My Science School

 

In order to survive, living things must be able to detect changes in their environment and react to them. This includes adapting to changing weather conditions and the threat of living things that may approach them.

Animals have up to five senses – sight, smell, hearing, taste and touch – to help them to detect changes around them. A dog may react to the smell of food by running towards it; an earthworm will react to light by burrowing underground; and a chameleon changes its skin colour and patterns to match its background. Plants don’t have senses of this kind but they can still detect changes in their environment.

 

Plants can react to certain changes in their environment. We have seen how plants grow towards light and water. This sunflower gradually turns as it follows the path of the Sun during the day. Some flowers, such as lilies, open during the day and close at night. Plants are remarkably sensitive to heat; light, drought, certain chemicals and gravity, but they have no special organs for detecting change.

 

 

 

 

 

 

 This sea anemone reacts to touch by retracting its tentacles.

 

 

 

 

 

 

An Arctic fox’s fur turns from brown to white in winter to camouflage it in the snow.

When we react to a changing environment, conditions inside our bodies change. Your body’s main instinct is survival, so it reacts to potentially dangerous situations.

When you exercise, most of the energy in your body is released as heat energy and your temperature rises. To lower your body temperature, blood moves to the surface of your skin where it can cool down. Water also evaporates from your skin as sweat, helping to cool your body. During the winter months, physical changes can also help an animal to hibernate, whilst food is scarce.

 

 

 

 

In the winter months, some animals, like dormice, are no longer able to find food. Their bodies are able to adapt, and they “hibernate”. The animal “sleeps” for the winter. Its body gradually gets colder, its heartbeat slows down and it breathes less often. In this condition animals use little energy. They can survive without eating and live off stores of fat inside their body.

 

 

 

 

 

 

 

In the fall, many birds migrate to a warmer winter climate.

 

 

 

 

 

 

It is important to drink after exercise to replace fluid lost through perspiration.

 

 

As plants and animals develop, they grow and get larger and heavier. How does this growth take place? We know that living things take substances, like food, into their bodies. Some of these substances become part of body cells. Cells get bigger until they cannot grow anymore and they divide into two. As more cells are formed, a living thing grows.

 

When living things are fully developed they are able to ‘reproduce’ and create new members of their species. Most living things in the animal world reproduce when special ‘sex cells’ from the mother and father join together. As this cell grows and divides, a new living thing develops.

 

 

 

 

This cell is ready to divide. The threads inside its nucleus, called “chromosomes”, have been duplicated. The nucleus now starts to divide and each new nucleus gets a complete set of chromosomes. The cell membrane then divides to form two separate cells. These are identical to the original cell with the same number of chromosomes. They will grow and eventually divide themselves into two new cells.

 

 

 

 

 

 

 

This calf will grow and develop for up to seven years before it becomes fully-grown.

 

 

 

 

 

 

 

Yew trees take 1,000 years to mature, while pine trees only take 30 years.

Many living things can pass information to each other – they ‘communicate’. The expression on the face of a cat may show that it is angry or frightened. Bees perform complicated dances to tell each other where to find good sources of food, and monkeys show each other affection by grooming each other and cuddling their young.

Some animals communicate by producing chemicals. Cheetahs mark out their territories by spraying urine and scent onto plants. Birds and mammals also communicate by making sounds. Humans, as the most intelligent of all animals, have developed the most complicated and successful form of communication – speech.

 

 

We usually associate communication with animals, but some plants can communicate. For example, some trees produce poison in their leaves when they are attacked by insects. Some of these trees can also warn nearby trees by passing a chemical signal through the air, enabling trees downwind to prepare for attack. In a similar way, plants also communicate with insects. If corn, cotton or tobacco plants are attacked by caterpillars they emit chemicals that simultaneously attract parasitic wasps. These wasps eat the caterpillars and discourage other worms and moths from laying their eggs on the plants.

 

 

 

 

Monkeys use a number of vocal, visual and tactile forms of communication.

 

 

 

 

 

 

Dolphins communicate using a system of whistles, squeaks, moans and clicks.

 

 

 

 

 

 

Elephants show aggression by locking tusks and wrestling with their trunks.