REACTING TO CHANGE



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.


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.