geographic isolation The separation of a population from the rest of its species due to
some physical barrier, such as a mountain range, an ocean, or great distance.
macroevolution Big evolutionary changes that result in new species.
microevolution Small changes in inherited traits; does not lead to the creation of a new
species.
natural selection Causes beneficial heritable traits to become more common in a popu-
lation, and unfavorable heritable traits become less common.
primate A group of related mammal species that have binocular vision, specialized hands
and feet for grasping, and enlarged and differentiated brains; includes humans, chim-
panzees, the apes, monkeys, and lemurs.
reproductive isolation allopatric and sympatric speciation; isolation due to geography
or behavior, resulting in the inability to reproduce.
speciation The creation of a new species; either by natural or artificial selection.
sympatric speciation Speciation that occurs when groups from the same species stop
interbreeding, because of something other than physical separation, such as behavior.
temporal isolation Isolation due to different mating seasons.
Points to Consider
- How long do you think humans have been around?
- How long do you think Earth existed before life formed?
- For how much of Earth’s history have humans existed?
7.4 Lesson 7.4: History of Life on Earth
Lesson Objectives
- KnowthatgeologistsandpaleontologistsuseevidencetodeterminethehistoryofEarth
and life on Earth. - Know that geologists and paleontologists measure the radioactivity in certain rocks to
determine the age of the earth and fossils. - Know that the earth is between four and five billion years old.
- Know that scientists need to know what the environment (what chemicals were around,
the temperature, etc.) was like on Earth billions of years ago to know how life formed.