Ch. 7. Populations: Characteristics & Issues

Under what conditions might a death phase occur? (5)

A death phase occurs when there is a decline in population size. This occurs as the result of disease, increased predation, low food supply, toxins entering the ecosystem, or any other limiting factor

Death rate

the number of people who die per 1,000 individuals per year. In order for the size of a population to grow, the number of individuals added by reproduction must be greater than the number leaving it by dying.

List three characteristics populations might have. (2)

Natality, mortality, sex ratio, age distribution, growth rate, density, and spatial distribution.

Why do people who live in overpopulated countries use plants as their main source of food? (19)

People who live in overpopulated countries use plants as their main source of food because they cannot afford the 90-percent energy loss that occurs when plants are fed to animals. The same amount of grain can support ten times more people at the herbivore level than at the carnivore level.

Why do economic well-being and the status of women influence the number of children born in a country? (17)

There is a strong correlation between the higher status of women and lower fertility rates

I = P x A x T

(Impact on the environment = Population size × Affluence (amount of resources consumed per person) × Technology (effects of methods used to provide items consumed). - Several factors interact to determine the impact of a society on the resources of its country. These include the land and other natural resources available, the size of the population, the amount of resources consumed per person, and the environmental damage caused by using resources. The following equation is often used as a shorthand way of stating these relationships.

Limiting Factors

- Conditions in the environment that put limits on where an organism can live - The factors that prevent unlimited population growth

demographic transition

- Countries with the highest standard of living have the lowest population growth rate, and those with the lowest standard of living have the highest population growth rate. Go through a series of stages

Social Factors

- Culture and traditions: lack of literacy so reduced chances for jobs, marriage early in fertile years, childbearing practices (breastfeeding) [The educational level of women is strongly correlated with the total fertility rate and economic well-being of a population.] - Attitudes toward birth control: better educated women are more likely to have access to and use birth control, financially independent can afford to marry later in life and have kids later. [In many of the less-developed countries, contraceptive use is much lower—about 35 percent in Africa and about 56 percent in Asia if China's rate of 85 percent is excluded.]

Immigration Policy

- Current immigration policy in the United States is difficult to characterize. Strong measures are being taken to reduce illegal immigration across the southern border. This is in part due to pressures placed on Congress by states that receive large numbers of illegal immigrants. Illegal immigrants add to the education and health care costs that states must fund. - At the same time, some segments of the U.S. economy (agriculture, tourism) maintain that they cannot find workers to do certain kinds of work. - Most immigration policy is the result of political decisions and has little to do with concern about the rate at which the U.S. population is growing or other demographic issues. - Projections based on the 2010 census indicate that the population will continue to grow and does not seem to be moving toward zero growth despite the fact that the total fertility rate of 1.8 is slightly less than the replacement rate of 2.1. A primary reason for this situation is that immigration adds over a million people per year, and new immigrants typically are young and have larger numbers of children than non-immigrants.

Biotic Potential

- Each species has a biotic potential or inherent reproductive capacity, which is its biological ability to produce offspring.

Political Factors

- Government population policy: For example, Hungary, Sweden, and several other European countries provide paid maternity leave for mothers during the early months of a child's life and the guarantee of a job when the mother returns to work. Many countries provide childcare facilities and other services that make it possible for both parents to work. This removes some of the economic barriers that tend to reduce the birth rate. By contrast, most countries in the developing world publicly state that their population growth rates are too high. To reduce the birth rate, they have programs that provide information on maternal and child health and on birth control. The provision of free or low-cost access to contraceptives is usually a part of their population-control effort as well. - Immigration: Birth rates are currently so low in several European countries, Japan, and China that these countries will likely have a shortage of working-age citizens in the near future. One way to solve this problem is to encourage immigration from other parts of the world.

HUMAN Population Growth

- Has a long lag phase followed by a sharply rising exponential growth phase that has only recently shown signs of slowing. - A major reason for the continuing increase in the size of the human population is that the human species has lowered its death rate. - The world population is currently increasing Page 159at an annual rate of 1.1 percent. This is actually a rapid rate.

