Category Social Sciences

MORE ABOUT THE UNIVERSE

 

Life and death of a star

When a star like our Sun first forms it is different from the way we see it today. At first the Sun was a very hot, blue star. As it grew bigger it cooled down and looked white. The Sun will shine as it is for about 10,000 million years. Eventually it will swell and form a ‘Red Giant’. Some of the stars we see are Red Giants. They are cooler than the Sun. But as they are many times bigger, they appear brighter. A Red Giant slowly cools and shrinks. Its outer layers of gas drift away and a small hot star called a ‘White Dwarf’ is left. This slowly cools and becomes a ‘Black Dwarf’.

 

 

 

 

 

Very large stars

Stars much bigger than our Sun also become Red Giants, but they blow up in a huge explosion called a ‘supernova’. They shrink into themselves and form a ‘Black Hole’. Anything nearby gets sucked into a black hole. Even its own light cannot escape!

What is seashore?

 

 

 

The seashore is where the land meets the sea. Sometimes seashores are rocky and have high cliffs. Other seashores are gently sloping, sandy beaches. In some places seashores are made from lots of smooth stones.

 

 

 

 

 

These waves are crashing against cliffs.

This seashore is made from hard rock and has steep cliffs. When waves smash against the cliffs, they slowly wear them away or crack the rock. Sometimes the cliff breaks apart and large pieces of rock fall down into the sea. Under the water, the fallen rocks are tumbled together by the waves and break up into tiny pieces.

 

 

 

 

A sandy beach slopes down into the sea.

When land made from soft rocks meets the sea, the seashore is flat and sandy. Sand is made up of billions of tiny pieces of rock and broken shells.

 

 

 

 

Shingle beaches are covered with stones.

Shingle beaches are made up of small pebbles that have been smoothed by the waves. Shingle seashores are hard places for animals and plants to live because the sea moves the stones around. Most wildlife lives high up on the shore out of reach of the waves.

Different seashores

 

 

 

There are different seashores all over the world. Some seashores are hot and some are icy cold. The animals found on icy seashore can live where it is very cold. They keep warm by having thick fur or oily feathers and a layer of fat under their skin.

 

 

 

 

These birds are looking for food in the mud.

When rivers reach the sea they spread out into wide, muddy seashore called an estuary. Huge flocks of birds feed on muddy estuaries. They hunt for worms, shellfish or crabs in the mud. When the sea flows into the estuary and covers the mud, the birds fly ashore and wait until it goes out again.

 

 

 

 

These penguins live on cold, icy seashore.

In very cold parts of the world, the seashore is icy. Penguins nest on the icy seashores of the Antarctic. It is so cold that they huddle together to keep warm. They keep their egg on top of their feet to stop it from freezing on the ice.

 

 

 

 

 

This seashore is in a hot part of the world.

Coral reefs grow in warm, shallow seas. Coral reefs are made by small animals that live close together. They protect themselves by building hard cases. It is the hard cases that form the coral reef. Coral reefs are important because they are home to many animals.

Seashore plants and animals hold on tight

The waves that crash on to a seashore are very strong. Seashore plants and animals must hold on tight to keep themselves safe. If they let go, they could be washed away or smashed on the rocks.

 

 

These limpets are holding on to a rock.

Seashore animals have different ways of holding on. Limpets use their strong foot to grip tightly on to rocks and stop them from being washed away. Some animals, like sea urchins, cling on to rocks with lots of tiny feet that look like tubes. Mussel shellfish anchor themselves down to rocks with tough threads.

 

 

 

 

This seaweed grips on tightly to the rocks.

Seaweeds anchor themselves on to rocks to stop them from being washed away by strong waves. Large seaweeds grip on to rocks with strong, finger-like rootlets called holdfasts. During storms, seaweed is ripped off rocks.

 

 

 

 

 

Sea otters wrap themselves in seaweed.

When sea otters sleep, they wrap themselves in giant kelp seaweed. They grab a floating end of kelp and spin around in the water. The kelp wraps around the otter and anchors it down. It stops the sea from carrying the sea otter away in its sleep.

 

Seashore Shells

 

 

 

Shellfish are small animals that live inside shells. Their hard shells help to keep them safe from being eaten by other animals or smashed by waves. When shellfish are out of water, their shells stop them from drying out.

 

 

 

 

 

      These shellfish live in one shell.

Some shellfish live in one shell. The animal that lives inside has a very strong, muscular foot which it uses to move itself and to cling to rocks with. If the animal is in danger, it withdraws and hides inside its shell. These shellfish feed on seaweed or on other animals.

 

 

 

 

This shellfish has two shells joined together.

Some shellfish have two shells that are hinged together. Scallop shellfish swim by flapping their shells open and shut. Shellfish with two shells feed by sucking in water, and straining out small bits of food.

 

 

 

 

 

This hermit crab lives in an old shell.

Hermit crabs have a long soft body which they protect by living in an empty shell. They have a pair of strong hooks on their rear end to hold them safely in their shell. When a hermit crab grows too big for its shell, it will find a bigger shell to live in.

Life in a rock pool

 

 

When the tide goes out, some water is left behind in hollows in the rocks. Many different seaweeds and animals live in these rock pools. They can stay safely underwater in the rock pool until the sea comes in again.

 

 

 

 

 

Starfish live in rock pools.

 

The underside of a starfish is covered with lots of tiny tube feet. It uses the feet to move and to grip on to rocks. Starfish feed on shellfish and use their arms to force open the shells to reach the soft animal inside. If a starfish loses any of its arms, it can grow new ones.

 

 

 

 

 

Sea anemones are animals.

Sea anemones look like flowers, but they are animals. They catch food with their tentacles. When a sea anemone is out of the water, it pulls in its tentacles to stop itself from drying out. It looks like a blob of jelly!

 

 

 

 

 

This is a rock pool food chain.

A food chain shows the link between plants and animals in a habitat. All food chains start with plants, which are eaten by plant-eating animals. Plant-eaters are eaten by flesh-eating animals. In a rock pool, seaweeds are food for animals like limpets. Limpets are eaten by whelks.