Sex on the Reef and promiscuity of organisms
Reproductive strategies for survival
Great Barrier Reef
•Stretches about 2300km along the Queensland coast. •Contains many reefs, of differing types•Platform•Fringing•Barrier•Ribbon
Coral
Colonial animals, called POLYPS
Lives in calcerious cup
Sticks out tentacles to feed
Polyps are carnivorous
Reef zones
Shallow waters/ reef flats-Find rays and sharks-Other light-dependent organisms-Warm waters
Deeper “barrier” habitats-Likely to find more plentiful small fish-Turtles-Octopus -Cooler water, less light available
Broadcast spawningSimultaneous
release of eggs and sperm into water
Usually occurs in areas with some current to distribute gametes
Happens in many fish species, as well as the coral polyps
Broadcast spawning continuedCurrent takes
fertilised eggs away from reef (and predators)
Floating eggs are called PELAGIC eggs
Boxfish mate in pairs by meeting up and releasing their gametes together
Large groups broadcast spawn together. This is called a MASS SPAWNING event
Other broadcast spawnersNot only reef fishFlood plain river fish (needs to be quick)Open ocean fish such as the mackeral
Energy needs for broadcast spawningHigh energy needsProduction of many gametesHowever, no energy required for care of
young
Demersal spawningDemersal eggs do not
floatFemale lays eggs in nest
or creviceMale drops sperm on
themTake care or protect
eggs until hatchingLess eggs = less energy
used, but care of eggs = more energy used
Higher chance of offspring survival than broadcast spawning
Clownfish reproduce using demersal spawning
Despite impressions given by Finding Nemo, clownfish receive no parental care after hatching
ActivitiesGlossary: polyps, broadcast spawning, mass
spawn, demersal spawning, pelagic
Quick check questions pg 376
Reproductive strategiesReproductive strategies we’ve already looked at
New reproductive strategies
Type of reproduction (asexual/sexual)
Gender systems (separate male/female, hermaphrodite)
Mode of fertilisation (internal/external)
Mating system (monogamy, polygamy, promiscuity)
Number of offspring (K selection, r selection)
Place of development and nutrition for embryo (oviparity, viviparity)
Investment of care into offspring (one parent, both parents, neither parent)
Mating systemsMating systems refer to the number of
partners and therefore sexual encounters an organism experiences
Monogamy – just us two!Pair bonds (like most humans)>90% of bird species are monogamousFew mammalian monogamous species
Usually occurs when care of young is required by both parentsDefending nest/homeIncubation of eggs (mostly Aves)Feeding offspring
Helpless baby monogamistsYoung monogamists are usually born
helpless – blind, hair/featherless, unable to fend for themselves
Parrot hatchlings Newborn gibbon
Polygamy – many partnersMale or female may have many partnersOne parent can ensure survival of young
Polygyny – one male has many female partners in one season
Polyandry – one female has many male partners in one seasonPoly = many
gyny = women andry = men
Polygyny – many femalesHarem polygyny Serial polygyny
One dominant males lives with a group of females.
Mates with each of them during the mating season.
Examples: Magpies, wood mouse, Elephant seals
One male attracts passing females for mating
Males must advertise themselves
In bird species, male is often highly decorated to attract female
Male usually does not care for young
Examples: Lyrebird, Bowerbird, Peacock, Horseshoe bats
Bowerbird – a case studySatin Bowerbirds build nests which are covered in blue found
objectsAlso will sing and dance in front of his bower when a female walks
by If she is impressed, she enters the bower and the pair mateFemale mates with only one male a seasonMale mates with as many females as he can impress with his
displayAll male’s energy is put into creating, maintaining and presenting
his bowerFew will father young
LekkingSerial polygyny sometimes involves LEKKINGMales all gather together and display for passing
femalesMay be visual or vocal displays, including violent
displays
Polyandry – many menRare in natureFemale mates with more than one male in a
breeding seasonFemale often more ornate than maleFemale cassowary mates with a male, lays a
clutch of eggs in a nest he’s made, then leaves him to incubate the eggs and care for the young, while she looks for another mate.
Marmosets also exhibit polyandry
Marmoset young
Cassowary
PromiscuityMales and females in a social group engage
in indescriminate, multiple, numerous matings every season.
All males approximately equally likely to produce offspring
More likely to occur in males, as the production of sperm is relatively low-energy, whereas the production of an egg requires more energy
ActivitiesGlossary: monogamy, polygamy, polygyny,
polyandry, harem polygyny, serial polygyny, lekking, promiscuity
Quick Check questions pg 381