At the end of the school year, there are certain conceptual understandings that we want our students to have. Achieving these learning goals lays the groundwork for more sophisticated understandings as students proceed through their learning experiences. The Understanding Evolution Conceptual Framework is an effective tool for identifying a sequence of age-appropriate conceptual understandings (K-16) to guide your teaching. The Framework is divided into five strands, and a selection of teaching resources (i.e., lessons, activities, readers, and interactive online modules) targeting most concepts has been identified.

Jump to: History of Life | Evidence of Evolution | Mechanisms of Evolution | Nature of Science | Studying Evolution

History of Life concepts for undergraduates

1. Biological evolution accounts for diversity over long periods of time. (See Lessons)
   1. 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. (See Lessons)
   2. Life forms of the past were in some ways very different from living forms of today, but in other ways very similar. (See Lessons)
   3. Evolution is still continuing today. (See Lessons)
   4. Humans directly impact biodiversity, which may then impact future evolutionary potential.
2. Present-day species evolved from earlier species; the relatedness of organisms is the result of common ancestry. (See Lessons)
   1. Life on Earth 3.8 billion years ago consisted of one-celled organisms similar to present-day bacteria. (See Lessons)
   2. There is evidence of eukaryotes in the fossil record from about one billion years ago; some were the precursors of multicellular organisms.
   3. The early evolutionary process of eukaryotes included the merging of prokaryote cells. (See Lessons)
3. Geological change and biological evolution are linked. (See Lessons)
   1. Tectonic plate movement has affected the evolution and distribution of living things. (See Lessons)
   2. Living things have had a major influence on the composition of the atmosphere and on the surface of the planet.
4. During the course of evolution, only a small percentage of species have survived until today. (See Lessons)
   1. Background extinctions are a normal occurrence. (See Lessons)
   2. Rates of extinction vary. (See Lessons)
   3. Mass extinctions occur. (See Lessons)
   4. Extinction can result from environmental change. (See Lessons)
   5. Human influence may be causing a modern mass extinction.
   6. Extinctions may create opportunities for further evolution in other lineages to occur.
5. Rates of evolution vary. (See Lessons)
   1. Rates of speciation vary. (See Lessons)
   2. Evolutionary change can sometimes happen rapidly. (See Lessons)
   3. Some lineages remain relatively unchanged for long periods of time. (See Lessons)

To help you teach these concepts, you may want to explore Definition of Evolution, Patterns of Evolution, or Patterns in Macroevolution.

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Evidence of Evolution concepts for undergraduates

1. The patterns of life’s diversity through time provide evidence of evolution. (See Lessons)
2. Evolution can sometimes be directly observed. (See Lessons)
3. An organism’s features reflect its evolutionary history. (See Lessons)
   1. There is a fit between organisms and their environments, though not always a perfect fit. (See Lessons)
   2. There is a fit between the form of a trait and its function, though not always a perfect fit. (See Lessons)
   3. Some traits of organisms are not adaptive. (See Lessons)
   4. Features sometimes acquire new functions through natural selection. (See Lessons)
4. The fossil record provides evidence for evolution. (See Lessons)
   1. The fossil record documents the biodiversity of the past. (See Lessons)
   2. The fossil record contains organisms with transitional features. (See Lessons)
   3. The fossil record documents patterns of extinction and the appearance of new forms. (See Lessons)
   4. The sequence of forms in the fossil record is reflected in the sequence of the rock layers in which they are found and indicates the order in which they evolved. (See Lessons)
   5. Radiometric dating can often be used to determine the age of fossils. (See Lessons)
5. There are similarities and differences among fossils and living organisms. (See Lessons)
6. Similarities among existing organisms (including morphological, developmental, and molecular similarities) reflect common ancestry and provide evidence for evolution. (See Lessons)
   1. Not all similar traits are homologous; some are the result of convergent evolution. (See Lessons)
7. The geographic distribution of species often reflects how geologic change has influenced lineage splitting. (See Lessons)
8. Artificial selection provides a model for natural selection. (See Lessons)
   1. People selectively breed domesticated plants and animals to produce offspring with preferred characteristics. (See Lessons)

To help you teach these concepts, you may want to explore Lines of Evidence or Adaptation.