Economic factors

- In less-developed countries, the economic benefits of children are extremely important. Even young children can be given jobs that contribute to the family economy. They can protect livestock from predators, gather firewood, cook, or carry water. - In the developed world, large numbers of children are an economic drain. They are prevented by law from working, they must be sent to school at great expense, and they consume large amounts of the family income

Age Distribution

- Is the number of individuals of each age in the population. This greatly influences the population growth rate. - If the majority of a population is made up of reproducing adults, the population should be growing. If the population is made up of old individuals whose reproductive success is low, the population is likely to fall.

Population Density

- Is the number of organisms per unit area. - Ex: fruit fly populations are very dense around a source of rotting fruit, while they are rare in other places. Similarly, humans are often clustered into dense concentrations we call cities, with lower densities in rural areas. - When the population density is too great, all individuals within the population are injured because they compete severely with each other for necessary resources. Plants may compete for water, soil nutrients, or sunlight. Animals may compete for food, shelter, or nesting sites.

Immigration

- Migration to a new location - May introduce characteristics that were not in the population originally. - Ex: When Europeans immigrated to North America, they brought genetic and cultural characteristics that had a tremendous impact on the existing Native American population. Among other things, Europeans brought diseases that were foreign to the Native Americans. Since Europeans were resistant to these diseases and Native Americans were not, these diseases increased the death rate and lowered the birth rate of Native Americans, resulting in a sharp decrease in the size of their populations.

K-strategist

- Organisms that typically reach a stable population as the population reaches the carrying capacity. - K-strategists usually occupy relatively stable environments and tend to be large organisms that have relatively long lives, produce few offspring, and provide care for their offspring. Their reproductive strategy is to invest a great deal of energy in producing a few offspring that have a good chance of living to reproduce. - Ex: Deer, lions, and swans are examples of this kind of organism - Humans generally produce single offspring, and even in countries with high infant mortality, 80 percent of the children survive beyond one year of age, and the majority of these will reach adulthood. - Generally, populations of K-strategists are controlled by density-dependent limiting factors that become more severe as the size of the population increases - For example, as the size of the hawk population increases, the competition among hawks for available food becomes more severe. The increased competition for food is a density-dependent limiting factor that leads to less food for the young in the nest. Therefore, many of the young die, and the population growth rate slows as the carrying capacity for the area is reach

Sex ratio

- Refers to the relative numbers of males and females. - (Many kinds of organisms, such as earthworms and most plants, have both kinds of sex organs in the same body; sex ratio has no meaning for these species.) - The number of females is very important, since they ultimately determine the number of offspring produced in the population. There are a few species of animals that are truly monogamous. - In humans, about 106 males are born for every 100 females. However, in the United States, by the time people reach their mid-twenties, a higher death rate for males has equalized the sex ratio. The higher male death rate continues into old age, when women outnumber men.

Aging of baby boomers

- The U.S. population includes a postwar baby boom component, which has significantly affected population trends. These baby boomers were born during an approximately 15-year period (1947-61) following World War II, when birth rates were much higher than today, and constitute a bulge in the age distribution profile. - As this population bulge ages and younger people limit their family size, the population will gradually age. By 2030, about 20 percent of the population will be 65 years of age or older compared to about 15 percent in 2016.

Ecological footprint

- The environmental impact of the developed world is often underestimated because the population in these countries is relatively stable and local environmental conditions are good. However, developed countries purchase goods and services from other parts of the world, often degrading environmental conditions in less-developed countries. Thus, the environmental impact of highly developed regions such as North America, Japan, Australia, New Zealand, and Europe is often felt in distant places, while the impact on their own resources may be minimal. - is a measure of the land area required to provide the resources and absorb the wastes of a population - Most of the more-developed countries of the world have a much larger ecological footprint than is represented by their land area. - For example, Japan has a highly developed economy but few resources. Thus, it must import most of the materials it needs. One study calculated that the ecological impact of Japan is nearly five times larger than its locally available resources. - While controlling world population growth would not eliminate all environmental problems, it could reduce the rate at which environmental degradation is occurring. It is also generally believed that the quality of life for many people in the world would improve if their populations grew less rapidly.

