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Lecture 6

BIOLOGY 321 Lecture Notes - Lecture 6: Sperm Competition, Vocal Folds, Vas DeferensPremium

5 pages42 viewsSpring 2017

Department
Biology
Course Code
BIOLOGY 321
Professor
Dr.Drea
Lecture
6

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Primate Sexuality
I. Polygyny & higher order societies
a. (see last lecture notes)
b. Higher order societies: when one male harems come together to form more complex
and larger groups
i. Aka aggregates of polygyny
ii. Illustrates the need for males to herd and protect their females
c. Males have a great need to protect their females 24/7; however, this is extremely
difficult for a single male to do
i. This opens the possibility for female choice through “sneak” copulations as
males cannot guard always
d. When paternity tests are done, the alpha male is very often the father, however it is
not always so
e. Is there one male for every female? Should one alpha male be ideal for every female?
i. If the “best” male is the females brother, that certainly isn’t the best choice for
her
f. Infantacide
i. Females form friendships with males, which is hypothesized to be a way to
decrease risk of infanticide
ii. Infanticide is rare in societies, and yet many researchers argue that friendships
are for decreasing infanticides; their evidence is only the absence of
infanticide, which is not a strong case
iii. Bruce effect: when you have a pregnant male, and a new male is introduced, a
female aborts her child and mates with the new male
1. When the harem is taken over, this abortion may be because this
prevents birth of children and thus investment of time in children that
may be killed by the new male
2. This is strong evidence
iv. There are always exceptions to the reasons for infanticidein lemurs,
infanticide by a child’s aunt occurred, and lemurs cannot be brought to
reproduce sooner through this
II. Multi-Male Multi-F
a. Mating tactics:
i. Dominance hierarchies
1. Mating success /= reproductive success
2. However, may allow for consortships (mate guarding) for higher
ranking members, or sneak copulations for lower ranking members
3. Interruptions of mating, harassment, and infanticide
ii. Lots of female female competition
iii. Again uses tactic of multiple mating in order to “cast doubt” about who the
father isdecrease infanticide risk
b. Anatomical and behavioral correlates
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i. Great MM competition for access to F
ii. Pronounced sexual dimorphisms
1. And thus different maturation rates
iii. Sperm competition, larger testes with bright coloration
1. Unlike other societies, males who gain access do not then have
exclusive access
2. Coloration is to attract female attention
iv. Female advertisement of sexual status
1. Scent markings
2. Swellings
III. Dispersed
a. Mating tactics
i. MM comcpetition, overlap of territory with females
1. Have to defend larger territories
ii. F advertisement (scent markings) or initiation (consortship)
iii. Orangutans only: forced copulation
b. Anatomical and behavioral correlates
i. Prosimians are small to avoid predator detection
1. Therefore, not much sexual dimorphism despite MM competition
ii. Orangutans have strong sexual dimorphisms (with alternate mating strategies
ie forced)
iii. F anatomical barriers (prosimians)only an opening during the breeding
period
iv. Orangutans: concealed ovulation, to promote consortship and not forced
copulation
Male Reproductive System human will be used as the example mostly
Review of Reproductive Organism
I. Functions
a. Testes: spermatogenesis (production of male reproductive cells) and androgen
production (T will be used to represent androgens now; involved in 2dary sex
characteristics)
i. Androgens are also produced in the adrenal glands
ii. Both processes start at puberty and continue throughout life
iii. Testes are usually descended at birth, at latest for it to be normal is 1 year;
descending is necessary to produce functional sperm
b. Scrotum: keep testes cooler (about three degrees Celsius lower than body
temperature)
c. Penis:
i. excretion of urine
ii. ejaculation of sperm as far into female as possible
II. Male Pubertal Changes
a. Secondary Sexual Characteristic
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