THE EVOLUTION OF POPULATIONS

KEY CONCEPT

• New species can arise when populations are isolated

THE ISOLATION OF POPULATIONS CAN LEAD TO SPECIATION

• Isolation stops gene flow between two populations
• Many factors can change the gene pool between populations
• Ex) adaptations to environment, mutations, behavior, ect.
• Reproductive isolation is when two populations can no longer mate successfully
• This is the final step of becoming separate species

CONTINUE

• Speciation is the rise of two or more species from one existing species
• Mutations can lead to speciation ex) tropical fruit flies and temperate fruit flies

POPULATIONS CAN BECOME ISOLATED IN SEVERAL WAYS

• Behavioral, geographic, and temporal behaviors prevent mating between populations

BEHAVIORAL BARRIERS

• Normally, signals such as chemical scents, dances, and songs are used to attract mates
• Behavioral isolation is isolation caused by changes in courtship or mating signals
• Behavioral isolation can prevent mating between populations

GEOGRAPHIC BARRIERS

• Geographic isolation are physical barriers that divide a population in two or more groups
• Ex) rivers, mountains, dried lake beds, ect.
• If members of the same species are isolated due to geographic isolation...
• They evolve into different species and will no longer mate with one another.

TEMPORAL BARRIERS

• Temporal isolation exists when time time prevents reproduction between populations
• Members of a population may show signs of courtship at different times
• Competition for mates
• Reproductive periods may change to a different time or day (day or night)
• These differences lead to speciation