More than 70% of the surface of the Earth is covered in water. Almost all of this enormous body of water consists of oceans. They are home to a tremendous variety of species – from microscopic plankton to the largest marine animal – the blue whale. Corals are a very important part of the ocean life. Contrary to what a lot of people may think, corals are animals. Usually they live in colonies; an individual coral is called a polyp and is just a couple of centimeters in length. Corals have tentacles which help them capture their food. They also have one more very interesting way of getting energy – through symbiosis. Corals host in their tissue an one-cell alga called zooxanthellae. The algae get energy from the sunlight and pass it through to the corals. Corals provide the algae with nutrients and shelter in return. Zooxanthellae also give the corals a variety of beautiful colours.

   There are a lot of different coral species which explains the diversity of their colours and shapes.  Some of them are hard corals. They are also called reef builders and are able to secrete calcium carbonate. It forms a skeleton and the coral actually lives on its outside. Soft corals do not have this ability, as their name suggests. Usually corals thrive in warm shallow water, with temperature around 29°C. The easy access to sunlight gives plenty of energy to the zooxanthellae which gives the corals the opportunity to grow immensely. When a lot of coral skeletons grow together, they form a reef! There are fringing reefs, barrier reefs and attols. It is due to the fact that reefs provide a habitat for a great diversity of marine life that they are considered to be rainforests of the oceans. Probably the most famous one is the Great Barrier Reef. It is situated in the Coral Sea, along the coast of Queensland, Australia. It is so big that it can be seen form space! With its 2500 individual reefs and more than 900 islands, it is the largest living structure on the planet! Corals grow very slowly, just a couple of centimeters per year and to get to its present-day size, the Great Barrier Reef began forming as early as 20 million years ago! There are fossilized corals dating from 500 million years ago.

   Considered one of the 7 natural wonders of the world, the Great Barrier Reef is a very popular attraction. However, this impressive ecosystem is also a home to more than 1500 fish species, sea turtles and birds. Predators like dolphins and sharks hunt the smaller fish that live there. The range of biodiversity there is one of a kind.

   There is one immense threat to the reefs and that is global warming. The increasing ocean water temperature causes the zooxanthellae to die, which leads to discolouration of the hard skeleton of the corals, better known as bleaching.



plankton – small plant or animal drifting on the surface of seas or lakes

alga, pl. algae – a red, brown or green plant-like organism that usually grow in water

symbiosis – the living together of two organisms, usually this relationship benefits both of them

tentacles – a narrow, flexible part of the body of an animal,such  as an octopus or jellyfish

calcium  carbonate – a chemical compound consisted of carbon, oxygen and calcium. It can be found in rocks and the shells of eggs, marine animals, snails

habitat – the natural home of an animal or a plant



   Polar bears live around the coast of the Arctic Ocean, near the North Pole. They can survive in such a cold weather thanks to their white fur coat that isolates them from the low external temperature. Under that coat their skin is black  and we all know that black colour is said to absorb more heat than any other colour. In addition to all that, polar bears have a very thick layer of fat under their skin. Its purpose is to keep them warm too.

  During the winter season these bears withdraw in caves dug in the ice. There, they stay in a state similar to lethargy in order to save up some energy without having anything to eat. And speaking of eating, you should know that polar bears’ favourite meal is seals and fish. They know very well how to catch them by making holes in the thick ice and waiting patiently for the prey to come.

  Male polar bears weigh about 680 kg, whereas the females’ weight is just half of this number. Polar bears can reach the speed of 10 km/h swimming! Curious fact to mention is that they have 42 teeth and that males and females spend separate lives. However, when the cubs are born in mid-December, they remain in the company of their moms until the spring comes.

  Unfortunately, these beautiful and majestic animals are an endangered species.  Scientists say that there are only about 20 000 of them today.

  The reason why polar bears are in danger of extinction is the global warming. The climate changes cause the ice in the Arctic to melt which directly affects polar bears’ natural habitat ! Although they are great swimmers, nowadays polar bears are forced to cover greater and greater distances in order to reach land. Sadly, not all of them make it and that is why more and more die of exhaustion from swimming.

  The good news is that there are plenty of non-profit organizations which are trying to save their habitat!!!




to withdraw – to leave a place

lethargy – some animals fall into deep sleep for a long period of time having low body temperature in order to save energy 

seals – fish-eating mammal animals that live in cold waters (the Arctic Ocean for example)

prey – an animal that is killed by another animal for food

cubs – the young of a fox, bear, lion and some other animals

endangered species – an animal or plant that is at serious risk of extinction / disappearing

extinction – reduction to zero

to melt – the transformation of ice into water

habitat – the natural home of an animal or a plant

non-profit – not making money (for example an organization) 



   Nowadays, our life is very different from what it used to be 200, 100 or even 50 years ago. All the achievements of modern society make people’s days much easier and give us plenty of choices and possibilities. However, they have a negative side as well. We produce too much carbon dioxide (CO2) which remains in the atmosphere, does not allow heat to escape and little by little warms up the Earth. The average temperature on the planet is rising and unfortunately, this leads to disastrous and sometimes even irreversible consequences.


  There are a lot of causes for the global warming. The main one is burning coal and oil as energy supplies. During this process carbon dioxide is emitted  and acts as a blanket, slowly raising the temperature on Earth. Another factor contributing to climate change is all the industries that we rely on today. Not only the factories but also all means of transportation – cars, trucks and planes – produce greenhouse gases like CO2. To make matters worse, we cut down entire forests because we need the trees to make paper of; and the land to build on. Bur trees can absorb CO2 from the air which can really help reducing the pollution.


   What are the global warming effects? Temperature of not only the air but also the oceans, rivers and lakes rises. This causes ice to melt, ocean levels to rise and at the same time, less fresh water to drink in some parts of the world. Another effect is the large number of natural disasters, occurring all over the planet – forest fires, hurricanes and heat waves. Also very disturbing is the fact that the natural habitat of a lot of species is altered or disappears completely. For example, animals have to migrate to another place because they can not find enough food, the polar bears and penguins can lose their habitat altogether, the coral reef and sea life change as well.


   So what can we do? It comes without saying that we need to find a way to reduce CO2 emissions produced by the industries, commercial farmers and cars. Fortunately, nowadays there are cars that use less gasoline or cars powered by hybrid or even electric engines! A very good source of energy is the sun. This is why the use of solar panels has become very common. There are a lot of little things we all can do – from taking shorter showers to save water, walking or riding a bike instead of driving, planting trees; to recycling or using recycled things – they can all add up to help us reduce global warming!!!




atmosphere – a mixture of gases, mostly nitrogen and oxygen, that surrounds the Earth

CO2 – carbon dioxide, a gas without colour or smell, one of the components of the atmosphere of the Earth

irreversible – that can not be changed back; permanent

to emit – to send out, let out, discharge

industry – the process of making products by using machinery and factories

to absorb – to take in something, to use up

pollution – the process of making land, water, air dirty

habitat – the place where a plant or animal naturally lives or grows

to migrate – to move from one area to another at different times of the year

hybrid car – a car that uses two or even more different sources  of power