Reproductive strategies for survival

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

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

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

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