BIO.9.B

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The student is expected to examine scientific explanations for varying rates of change such as gradualism, abrupt appearance, and stasis in the fossil record.
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Knowledge and Skills Statement

Science concepts--biological evolution. The student knows evolutionary theory is a scientific explanation for the unity and diversity of life that has multiple lines of evidence.

As an educator, it is helpful to know that about 530 million years ago, more than half of the major animal groups (called phyla) appear suddenly in the fossil record during the Cambrian Explosion.

the theory in biology postulating that the various types of plants, animals, and other living things on Earth have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations

a tenet in evolutionary theory that explains the long periods of geologic time over which species evolve slowly and continuously

when a species is not undergoing any reactive evolutionary change over a long period of time

Research

Clark, Christopher James. "Harmonic Hopping, and Both Punctuated and Gradual Evolution of Acoustic Characters in Selasphorus Hummingbird Tail-feathers." PLoS ONE 9, no. 4 (April 2014): e93829. https://doi.org/10.1371/journal.pone.0093829

Summary:  Models of character evolution often assume a single mode of evolutionary change, such as continuous, or discrete. Here I provide an example, Hummingbirds in the genus Selasphorus, in which a character exhibits both types of change.

Research

Lord, Richard. "Changing Life on Earth." The Science Teacher 77, no. 9 (December 2010): 80-81.

Summary:  Evidence supporting Darwin's ideas of natural selection--such as fossils, comparative anatomy, homology, and DNA--is presented, and a brief explanation of Stephen Jay Gould's ideas on punctuated equilibrium is included. The various characteristics and changes throughout the sequential geological eras of Earth history are presented, and the ancestry of humans is depicted with pictures and descriptions of the skulls of fossil hominids. A discussion of how evolution is used to make predictions uses examples such as uncovering useful drugs from the rainforest and understanding the problem of antibiotic resistance.

Research

Ispolatov, Iaroslav, Evgeniia Alekseeva, and Michael Doebeli. "Competition-driven Evolution of Organismal Complexity." PLoS Computational Biology 15, no. 10 (October 2019): e1007388. https://doi.org/10.1371/journal.pcbi.1007388

Summary:  Non-uniform rates of morphological evolution and evolutionary increases in organismal complexity, captured in metaphors like "adaptive zones", "punctuated equilibrium" and "blunderbuss patterns", require more elaborate explanations than a simple gradual accumulation of mutations. Here we argue that non-uniform evolutionary increases in phenotypic complexity can be caused by a threshold-like response to growing ecological pressures. Acquisition of a new phenotypic feature allows an evolving species to escape this pressure but can carry significant physiological costs.