Sex and behaviour

• Female gametes


  large, nutrient-filled, expensive to produce, limited in number, and produced infrequently. If fertilised this will lead to high cost to the female
• Male gametes


  small, have no nutrients, cheap to produce, constantly made throughout life
• Reproductive capability


  females are classed as the 'slow sex' and males the 'fast sex'
• Nurturant females


  in most animals, and almost all mammals, females provide for more parental investment than just the eggs
• Parental investment


  costly but increases the probability of production and survival of the young
• classification of R-selected and K-selected organisms

  based on level of parental investment in offspring and number of offspring produced
• R-selection


  mature young, many offspring, frequent breeding, small offspring, high mortality rate, occurs in unstable environments where the species has not reached it's reproductive capacity
• K-selection


  older maturation, few offspring, infrequent breeding once a season, larger offspring, low mortality rates, occurs in stable environments
• benefits of internal fertilisation

  fewer eggs needed, higher offspring survival rate, increased chance of fertilisation, offspring can be retained internally for protection/development
• cost of internal fertilisation

  locating a mate requires energy, requires direct transfer of gametes from one partner to another
• Benefit of external fertilisation


  very large numbers of offspring can be produced
• cost of external fertilisation

  many gametes predated, many gametes unfertilised, limited parental care= few offspring survival
• mating systems


  based on how many mated an individual has during one breeding season
• monogamy


  pairs mate to the exclusion of all others
• Polygamy


  individuals of one sex have more than one mate
• polygyny


  one male mates exclusively with a group of friends
• polyandry


  one female mates with a number of males in the same breeding season
• many animals have mate-selection courtship rituals as a result of species-specific sign stimuli with fixed action pattern responses
• sexual dimorphism


  larger males compared to females of the species, more colour full males, and general distinct differences in the male
• Reversed sexual dimorphism


  females are drastically larger females than males
• successful courtship behaviour in birds and fish can be a result of species-specific sign stimuli and fixed action pattern responses
• Sexual selection selects for characteristics that have little survival benefit for the individual, but increase their chances of mating
• many species exhibit sexual dimorphism as a product of sexual selection
• female choice involves females assessing honest signals of the fitness of males
• success in male-male rivalry through conflict (real or ritualised), increases access to females for mating
• In lekking species, males gather to display at a lek, where female choice occurs