Question

Evolutionary Biology - Essay Type Question

Using examples, discuss the proposition that the biota of New Zealand is both continent-like and island-like in nature. In answering the question outline what geological phenomenon is responsible for this idea. (15 marks)

Answer 1

The biota proposition of Newzealand is the most interesting and lively topic to discuss with. Newzealand has its own, unique flora and fauna. New Zealand had drifted from the super continent Gondwana and thus boasts a million years rich of ancestral biota in it. Gondwanian plants dominate New Zealand.

Geography of New Zealand

New Zealand's landscape ranges from the fjord-like steep slides in the southwest to the tropical beaches of the far north. The South Island comprises the Southern Alps, the highest peak of which is Aoraki 3724m. The tallest peak in the North Island is an active, cone-shaped volcano. Mount Ruapehu 2,797 m.  The geography and geology of New Zealand is one of the most unique and different in the entire world. The main form of rock within New Zealand is Sedimentary. Limestone and sandstone are very populous among the rocks in New Zealand. Not as common we see bits of igneous, metamorphic, as ell as volcanic rock. As for the terrain of the country it is mostly mountainous however there are several coastal areas. Within this one can find active volcanoes and tall mountains that stretch across the land. Some of these include Mt. Taranaki and Mt. Tongario. Due to the fact that New Zealand is an island it is surrounded by Pacific Ocean. In addition to the ocean, there are also many rivers that flow through the land. The largest of them being the Waikato River.

Smaller islands include Stewart Island, that lies south of the South Island; Waiheke and Great Barrier islands, near the north end of the North Island; and the Chatham Islands, more than 800 km east of the South Island. About 93% of the Zealandian continent remains below the sea.

Climate

The temperatures fluctuate immensely based on the time of year. It will be anywhere from -20 Degrees Celsius to about 30 degrees Celsius.

Biodiversity in Newzealand (floral and fauna)

During the Middle Jurassic times, Rangitata Orogeny earth movements began to create considerable areas of land in the New Zealand region. By Late Jurassic and Early Cretaceous times, a large landmass had been developed, extending northwards towards New Caledonia, eastwards to the Chatham Islands, westwards to the Lord Howe Rise and southwards to the edge of the Campbell Plateau. Creation of this landmass, and its associated land and marine links, together with the equable warm-temperate conditions then apparent over large areas of Gondwana, provided favourable conditions for the dispersal of Gondwana elements into New Zealand. Ancestral stocks of at least some of New Zealand’s archaic endemic terrestrial biota may have dispersed from eastern Gondwana into New Zealand at this time. Femur and mandibe fossils were found in Newzealand.

Although land connections had been broken in the Late Cretaceous, shallow-water marine links continued to exist between New Zealand and West Antarctica So we can see seals,sea lions,,dolphins, penguins that is characteristic of cold Island habitats in New Zealand. However, as New Zealand moved progressively northwards and the Southern Ocean widened, to northern (Australian and Malayo-Pacific) links and is characterized by whales, stone fish.anemones etc.

In the Early Cretaceous, land connections to eastern Gondwana became weakened by the onset of rifting along the future sites of the Tasman Sea and Southern Ocean. The eastern edge of Gondwana was rotated into high latitudes, and cool-temperate climates returned to New Zealand and Antarctica. Cool-temperate Australian marine faunas developed and were shared between New Zealand, Antarctica and southern South America. Land links between New Zealand and West Antarctica provided access for early angiosperms. Several elements of Gondwana biota are present in New Zealand today: predominantly plants, such as the podocarps and the southern beeches like rimu.

However, all land links between New Zealand and Australia/Antarctica were broken after 85 Ma. From this time onwards the ancestral Tasman Sea and Southern Ocean became effective barriers to overland dispersal between eastern Gondwana and New Zealand The yellow flowers of the kowhai tree is a native tree that brings colour to the NewZealand landscape. In the north of New Zealand the podocarp forests were dominated by the ancient giant kauri. New Zealand have grassland withgrass and tussock, usually associated with the subalpine areas, and the low shrublands between grasslands and forests.

The tuatara is a unique relic of the past - the only beak-headed reptile left in the world. Kiwi ia a unique endemic bird of NewZealand. Newzealand pigeon, falcon,rails, waders and seabirds show affinity towards Australis.The most famous of New Zealand's ground living insects, the wetas, are relatives of the crickets is seen along with grasshoppers and beetles.

The immigrants arrived long enough ago that their affinities to their Australian ancestors became certain; when an unusual short-tailed bats - Mystacinidae fossils from the Miocene were found in Australia. Cyanoramphus parakeets are thought to have originated in New Caledonia and have been successful at reaching many islands in the region.

Thus the biodiversity of NewZealand is unique by exhibiting continental and island like biotic characteristics.