US Population Picture

- Three significant changes are expected to occur to the U.S. population over the next 50 years: 1. The population is expected to continue to increase 2. the age structure is expected to shift to a larger proportion of older people 3. the population is expected to become more racially diverse. - Two main factors will drive these changes; 1. the aging of the baby boom generation 2. immigration policy.

What does the future hold?

- We are subject to the same limiting factors as other species. - Our population cannot increase beyond our ability to acquire raw materials and energy and safely dispose of our wastes. We also must remember that interactions with other species and with other humans will help determine our carrying capacity. - when we think about the human population and carrying capacity, we need to distinguish between the biological carrying capacity, which describes how many people the Earth can support, and a cultural carrying capacity, which describes how many people the Earth can support with a reasonable standard of living Four factors that determines our carrying capacity: 1. Available raw materials 2. Available energy 3. Waste disposal 4. Interaction with other organisms

Stable Equilibrium Phase

- When the birth rate and death rate become equal, the population will stop growing and reach a relatively stable population size. This stage is known as the stable equilibrium phase. - It is important to recognize that although the size of the population may not be changing, the individuals are changing. As new individuals enter by birth or immigration, others leave by death or emigration. - For most organisms, the first indication that a population is entering a stable equilibrium phase is an increase in the death rate. A decline in the birth rate may also contribute to the stabilizing of population size. Usually, this occurs after an increase in the death rate.

Exponential Growth Phase (Log phase)

- When the offspring have matured and begin to mate and have young, the parents may be producing a second set of offspring. Since more organisms now are reproducing, the population begins to increase at an accelerating rate. - This stage is known as the exponential growth phase (log phase). The population will continue to grow as long as the birth rate exceeds the death rate

Standard of living

- an abstract concept that attempts to quantify the quality of life of people. Standard of living is a difficult concept to quantify, since various cultures have different attitudes and feelings about what is desirable. - several factors can be included in an analysis of standard of living: economic well-being, health conditions, and the ability to change one's status in the society.

Density-Independent limiting factors

- are population-controlling influences that are not related to the density of the population. - They are usually accidental or occasional extrinsic factors in nature that happen regardless of the density of a population. A sudden rainstorm may drown many small plant seedlings and soil organisms. Many plants and animals are killed by frosts that come late in spring or early in the fall. A small pond may dry up, resulting in the death of many organisms. - The organisms most likely to be controlled by density-independent limiting factors are small, short-lived organisms that can reproduce very rapidly.

Density-dependent limiting factors

- are those that become more effective as the density of the population increases. - Ex: The larger a population becomes, the more likely it is that predators will have a chance to catch some of the individuals. A prolonged period of increasing population allows the size of the predator population to increase as well. Disease epidemics are also more common in large, dense populations because dense populations allow for the easy spread of parasites from one individual to another. - In general, whenever there is competition among members of a population, its intensity increases as the population density increases. Large organisms that tend to live a long time and have relatively few young are most likely to be controlled by density-dependent limiting factors.

Carrying Capacity

- is the maximum sustainable population for a species in an area. The carrying capacity is determined by a set of limiting factors. - Often such environmental differences as successional changes, climate variations, disease epidemics, forest fires, or floods can change the carrying capacity of an area for specific species - Ex: In aquatic ecosystems one of the major factors that determine the carrying capacity is the amount of nutrients in the water. In areas where nutrients are abundant, the numbers of various kinds of organisms are high. Often nutrient levels fluctuate with changes in current or runoff from the land, and plant and animal populations fluctuate as well

extrinsic limiting factors

- limiting factors that act from outside the population - Predators, loss of a food source, lack of sunlight, or accidents of nature are all extrinsic factors

Dispersal

- movement from densely populated locations to new areas - Often, it is juvenile individuals that relieve overcrowding by leaving

Emigration

- movement of individuals out of an area - The pressure to migrate from a population may be a result of seasonal reproduction leading to a rapid increase in population size or environmental changes that intensify competition among members of the same species. For example, as water holes dry up, competition for water increases, and many desert birds migrate to areas where water is still available.

Less-developed countries

- typically have a per capita income of less than US $15,000. - The population of these countries totals about 6 billion people, nearly 900 million of whom live on less than US $1.90 per day - majority of Asian, Latin American, and African citizens are much less well off economically than those who live in the more-developed countries - The less-developed regions of the world, however, have high population growth rates and are expected to grow by about 39 percent between 2016 and 2050.

