gradualism

Examples of gradualism in the following topics:

• Varying Rates of Speciation

  • Two patterns are currently observed in the rates of speciation: gradual speciation and punctuated equilibrium.
  • In terms of how quickly speciation occurs, two patterns are currently observed: the gradual speciation model and the punctuated equilibrium model.
  • In the gradual speciation model, species diverge gradually over time in small steps.
  • While punctuated equilibrium suggests a faster tempo, it does not necessarily exclude gradualism .
  • In (a) gradual speciation, species diverge at a slow, steady pace as traits change incrementally.

• What is Evolution?

  • Although it may seem that living things today stay the same, this is not the case: evolution is a gradual and ongoing process.
  • During this time, a Scottish naturalist named James Hutton proposed that geological change occurs gradually by the accumulation of small changes over long periods of time.
  • The greater age of the earth proposed by Lyell supported the gradual evolution that Darwin proposed, and the slow process of geological change provided an analogy for the gradual change in species.

• Evolution of Land Plants

  • The evolution of plants occurred by a gradual development of novel structures and reproduction mechanisms .
  • The adaptation of plants to life on land occurred gradually through the stepwise development of physical structures and reproduction mechanisms

• The Fossil Record and the Evolution of the Modern Horse

  • The sequence of transitional fossils was assembled by the American Museum of Natural History into an exhibit that emphasized the gradual, "straight-line" evolution of the horse.
  • Although some transitions were indeed gradual progressions, a number of others were relatively abrupt in geologic time, taking place over only a few million years.
  • Both anagenesis, a gradual change in an entire population's gene frequency, and cladogenesis, a population "splitting" into two distinct evolutionary branches, occurred, and many species coexisted with "ancestor" species at various times.
  • The series of fossils tracks the change in anatomy resulting from a gradual drying trend that changed the landscape from a forested habitat to a prairie habitat.

• Nonrandom Mating and Environmental Variance

  • One type of geographic variation, called a cline, can be seen as populations of a given species vary gradually across an ecological gradient.
  • If there is gene flow between the populations, the individuals will likely show gradual differences in phenotype along the cline.

• Biofilms and Disease

  • Biofilm infections develop gradually and often do not cause immediate symptoms.

• Characteristics of the Animal Body

  • However, there is also evidence of a more gradual development of body plans.

• Biogeography

  • For example, if you were to begin a journey at the equator and walk north, you would notice gradual changes in plant communities.
  • This trek north reveals gradual changes in both climate and the types of organisms that have adapted to environmental factors associated with ecosystems found at different latitudes.

• Biodiversity Change through Geological Time

  • The transition in fossils from one period to another reflects the dramatic loss of species and the gradual origin of new species .
  • The extinction event occurred just before the breakup of the supercontinent Pangaea; although, recent scholarship suggests that the extinctions may have occurred more gradually throughout the Triassic.

• Immunological Memory

  • If the pathogen is not encountered again during the individual's lifetime, B and T memory cells will circulate for a few years or even several decades, gradually dying off, having never functioned as effector cells.