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EV: Evolution Overview

Evolution: The Change Over Time

Evolution is a basic concept throughout all disciplines of biology. Whether we are talking about endangered species, diseases, or growing food, evolution plays a role in making decisions that affect these ideas (and many more). Every human starts out as a single cell that replicates until developing into a multicellular human with specialized groups of cells. Some of those specialized cells can divide to produce gametes that may contribute to another offspring!

Module Lessons Preview

In this module, we will study the following topics:

Natural Selection, Adaptation, Evolution Evidence, Evolution Mechanisms, Geological Time Scale

Module Key Terms

Key Terms

  • Evolution: change over time
  • Natural Selection: organisms with adaptations that allow the organism to be more “fit” than others will be “selected” by nature to survive. Example: Polar bear's white fur helps it camouflage
  • Adaptation: a characteristic (structural, physiological, behavioral), that gives an organism a selective advantage in its environment. Example: wings of birds
  • Fitness: the ability to breed and produce healthy offspring
  • Common Descent: the idea that all organisms have evolved from a common ancestor
  • Natural Variation: differences within organisms of the same species that occur naturally, like the color of fur, feathers, skin, eye color
  • Era: the largest division of geological time. There are three Eras: Paleozoic, Mesozoic, and Cenozoic
  • Period: eras are subdivided into periods, which range in length from tens of thousands of years to less than 2 million years
  • Endosymbiotic Theory: the idea that a small prokaryote was engulfed by and became a permanent structure of a larger one. Each was beneficial to the other in some way, so the partnership was naturally selected
  • Paleontologist: a scientist who studies fossils
  • Fossil: preserved remains of ancient organisms
  • Extinct: an organism that has died out and no member of the species exists. Example: dodo bird
  • Index Fossil: fossils of organisms that only survived for short periods of time and can help determine the age of fossils
  • Relative Dating: the process of using the Law of Superposition along with index fossils to determine the age of fossils
  • Half-life: the length of time required for half of a radioactive sample to decay
  • Radioactive Dating: by determining the amount of carbon 14 left in a fossil and knowing it’s the half-life, scientists can use a mathematical formula to determine the age of the fossil
  • Speciation: the evolution of new species that occurs when two similar reproducing beings evolve to become too dissimilar to share genetic information or produce fertile offspring
  • Geographical Isolation: the evolution of a new species that occurs when a population gets separated and can no longer share genetic material
  • Prezygotic Barrier: things that physically or behaviorally keep male and female sex cells from uniting
  • Postzygotic Barrier: barriers that occur after the zygote has formed
  • Disruptive Selection: favors the extreme phenotype; in the case of petunias, if bees preferred the red or white flowers, but not the pink, then the pink ones decrease because bees were not pollinating them
  • Stabilizing Selection: favors the intermediate phenotype; if bees preferred the pink flowers instead of the red or white flowers, the pink flowers would increase
  • Directional Selection: favors one extreme over the other; if bees preferred white instead of red or pink flowers, the white would increase while the other colors would decline.
  • Macroevolution: large-scale evolutionary changes that take long periods of time
  • Coevolution: a process where two very different species evolve in response to each other over time. An example would be the hummingbird’s beak pollinating a flower with long tubes
  • Artificial Selection: when humans choose which organisms to be bred or crossed with each other to produce an organism with desired traits. For example, breeding top racehorses only with other top racehorses will produce fast horses
  • Punctuated Equilibrium: the idea that something periodically disrupts the equilibrium and many species begin to change rapidly after long periods of stability
  • Mutation: a change in the DNA of an organism, which can result in variations within a population
  • Gene Pool: the set of all genes for a species (or a specific population)
  • Genetic Drift: occurs when a population’s gene pool represents a few individuals by chance and not because of fitness or mutations and will not produce adaptations
  • Founder Effect: a type of genetic drift that occurs when a small group of individuals colonizes an area
  • Bottleneck: a type of genetic drift in which a population’s size decreases dramatically over a short period of time due to a chance environmental event
  • Proteinoid Microspheres: tiny per-cells with selectively permeable membranes that could store and release energy