• Skip to primary navigation
  • Skip to main content
  • Skip to footer
  • About
  • Image & Use Policy
  • Translations
  • Glossary

SUPPORT UE

  • Email
  • Facebook
  • Twitter

UC MUSEUM OF PALEONTOLOGY

UC Berkeley logoUC Berkeley

Understanding Evolution

Understanding Evolution

Your one-stop source for information on evolution

Understanding Evolution

  • Home
  • Evolution 101
    • An introduction to evolution: what is evolution and how does it work?
      • 1_historyoflife_menu_iconThe history of life: looking at the patterns – Change over time and shared ancestors
      • 2_mechanisms_menu_iconMechanisms: the processes of evolution – Selection, mutation, migration, and more
      • 3_microevo_menu_iconMicroevolution – Evolution within a population
      • 4_speciation_menu_iconSpeciation – How new species arise
      • 5_macroevo_menu_iconMacroevolution – Evolution above the species level
      • 6_bigissues_menu_iconThe big issues – Pacing, diversity, complexity, and trends
  • Teach Evolution
    • Lessons and teaching tools
      • Teaching Resources
      • Image Library
      • Using research profiles with students
      • Active-learning slides for instruction
      • Using Evo in the News with students
      • Guide to Evo 101 and Digging Data
    • Conceptual framework
      • Alignment with the Next Generation Science Standards
      • teach-evo-menu-icon
    • Teaching guides
      • K-2 teaching guide
      • 3-5 teaching guide
      • 6-8 teaching guide
      • 9-12 teaching guide
      • Undergraduate teaching guide

    • Misconceptions about evolution

    • Dealing with objections to evolution
      • Information on controversies in the public arena relating to evolution
  • Learn Evolution

Home → Examples of microevolution
  • ES en Español

Examples of microevolution

Microevolution is defined as a change in gene frequency in a population. Because of the short timescale of this sort of evolutionary change, we can often directly observe it happening. We have observed numerous cases of natural selection in the wild, as exemplified by the three shown here.

The size of the sparrow

House sparrows were introduced to North America in 1852. Since that time the sparrows have evolved different characteristics in different locations. Sparrow populations in the north are larger-bodied than sparrow populations in the south. This divergence in populations is probably at least partly a result of natural selection: larger-bodied birds can often survive lower temperatures than smaller-bodied birds can. Colder weather in the north may select for larger-bodied birds.

Northern and southern house sparrows
At left, smaller, lighter-bodied sparrow from southern North America. Photo © Michael under CC-BY-NC.  At right, larger, darker-bodied sparrow from northern North America. Photo © Mark Rosenstein under CC-BY-NC-SA.

As this map shows, sparrows in colder places are now generally larger than sparrows in warmer locales. Since these differences are probably genetically based, they almost certainly represent microevolutionary change: populations descended from the same ancestral population have different gene frequencies.

Map of the US showing larger sparrows in the far north and smaller sparrows in the south and far west.
Sparrow map adapted from Gould, S.J & Johnston, R.F. (1972) Geographic Variation. Annual Review of Ecology and Systematics. 3:457-498

Coping with global warming

We observe natural selection following many human-induced changes in the environment. For example, global warming has caused slightly higher temperatures and longer summers. What are the evolutionary effects of this environmental change? We are just beginning to figure out the answers to this question as new data are collected.

Mosquito inside pitcher plant
Wyeomyia smithi photo courtesy of William E. Bradshaw and Christina M. Holsapfel, Center for Ecology and Evolutionary Biology, University of Oregon

Consider the potential effect of global warming on organisms that are dormant during the winter. These organisms stop growth and reproduction during the winter. They would probably be more “fit” if they could spend more of their time reproducing and gathering resources for reproduction, but the low temperatures don’t allow it. However, global warming would allow them to do just that: spend more time growing and reproducing — but taking advantage of this opportunity is likely to require evolutionary change.

The mosquito species Wyeomyia smithii, shown here in a pitcher plant, has evolved in response to global warming. Mosquitoes use day length (not temperature) as a cue to tell them what time of year it is and when to overwinter — this “cuing” is genetically controlled. In a warmer climate with shorter winters, we’d expect mosquitoes that waited a little longer to go dormant to have higher fitness and be selected for. And in fact, researchers who have been collecting data on these mosquitoes for almost 30 years have observed exactly this sort of change. Mosquito populations have evolved so that slightly shorter days are required as a cue for going dormant.

Graph showing rise in temperature deviations from mean, with clear warming between 1970 and 2000.
This graph illustrates changes in global temperature from 1880 to 2000. Between 1972 and 1996 mosquito populations at 50 N latitude evolved to wait 9 days later to go dormant. Mosquito information from Bradshaw & Holzapfel, 2001. Global climatic data from the National Climatic Data Center

Building resistance

Microscope image of sphere-shaped bacteria
Bacteria photo courtesy of the CDC/Janice Carr.

Pesticide resistance, herbicide resistance, and antibiotic resistance are all examples of microevolution by natural selection. The enterococci bacteria, shown here, have evolved a resistance to several kinds of antibiotics.

  • Evo Examples
  • Teaching Resources

Learn more about microevolution that has occurred in response to global warming: Warming to evolution, a news brief with discussion questions.

Learn more about the evolution of resistance:

  • Antibiotic resistance: Delaying the inevitable, a case study.
  • Battling bacterial evolution: The work of Carl Bergstrom, a research profile.
  • Livestock kick a drug habit, a news brief with discussion questions.

Find lessons, activities, videos, and articles that focus on the evolution of antibiotic resistance.

Footer

Connect

  • Email
  • Facebook
  • Twitter

Subscribe to our newsletter

Teach

  • Teaching resource database
  • Correcting misconceptions
  • Conceptual framework and NGSS alignment
  • Image and use policy

Learn

  • Evo 101
  • Evo in the News
  • The Tree Room
  • Browse learning resources
  • Glossary

Copyright © 2023 · UC Museum of Paleontology Understanding Evolution · Privacy Policy