Sexual

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Sexual Reproductive behaviors

• Dr. Kline
• FSU

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I. Mating Behaviors

• What is the main reason animals mate?
• For most animals (excluding human beings), mating
  serves one purpose the reproduction of
  offspring.
• Mating behavior is necessary because it leads to
  conception subsequently the birth of offspring.

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Who controls mating behavior? Males or Females

• Mating sexual behavior are largely under the
  control of the female of a species.
• This includes human beings.

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The Traditional view of Female Sexual Behavior

• Historically, females have been viewed as
  sexually receptive to male advances.
• That is, the female will passively accept rather
  than resist male sexual overtures, mating will
  result.
• Males are always viewed as available motivated
  to copulate while females are usually reluctant
  to mate, but will occasionally give in.
• Recent research (lab field) has shed light on
  the problems with this traditional view. Females
  are far from passive recipients.

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Modern view of Female Sexual Behavior

• 1. Females are active initiators of mating not
  passive recipients. Called proceptivity, the
  female may exert great effort to achieve sexual
  contact with a male.
• (E.g., Females dart in front of indifferent
  males hopping wiggling her ears to signal
  interest.)
• Females rodents also control the timing of
  mating copulate relatively indiscriminately
  with all males that respond.

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2. Females are not inherently monogamous as was
once thought.

• In many species, females will choose to mate with
  several males.
• While females tend to be selective in who they
  mate with, this shouldnt be confused with
  monogamy.
• E.g., Female monkeys mate with several males,
  not just the dominant monkey.
•  
• It has been shown that some female birds will
  choose a partner to nest with, but actually
  reproduce offspring by mating with another male.

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3. Females do not always put more investment
into reproduction.

• Female spotted sandpiper displays defends
  breeding territory, duties assumed by the male in
  most birds species.
•  
• Female lions do most of the prides hunting (not
  the male) share responsibility for each others
  cubs.
• Male seahorses carry the young in their bodies.
•  

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II. When are non-human females most likely to
engage in sexual behavior?

• During estrus (in non-human animals).
•  
• During estrus the non-human female is
• fertile
• receptive to mating
• proceptive
• sexually attractive (pheromones)
•  

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What influences the estrus cycle?

• Hormones!!! Estrogen progesterone increase
  over a period of a few days prior to ovulation.
• Estrus is initiated following the increases in
  these hormones.
• Removing the ovaries (ovariectomy) in rats, will
  produce a rapid decline of both proceptive
  receptive behaviors in females.  
• This can be reversed with injections of estrogen
  progesterone. Thus the role of hormones in the
  estrus cycle is critical.

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When are human females most likely to engage in
sexual behavior?

• Unlike the estrus cycle, in the menstrual cycle
  sexual interest can occur throughout the cycle.
• However, women are more likely to report
  increased sexual interest during the
  periovulatory period when ovulation occurs.
• This four day period corresponds to the highest
  surge of estrogen.

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Evidence that women are more sexually excited
during periovulatory period.

• Two studies have reported that women initiate
  more sexual activity (with partner or by
  auto-erotic means) during the periovulatory
  period than at other times of the month.
• Women rate an erotic video as more pleasant
  arousing if they watch if during the
  periovulatory period than at other times (Slob et
  al., 1996).

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The effect of hormones on mens sexual behavior?

• Male sexual arousal is highest when testosterone
  levels are highest. The peak is between 15-25
  yrs.
• This declines with age.
• Oxytocin also plays a role in male sexual
  behavior large amounts are released during
  orgasm (also increases pair bonding behavior).
• Question It is known that men fall in love
  more easily out of love more slowly than women,
  could this be influenced by oxytocin??? Food for
  thought!!!

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Will changing testosterone levels influence
sexual activity in men?

• Yes!!! Increase levels increases interest
  decreasing levels decreases interest.
• (e.g., castrated males show less interest in
  sex.)
• Testosterone reduction has been used as a means
  to control sex offenders has shown some success
  (although on average their levels were normal).

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III. Pheromones

• chemicals secreted from one organism to another,
  having sexually attracting or repulsing effects.
• Pheromones are secreted by the body (urine,
  feces, sweat glands) at low concentrations can
  act at fairly long distances.
•   (e.g., Male luna months have antenneae
  capable of sensing pheromones released by
  females.)
•  
• Humans have evidence of vomeronasal organ (VNO)
  in nose, our pheromone detecting structure,
  suggesting we respond to pheromones.

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Do humans respond to pheromones?

• It appears there is some evidence that pheromones
  influence our behaviors.
• McClintock effect (1970s, 1998) female college
  students living in a dorm for 7-8 month period
  synchronize menstrual cycles.

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IV. Hormones chemicals released by glands

• Two types of glands
• 1. Exocrine- release substances into outside
  world. (E.g., sweat glands)
• 2. Endocrine- release hormones into bodys
  circulatory system. Travels to target organ to
  exert its effects.
• E.g., pituitary gland, ovaries testes

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V. Gonads

• testes for males - produce sperm cells
• ovaries for females- produce ova (eggs)
• After copulation, a single sperm cell may combine
  with an ovum to form a zygote
• zygote- contains all information necessary for
  growth of a complete adult organism.
• Except ova sperm cells, each cell has 23 pairs
  of chromosomes

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VI. Sex Chromosomes-the genetic programs that
direct sexual development

• Females- XX shaped chromosomes.
• Males -have one X one Y shaped chromosome.
• Male determines childs chromosomal sex. Each
  ovum has an X, sperm may be an X or a Y.
• Gonads - also produce release hormones.
• Ovaries testes release same hormones
  androgens, estrogens, progestins.

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VII. Is it a boy or a girl???

• Both genetic male females are programmed to
  develop female bodies (female is the prototype).
• Programmed development of the female body must be
  overridden in order for a male to develop. This
  occurs via hormones (androgens) that must be
  present at right time for the male body to
  develop.
• Otherwise, a chromosomal male will have a female
  body.

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Its a Boy!!!!!

• Six weeks after fertilization-
• male female embryo have same structures.
• Primordial gonads-
• medulla- may develop into testis
• cortex- may develop into an ovary
• Y-chromosome -triggers manufacture of a protein
  called H-Y antigen. This causes medulla to
  develop into a testis.
• Lack of H-Y antigen leads cortex to develop into
  an ovary (no antigen is needed for female
  development).

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Internal Reproductive Ducts

• Six weeks after fertilization, both males
  females have two complete sets of reproductive
  ducts.
• Male- Wolfian system
• Female-Mullerian system
• In 3rd month of fetal development, testes of male
  fetus secrete androgens. This stimulates Wolfian
  system, inhibits Mullerian system.
• Without presence of testosterone, Mullerian
  system develops. Opps, its a girl!!!!!

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VIII. Its a boy, its a girl, its Pat!!!!

• There are some individuals who are not exactly
  male or female, but intermediate.
• For instance, some are born chromosomally male or
  female, but have a defective gene that leads to
  the development of an ovary a testis, or two
  testes, or a mixture of testis ovary tissue on
  each side.