WHere do New species come from?
A species is often defined as a group of individuals that actually or potentially interbreed in nature. That definition of a species might seem cut and dried, but it is not — in nature, there are lots of places where it is difficult to apply this definition.
/ Ii / Investigate
/ iII / Level Up!
During this lesson you will learn more about how the environment influences populations of organisms over multiple generations.
✎Notes:
- Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions.
- Traits that support successful survival and reproduction in the new environment become more common; those that do not become less common. Thus, the distribution of traits in a population changes.
- In separated populations with different conditions, the changes can be large enough that the populations, provided they remain separated (a process called reproductive isolation), evolve to become separate species.
/ IV / Choose your path
ACCOMPLISHED [+3 points]
The Carolina parakeet is an extinct species of small green neotropical parrot with a bright yellow head, reddish orange face, and pale beak that was native to the Eastern, Midwest, and Plains states of the United States. It was the only indigenous parrot within its range, as well as one of only three parrot species native to the United States. Reasonably explain how an environmental shift could cause this species to go extinct according to the process of natural selection. |
ADVANCED [+4 points]
Using data from one of the lab investigations use mathematical evidence to support an explanation of how natural selection may lead to increases or decreases of specific traits in populations over time (i.e. forkbird population changes, worm population changes, deer mouse population changes, or gummy bear population changes). |
EXPERT [+5 points]
Demonstrations of evolution by natural selection can be time consuming. Peter and Rosemary Grant and their colleagues have studied Galápagos finch populations every year since 1976 and have provided important demonstrations of the operation of natural selection. The Grants found changes from one generation to the next in the beak shapes of the medium ground finches on the Galápagos island of Daphne Major. The medium ground finch feeds on seeds. The birds have inherited variation in the bill shape with some individuals having wide, deep bills and others having thinner bills. Large-billed birds feed more efficiently on large, hard seeds, whereas smaller billed birds feed more efficiently on small, soft seeds. |
During 1977, a drought period altered vegetation on the island. After this period, the number of seeds declined dramatically; the decline in small, soft seeds was greater than the decline in large, hard seeds. The large-billed birds were able to survive better than the small-billed birds the following year.
The year following the drought when the Grants measured beak sizes in the much-reduced population, they found that the average bill size was larger. This was clear evidence for natural selection of bill size caused by the availability of seeds. The Grants had studied the inheritance of bill sizes and knew that the surviving large-billed birds would tend to produce offspring with larger bills, so the selection would lead to evolution of bill size. Subsequent studies by the Grants have demonstrated selection on and evolution of bill size in this species in response to other changing conditions on the island. Using the mean beak depth data above, accurately explain what you predict would happen to the mean beak depth of the birds on Daphine if there was a season of tremendous rainfall. |
/ V / Knowledge Check
Use the natural selection simulation and the directions below to answer the following question:
Simulation Directions
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/ VI / redemption pointsRemediation Points
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/ VI / enrichment bonusEnrichment Bonus
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/ VII / Next Level (✓) Checklist:
- Can you use data to describe how over many generations a species can adapt, or not, through the process of natural selection?
- Can you identify explanations for phenomena that include characteristics of a species that change over time by natural selection, traits that are better or do not support survival and reproduction in a new environment, and when environmental shifts are too extreme?
- From a given mathematical and/or computational representation can you identify population changes, distribution of specific traits over time, or environmental conditions from data and/or simulations?
- Can you analyze data to describe evidence that distributions of traits in populations can change over time in response to changes in environmental conditions?
- Can you describe that because there are multiple cause-and-effect relationships contributing to the phenomenon of adaptation each different cause is not possible to predict with 100% certainty?
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, MS-LS4-6
Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time. (Cause and Effect) [MS-LS4-6]
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, MS-LS4-6
Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time. (Cause and Effect) [MS-LS4-6]