More-developed countries

- typically have a per capita income that exceeds US $25,000; - they include all of Europe, Canada, the United States, Australia, New Zealand, and Japan, with a combined population of about 1.25 billion people. - Collectively, the more-developed countries of the world have relatively stable populations and are expected to grow by about 5 percent between 2016 and 2050.

r-strategists

- typically small organisms that have a short life, produce many offspring, exploit unstable environments, and do not reach a carrying capacity. - Examples are bacteria, protozoa, many insects, and some small mammals - The reproductive strategy of r-strategists is to expend large amounts of energy producing many offspring but to provide limited care (often none) for them. Consequently, there is high mortality among the young. - For example, one female oyster may produce a million eggs, but of those that become fertilized and grow into larvae, only a few find suitable places to attach themselves and grow into mature oysters. - These populations of r-strategists are limited by density-independent limiting factors; These factors can include changing weather conditions that kill large numbers of organisms, habitat loss such as occurs when a pond dries up or fire destroys a forest, or an event such as a deep snow or flood that buries sources of food and leads to the death of entire populations. - The population size of r-strategists is likely to fluctuate wildly. They reproduce rapidly, and the size of the population increases until some density-independent factor causes the population to crash; then they begin the cycle all over again.

Total Fertility Rate

-- The number of children born per woman in her lifetime. A total fertility rate of 2.1 is known as replacement fertility, since parents produce 2 children who will replace the parents when they die. - A rate of 2.1 is used rather than 2.0 because some children do not live very long after birth and therefore will not contribute to the population for very long - When a population is not growing, and the number of births equals the number of deaths, it is said to exhibit zero population growth - For several reasons, however, a total fertility rate of 2.1 will not necessarily immediately result in a stable population with zero growth. First, the death rate may fall as living conditions improve and people live longer. If the death rate falls faster than the birth rate, there will still be an increase in the population even though it is reproducing at the replacement rate.

Factors the influence population growth

1. Biological factors - Birth and Death rate - Total Fertility rate - Age distribution 2. Social factors - Culture and traditions - Attitudes toward birth control 3. Economic Factors 4. Political factors - Government population policy - Immigration

Pattern of population growth

1. Lag Phase 2. Exponential Growth Phase 3. Deceleration Phase 4. Stable equilibrium Phase

Current population growth has led to the following:

1. famine in areas where food production cannot keep pace with increasing numbers of people; 2. political unrest in areas with great disparities in the availability of resources (jobs, goods, food); 3. environmental degradation (erosion, desertification, strip mining, oil spills, groundwater mining) caused by poor agricultural practices and the destructive effects of exploitation of natural resources; 4. water pollution caused by human and industrial waste; 5. air pollution caused by the human need to use energy for personal and industrial applications; and 6. extinctions caused by people converting natural ecosystems to managed agricultural ecosystems.

Population

A group of individuals that belong to the same species and live in the same area. The terms species and population are interrelated because a species is a population—the largest possible population of a particular kind of organism. Population is often used to refer to portions of a species by specifying a space and time.

asexual reproduction

A reproductive process that involves only one parent and produces offspring that are identical to the parent. Ex: Plants and many kinds of animals, such as sponges, jellyfish, and several kinds of worms, reproduce asexually by dividing into two parts or by budding off small portions of themselves that become independent individuals.

environmental resistance

All the limiting factors that act together to limit the growth of a population.

List four factors that could determine the carrying capacity of an animal species. (6)

Are the availability of raw materials, availability of energy, accumulation of waste products, and interactions among organisms

As the human population continues to increase, what might happen to other species? (11)

As human population continues to increase and everyone thrives to survive, we will have to take other animals' resources and habitat to satisfy our needs. We will displace the habitats and resources of other species, and some of them will become instinct as we over harvest them.

