Extinction and Speciation

pacing-guide-wheel-for-extinction-and-speciation-the-seventh-unit-of-the-year

Phenomenon

The pattern of unity and biodiversity observed on Earth today has existed in the long history of life on Earth as evident by the fossil record. Over time, the number of species on Earth has fluctuated, going up and down over time.

Sub-Phenomenon: Modern birds are believed to be descendants of ancient dinosaurs.

Question

What happens when the number of species on Earth changes and specifically how do new species form?

–Sub-Question: Where did all these different species of birds come from?

Model Ideas

  1. New species come from existing species.
     
  2. New species come about when existing species branch off and each branch changes over time. Those branches may persist in a similar form, change, branch again, or go extinct.
     
  3. When one group of organisms is separated into different populations, the separated populations may be under different natural selection pressures, leading to a change in traits over time. 
     
  4. When the changes between populations are such that they can no longer mate and produce fertile offspring, they are considered distinct species.

Advanced Planning

There are two activities in this unit. The first is a slight variation on the Wormeaters game from Natural Selection. All the same equipment is needed plus 4 new items to replace the rubber bands as prey. See notes for details. The second activity only requires some color copies of data cards for students.

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