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58 Cards in this Set
- Front
- Back
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population |
a group of individuals of the same species inhabiting an area. often used to refer to portions of a species by specifying a specific space and time. |
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subspecies |
when a species has several genetic differences among different populations that occupy a variety of different habitats. different local conditions results in each population having these differences. |
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natality |
the number of individuals added to the population through reproduction over a particular time period. most species have very high natality rates and produce more offspring than are needed to replace the parents. |
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birthrate |
the natality of humans, usually measured as number of individuals born per 1,000 individuals. |
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mortality |
the number of deaths in a population over a particular time period. most species have very high mortality rates, especially among younger individuals. longer lived animals normally have lower young mortality rates |
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death rate |
mortality rate of humans as measured as number of people who die per 1,000 individuals |
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survivorship curve |
shows proportion of individuals likely to survive to each age. 3 general types 1. species that have high mortality among their young 2. species in which mortality is evenly spread over all age groups 3. species in which survival is high until old age, when mortality it high |
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population growth rate |
birthrate minus the death rate. for humans its expressed as a % of the total population |
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sex ratio |
refers to the relative numbers of males and females. most species have a 1:1 sex ratio in many social insect populations, number of females greatly outnumber number of males (though most are sterile). |
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age distribution |
number of individuals of each age in the population 3 general types 1. large number of prereproductive individuals will lead to a population boom in the future 2. large numbers of reproductive "adults" will result in a current population boom 3. population made up of older postreproductive adults, population levels will fall. |
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population density |
the number of organisms per unit area. organisms are distributed unevenly due to differences in soil type, habitat quality, and availability of water if density is too high, all individuals within the population are injured because they compete severely with each other for necessary resources. |
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dispersal |
movement from densely populated locations to new areas in animals. relieves overcrowded conditions i the home area and increase the population in the places migrated to often juvenile individuals are the ones that emigrate (move away) |
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immigration |
movement of species into a new population. may introduce characteristics that were not in the population originally |
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biotic potential |
a species inherent reproductive capacity, which is its biological ability to produce offspring. most species have a high biotic potential, creates a natural tendency for population growth. |
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exponential growth phase |
low mortality rates easily lead to population rate doubling each year. results from drops in mortality rates populations have periods of exponential growth but can't grow that way forever. population will continue to grow as long as birthrate exceeds the death rate |
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population growth curve |
consists of 5 stages 1. lag phase 2. exponential growth phase (log phase) 3. deceleration phase 4. stable equilibrium phase 5. death phase |
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lag phase |
population grows very slowly because there are few births. happens because the process of reproduction and growth of offspring takes time |
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deceleration phase |
population growth rate begins to slow as the death and birthrate closer to equal |
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stable equilibrium phase |
when the birthrate and death rate become equal. the population stops growing and reaches a relatively stable population size. |
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limiting factors |
factors that prevent unlimited population growth
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environmental resistance |
all of the different limiting factors that act on a population collectively |
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extrinsic limiting factors |
limiting factors that come from outside the population. examples: predators, loss of a food source, lack of sunlight, accidents of nature |
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intrinsic limiting factors |
limiting factors come from within the population of a species themselves examples: deer reproduce less after bad winters, deer more likely to have single offspring rather than 2 during bad times. |
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density dependent limiting factors |
limiting factors that become more effective as the density of the population increases. large organisms that tend to live a long time and have relatively few young are most likely to be controlled by these types of limiting factors. |
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density independent limiting factors |
population controlling influences that are not related to the density of the population. are usually accidental or occasional extrinsic factors in nature that happen regardless of the density of a population example: sudden rainstorm drowning many small plant seedlings and soil organisms, late or early frosts killing plants/animals small, short lived organisms that can reproduce quickly most likely to be effected |
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4 broad categories recognized as limiting factors of environmental resistance. |
1. availability of raw materials; 2. availability of energy 3. accumulation of waste products: doesn't normally effect plants since they generate little waste 4. interactions among organisms |
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death phase |
decline in population size that follows equilibrium phase. |
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carrying capacity |
the maximum sustainable population for an area. determined by a number of limiting factors not an inflexible number, can be changed by a variety of environmental differences, amount of nutrients, changes in other species population wildlife management practices encourage modifications to the environment that increase carrying capacity for the designated game species |
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k-strategists |
organisms that typically reach stable population as the population reaches the carrying capacity. 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.