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Mechanisms of Evolution concepts for undergraduates

1. Evolution is often defined as a change in allele frequencies within a population. (See Lessons)
   1. The Hardy-Weinberg equation describes expectations about the gene pool of a population that is not evolving — one that is very large, mates randomly, and does not experience mutation, natural selection, or gene flow.
2. Evolution occurs through multiple mechanisms. (See Lessons)
   1. Evolution results from natural selection acting upon genetic variation within a population. (See Lessons)
   2. Evolution results from genetic drift acting upon genetic variation within a population. (See Lessons)
   3. Evolution results from mutations. (See Lessons)
   4. Evolution results from gene flow.
   5. Evolution results from hybridization.
3. Natural selection and genetic drift act on the variation that exists in a population. (See Lessons)
   1. Natural selection acts on phenotype as an expression of genotype. (See Lessons)
   2. Phenotype is a product of both genotype and the organism’s interactions with the environment. (See Lessons)
   3. Variation of a character within a population may be discrete or continuous. (See Lessons)
   4. Continuous characters are generally influenced by many different genes.
4. New heritable traits can result from mutations. (See Lessons)
   1. Mutation is a random process. (See Lessons)
   2. Organisms cannot intentionally produce adaptive mutations in response to environmental influences. (See Lessons)
   3. Complex structures may be produced incrementally by the accumulation of smaller advantageous mutations. (See Lessons)
5. Inherited characteristics affect the likelihood of an organism’s survival and reproduction. (See Lessons)
   1. 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. (See Lessons)
   2. Traits that confer an advantage may persist in the population and are called adaptations. (See Lessons)
   3. Complex traits can arise through the cooption of another trait. (See Lessons)
   4. The number of offspring that survive to reproduce successfully is limited by environmental factors.
   5. Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental. (See Lessons)
6. Natural selection can act on the variation in a population in different ways. (See Lessons)
   1. 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. (See Lessons)
   2. Selection favoring an extreme trait value reduces genetic variation in a population.
   3. Natural selection may favor individuals with traits at each extreme of the range for that trait.
   4. Selection favoring individuals with traits at each extreme of a range maintains genetic variation in a population.
   5. Natural selection may favor individuals with an intermediate value for a trait.
   6. Selection favoring an intermediate value for a trait reduces genetic variation in a population.
   7. Natural selection sometimes favors heterozygotes over homozygotes at a locus. (See Lessons)
   8. Heterozygote advantage preserves genetic variation at that locus (i.e., within the population, it maintains multiple alleles at that locus). (See Lessons)
   9. Natural selection sometimes favors rare traits and acts against those that become too common in a population.
   10. Frequency-dependent selection preserves genetic variation in a population. (See Lessons)
7. Sexual selection occurs when selection acts on characteristics that affect the ability of individuals to obtain mates.
   1. Sexual selection can lead to physical and behavioral differences between the sexes.
8. An individual’s fitness (or relative fitness) is the contribution that individual makes to the gene pool of the next generation relative to other individuals in the population. (See Lessons)
   1. An organism’s fitness depends on both its survival and its reproduction. (See Lessons)
   2. Fitness is often measured using proxies like mass, number of matings, and survival because it is difficult to measure reproductive success. (See Lessons)
9. Natural selection is capable of acting at multiple hierarchical levels: on genes, on cells, on individuals, on populations, on species, and on larger clades. (See Lessons)
10. Random factors can affect the survival of individuals and of populations. (See Lessons)
    1. Smaller populations are more strongly affected by genetic drift than are larger populations.
    2. Genetic drift can cause loss of genetic variation in a population.
    3. Founder effects occur when a population is founded from a small number of individuals.
    4. Founder effects can affect the genetic makeup of a newly started population (and reduce its genetic variation) through sampling error.
    5. Bottlenecks occur when a population’s size is greatly reduced.
    6. Bottlenecks can affect the genetic makeup of a population (and reduce its genetic variation) through sampling error.
11. A species is often defined as a group of individuals that actually or potentially interbreed in nature.
    1. There are many definitions of species.
12. Speciation is the splitting of one ancestral lineage into two or more descendent lineages. (See Lessons)
    1. Speciation is often the result of geographic isolation. (See Lessons)
    2. Speciation can also occur without geographic isolation.
    3. Speciation requires reproductive isolation. (See Lessons)
    4. Reproductive isolation can occur through mechanisms that prevent fertilization from occurring.
    5. Reproductive isolation can also occur through mechanisms that act after fertilization, when a fertilized egg (or the individual resulting from that egg) has low fitness.
    6. Occupying new environments can provide new selection pressures and new opportunities, leading to speciation. (See Lessons)
13. Occasionally offspring, known as hybrids, result from matings between distinct species or between distinct parental forms. (See Lessons)
    1. Some hybrids have increased fitness relative to their parents.
    2. Some hybrids have decreased fitness relative to their parents.
14. Evolution does not consist of progress in any particular direction. (See Lessons)

