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Lines of Evidence
for Past Change

Looking at the Big Ideas:

Identifying the Evolution Concepts

Much of what we teach about evolution can be associated with the following:

V

 variation

I

 inheritance

S

 selection

T

 time

Teachers reflected on the primary concepts covered during this session, using the document entitled Evolution Concepts K-12, prepared by the UC Museum of Paleontology in 2002 for its Understanding Evolution web project. The following concepts were selected.

History of life

Biological evolution accounts for diversity over long periods of time.

  • Through billions of years of evolution, life forms have continued to diversify in a branching pattern, from single-celled ancestors to the diversity of life on Earth today.
  • Life forms of the past were in some ways very different from living forms of today, but in other ways very similar.

Evidence of evolution

The long history of the Earth and the long history of changing life are displayed in the many layers of sedimentary rock.

Form is often linked to function.

  • Anatomical similarities of living things reflect common ancestry.
  • The fossil record documents the sequential biodiversity of the past.

Mechanisms of evolution

Evolution results from selection acting upon genetic variation within a population.

  • Individual organisms with advantageous traits are more likely to survive and have offspring.
  • Occupying new environments can provide both new selection pressures and isolation, leading to speciation.

Adaptations are preserved in a population by natural selection.

Inherited characteristics affect the likelihood of an organism's survival and reproduction.

  • Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental.
  • The amount of genetic variation within a population may affect the likelihood of survival of the population; the less the available diversity, the less likely the population will be able to survive environmental change.
  • Random factors affect the survival of individuals and of populations.
  • Natural selection acts on individuals and populations in a nonrandom way.
  • The number of offspring that survive to reproduce successfully is limited by environmental factors.

Populations evolve.

  • The proportion of individuals with advantageous characteristics may increase due to their increased likelihood of surviving and reproducing.
  • Evolution does not consist of progress in a particular direction.
  • Evolution may occur as a result of genetic drift.
NOTE: Teachers raised the challenge of conceptualizing deep time and cautioned about analogies and foot-shootings. See teacher resources.

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