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In this lab, students design and conduct experiments to evaluate whether evolution by natural selection (or alternatively, genetic drift) may be induced in laboratory populations.
Morehouse College and Emory University
Demonstrating and measuring evolution in a laboratory environment with animal species is typically very challenging. However, insects are among the most amenable species for such studies and the bean beetle, Callosobruchus maculatus, is the easiest species in which such studies may be conducted. Bean beetles are agricultural pest insects of Africa and Asia. Females lay their eggs on the surface of beans (Family Fabaceae) and the entire pre-adult parts of the life cycle occur inside the host bean.
Instructors should caution students to prevent the accidental release of bean beetles from the laboratory environment. Callosobruchus maculatus is a potential agricultural pest insect that is not distributed throughout the United States and Canada. It is essential that you keep your cultures secured in a laboratory environment to ensure that they are not released to the natural environment. Disposal of cultures (and beans (seeds) exposed to live beetles of any life cycle stage) requires freezing (0°C) for a minimum of 72 hours prior to disposal as food waste. If you have any questions about the handling or disposal of bean beetles, please contact Larry Blumer at firstname.lastname@example.org or 404 658-1142 (voice or FAX). Information also is available at: www.beanbeetles.org in the Handbook section.
Correspondence to the Next Generation Science Standards is indicated in parentheses after each relevant concept. See our conceptual framework for details.
- Evolution occurs through multiple mechanisms.
- Evolution results from natural selection acting upon genetic variation within a population.
- Evolution results from genetic drift acting upon genetic variation within a population.
- Natural selection acts on phenotype as an expression of genotype.
- Inherited characteristics affect the likelihood of an organism's survival and reproduction.
- Over time, the proportion of individuals with advantageous characteristics may increase (and the proportion with disadvantageous characteristics may decrease) due to their likelihood of surviving and reproducing.
- Natural selection can act on the variation in a population in different ways.
- Natural selection may favor individuals with one extreme value for a trait, shifting the average value of that trait in one direction over the course of many generations.
- Selection favoring an extreme trait value reduces genetic variation in a population.
- Natural selection may favor individuals with traits at each extreme of the range for that trait.
- Selection favoring individuals with traits at each extreme of a range maintains genetic variation in a population.
- Natural selection may favor individuals with an intermediate value for a trait.
- Selection favoring an intermediate value for a trait reduces genetic variation in a population.
- Smaller populations are more strongly affected by genetic drift than are larger populations.
- Genetic drift can cause loss of genetic variation in a population.
- Founder effects occur when a population is founded from a small number of individuals.
- Founder effects can affect the genetic makeup of a newly started population (and reduce its genetic variation) through sampling error.
- Bottlenecks occur when a population’s size is greatly reduced.
- Bottlenecks can affect the genetic makeup of a population (and reduce its genetic variation) through sampling error.