MATING SYSTEMS AND REPRODUCTION Flashcards
a) What is monogamy?
b) What are the different forms of polygamy?
a) pair matings
b) - polyandrous, where female mates with many males
- polygynous, where male mates with many females
- promiscuity, both sexes have multiple partners
What drives reproductive conflict?
ANISOGAMY
How has monogamy evolved in some species?
- male parental care is indispensable
- males are forced away from future mates due to aggression from already mated females
- an unmated male may be more advantageous
- males may prove successful by defending exclusive access to female
- males are less successful with 2 females than one
3 hypotheses for monogamy evolution
- mate assistance hypothesis
- mate guarding hypothesis
- female enforced monogamy
Distinguish between obligate and facultative monogamy
OBLIGATE - both parents required for offspring survival
FACULTATIVE - density of food and mates v low
a) Pure polyandry is vanishingly (a)
b) Whereas, polygyny is very (b)
2 forms?
c) How does polygyny play out when there are widely dispersed females and resources?
a) rare
b) popular
- female defence monogamy, one male defends a group of females
- resource defence monogamy, one male defends a resource that females require
c) lekking
OR scramble competition monogamy
Why would females be promiscuous?
- avoid male harassment
- dubiously, males provide support for young
- offsets risk of male infertility
- sperm competition
- increase genetic diversity
- cryptic female choice through sperm competition
In monogamy, there is (a) sexual selection. In polygyny there is loads of sexual selection, leading to sexual (b).
a) little
b) dimorphism
3 factors leading to sociality
- large brain
- endotherm
- strong mother offspring bond
2 ways in which lactation is performed
1) aereolar patches are milk glands open to surface
- nipples or teats
Where did mammary glands develop from?
- from apocrine and sebaceous glands
Why lactate?
- allows rapid growth of tiny young
- may buffer young against food shortage
- transfer of maternal immunity, hormones, antioxidants,
- limits lack of paternal care
What does oriparous mean?
egg laying
What is the function of placenta?
to nourish embryo whilst inside uterus
In some mammals with no placenta, there is no direct link between the embryo and the mother, all they have is ___.
endometrium
Distinguish between a chorioallantoic placenta and a choriovitelline placenta
chorioallantoic - formed from chorion and allantois fused
choiovitelline formed from yolk sac or vitelline membrane
What do all therians begin with? (placenta)
a chorioallantoic placenta
How do eggs develop in prototherian early amniotes?
1) ovum released from ovary
2) fertilised prior to entering oviduct
3) mucoid coat secreted around egg
4) basal shell layer secreted around egg
5) second layer added
6) embryo develops
7) uterine section nourishes embryo
8) 3rd shell layer added and it is laid
What has changed between prototherian reproduction and metatherian reproduction?
1) separate rectum from urogenital sinus
2) paired lateral vaginae for sperm passage
3) midline pseudovaginal canal for birth of young
How are metatharians born?
- they are born severely underdeveloped and have to climb in to a pouch to suckle
How does milk composition vary?
Begins high in protein and low in fat then switches to low in protein high in fat
What characteristics are changed in the transition from metatheria to eutheria?
b) how about egg development?
1) further separation of rectum and urogenital sinus
2) single middle vagina
3) have divided uterus
b) begins as chorovitelline placenta and becomes chorioallantoic
Different degrees of integration between mother and foetus?
1) EIPTHELIO
- all 6 layers present
2) syndesmo
uterine epithelium lost
3) endothelio
- embyro in contact with maternal capillaries
4) hemo
- chorion in direct contact with maternal blood
5) homoendo
- fetal capillaries in direct contact with maternal blood
Final key eutherian distinctive characteristics
- long gestation period
- shorter relative lactation period
