Population Ecology - AP Environmental Science

All of these can potentially influence the growth of human population. When people have access to more medical care, they both live longer and have higher rates of survival. Religions that oppose the use of contraceptives can also influence the size of a population; they are often found in areas or countries experiencing higher rates of population increase. In societies where women have access to more education, they are less likely to become pregnant at a young age, and also likely to have fewer children than women who do not have access to similar educational opportunities.

In his seminal work An Essay on the Principle of Population, Thomas Malthus theorized that eventually the human population would be halted by either famine, disease, or both. While his estimates on when this would occur proved dramatically incorrect, his work was very influential, and he has been studied by such critically important figures as Charles Darwin and Alfred Russel Wallace.

K-strategist populations are more commonly regulated by density-dependent limiting factors. Their population sizes hover around a carrying capacity that is dependent on factors that increase in severity with the density of the population. On the other hand, r-strategist populations are regulated by density-independent limiting factors. They reproduce rapidly until a density-independent factor causes many of them to die.

Replacement level fertility is the number of children required by a couple to replace them. Currently, in the United States, this number is just above two. This number accounts for infant mortality and varies by region.

Cultural carrying capacity suggests that humans have secondary needs, such as entertainment, palatable food, and mental/spiritual development. These non-vital resources can only be spread equally among a population of a limited size. Cultural carrying capacity describes the limitation on population size after taking into account these factors.

A frequent questions asked by sustainability scientists is: Should the optimum sustainable population be based on cultural carrying capacity? Many would agree yes, for the reason that when cultural capacity is transgressed, living conditions spiral downwards and life is reduced to the struggle for mere survival. In such conditions, human inventiveness and creativity become obsolete.

Population growth can follow either a J curve trend or an S curve trend. A J curve represents exponential, or unrestricted growth. An S curve represents logistic, or restricted, growth and accounts for the carrying capacity of an environment.

In a J curve model, the population will continue to grow even when it has reached capacity. In an S curve model, the population will stagnate and stabilize at a maximum value when capacity is reached.

Clumped distribution patterns localize individuals around scarce resources in environments where they are not equally distributed throughout. The clumping of organisms around these resources attracts predators and makes for easy predation. Because of the scarcity of water in desert, plain and tundra biomes, it is seen in large quantities in nature.

The carrying capacity of a certain habitat is the maximum number of individuals that it can support. Population numbers are limited by resources such as space, food, and water. Current estimates of Earth's carrying capacity are around 10 billion.

The population's new size at the start of 2012 was = original population + (births + immigrations) - (deaths + emigrations) = 120 + (18 + 2) - (2 + 3) = 135. Then, the net population growth rate is equal to (net change in population / size of old population) = 15/120 = .125.

Species described as "r-strategist" have a survival strategy of producing large numbers of offspring, a short life expectancy, and typically smaller body sizes. Examples include mice, locusts, and frogs. These species survive by producing lots of offspring, since many individuals don't survive to adulthood.

The correct response is density independence. The leafhopper population was not regulated by density. The only thing that regulated the population was abiotic events, such as forest fires.

Species designated as K-strategists thrive through longevity and have a higher survival rate at birth, but produce far fewer offspring. Examples include elephants and whales. Consider an elephant; it may produce relatively few baby elephants, but these baby elephants each have the potential to live relatively long lives. On the other hand, contrast K-strategists like elephants with r-strategists like rats, locusts, and flies. These species are designated as r-strategists because in contrast, they produce numerous offspring, few of which may survive to adulthood, and each one of which reaches maturity quickly and lives a relatively short life. K-strategists in general spend more time than r-strategists caring for and raising their offspring; they have fewer offspring, so they put more care into ensuring the survival of each one. Contrast elephants with frogs to see this difference; elephants care for their young, while frogs lay their eggs and care for their offspring very little, if at all.

In terms of population trends, Nigeria can expect to see exponential growth in the following years for two reasons: Fertility rates are already quite high (e.g. a stable population is at births per female) and a large portion of the population is under the age of fifteen. Present fertility rates ensure current exponential growth, while a large proportion of the population reaching reproductive age ensures future population growth, especially if the fertility rate remains inflated.

R-selected individuals are characterized by the following: early age of sexual maturity, many lifetime reproductive events, large numbers of offspring per event, and minimal parenting. Many of the offspring of r-selected species will die before adulthood. On the other hand, K-selected individuals have only one or few offspring at once and invest larger amounts of time and energy into parenting to ensure survival. The rabbit is the only species listed whose life traits can be categorized as being r-selected.

Use the Rule of 72:

is rate of growth

is time (in years) it takes to double

By manipulating the equation to divide 72 by the given growth rate, you can find the number of years it takes for the population to double.

Mutations occur at low rates. They are rare and not very common in most individuals. This explains why the process of evolution and adaptation occurs over long periods of time.

The use of child laborers leads to higher birth rates. More children are needed to support families and households. Educating women also decreases birth rates. This is the reason why developing countries tend to have higher birth rates than developed countries. A lower average marriage age leads to an increase in birth rates. Religion can influence birth rates, either raising or lowering (generally it raises the birth rate).

The correct response is density dependence. Since the population growth rate is dependent on the size of the population, it is therefore regulated by density. This is the perfect example of a density dependent population.

Corals are r-selected species, categorized by producing many offspring at once, which individually have low chances of survival, and short lifespans. Other r-strategists include rodents, insects, and other small-bodied, early-maturing animals. K-selected species produce few offspring and invest lots of parental care to ensure a higher chance of survival. Humans are an example of a K-selected species.