7 Essential Knowledge

Below is the essential knowledge identified in the AP® Course Description and Exam publication:

Understanding(s):

1.   Natural selection is a major mechanism of evolution.

2.   According to Darwin’s theory of natural selection, competition for limited resources results in differential survival. Individuals with more favorable phenotypes are more likely to survive and produce more offspring, thus passing traits to subsequent generations.

3.   Evolutionary fitness is measured by reproductive success.

4.   Biotic and abiotic environments can be stable/fluctuating, and this affects the rate and direction of evolution; different genetic variations can be selected in each generation.

5.   Natural selection acts on phenotypic variations in populations.

6.   Environments change and apply selective pressures to populations.

7.   Some phenotypic variations significantly increase or decrease fitness of the organism in particular environments

8.   Through artificial selection, humans affect variation in other species.

9.   Convergent evolution occurs when similar selective pressures result in similar phenotypic adaptations in different populations or species

10. Evolution is also driven by random occurrences

a.        Mutation is a random process that contributes to evolution.

b.   Genetic drift is a nonselective process occurring in small populations— Bottlenecks & Founder effect.

c.        Migration/gene flow can drive evolution.

11. Reduction of genetic variation within a given population can increase the differences between populations of the same species.

12. Mutation results in genetic variation, which provides phenotypes on which natural selection acts.

13. Hardy-Weinberg is a model for describing and predicting allele frequencies in a nonevolving population. Conditions for a population or an allele to be in Hardy-Weinberg equilibrium are

a.         a large population size

b.   absence of migration

c.        no net mutations

d.   random mating

e.        absence of selection.

14. These processes, and/or models in applied contexts.

15. These conditions are seldom met, but they provide a valuable null hypothesis.

16. Allele frequencies in a population can be calculated from genotype frequencies.

17. Changes in allele frequencies provide evidence for the occurrence of evolution in a population.

18. Small populations are more susceptible to random environmental impact than large populations.

19. Evolution is supported by scientific evidence from many disciplines (geographical, geological, physical, biochemical, and mathematical data)

20. Molecular, morphological, and genetic evidence from extant and extinct organisms adds to our understanding of evolution

a.        Fossils can be dated by a variety of methods. These include:

                                                               i.      The age of the rocks where a fossil is found

                                                             ii.      The rate of decay of isotopes including carbon-14

                                                           iii.      Geographical data

b.   Morphological homologies, including vestigial structures, represent features shared by common ancestry.

21. A comparison of DNA nucleotide sequences and/or protein amino acid sequences provides evidence for evolution and common ancestry

22. Many fundamental molecular and cellular features and processes are conserved across organisms.

23. Structural and functional evidence supports the relatedness of organisms in all domains

24. Structural evidence indicates common ancestry of all eukaryotes—

a.        Membrane-bound organelles

b.   Linear chromosomes

c.        Genes that contain introns

25. Populations of organisms continue to evolve.

26. All species have evolved and continue to evolve

a.        Genomic changes over time.

b.   Continuous change in the fossil record

c.        Evolution of resistance to antibiotics, pesticides, herbicides, or chemotherapy drugs.

d.   Pathogens evolve and cause emergent diseases.

27. Phylogenetic trees and cladograms show evolutionary relationships among lineages

a.        Phylogenetic trees and cladograms both show relationships between lineages, but phylogenetic trees show the amount of change over time calibrated by fossils or a molecular clock.

b.   Traits that are either gained or lost during evolution can be used to construct phylogenetic trees and cladograms

  i.       Shared characters are present in more than one lineage.

  ii.      Shared, derived characters indicate common ancestry and are informative for the construction of phylogenetic trees and cladograms.

iii.      The out-group represents the lineage that is least closely related to the remainder of the organisms in the phylogenetic tree or cladogram.

c.        Molecular data typically provide more accurate and reliable evidence than morphological traits in the construction of phylogenetic trees or cladograms.

28. Phylogenetic trees and cladograms can be used to illustrate speciation that has occurred. The nodes on a tree represent the most recent common ancestor of any two groups or lineages.

29. Phylogenetic trees and cladograms can be constructed from morphological similarities of living or fossil species and from DNA and protein sequence similarities.

30. Phylogenetic trees and cladograms represent hypotheses and are constantly being revised, based on evidence

31. Speciation may occur when two populations become reproductively isolated from each other.

32. The biological species concept provides a commonly used definition of species for sexually reproducing organisms. It states that species can be defined as a group capable of interbreeding and exchanging genetic information to produce viable, fertile offspring.

33. Describe the rate of evolution and speciation under different ecological conditions.

34. Punctuated equilibrium is when evolution occurs rapidly after a long period of stasis.  Gradualism is when evolution occurs slowly over hundreds of thousands or millions of years.

35. Divergent evolution occurs when adaptation to new habitats results in phenotypic diversification. Speciation rates can be especially rapid during times of adaptive radiation as new habitats become available.

36. Speciation results in diversity of life forms.

37. Speciation may be sympatric or allopatric.

38. Various prezygotic and postzygotic mechanisms can maintain reproductive isolation and prevent gene flow between populations.

39. Extinctions have occurred throughout Earth’s history

40. Extinction rates can be rapid during times of ecological stress

41. Human activity can drive changes in ecosystems that cause extinctions.

42. The amount of diversity in an ecosystem can be determined by the rate of speciation and the rate of extinction

43. Extinction provides newly available niches that can then be exploited by different species.

44. The level of variation in a population affects

45. population dynamics—

a.        Population ability to respond to changes in the environment is influenced by genetic diversity. Species and populations with little genetic diversity are at risk of decline or extinction.

b.   Genetically diverse populations are more resilient to environmental perturbation because they are more likely to contain individuals who can withstand the environmental pressure.

c.        Alleles that are adaptive in one environmental condition may be deleterious in another because of different selective pressures

46. Several hypotheses about the origin of life on Earth are supported with scientific evidence

a.        Geological evidence provides support for models of the origin of life on Earth.

                                                               i.      Earth formed approximately 4.6 billion years ago (bya). The environment was too hostile for life until 3.9 bya, and the earliest fossil evidence for life dates to 3.5 bya. Taken together, this evidence provides a plausible range of dates when the origin of life could have occurred.

b.   There are several models about the origin of life on Earth

                                                               i.       Primitive Earth provided inorganic precursors from which organic molecules could have been synthesized because of the presence of available free energy and the absence of a significant quantity of atmospheric oxygen (O2).

                                                             ii.      Organic molecules could have been transported to Earth by a meteorite or other celestial event.

c.        Chemical experiments have shown that it is possible to form complex organic molecules from inorganic molecules in the absence of life

                                                               i.      Organic molecules/monomers served as building blocks for the formation of more complex molecules, including amino acids and nucleotides.

d.   The joining of these monomers produced polymers with the ability to replicate, store, and transfer information.

47. The RNA World Hypothesis proposes that RNA could have been the earliest genetic material.