Martin Rowland

Inheritance and Variation

It is through the genes in our chromosomes that we inherit characteristics from our parents. It is through one of the two alleles of each gene in each chromosome that we pass on to our children in gametes half of what we have inherited.

Birth to Old Age

Independent life begins at birth. The baby grows into a child, an adolescent and an adult who ages and finally dies.

Human Effects on the Environment

More than a million years ago the earliest humans moved through the land in search of food. They killed animals for meat and collected and ate parts of wild plants. Once humans had discovered fire, they stayed longer in one place and began to change their surroundings by clearing away trees and other plants from the places where they cooked, ate and slept.

Variety of Living Things

Next time you are walking out of doors, look at the plants and animals around you. Even in the towns you will see trees, shrubs, grass, moss, a few flowers, birds, dogs, cats, humans and occasionally horses. If you search, you may find butterflies, moths, bees, flies, earwigs, spiders, earthworms and snails. We call all these living things organisms. All around you are millions more organisms too small for you to see. We make use of many organisms throughout our daily lives: we could not live without them.

Inheritance, Variation and Natural Selection

It is through the genes in our chromosomes that we inherit characteristics from our parents. It is through one of the two alleles of each gene in each chromosome that we pass on to our children in gametes half of what we have inherited.

Health and Population Dynamics

Everyone wants good health: at its simplest, health is a state of physical and mental well-being. The World Health Organisation (WHO) makes it more complicated: all people should be able to fulfil their genetic potential, to grow and develop physically and mentally ○ with adequate food ○ with protection, as far as possible, from infectious disease ○ without environmental pollution Hygiene is the term used to describe the principles and practice of preserving health. Much of Part 2 of this book, Human and Social Biology, has been concerned with the principles of health. This unit presents a summary.

Eating and Diet

When we eat, we take food in at the mouth, chew it and swallow it. This is how food enters the gut, a continuous tube which includes the stomach, the small intestine and the large intestine and which goes all the way from the mouth to the anus. Some food is absorbed into the body from the gut. What is not absorbed is got rid of from the anus as faeces.

Temperature Control and Homeostasis

The human body works best at an internal temperature at about 37°C. In most parts of the world the outside temperature is rarely as high as this. We think it is hot when the surrounding temperature is higher than 30°C. At 30°C a naked inactive person is comfortable because the heat lost from the body is matched by the heat released in respiration of the cells.

Heart and Circulation

The heart and the blood circulation are the transport system of the body. Blood carries substances and heat around the body. Blood is forced around the body, through arteries, narrow capillaries and veins, by a muscular pump, the heart. Figure 19.1 shows that arteries always take blood from the heart to the capillaries of the lungs and to other parts of the body and that veins always take blood back to the heart. Blood flows from arteries to veins through capillaries.

Movement, Support and Exercise

Muscles provide the power for us to move. Muscles are attached at various points throughout our body to the bones that form our skeleton. These muscles are our skeletal muscles; we can control them consciously and make deliberate fine movements with them. The control we have over skeletal muscles is different from the unconscious control we have over the muscles of the gut that bring about peristalsis (see Section 16.1).