World population, total quantity and annual increase, 1950–2000 (US Bureau, 2001)

Progress in science and technologies, medicine and sanitation are key factors of significant decrease of human mortality. Since the end of 19 century, most regions of the planet demonstrate stabile tendencies in mortality decrease. Implementation of newest achievements of medicine in second part of 20^th century significantly improved this indicator in developing countries. At the same time birth rate in developing countries remains at the same high level. Since 1960^th some countries have demonstrated tendencies of slight decrease in birth rate. It does not relate to the developing countries of equatorial and southern Africa and Middle East.

Rapid growth of population in some regions causes lot of negative consequences and problems, which is burdensome to world community. Sustenance of human life and society development require enormous amount and variety of natural resources. Regretfully, many developing countries are not capable to support citizens by necessary means – food, water, dwellings, education and job. Ironically, these countries have highest birth rate therefore the problems of life support are worsening. Population growth results in increasing pressure on environment, unsustainable consumption of natural resources and deterioration of life support capacity. Exhaustion of natural resources undermines abilities of both present and future generations.

According to the laws of classic ecology, development of the population of any species depends on resources availability and competitive species consuming the same resources. In spite of social character of Homo sapiens, development of human society and population increase depends as well on resources availability. Therefore we may assert that maximum of population is restricted by resource capacity of Earth and human capability to reproduce resources needed to support life and development.

SUMMARY

Three systems of the body – the skeletal, muscular, and integumentary – provide support, movement, and protection.

Bones develop and grow through a process called ossification, in which bone replaces cartilage and membranous tissue. Several types of bones make up the skeleton, including long bones, flat bones, and short bones. Movement occurs between bones at joints. Some joints are movable and others do not move. Bones are held together at joints by ligaments.

The body has 3 types of muscle tissue: skeletal, smooth, and cardiac. Contraction of a skeletal muscle occurs when a nerve impulse causes chemical changes in muscle cells. The reactions enable actin filaments to slide over myosin filaments of the myofibril within the cell. This movement causes the muscle to contract. When the impulse stops, the muscle relaxes.

Skin covers all body surfaces. It consists of the epidermis and the dermis. New cells are made in the epidermis. Skin pigment, called melanin, is also in the dermis. Glands, nerves, blood vessels, and hair follicles are in the dermis. A subcutaneous layer under the dermis attaches the skin to the tissues below.

Test questions

1. What are four traits that characterize all primates?

2. Name five traits that distinguish humans from other primates?

3. What behaviors are characteristic of humans?

4. How could an archaeologist determine if a set of bones were human or ape?

5. What are the three types of epithelial tissue? Give an example of where each is located.

6. What four tissue groups make up the human body? What is the function of each?

7. Name three other systems of the body and give a major function of each.

8. What systems are separated into single body cavities, and why is this so?