Card Set Information
What is sex?
mode of reproduction
behaviours associated with copulation
'sex' sometimes used to describe maleness or femaleness
sex is not necessary for reproduction
self fertilisation can occur eg in plants
: males and female flowers in the one plant
many adaptations to prevent self fertilisation
What is a disadvantage for asexual reproduction?
no genetic variation
What is a fission?
the separation of a parent organism into two individuals of approximately equal size
form of preproduction in which the ovum develops into a new individual without fertilisation.
e.g. bees and wasps
: females are diploid adults that develop from fertilised eggs. Males are fertile haploid adults that arise by parthenogenesis
What is sexual reproduction?
reproduction that generates a new individual combining the genes of two parent individuals
fusion of the haploid (n) gametes = diploid (2n) zygote. consists of 2 sets (2n=46)
male gamete = sperm
female gamete = ovum/egg/oocyte (usually larger than sperm)
gamete also called germ cell
What is the only universal truth about sex?
parthenogenesis can occur many ways but in sexual reproduction meiosis is always the same.
Costs of Sex
recombination scrambles genotypes, disrupting favourably adapted gene combinations
parthenogenesis preserves advantageous genotypes
meiosis and sngamy takes longer than miotosis, slowing the pace of reproduction
decreased population growth rates
in higher organisms, courtship and mating is risky (risk from predation, STD's, wastage of gametes, costs associated with maintenance of sexual dimorphism, sexual competition)
at low population densities sexual reproduction may be difficult to coordinate
parthenogenesis ensures that reproduction will be possible at any time
advantages of sex?
Recombination (sex) purges deleterious mutations
facilitating response to environmental change
parthenogenetic organisms more easily attacked by parasites
sex is needed to fight disease
allows selection to more easily work on combinations of traits
allows genome of species to carry significantly more information than genome of an individual
encourages fruitful collaborations
asexually producing species often thrive for a time but are slower to adapt to change
many organisms only reproduce sexually only in times of stress, reproduce asexually normally
What is gender?
Gender assignment needs to take into account all three of the following aspects:
How is gender det