• Explain how the evolution of these reproductive adaptations has increased the chanced of continuity of the species in the Australian Environment

Asexual reproduction
Organisms that reproduce asexually do not have to rely on another individual organism to provide gametes and are at an advantage when sudden or unexpectedly favourable conditions arise because they can quickly reproduce themselves (with offspring identical to the parent). This can become a competitive edge if the organism lives in an environment that is often disturbed, and they are particularly well suited to a certain environment or habitat. Asexual reproduction among plants is far more common in harsh environments where there is little margin for variation. The main disadvantage to asexual reproduction is if extremely harsh conditions arise, the whole group of species is particularly vulnerable to these conditions, or to disease, parasitism and predation.

Sexual reproduction
Sexual reproduction produces offspring that are genetically different and possibly better adapted to new and changing environmental conditions than their parents. This gives the species a better chance at surviving in ever-changing environments. However, sexual reproduction is often a more energetically expensive process, compared to asexual reproduction, and may be the first thing an organism abandons in times of hardship.

External fertilisation
The chances of successful external fertilisation are increased by the synchronisation of the release of gametes, reproductive cycles and the mating behaviours of each species. External fertilisation and development means that parents spend less time looking after the young, but more gametes have to be produced to ensure that some eggs get fertilised. The advantage of this method is the high dispersal of young. The gametes are thrown into the sea and fertilised eggs are carried away to settle in an area different to their parents. This reduces competition for food and living space for the parent generation, and allows quick recovery of populations away from damaged areas.

Internal fertilisation
Fewer gametes are produced because there is a much higher rate of fertilisation and survival. The move to internal fertilisation and development has demonstrated new adaptations for reproduction on land, which may have started with the ovules of flowers becoming enclosed in the ovary to provide adequate protection from desiccation.

Parental care
Many aquatic species simply abandon the fertilised eggs and leave them to risk development in the open sea. This means that less energy is put into caring for the young and the survival rate of the young is much lower; therefore, more eggs have to be produced to compensate. Mammals are generally viviparous, fish, birds, some reptiles and many invertebrates are oviparous (egg-laying). Oviparous animals will devote varying amounts of energy to caring for their eggs. Some oviparous animals brood their eggs until they hatch to increase the survival rate of their eggs, while others will stand guard over a nest of eggs until they hatch.

Plants
In plants, self-pollination expends less energy in the production of pollinator attractants and can grow in areas where the kinds of insects or other animals that might visit them are absent or very few. These plant species contain high proportions of individuals well-adapted to their particular habitats. In cross-pollinators, animal agents such as insects, birds and mammals have become a more effective way of transferring pollen to the stigma. As flowers become increasingly specialised, so do their relationships with particular groups of insects and other animals.

The transfer of pollen between flowers of separate plants ensures cross-pollination and may have been important in the early success of angiosperms. The various means of effective fruit dispersal that evolved in the group were also significant in the success of angiosperms. As early angiosperms evolved, all of these advantageous features became further elaborated and developed, and the pace of their diversification accelerated. In addition to insects, birds and mammals now assist in pollination and seed dispersal.

Adaptations for colonization and survival
Reproductive adaptations are needed for successful colonisation and survival in the Australian environment. Australia has many areas of harsh arid conditions, making it difficult for effective fertilisation and development. Reproducing offspring in times favourable to the organism— suitable climate and resources, available water and food supply— increases the chances of continuity of the species.

Species need to survive the harsh times and maintain their population numbers (without becoming extinct) until conditions improve, then utilise adaptations to rapidly increase species numbers afterwards (e.g. the kangaroo with its embryo on standby). Many Australian plants possess adaptations to harsh conditions like fire, for example hakeas have woody seed pods able to survive the high temperatures of fire. The pods do not usually open unless stimulated by the heat of fire, landing on soil enriched by ash from the fire. This means that the seed is not released and dispersed until environmental conditions are favourable for rapid increase and therefore continuity of the species. Hakeas also regenerate and ensure continuity of the species after fire by growing lignotubers from the fi re-damaged plant.

• Describe the conditions under which asexual reproduction is advantageous, with reference to specific Australian examples.

Only one parent is required so energy is not wasted on producing large numbers of gametes or on finding a mate.

This is advantageous:

• in arid conditions or where environmental conditions are not as favourable; for example, spinifex grass survives and reproduces successfully by sending out runners in harsh sand dune conditions such as high temperatures, high salinity and wind erosion

• when food supply may be short and there is a need to use less energy to reproduce.

• when there is a small mating population or time constraints on finding a mate.

• It is a relatively quick process and large numbers of offspring can be produced rapidly. This is an advantage when rapid recovery is needed after a decline in numbers (e.g. after a bushfire or drought). The colony wattle can send up shoots from the outer roots which grow into separate plants if the parent shrub dies. This allows for re-growth to occur quickly. It often forms colonies from root suckers.

• If there is no variation in the environment then the identical offspring will always be adapted to their surroundings and survive to reproduce successfully. Corals, such as the grooved brain coral reproduce by budding when conditions are favourable, however if the environment does change the entire species may rapidly decline and die out.

• Asexual reproduction is advantageous when environmental conditions are stable. In this situation the offspring of the parent plants are identical, having features that make them suited to the environment and likely to survive to reproduce themselves. This type of reproduction allows rapid colonisation after harsh conditions such as fire or drought which may decrease the species population numbers. Many Australian plants have adaptations for survival in this situation.