BIOC51H3 Lecture 20: BGYB51H3 Lecture 20 Notes Nov 17
11 Aug 2010
School
Department
Course
Professor
BGYB51H3 Lecture 20 Notes
-sexual dimorphism is where males and females in a species have different features and
behaviour
-males are more affectionate in that they seek out more mates to copulate
-sexual dichromatism is differences in colour
-structural dimorphism is differences in structure
-sexual size dimorphism is differences in behaviours
-many traits that are dimorphic reduce survival
-selection for survival unlikely explains differences between sexes
-differences in selective pressures are due to females investing more in offspring than males
-parental investment is anything that increases the chances of survival of current offspring
while decreasing the ability to produce future offspring
-females are defined as producing large and relatively few eggs while males have inexpensive
sperm
-usually maternal care is more than paternal care
-in any given species, sperm are present in excess compared to eggs
-male reproductive output is limited by access to eggs
-female reproductive output is limited by access to resources
-males can increase fitness by increasing mating fitness
-males have higher maximum reproductive output than females
-increasing the amount of mates a female acquires has little effect on reproductive output
-females have the same fitness as males although some males have variation in mating success
-sexual selection is a subset of natural selection that focuses on traits that have higher mating
success
-sexual selection has its strongest effects on the sex (male or female) whose reproductive
output is limited to access to mates
-intrasexual selection has success in competition for females being the agent of selection
-]vƵoo]}v]vÀ}oÀZu[ choosiness being the agent of selection
-members of the sex with more variable reproductive success will compete
-traits favoured in intrasexual selection are
x large body size
x armour
x weapons
-alternate tactics involve strategies that would normally be advantageous in competition but
are ways in which sneaky males can increase reproductive success
-sperm competition involves competition between sperm of different males that occurs
inside the body of the female
-different adaptations for sperm competition
-in intersexual selection, females are usually choosy and males try to convince them to mate
-traits favoured in intersexual selection are
x displays
x ornamentation
www.notesolution.com
Document Summary
Sexual dimorphism is where males and females in a species have different features and behaviour. Males are more affectionate in that they seek out more mates to copulate. Selection for survival unlikely explains differences between sexes. Differences in selective pressures are due to females investing more in offspring than males. Parental investment is anything that increases the chances of survival of current offspring while decreasing the ability to produce future offspring. Females are defined as producing large and relatively few eggs while males have inexpensive sperm. Usually maternal care is more than paternal care. In any given species, sperm are present in excess compared to eggs. Male reproductive output is limited by access to eggs. Female reproductive output is limited by access to resources. Males can increase fitness by increasing mating fitness. Males have higher maximum reproductive output than females. Increasing the amount of mates a female acquires has little effect on reproductive output.
