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HUMAN REPRODUCTIONBIOLOGY 269
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HUMAN REPRODUCTIONBIOLOGY 269

• COURSE HOMEPAGE
• http//course1.winona.edu/ethompson/269.htm
• Instructor
• Ed W. Thompson Ph.D.
• Pasteur 224
• ethompson_at_winona.edu

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Reproduction
Asexual
Sexual
So If asexual reproduction is so much easier,
why would any animal reproduce sexually?
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Bacteria and other one-celled organisms With
only a couple of exceptions
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Two Advantages to Sexual Reproduction
1. Genetic
Asexual
Sexual
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Two Advantages to Sexual Reproduction
2. Care of Offspring
Asexual
Sexual
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Sexual reproduction involves the formation of
special reproductive cells called
All but lowest organisms male and female gametes.

• By definition, each gamete
• Combination malefemale gametes FERTILIZATION
• Offspring now carries same amount of genetic
  information as either parent
• Fertilization may be external or internal

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Gametes are often unequal in both size and
number.Typically, the male produces while the
female produces
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Sexual reproduction requires two sexes which have
different reproductive strategies.
As expected
Males and females Males and females Males and
females However Both sexes have the same
objective
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This involves

• .
• .
• .
• .
• .

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Different species use different strategies

• Some (e.g. fish) produce very large numbers of
  fertilizations and young from large numbers of
  both males and females
• Some (e.g. humans) produce small number of
  fertilizations and young from large numbers of
  both males and females
• Some (e.g. deer) produce small number of
  fertilizations and young from many females but a
  limited number of males
• Some (e.g. bees) produce a large number of
  fertilizations and young from a limited number of
  both males and females

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Different species use different strategies

• Some (e.g. fish) invest no energy in raising the
  offspring
• Some (e.g. birds, mammals) invest large amounts
  of energy in raising the offspring

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Common feature

• Offspring which Are produced
• and Survive to adulthood
• and Reproduce the next
  generation
• should be

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With that background in mind

• Gather in groups of 4 - 6 individuals and discuss
  what reproductive strategies are important in
  humans, and how this affects our reproductive
  (sexual) behaviors.
• In about 5 minutes, each group will be asked to
  briefly present their conclusions

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Sexual reproduction requires two sexes which have
different reproductive strategies.

• Typically in mammals
• Females invest large amounts of energy in
• .
• .
• .
• .

• Males invest large amounts of energy in
• .
• .

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• Most mammals
• Sexually active only certain times of year
• Females display physical signs when ovulating and
  sexually receptive
• Infants mature in relatively few years
• Short-term care of offspring

• Humans
• Sexually active at all times of year
• No physical changes in female when ovulating
• Long infancy and childhood
• Long-term care of offspring