Identify your learning goals
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 below 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.
Some teachers may wish to assess students' current understanding of evolution with a pretest and then select teaching materials based on areas of weakness. For test items that can be used for this purpose, check out the evolution items on the AAAS Science Assessment website. Access to items is free, but teachers will have to register with the site.
|History of Life concepts for 9-12
- 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.
- Present-day species evolved from earlier species; the relatedness of organisms is the result of common ancestry.
- Life on Earth 3.8 billion years ago consisted of one-celled organisms similar to present-day bacteria.
- There is evidence of eukaryotes in the fossil record from about one billion years ago; some were the precursors of multicellular organisms.
- The early evolutionary process of eukaryotes included the merging of prokaryote cells.
- Geological change and biological evolution are linked.
- Tectonic plate movement has affected the evolution and distribution of living things.
- Living things have had a major influence on the composition of the atmosphere and on the surface of the planet.
- During the course of evolution, only a small percentage of species have survived until today.
- Background extinctions are a normal occurrence.
- Rates of extinction vary.
- Mass extinctions occur.
- Extinction can result from environmental change.
- Extinctions may create opportunities for further evolution in other lineages to occur.
- Rates of evolution vary.
- Rates of speciation vary.
- Evolutionary change can sometimes happen rapidly.
- Some lineages remain relatively unchanged for long periods of time.
|Evidence of Evolution concepts for 9-12
- The patterns of life's diversity through time provide evidence of evolution.
- An organismís features reflect its evolutionary history.
- There is a fit between organisms and their environments, though not always a perfect fit.
- There is a fit between the form of a trait and its function, though not always a perfect fit.
- Some traits of organisms are not adaptive.
- Features sometimes acquire new functions through natural selection.
- The fossil record provides evidence for evolution.
- The fossil record documents the biodiversity of the past.
- The fossil record contains organisms with transitional features.
- The fossil record documents patterns of extinction and the appearance of new forms.
- 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.
- Radiometric dating can often be used to determine the age of fossils.
- There are similarities and differences among fossils and living organisms.
- Similarities among existing organisms provide evidence for evolution.
- Anatomical similarities of living things reflect common ancestry.
- There are similarities in the cell function of all organisms.
- All life forms use the same basic DNA building blocks.
- Developmental similarities of living things often reflect their relatedness.
- Not all similar traits are homologous; some are the result of convergent evolution.
- Artificial selection provides a model for natural selection.
- People selectively breed domesticated plants and animals to produce offspring with preferred characteristics.
|Mechanisms of Evolution concepts for 9-12
- Evolution occurs through multiple mechanisms.
- Evolution results from selection acting upon genetic variation within a population.
- Evolution results from genetic drift acting upon genetic variation within a population.
- There is variation within a population.
- Natural selection acts on the variation that exists in a population.
- Natural selection acts on phenotype as an expression of genotype.
- 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.
- New heritable traits can result from recombinations of existing genes or from genetic mutations in reproductive cells.
- Mutations are random.
- Organisms cannot intentionally produce adaptive mutations in response to environmental influences.
- Complex structures may be produced incrementally by the accumulation of smaller useful mutations.
- 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.
- Populations, not individuals, evolve.
- Traits that confer an advantage may persist in the population and are called adaptations.
- Natural selection is dependent on environmental conditions.
- The number of offspring that survive to reproduce successfully is limited by environmental factors.
- Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental.
- Environmental changes may provide opportunities that can influence natural selection.
- Fitness is reproductive success - the number of viable offspring produced by an individual in comparison to other individuals in a population/species.
- Fitness is often measured using proxies like mass, number of matings, and survival because it is difficult to measure reproductive success directly.
- Random factors can affect the survival of individuals and of populations.
- Speciation is the splitting of one ancestral lineage into two or more descendent lineages.
- Speciation is often the result of geographic isolation.
- Speciation requires reproductive isolation.
- Occupying new environments can provide new selection pressures and new opportunities, leading to speciation.
- Evolution does not consist of progress in any particular direction.
|Nature of Science concepts for 9-12
- Science focuses on natural phenomena and processes.
- Scientific knowledge is open to question and revision as we come up with new ideas and discover new evidence.
- A hallmark of science is exposing ideas to testing.
- Scientists test their ideas using multiple lines of evidence.
- Scientists use multiple research methods (experiments, observational research, comparative research, and modeling) to collect data.
- Scientists can test ideas about events and processes long past, very distant, and not directly observable.
- Scientists may explore many different hypotheses to explain their observations.
- The real process of science is complex, iterative, and can take many different paths.
- Accepted scientific theories are not tenuous; they must survive rigorous testing and be supported by multiple lines of evidence to be accepted.
- Science is a human endeavor.
- Authentic scientific controversy and debate within the community contribute to scientific progress.
|Studying Evolution concepts for 9-12
- Our knowledge of the evolution of living things is always being refined as we gather more evidence.
- Our understanding of life through time is based upon multiple lines of evidence.
- Scientists use the similarity of DNA nucleotide sequences to infer the relatedness of taxa.
- Scientists use anatomical evidence to infer the relatedness of taxa.
- Scientists use developmental evidence to infer the relatedness of taxa.
- Scientists use fossils (including sequences of fossils showing gradual change over time) to learn about past life.
- Scientists use physical, chemical, and geological evidence to establish the age of fossils.
- Scientists use the geographic distribution of fossils and living things to learn about the history of life.
- Scientists use experimental evidence to study evolutionary processes.
- Scientists use artificial selection as a model to learn about natural selection.
- Classification is based on evolutionary relationships.
- Evolutionary trees (i.e., phylogenies or cladograms) portray hypotheses about evolutionary relationships.
- Evolutionary trees (i.e., phylogenies or cladograms) are built from multiple lines of evidence.
- As with other scientific disciplines, evolutionary biology has applications that factor into everyday life.