World populationand its regulation

Population is totality of people capable for self-reproduction and self-development, and occupying certain territory namely country, region, continent or any other part of the planet. Population accompanied by natural environment, mode of production, and system of social relations composes background of human society. Level of development of the society depends on the population’s capability to utilize and reproduce natural resources. On other hand, this capability influences on structure and dynamic of population itself.

Number and other indices are been in use to characterize population. The term natality, or birth rate was given to the integral indicator reflecting social, economic and environmental conditions of human life. Birth rate is annual difference between total births and deaths per 1000 people. Fertility coefficient (annual ratio of born children to total females’ number) is another important characteristic of population. Average lifetime depends on quality of life and indirectly describes the development level of community of society. Number of structural indicators is used to describe population. Gender structure, i.e. quantitative ratio of males and females, characterize reproduction capability of population. Age-specific structure, i.e. distribution of population by age, is important indicator representing part of population able to work and perspectives of reproduction. Ratio of rural and urban population, distribution by nationalities, education level, income, literacy, languages are very important characteristics for understanding and forecasting of population’s dynamic.

The key issue of demography is reproduction of population, i.e. process of generations’ shift. Reproduction is positive in the case if the coefficient of natural increase is more zero. In this case the fertility coefficient should be more than 2.

Demographical processes of variation in structure and numbers have country and regional specific. Therefore both general characteristics and regional features have to be taken into account while forecasting the tendencies in human society development.

Lack of statistic data was the reason of domination of estimation methodology in population evaluation and forecast. According to such estimation the Earth population has reached one billion by 20^th century. In 125 years the population has been increased as much as two times. Population has been increased by one more billion people during 35 years only; it’s happened in 1960 (Table 6.4). Analysis of dynamic and tendencies of human society development resulted in conclusion that 10 billion people will be living on the planet by 2025. However, it is expected that population growth rate is going to decrease so that “the only” 14 billion people will share Earth resources by the end of 21 century. Most optimistic forecasts indicate that Earth population will be stabilized at the level of 10–11 billion.

Table 6.4.

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?

Date: 2014-12-22; view: 1347