The Demographic Transition Model

Based on the historical, social, and economic development of Europe and North America. Has 4 stages: 1. Initially, countries have a stable population with a high birth rate and a high death rate. Death rates often vary because of famine and epidemic disease. 2. Improved economic and social conditions (control of disease and increased food availability) bring about a period of rapid population growth as death rates fall, while birth rates remain high. 3. As countries develop an industrial economy, birth rates begin to drop because people want smaller families and use contraceptives. 4. Eventually, birth rates and death rates again become balanced. However, the population now has low birth rates and low death rates.

Why is your ecological footprint larger than that of a person in Africa? (15)

Because I have more energy-consuming items than they do.

Population growth causes many environmental problems. Identify some of these problems. What role do you think technology will play in solving these problems? Are you optimistic or pessimistic about these problems being solved through technology? Why?

Because of population growth the environment cannot provide food and drinking water. Energy resources are decreasing. Forests, grasslands, and other ecosystems are destroyed and this has led to the extinction of several animal and plant species. There is an unequal distribution of natural resources. Pollution increased beyond the ability of nature to recycle. During the past few decades, technological advancement has increased the life span of humans. Has provided better health care, better food, purified water, and decreased epidemic diseases. However technology cannot solve all of the problems associated with population growth.

How do the concepts of birth rate and population growth differ? (7)

Birthrate is defined as the number of individuals born into a population, whereas population growth is the result of birthrate and immigration minus death rate and emigration, or the total net increase in the population size.

Why do you suppose some organisms display high natality and others display lower natality? For example, why do cottontail rabbits show high natality and wolves relatively low natality? Why wouldn't all organisms display high natality?

Cottontail rabbits show high natality due to low survival rates of the offspring (due to high rate of predation), limited parental care and high mortality rate in the young. Wolves on the other hand show low natality rate because offspring receives parental care, they are at higher levels in the food chain, mortality rate of the offspring is low and predators of these organisms are less.

What is demographic transition? What is it based on? (13)

Demographic transition is the hypothesis that economies proceed through a series of stages, resulting in stable populations and high economic development. The model is based on the historical, social, and economic development of Europe and North America.

Affluence

Differences in Affluence The kitchen facilities these two women use to prepare meals shows a great difference in their levels of affluence. The woman from Nepal uses a wood stove to make pancakes and boil water for tea. The woman from North America is emptying a dishwasher and has several other electric appliances (microwave, oven, and electric lighting) at her disposal.

Deceleration Phase

Eventually, however, the population growth rate will begin to slow as the death rate and the birth rate come to equal one another. This is the deceleration phase.

Which three areas of the world have the highest population growth rate? Which three areas of the world have the lowest standard of living? (20)

Latin America, Africa, and Asia have both the highest population growth rate and the lowest standard of living.

Lag phase

First stage. the population grows very slowly because there are few births, since the process of reproduction and growth of offspring takes time. Organisms must mature into adults before they can reproduce.

List ten differences between your standard of living and that of someone in a less-developed country. (18)

Higher gross national product, higher gross national product, higher individual income, lower infant mortality rate, higher age expectancy, lower birth rate, greater availability of food, higher consumption of energy, greater access to education, greater availability of jobs, and greater waste.

Examples of Age Distribution

Human populations exhibit several types of age distribution: - Kenya's population has a large prereproductive and reproductive component. This means that it will continue to increase rapidly for some time. - The United States has a very large reproductive component with a declining number of prereproductive individuals. Eventually, if there were no immigration, the U.S. population would begin to decline if current trends in birth rates and death rates continued. - Italy has an age distribution with high postreproductive and low prereproductive portions of the population. With low numbers of prereproductive individuals entering their reproductive years, the population of Italy has begun to decline, but part of that decline is offset by immigration.

The demographic changes occurring in Mexico have an influence on the United States. What problems does Mexico face regarding its demographics? Should the United States be involved in Mexican population policy?

I believe that every country should make their own policies regarding the regulation of their own population. However, it is understandable to fear that a high population growth in Mexico could lead to a high population of illegal immigrants in the U.S. But instead of getting involved with Mexico's population policy, both countries should come together to find a better solution to control illegal immigration.

How does the age distribution of a population affect the rate at which a population grows? (16)

If the population has a large number of pre-reproductive juveniles, it would be expected to grow in the future as the young become sexual mature.

