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Reproductive strategies for survival

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Presentation on theme: "Reproductive strategies for survival"— Presentation transcript:

1 Reproductive strategies for survival
Sex on the Reef and promiscuity of organisms

2 Great Barrier Reef Stretches about 2300km along the Queensland coast.
Contains many reefs, of differing types Platform Fringing Barrier Ribbon

3 Coral Colonial animals, called POLYPS Lives in calcerious cup
Sticks out tentacles to feed Polyps are carnivorous

4 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

5 Broadcast spawning Simultaneous 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

6 Broadcast spawning continued
Current 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

7 Other broadcast spawners
Not only reef fish Flood plain river fish (needs to be quick) Open ocean fish such as the mackeral

8 Energy needs for broadcast spawning
High energy needs Production of many gametes However, no energy required for care of young Spawn event Fertilised egg nourishes larva with yolk Larva hatches, floats around in ocean Juvenile fish Sexually mature adult fish

9 Demersal spawning Demersal eggs do not float
Female lays eggs in nest or crevice Male drops sperm on them Take care or protect eggs until hatching Less 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

10 Activities Glossary: polyps, broadcast spawning, mass spawn, demersal spawning, pelagic Quick check questions pg 376

11 Reproductive strategies
Reproductive 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)

12 Mating systems Mating systems refer to the number of partners and therefore sexual encounters an organism experiences

13 Monogamy – just us two! Pair bonds (like most humans)
>90% of bird species are monogamous Few mammalian monogamous species Usually occurs when care of young is required by both parents Defending nest/home Incubation of eggs (mostly Aves) Feeding offspring

14 Helpless baby monogamists
Young monogamists are usually born helpless – blind, hair/featherless, unable to fend for themselves Parrot hatchlings Newborn gibbon

15 Polygamy – many partners
Male or female may have many partners One 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 season Poly = many gyny = women andry = men

16 Polygyny – many females
Harem 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

17 Bowerbird – a case study
Satin Bowerbirds build nests which are covered in blue found objects Also 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 mate Female mates with only one male a season Male mates with as many females as he can impress with his display All male’s energy is put into creating, maintaining and presenting his bower Few will father young

18 Lekking Serial polygyny sometimes involves LEKKING
Males all gather together and display for passing females May be visual or vocal displays, including violent displays

19 Polyandry – many men Rare in nature
Female mates with more than one male in a breeding season Female often more ornate than male Female 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 Cassowary Marmoset young

20 Promiscuity Males 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

21 Activities Glossary: monogamy, polygamy, polygyny, polyandry, harem polygyny, serial polygyny, lekking, promiscuity Quick Check questions pg 381

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