Topic 13 Flashcards
Asexual reproduction
originally organisms would have reproduced using binary fission (similar to biotic cell division) all new individuals would have been clones of the original.
Evolution in asexual reproduction would only have occurred due to..
mutations of the original cell line (no genetic diversity)
Sexual reproduction major advantage
genetic diversity within a population of species
Sexual reproduction disadvantages
- only half of individuals genes are passed onto next generation
- growth rate is half that of asexual reproduc. (takes 2 organisms to make 1)
- some unfavourable recombinations
All the sexual disadvantages can serve to reduce..
fitness
Although not ubiquitous most prokaryotes, bacteria and single cell organisms still reproduce through..
binary fission (sometimes budding)
Fungi have simplest form of
sexual reproduction: isogamy (equal gametes)
Plants
evolved complex life cycles and strategies to fertilize eggs, often relies on environment or other species
Typical pattern of gender biases in animals
males do the courting and females do the choosing
Male fitness often dependant on
acquiring multiple mates
Female fitness often dependent on
access to abundant resources
Anisogamy
gender biases are a result of unequal investment in gametes
Egg cells are more ..
energetically costly to produce than sperm cells
Theoretically a single man could ..
fertilize all the eggs of all the women in the world
Male fitness increased by..
fertilizing multiple eggs
Female fitness increased by..
continued investment in costly egg
Females having already invest more in gamete production to continue to ..
invest in parental care
Male evolution driven by sexual selection
- traits to enhance attractiveness
- triats to enhance competitive ability w other males
Traits to enhance attractiveness
hypothesizes the displays advertise good genes and healthy conditions. enforce runaway selection
Traits to enhance competitive ability w other males
impose dominance heiarchy, sneaky male strategy, mate guarding, sperm competition and nuptial(food) gifts
Runaway selection
- males inherit genes for impressive display
- females inherit preferences for display
Mating system
number of partners that males and females have. can vary among species, includes aspects of parents care
4 general categories of mating system
- polygyny (most common)
- polyandry
- monogamy
- promiscuity
Polygyny
single male takes multiple female mates. most common.
Polygyny female defence
where females cluster together for predator defence or resource patches
Polygyny resource defence
where resources are clumped and male will control area that is attractive for females
Lek polygyny
area where a male will set up an often elaborate mating display to attract mates (no resources involved)
Polygyny scramble competition
where timing window for mating may be short, so it is a first come first serve basis
Polyandry
single female takes multiple mates, rare in nature. when something limits the brood size of the female below that of which is capable it may take multiple mates.
Spotted sandpiper
polyandry, gender role reversal. lay up to 12 eggs and needs more partners to help incubate the eggs
Monogamy
single pair of bond between one male and one female. common in some animals like fish and birds. when there is a high risk that female may take multiple partners in absence of mate guarding, when male offers up energetically costly support
Seahorse
brood pouch means that male seahorse bears the burden of “pregnancy”. monogamy
Promiscuity
females and males both take multiple partners. result of coevolution of other mating systems between males and females. increase fitness by multiple partners.
Parthenogenesis
reproduction through the development of unfertilized female gamete, doesn’t require male input.
Parthenogenesis is what reproduction..
asexual reproduction of haploid cell, life cycle includes sexual cycle to maintain genetic diversity
Hermaphroditism
individual that produces the gametes associated w both the male and female sex. not typically self fertilizing (lower genetic diversity) often unlucky one of the pair will have to bear motherhood.
Sequential hermaphroditism
rare in species individuals can actually change their gender over the course of their life.
Clownfish
sequential hermaphroditism, largest one is female, second largest is reproductive male, other non reproductive. when females dies, next largest becomes female.