Describe three reasons why women in the less-developed world might desire more than two children. (21)

In areas where infant mortality is high, it is traditional to have large families, since several of a woman's children may die before they reach adulthood. This is particularly important in the less-developed world, where there is no government program of social security. Parents are more secure in old age if they have several children to contribute to their needs when they become elderly and can no longer work.

How are age distribution, total fertility rate, and immigration affecting the way the U.S. population is changing? (22)

In the US older populations are increasing in numbers because of a lower fertility rate

Give examples of intrinsic, extrinsic, density-dependent, and density-independent limiting factors. (9)

Intrinsic: when times are bad the female white-tail deer are more likely to have single offspring than twins. Extrinsic: predators' loss of food source, lack of light, or accidents of nature. Density-dependent: the larger a population becomes, the more likely it is that predators will have a chance to catch some of the individuals. Density-independent: a sudden rainstorm may drown many small plant seedlings and soil organisms.

How is biotic potential related to the rate at which a population will grow? (1)

It is the ability of each species to produce offspring; it is directly dependent on the number of individuals, especially females, of reproductive age.

How do K-strategists and r-strategists differ? (10)

K-strategists usually occupy relatively stable environments ant tend to be large organisms that have relatively long lives, produce few offspring, and provide care for their offspring. r-strategists - are typically small organisms that have a short live, produce many offspring, exploit unstable environments, and do not reach a carrying capacity.

Consider the differences between K-strategists and r-strategists. What costs are incurred by adopting either strategy? What evolutionary benefits does each strategy enjoy?

K-strategists: organisms that inhibit relatively stable environments. The organisms are competitively large, and have a longer life span. Costs: They produce few offspring and provide extensive parental care for them.o Benefit: the survival rate of the offspring is pretty high.• R-strategist: organisms that inhibit unstable environments and do not reach carrying capacity. Cost: incur a lot of energy in reproduction and bearing the offspring. Very few organisms survive to maturity since the offspring are weak. Benefit: can colonize a new ecological niche and can start an ecological succession

All successful organisms overproduce. What advantage does this provide for the species? What disadvantages may occur? (12)

Overproduction is advantageous to ensure population density, dispersal, and colonization of a habitat. The disadvantage is high mortality due to environmental resistance factors. In the case of human overproduction, the physical environment and food animals can be over utilized.

How does the population growth curve of humans compare with that of bacteria on a petri dish? (8)

Population growth of bacteria growing in a petri dish begins with a lag phase, continues through an exponential growth, and then levels off due to an accumulation of toxic waste. Human population growth has a long lag phase followed by a sharply rising exponential growth phase that is still rapidly increasing.

Do you think it is appropriate for developed countries to persuade less-developed countries to limit their population growth? What would be appropriate and inappropriate interventions, according to your ethics? Now imagine you are a citizen of a less-developed country. What might be your reply to those who live in more-developed countries? Why?

Population increase puts a lot of pressure on natural resources because these resources are limited and cannot cater the needs of the growing population. However, we also need to be aware that most of the underdeveloped countries, at some point, were exploited by developed countries for their resources. It would be hypocritical of us to tell them to limit their population for the sake of the environment, considering that developed countries are responsible for most of the pollution on this earth and the one's that suffer the consequences are the underdeveloped and poorest people in these nations. Climate changes are depriving these people of the natural resources which provide their livelihood.

Why do some populations grow? What factors help to determine the rate of this growth? (3)

Populations have an inherent tendency to increase in size. Population growth is determined by the combined effects of birthrate and death rate. Other factors include emigration, immigration, sex ratio, and age distribution.

Do you think that demographic transition will be a viable option for world development? What evidence leads you to your conclusions? What role should the developed countries play in the current demographic transition of developing countries? Why?

The demographic transition model suggests that as a country develops technologically, it automatically experiences a drop in the birth rate. This certainly has been the experience of the developed countries of the world. However, the developed countries make up less than 20 percent of the world's population. It is doubtful whether the less-developed countries can achieve the kind of technological advances experienced in the developed world.

Doubling rate

The doubling time for the human population is easily calculated by dividing the number 70 by the annual rate of increase. Thus, at a 1 percent rate of annual increase, the population will double in 70 years (70/1). At a 2 percent rate of annual increase, the human population will double in 35 years (70/2).

