Transcript Natural Selection in Action

Natural Selection in
Action
Chapter 7
Section 3
Changes in Populations
 Through ongoing natural selection, a
population adapts to its environment.
 Well-adapted individuals will likely
survive and reproduce.
• Because of hunting,
fewer elephants with
tusks survive to
reproduce, leaving
more of the tuskless
elephants to survive.
• When the tuskless
elephants reproduce,
they pass the
tuskless trait to their
offspring.
Insecticide Resistance
Generation Time
Definition: the average time between one
generation and the next
 Insects: short generation time (hours or
days)
 Humans: long generation time (80 years)
Speciation
Definition: the formation of a new species
as a result of evolution
 Occurs after a group becomes separated
from the original population
 New population adapts to new environment
 New population & old population are now so
different that they can no longer mate
successfully