To help you teach these concepts, you may want to explore Mechanisms of Evolution, Speciation, or Misconceptions about How Evolution Works.

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Nature of Science concepts for undergraduates

1. Science focuses on natural phenomena and processes. (See Lessons)
2. Scientific knowledge is open to question and revision as we come up with new ideas and discover new evidence. (See Lessons)
3. A hallmark of science is exposing ideas to testing. (See Lessons)
   1. Scientists test their ideas using multiple lines of evidence. (See Lessons)
   2. Scientists use multiple research methods (experiments, observational research, comparative research, and modeling) to collect data. (See Lessons)
   3. Scientists can test ideas about events and processes long past, very distant, and not directly observable. (See Lessons)
4. Scientists may explore many different hypotheses to explain their observations. (See Lessons)
5. The real process of science is complex, iterative, and can take many different paths. (See Lessons)
   1. Scientific findings and evidence inspire new questions and shape the directions of future scientific research. (See Lessons)
6. Accepted scientific theories are not tenuous; they must survive rigorous testing and be supported by multiple lines of evidence to be accepted. (See Lessons)
7. Science is a human endeavor. (See Lessons)
8. Authentic scientific controversy and debate within the community contribute to scientific progress. (See Lessons)

To help you teach these concepts, you may want to explore Nature of Science.

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Studying Evolution concepts for undergraduates

1. Our knowledge of the evolution of living things is always being refined as we gather more evidence. (See Lessons)
2. Our understanding of life through time is based upon multiple lines of evidence. (See Lessons)
   1. Scientists use multiple lines of evidence (including morphological, developmental, and molecular evidence) to infer the relatedness of taxa. (See Lessons)
   2. Scientists use fossils (including sequences of fossils showing gradual change over time) to learn about past life. (See Lessons)
   3. Scientists use physical, chemical, and geological evidence and comparative anatomy to establish the age of fossils.
   4. Scientists use the geographic distribution of fossils and living things to learn about the history of life. (See Lessons)
   5. Scientists use experimental evidence to study evolutionary processes. (See Lessons)
   6. Scientists use artificial selection as a model to learn about natural selection. (See Lessons)
3. Classification is based on evolutionary relationships. (See Lessons)
   1. Evolutionary trees (i.e., phylogenies or cladograms) portray hypotheses about evolutionary relationships. (See Lessons)
   2. Evolutionary trees (i.e., phylogenies or cladograms) are built from multiple lines of evidence. (See Lessons)
   3. The principle of parsimony suggests that the phylogenetic hypothesis most likely to be true is the one requiring the fewest evolutionary changes. (See Lessons)
   4. Evolutionary trees can be used to make inferences and predictions. (See Lessons)
4. As with other scientific disciplines, evolutionary biology has applications that factor into everyday life, for example in agriculture, biodiversity and conservation biology, and medicine and health. (See Lessons)
   1. Because of common ancestry, model organisms can be used to provide insight into the biology of other organisms.

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