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