WHY DO SOME SPECIES SURVIVE AND WHY DO SOME SPECIES GO EXTINCT?
Natural selection is the result of four factors:
(1) the potential for a species to increase in number
(2) the genetic variation of individuals in a species due to mutation and sexual reproduction
(3) competition for an environment’s limited supply of the resources that individuals need in order to survive and reproduce
(4) the ensuing proliferation of those organisms that are better able to survive and reproduce in that environment.
(1) the potential for a species to increase in number
(2) the genetic variation of individuals in a species due to mutation and sexual reproduction
(3) competition for an environment’s limited supply of the resources that individuals need in order to survive and reproduce
(4) the ensuing proliferation of those organisms that are better able to survive and reproduce in that environment.
Natural selection leads to adaptation—that is, to a population dominated by organisms that are anatomically, behaviorally, and physiologically well suited to survive and reproduce in a specific environment. That is, the differential survival and reproduction of organisms in a population that have an advantageous heritable trait leads to an increase in the proportion of individuals in future generations that have the trait and to a decrease in the proportion of individuals that do not. Adaptation also means that the distribution of traits in a population can change when conditions change.
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Changes in the physical environment, whether naturally occurring or human induced, have thus contributed to the expansion of some species, the emergence of new distinct species as populations diverge under different conditions, and the decline—and sometimes the extinction—of some species. Species become extinct because they can no longer survive and reproduce in their altered environment. If members cannot adjust to change that is too fast or too drastic, the opportunity for the species’ evolution is lost such as many of the dinosaurs.
Topic Summary:
When an environment changes, there can be subsequent shifts in its supply of resources or in the physical and biological challenges it imposes. Some individuals in a population may have morphological, physiological, or behavioral traits that provide a reproductive advantage in the face of the shifts in the environment. Natural selection provides a mechanism for species to adapt to changes in their environment. The resulting selective pressures influence the survival and reproduction of organisms over many generations and can change the distribution of traits in the population. This process is called adaptation. Adaptation can lead to organisms that are better suited for their environment because individuals with the traits adaptive to the environmental change pass those traits on to their offspring, whereas individuals with traits that are less adaptive produce fewer or no offspring. Over time, adaptation can lead to the formation of new species. In some cases, however, traits that are adaptive to the changed environment do not exist in the population and the species becomes extinct. Adaptive changes due to natural selection, as well as the net result of speciation minus extinction, have strongly contributed to the planet’s biodiversity. Adaption by natural selection is ongoing. For example it is seen in the emergence of antibiotic-resistant bacteria. Organisms like bacteria, in which multiple generations occur over shorter time spans, evolve more rapidly than those for which each generation takes multiple years.
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* Mastery Check *
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COLLEGE & CAREERS
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YOU CAN APPLY THESE SKILLS BY:
- Follow a career as an infectious disease doctor that treats illnesses anywhere in the body that are caused by microorganisms.
- Follow a career as a museum technician, designing exhibits to teach the public about science.
- Use your understanding to use artificial selection in agriculture, farming, or pet animals to create species with desired traits.
- Follow a career in scientific research studying the origin of life and developing a greater understanding of the process of evolution.
National Research Council 2012. A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas. Washington, DC: The National Academies Press. https://doi.org/10.17226/13165
This site contains original content that may not be authorized for use by the creator and is legally used under the fair use principles section 107 of the Copyright Act of 1986 (17 U.S. Code § 107)
The official NGSS website. https://www.nextgenscience.org
LS4.C, 3-LS4-3, MS-LS4-6, HS-LS4-3, HS-LS4-4
Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait. (Patterns)
Construct an explanation based on evidence for how natural selection leads to adaptation of populations. (Cause and Effect)
Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1) increases in the number of individuals of some species, (2) the emergence of new species over time, and (3) the extinction of other species. (Cause and Effect)
This site contains original content that may not be authorized for use by the creator and is legally used under the fair use principles section 107 of the Copyright Act of 1986 (17 U.S. Code § 107)
The official NGSS website. https://www.nextgenscience.org
LS4.C, 3-LS4-3, MS-LS4-6, HS-LS4-3, HS-LS4-4
Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait. (Patterns)
Construct an explanation based on evidence for how natural selection leads to adaptation of populations. (Cause and Effect)
Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1) increases in the number of individuals of some species, (2) the emergence of new species over time, and (3) the extinction of other species. (Cause and Effect)