BIOL150 Lecture Notes - Lecture 7: Plant Reproductive Morphology, Apomixis, Vegetative Reproduction
2 May 2018
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Life History
• Life history is the lifetime pattern of growth, development and reproduction
• Predicts how natural selection shapes the way organisms invest their resources offspring into
producing offspring to maximize fitness
• Life History traits
o Size at birth
o Growth pattern
o Age and size at maturity
o Number, size and sex of offspring
o Age and size specific reproductive effort
o Age and size specific survival rates
o Life span
• Types of reproduction
o Asexual: offspring are genetic clones of parents
▪ Types
• Fission - bacteria split in two
• Budding - grows in the side then buds off
• Parthenogenesis - Creating offspring without male fertilization
• Fungi asexual spores - mitosis
• Vegetative reproduction - e.g stolons and and rhizomes (plants)
• Apomixis
o Sexual
• Sexual vs. Asexual
o Asexual
▪ High fitness under current conditions
▪ Rapid population growth
▪ Low genetic variability - less adaptable to changing conditions
o Sexual
▪ portfolio effect: genetic diversity minimizes the volatility of the population’s
response to changes in environment conditions
▪ more raw material for natural selection to act on
▪ takes time and energy if resources are scarce and seasons short
• Modes of reproduction
o Animals
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▪ Unisexual: one male one female
▪ Hermaphroditic: individuals posses both male and female organs
• Rapid expansion followed by colonization
• Simultaneously hermaphrodite - individuals posses both male and
female organs
• Sequentially hermaphrodite - the removal of male stimulates the
largest female to replace him
o Plants
▪ Imperfect
• Monoecious
• Dioecious
▪ Perfect
• Bisexual (monoecious)
o hermaphrodite
• Mating systems: Animal
o Monogamy - single pair bond, co-parenting
▪ homogenous territories
o Polygamy - heterogeneous territories that are defended by the parent not rearing the
child
▪ Polygyny: 1 male, >1 female, female raise offspring
• Simultaneous
• Harem size related to synchronicity of sexual receptivity
▪ Polyandry: 1 female, >1 male, male raise offspring
• Typically sequential e.g Sandpipers
• Improved fitness of female: tortoises with mixed paternity clutches
• Eusocial: dominant breeding female, non-fertile siblings raise offspring
o Promiscuity: no pair bond - one parent provides no resources or care
• Sexual Selection
o Intrasexual selection
▪ within-sex competition for mates
▪ promotes sex traits like aggressiveness, antlers
o Intersexual selection:
o between sexes (attractiveness)
find more resources at oneclass.com
find more resources at oneclass.com
