Reproductive strategies for survival

Reproductivestrategies for survival

What we will be focusing on -

• the variety ofreproductive strategies in animals and plants

• how variousstrategies assist successful reproduction inparticular environments.

Sex at sea – Broad cast spawning

• reef fish gathering and simultaneously releasing their eggs and sperm into the water where fertilisation will occur.

• This process is known as

________________• usually occurs in regions of

the reef affected by strong currents and when an outgoing tide is flowing

Broadcast spawners• As a result, the fertilised

eggs are quickly carried away from the reef and from the many predators that live in this habitat.

• Eggs of this type that float within the water column are termed _________________

Creole Wrasse Spawning

Mass spawning - -Some reef fish mate in pairs, such as boxfish.

-Some reef fishthat engage in broadcast spawning, such as coral trouts and cardinalfish. They gather in very large groups at one location and release their eggs and sperm simultaneously in a so-called _______________________

Fresh water – broadcast spawnersAs well as reef fish, fish of the open ocean, such as mackerel, tuna and cod,are also broadcast spawners.

Another group of broadcast spawners are freshwater fish that live in large flood-plain river systems, such as the deltas of the AmazonRiver. Freshwater fish living in these habitats spawn either immediately before or during river floods. This is an optimal time for spawning because - .............

Pelagic Eggs – free floating in waterBroadcast spawners, put all their energy into egg production and produce very _____numbers of eggs.

Any fertilised eggs, however, are immediately on their own as they drift away in the ocean currents.

Embryonic development takes place within the membranes that enclose the egg. The original single egg cell divides many times, forminglayers of cells and then organs. The egg yolk provides energy and nutrients to the developing embryo.

Larva – Zooplankton – Juvenile FishAfter several days, a _______(immature fish) breaks free from the membranes that surround the egg. A newly hatched larva is small, has little power of locomotion, still has some yolk reserves and floats in the ocean as a temporary member of the so-called_________________.When the yolk supply is used, however, the larva must find its own food. After some time, the larva is transformed into a ____________ fish and later the juvenile becomes a sexually mature adult fish, a transition that may take years. Pacific salmon.

Salmon alevins – newly hatched fish

larva

Demersal spawningSome fish produce ______________. Demersal eggs do not float, they are laid in a ‘nest’ in the sand or in a crevice in the reef or she may attach them to some part of the reef surface. After being laid, the eggs are fertilised by sperm released by the male. Demersal spawning occurs, for example, in the anemone clownfish usually on coral, close to the anemone with which she shares living space. (What advantage might this location offer?) The male clownfish then releases sperm to fertilise the eggs.

Nemo – a demersal egg

Demersal spawners invest energy into guarding and cleaning their eggs, these fish produce fewer and larger eggs than broadcast spawners. The developing embryos within demersal eggs have a greater chance of survival than eggs that float in the sea unguarded. After demersal eggs have hatched, the larvae usually swim away and become part of the zooplankton community of the open seas.

Problems in reproduction – Cooking Nemo