species generally invest great amount of energy raising few young, most young have a good chance of surviving and reproducing. population grows exponentially followed by equilibrium stage at the carrying capacity. controlled by density dependent limiting factors as the population size increases |
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r-strategists |
typically small organisms that have a short life, produce many offspring, exploit unstable environments, and do not reach a carrying capacity. expand large amounts of energy producing many offspring but provide limited to no care. high mortality rate among offspring limited by density independent limiting factors population size fluctuate wildly and experience booms and busts. examples: bacteria, protozoa, many insects, some small mammals. |
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population cycles |
periods of relatively large populations followed by periods of small populations generally happens in northern regions of the world for animals happens because ecosystems are relatively simplistic with few organisms affecting one another |
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hypothesis for why population cycles occur |
1. heavy feeding by large populations of herbivores cause plants to produce increased levels of chemicals that are toxic or taste bad. 2. large herbivore populations results in many different predators shifting to eating them 3. interactions between prey and a specialized predator naturally lead to population cycles, length of cycle depends on reproductive biology of the prey and their predators. |
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human population growth |
had a long lag phase, followed by sharp rising exponential growth phase caused by a lowering death rate. current growth rates is 1.2% annually, compounds so grows very quickly doubling time for human population growth is 70/ the annua rate of increase example 1.2% growth will double world population within about 58 years |
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more-developed countries: |
per capita income exceeds US $25,000 includes all of Europe Canada, US, Australia, New Zealand, and Japan. have a combined population of 1.2 billion people population growth stable (estimate 7% between 2010 and 2050). |
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less-developed countries |
per capita income of less than US $15,000 all other countries 5.7 billion people, 3 billion of whom subside on US $2 or less per day population growth high (estimated 44% from 2010 to 2050) |
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factors contributing to environmentalaly negative impacts due to human population growth |
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 6. extinctions caused by people converting natural ecosystems to managed agricultural ecosystems. |
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equation to estimate impact of a human population on the environment |
I = P * A * T I = Impact on the environment P = Population size A = Affluence (amount of resources consumed per person) T = Technology (effects of methods used to provide items consumed). |
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human population population density |
number of people per unit of land. higher the amount of resources the higher the population density an area can sustain |
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ecological footprint |
a measure of the land area required to provide the resources and absorb the wastes of a population. generally the more a nation has to import resources the higher the ecological footprint |
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biological factors influencing human population growth |
1. birthrate and death rates
2. total fertility rate 3. age distribution |
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demography |
the scientific study of human populations, their characteristics, how these characteristics affect growth, and the consequences of that growth predicts future human population growth |
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total fertility rate |
the number of children born per woman in her lifetime |
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replacement fertility |
having a fertility rate of 2.1 the 2 children will replace 2 parents when they die not 2.0 because some children still die shortly after birth |
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zero population growth |
number of birth equals the number of deaths, population stabilizes and has no growth or decline |
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Age distribution |
the number of people of each age in the population the younger a population the higher the population increase generally |
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cultural and traditional factors of human population growth |
- family size is largely determined by the status and desires of woman in a culture. in male dominated cultures traditional role of woman is to marry and to raise children. often ties into religious beliefs. - little value on educating women and early marriage is encouraged. woman marrying younger increases fertility rates due to increased probability of pregnancy -educating women is the biggest factor in decreasing population growth, generally leads to delay of marriage -childbearing practices: breast feeding decreases infant mortality and decreases pregnancy rate during nursing period (1-2 years). |
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attitudes toward birth control influence no human population growth |
- as women become more educated they have more access and are more likely to use birth control - birth control use is much higher in developed countries - a population has to want to use birth control for it to be effective. |
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government population policy effect on human population growth |
- many developed countries financially give incentives for having children. This is to encourage an increase in available workers to support social systems. - developing countries try to decrease the birthrate through low cost reproductive health services and education. - China has decreased fertility rate by providing family planning services, encouraging abortion, and heavily taxing larger families. - |
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standard of living |
an abstract concept that attempts to quantify the quality of life of people. Can include economic well-being, health conditions, and the ability to change one's status in society. - there appears to be an inverse relationship between the rate at which the population of a country is growing and its standard of living. |
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gross national income (GNI) GNI PPP (gross national income purchasing power parity). per capita GNI PPP |
way to track purchasing power of citizens. 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. adjusts for the differences in the costs of goods and services between countries dividing the GNI PPP by the number of people in a country |
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Health criteria on human population growth |
- Access to health care, safe drinking water, and adequate foods are reflected in life expectancy, infant mortality, and growth rates of children. - developed countries generally do better in all regards as compared to developing nations |
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educational status effect on human population growth |
determines jobs available and the likelihood of being able to improve status men are more likely to get educated than women but educated women have a greater impact on birth rates and family well being |
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environmental impacts of food production |
- human population can only increase if the populations of other organisms decrease - agriculture destroys natural ecosystems by converting land to farming - agriculture mismanagement leads to outcomes like desertification and rainforest desturction |
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human energy pyramid |
- people in less developed countries feed at lower trophic levels than in the developed world - 90% of energy in plants is lost when feed to livestock when not using modern agricultural practices - lack of protein leads to malnutrition, is easiest to get by eating animals - cutting back on eating meat in the developed world decreases the amount of needed farmland substantially. |
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demographic transition what are the 4 stages |
natural series of stages that countries go through in their demographics 1. Initially, countries have a stable population with a high birthrate and 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. Birthrates remain high. 3. As countries develop an industrial economy, birthrates begin to drop because people desire smaller families and use contraceptives. 4. Eventually, birthrates and death rates again become balanced. However, the population now has low birthrates and low death rates. |
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problems with applying the demographic transition model to the developing world |
- greater population today than when North America, Europe, Australia, and Japan went through it, and would require far more resources than are available - requires access to large bodies of land for increasing populations to expand to - population growth is faster than the rate industrialization can take hold |
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united states population |
-baby boomers and lower modern birthrates are leading to an increase of the older nonworking population - immigration largely contributes current US population growth |
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4 factors affecting human population carrying capacity |
1. available raw materials 2. available energy 3. waste disposal: includes pollution, sewage treatment 4. interaction with other organisms: all people are dependent the broader ecological services provided by a diverse planet |
