Science and Geography - Page 3



Lichens are usually found high up on the splash zone, Tiny algae and fungus live together. Algae live on the inside and fungus on the outside – which provides shape and shelter for the algae (It’s such a beautiful relationship!!). Algae feed by using photosynthesis and then produce sugar which is consumed afterwards by the fungus.

Lichens do not have roots, but absorb water and gases through their upper surface, and are therefore sensitive to atmospheric pollution. For this reason they are rarely found around cities and grow best on the wetter west side of the British Isles. Those on trees thrive best on the sunny, south-west aspects of trunks and branches. Disappearance of lichen species can be used to detect rising levels of air pollution.

There are three main types. The encrusting forms, including the bright orange/dark yellow ‘Xanthoria’ grow on roofs, walls, gravestones, signs and tree trunks. Leaf-like species develop flat lobes spreading over bark or stones, and shrubby forms which grow vertically from the ground or hang from trees. Few have common names.

The main body of the lichen is called a Thallus and each species quite different. Thallus absorbs water from the rain, sea spray, fog and dew. Grow from some millimetres per year to a few centimetres per year, and can live in very typical difficult conditions.

Some Typical lichens:

Leaf encrusting form

Upright or erect form

Tufted form –

A lichen - Cladonia arbuscula subsp. squarrosa

Granular encrusting form – 

Bench Mark, Field Bavant






Seaweeds belong to the algae family. They are plant like organisms that live in water. They vary in size from small cells to plants 60 metres long. Some are found in seawater and others in fresh water.

Seaweed grows, makes food and reproduces only when covered with water; some survive without water longer than others.

They use photosynthesis to produce food. They don’t have leaves, stems, or roots but have fronds (to absorb light and water), a stipe, and a hold-fast to cling to surfaces


Types of Seashores


There are different types of seashores

Rocky  Shores

These are sometimes bedrock and sometimes boulders. Have lots of spaces for animals and plants to live. They have to deal robustly with strong waves and the constant rose and fall of the tide. Different types of rocks influence what you will fond living on the rock itself. If sheltered those rocks might be covered with seaweed and provides protection and food for a variety of animals. If exposed – by for example the constant hotting of the waves – then this prevents the growth of seaweed

Rock Pools

These are created when the tide goes to and water is trapped in the rocks – live animals can be left behind

Sandy and Muddy Shores

Here animals might leave a hole, burrow, tracks, or a swirl of sand as something buries itself. Sandy beaches contain billions of particles brought in by the waves. Muddy shores usually form near river estuaries (eg. River Avon) where large mudflats can occur. Soil from the fields turns to mud, and comes down the river. When it reaches the sea these mud left overs may end up on the seabed near the sea. This silt is sculptured by the waves into the soft banks.

Shingle Beaches

Lots of pebbles – hard for animals to attach themselves to the rocks. Will only find lichens.


The Irish Sea is Born


It was 20 millions years ago that Britain and Ireland ended up where they are now.  Almost 300 million years before that, the super continent Gondwanaland had began to separate in a north-south movement. Then 100 million years ago this shifted a an east-west separation, and by 40 million years ago the Atlantic Ocean was formed – and the continents as they are now were more or less in place 20 million years ago.

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