2. Section 24.3
Joe Smith

3.  Often
results in sexual
dimorphism
• More intense with
males
 Formof Natural
Selection
Female

4. 2 methods
• Intrasexual
 Competition within one sex for opportunity to mate with
opposite sex
• Intersexual
 “Mate choice”
 “Cryptic Female Choice”
 Less Obvious
 These two methods can overlap

6.  Competing between members of one sex
for opportunity to mate with the opposite
 Examples
• Horns on male goats
• Antlers on male deer
• Enlarged claws on male fiddler crabs

7.  Females are picky
• Seen in Indian peafowl
• “Classic” form of
intersexual selection
 “Cryptic female
choice”
• Less obvious
• Female reproductive
tract is selective for
genetically un-related
sperm

8.  NOT always beneficial for survival
• Female guppies prefer brightly colored mates
• Bright colors are easier seen by predators
 Effects can be measured by abundance of
traits

9.  Many different hypotheses
• Related to upbringing of offspring
• Dependant on fitness
 Age is a factor

10.  Governed by same processes
• Directional
• Stabilizing
• Diversifying
• Balanced

11. Feature Investigation
Seehausen and van Alphen Found That Male Coloration in African
Cichlids Is Subject to Female Choice

12.  Cichlidae family one of largest and most
diverse
• Vary by:
 Coloration
 Body Shape
 Behavior
 Feeding Habits
• Largest population in Eastern African lakes
• Known for complex mating behavior

13.  P. pandamilia and P. nyerierei can
interbreed
 Both found in Lake Victoria
• Certain areas of the lake have interbreeding;
others do not
 Coloration valued in female choice of mate