Ecosystem: The Ocean covers 2/3s of the Earth's surface.

Ocean covers two-thirds of Earth's surface and contains a variety of ecosystems with greater diversity than those found on land, from the frozen polar reaches, to the warm coral reefs of the tropics and down into the deep and lightless trenchs. There are three main oceans: the Atlantic, the Pacific and the Indian, through which great ocean currents swirl, some carrying warm water, others cool. These influence the world's weather systems.

Life in the oceans ranges from microscopic plankton to the massive blue whale, it is populated with terrifying hunters, deepsea creatures that look to have crawled from your nightmares and other life forms so strange that it is hard to believe they are real. The ocean floor is referred to as the benthic habitat whilst the water itself is the pelagic, both supporting a plethora of life. It is the coral reef, however, that is perhaps the richest in diversity.

There are many threats the ocean and its inhabitants must face, including over-fishing, bottom trawling and pollution. 80% of litter in the water comes from land: anything that ends up in our waterways eventually ends up at sea. Plastic bags, bottles and other non-biodegradable litter has been carried by the currents to form a massive patch of rubbish, known as the Great Pacific Garbage Patch. This plastic disintegrates into smaller and smaller pieces, being consumed by creatures and eventually killing them.

Ecosystem: Grasslands

True to their name, grasslands are areas dominated by a variety of grasses, sedge and rush. They occur on every continent excluding Antarctica. They grow in areas with an annual rainfall between 500 and 1,500mm, where the soil is too low in nutrients for woodland or frequently disturbed by fire or grazing. The roots of the grass form a dense mat, protecting the soil from wind and rain erosion. In many countries (such as Madagascar) degradation of forest habitat by humans has lead to the growth of grassland. Others, like the savannah of Africa and the pampas grasslands of South America, are a natural adaptation to the climate and resources. They provide a variety of habitat, especially for ruminants such as antelopes and their predators.

In countries not historically dominated by grasslands - such as Madagascar and New Zealand - native animals are few, but some - especially hawks - flourish with this more open hunting ground.

#884: Yuhina forage in mixed-species flocks, feeding on insects.

Surprise! You thought I was finished, didn't you?
Well, we recently unpacked my "Birds: The Definitive Visual Guide" book, turned to the index and found ... a bird that starts with Y and isn't "Yellow-something". So, how could I resist?
He will replace the Yellowhammer in my XYZ Animal Encyclopedia.

The Yuhina are a genus of Asiatic zosterops, inhabiting tropical and subtropical rainforests. All of the eleven species are crested. He is a sociable bird, occasionally gathering in mixed-species flocks with other Yuhina species. Here he forages on insects, gleaning them from tree branches, or nectar and fruit.

Ecosystem: The Waterways are the lifeblood of the Earth.

Waterways such as rivers, ponds, lakes and streams, are an important part of the ecosystem. Not only do they provide habitat for fish, aquatic mammals and many invertebrates, but they are also play an important role in the lifecycle of many insects and amphibians. Rivers begin at a source - or several sources - and flow towards the sea, entering it at a mouth. The longest river is the Nile in Africa, 6, 650 kms long and the Amazon is the widest - up to 40 kms wide in the rainy season.

Unfortunately, humans have had a powerful influence on many rivers - draining them or building dams, polluting them with both organic and inorganic effluence, and cluttering them with traffic. All of this has an impact on the wildlife that make their homes here. Many aquatic species face extinction - the axolotl's lake habitat has been drained and the extinction of the baiji dolphin resulted from pollution and river traffic.