Category Zoology

MORE ABOUT REPRODUCTION

 

Genes and chromosomes

Inside the nucleus of a human cell are 23 pairs of chromosomes. Along these chromosomes are “genes”. Genes control everything about you, including the way you look. Each of your cells has the same genes. You inherit two copies of every gene – one from your mother and one from your father. That is why you look like your parents.

 

 

 

 

Inheriting eye colour

The gene for brown eyes is known as a “dominant” gene – you only need to inherit one brown eye colour gene for your eyes to be brown. The gene for blue eyes is weaker. In general, a child will only have blue eyes if both inherited eye colour genes are blue. A man carries a gene for brown eyes and a gene for blue eyes, while the woman carries only a gene for blue eyes. One of their daughters has blue eyes because she has inherited two blue eye colour genes. The other daughter has brown eyes because she has inherited at least one brown eye colour gene.

 

 

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.

Seashores animals – Digging in

 

 

 

Many seashore animals bury themselves in the sand, mud or rock. They dig themselves in to try to keep themselves safe from being eaten. Some animals hide in the sand when the tide is out. This stops the animal from drying out in the wind or Sun.

 

 

 

 

 

These are lugworm casts on a sandy beach.

Lugworms live in U-shaped burrows on sandy or muddy seashores. They swallow mud and eat any pieces of food they find in it. The sand comes out of the worms’ bottom at the other end of the burrow, and makes a squiggly worm cast on the surface of the mud.

 

 

 

This dog whelk hides in cracks in rocks.

Some shellfish protect themselves by digging into rock or squeezing into gaps between rocks. Dog whelks hide under rocks, crawl into cracks and wedge themselves into crevices on rocky seashores when the tide goes out. When the tide comes back in the dog whelks come out to feed.

 

 

 

 

Cockles bury themselves in the sand.

Cockles use their muscular foot to bury themselves in the sand. This helps to protect them from being eaten by birds and animals. Cockles and razorshells feed using long siphons that suck water and strain food from it.