these traits become more common in the population, leading to adaptation as the population becomes better suited to its environment.

2. How do biotic factors influence natural selection and adaptation?

Biotic factors such as competition, predation, and symbiosis can affect which traits are advantageous. For example, a predator's presence may favor traits that enhance camouflage, leading to increased survival and adaptation in the prey population.

3. What role do abiotic factors play in the adaptation of populations?

Abiotic factors like temperature, climate, and light influence which traits are advantageous. For example, in a colder climate, individuals with traits for better insulation may have a survival advantage, leading to adaptation to the colder environment.

4. What is meant by change in gene frequency in the context of natural selection?

Change in gene frequency refers to the shift in the proportion of different alleles in a population over time. Natural selection increases the frequency of alleles associated with advantageous traits and decreases the frequency of alleles associated with less favorable traits.

5. How can data be used to provide evidence for adaptation?

Data can be used to track changes in trait distributions, survival rates, and reproductive success. Graphs, statistical analyses, and comparisons over time provide evidence that certain traits are becoming more common due to their advantages in specific environmental conditions.

6. What types of graphical representations can illustrate changes in trait frequencies?

Graphs such as line graphs, bar charts, and histograms can illustrate changes in trait frequencies. These visualizations help depict how the proportion of individuals with certain traits changes over time in response to natural selection.

7. What is the significance of geographic barriers in natural selection and adaptation?

Geographic barriers can isolate populations, leading to different selective pressures in each isolated environment. This isolation can result in distinct adaptations as populations evolve separately in response to their unique environmental conditions.

8. How do changes in environmental conditions contribute to adaptation?

Changes in environmental conditions can alter which traits are advantageous. For example, a change in climate can make certain traits more beneficial, leading to increased survival and reproduction of individuals with those traits and subsequent adaptation of the population.

9. Why is it important to analyze evidence from multiple sources to understand adaptation?

Analyzing evidence from multiple sources, such as field studies, experiments, and historical data, provides a more comprehensive understanding of how adaptation occurs. It helps validate findings and build a robust explanation of how natural selection drives evolutionary change.

10. How does natural selection contribute to evolutionary change over time?

Natural selection contributes to evolutionary change by favoring individuals with advantageous traits, leading to an increase in the frequency of these traits in the population. Over time, this process results in populations adapting to their environments and evolving in response to selective pressures.

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Disclaimer: The information provided is intended to serve as a study guide based on a contextual analysis of the NGSS standards for the Life Science Biology assessment. These study guides should be used as a supplement to your overall study strategy, and their alignment to the actual test format is not guaranteed. We recommend that you consult with your instructor for additional guidance on exam preparation.