Demography

The scientific study of human populations, their characteristics, how these characteristics affect growth, and the consequences of that growth

Technology

The technology used to provide the things people consume and use is an important contributor to environmental impact. Some methods are efficient and have minor impacts; others are very damaging.

Many people in developing countries hope to achieve the standard of living of those in the developed world. What might be the effect of this pressure on the environment in developing countries? On the political relationship between developing countries and already developed countries? What ethical perspective do you think should guide this changing relationship?

When the developed countries, such as Europe and North America, passed through the demographic transition, they had access to large expanses of unexploited lands, either within their boundaries or in their colonies. Today, less-developed countries may be unable to accumulate the necessary capital to develop economically, since they do not have uninhabited places to which their people can migrate and an ever-increasing population is a severe economic drain.

Gross national income (GNI)

an index that measures the total goods and services generated within a country as well as income earned and sent home by citizens of the country who are living in other countries.

intrinsic limiting factors

factors inside a population that limit its growth: changes in reproductive physiology, changes in behavior - Ex: A study of rats under crowded living conditions showed that as conditions became more crowded, abnormal social behavior became common. There was a decrease in litter size, fewer litters per year were produced, mothers were more likely to ignore their young, and adults killed many young. Thus changes in the behavior of the members of the rat population itself resulted in lower birth rates and higher death rates that limited population size.

Imagine a debate between an American and a Sudanese person about human population and the scarcity of resources. What perspectives do you think the American might bring to the debate? What perspectives do you think the Sudanese would bring? What might be their points of common ground? On what might they differ?

he United States contains large areas of uninhabited lands. The population and population density are less and resources are abundant. Therefore, an American may say that there is no sacristy of resources and the resources can support their population. In Sudan on the other hand, the population is very high. The country has limited natural resources; soils are infertile and are not very productive. Because of this, the Sudanese may claim that they suffer from scarcity of natural resources due to their large population size. Their point of common ground may be population and natural resources. Since both of these nations rely on natural resources for economic growth. But, they might differ in the population size and growth rate since a Sudanese may prefer large families as essential for social security, where as Americans are restricted to small families.

Mortality

he number of deaths in a population over a particular time period. Most species, mortality rate is high, especially among the younger individuals. Ex: of all the seeds that plants produce, very few will result in a mature plant that itself will produce offspring. Many seeds are eaten by animals, some do not germinate because they never find proper soil conditions, and those that germinate must compete with other organisms for nutrients and sunlight

Survivorship curve

hows the proportion of individuals likely to survive to each age. Three general types of survivorship curves can be recognized: species that have high mortality among their young (Dall sheep), species in which mortality is evenly spread over all age groups, and species in which survival is high until old age (White-crowned sparrow), when mortality is high (Cleome droserifolla)

population growth rate

is the birth rate minus the death rate. For example, in the United States, the birth rate is 12 births per thousand individuals in the population. The death rate is 8 per thousand. The difference between the two is 4 per thousand, which is equal to an annual population increase of 0.4 percent (4/1,000).

Interpret the meaning of I = P × A × T. (14)

mpact on the environment = Populations size x Affluence (amount resource consumed per person) x Technology (effects of methods used to provide items consumed)

Natality

refers to the number of individuals added to the population through reproduction over a particular time period Through sexual and asexual reproduction Birth rate- number of individuals born per 1,000 individuals per year

Demographic dividend

the concept that increased economic activity and improved standard of living will occur if the age structure of a country's population can shift from a large proportion of dependent children to an increased proportion of working-age adults. The sequence of events that creates this change is as follows: 1. Improvements in health care result in lower mortality in children and mothers. 2. As more children survive, the birth rate will fall as women seek to have fewer children. 3. Over time, as the birth rate falls, children will make up a smaller proportion of the population and working adults will make up a larger proportion of the population, and less money is spent on raising children. Often many women enter the workforce for the first time. 4. If appropriate economic policies can effectively utilize the growing workforce, the demographic dividend can lead to rapid economic growth. - Examples of countries that have experienced the demographic dividend as they go through demographic transition are China, South Korea, and Indonesia in addition to several South American countries.