Two life history patterns suggest that nature is more complex than it is.
strategist populations are at the end of a continuum, and most populations are between the two extremes.
Plants have two life cycles-- the sporophyte generation and the gametophyte generation.
The gametophyte should be left to fend for itself.
Strategies, retain and protect the gametophyte.
They produce seeds that contain the next generation.
The plants still release a lot of seeds despite the investment.
Adult size is not always a factor in life history.
Cod release gametes in vast numbers, the zygotes form in the sea, and the parents make no further investment in the developing offspring.
Only a few of the 6-7 million eggs released by a single female cod will become adult fish.
Predation has been reduced for selected species.
The human population places pressures on the Earth's resources.
The world's population has risen steadily to its present size of over 7.4 billion people.
Prior to 1750, the growth of the human population was relatively slow, but as more reproducing individuals were added, the curve began to slope upward, indicating that the population was undergoing exponential growth.
The number of people added to the world population peaked in 1990 at about 87 million, and is currently around 81 million per year.
This is roughly the same as the current populations of Argentina, Ecuador, and Peru.
Depending on the speed with which the growth rate declines, it is predicted that it will be between 9 and 11 billion by the year 2050.
It was thought to be in the range of 35-60 years for humans, but most experts think it will take longer to reach 12 billion.
Extreme demands on our ability to produce and distribute resources would be made by an increase in population size.
The world needs to double the amount of food, jobs, water, energy, and so on in the next 50 to 60 years.
Many people are gravely concerned about the increased amount of resources that will be needed to support the growth of the human population.
The first billion didn't occur until 1800, the second billion in 1930, the fourth billion in 1974 and the fifth billion in 1978.
Zero population growth can't happen until the birthrate is equal to the death rate.
There are two general groups for the countries of the world.
The people of the United States, Germany, Japan, and Australia enjoy a high standard of living.
The majority of people live in poverty in the LDCs, typified by Afghanistan, Ethiopia, Rwanda, and Haiti.
Between 1850 and 1950, the MDCs doubled their population.
The decline in the death rate was one of the reasons for the change.
The decline in the death rate followed by a decline in the birthrate led to modest growth in the population of the MDCs.
A demographic transition is a sequence of events that include a decrease in death rate and a decrease in birthrate.
There is no end in sight for the U.S.
Many people migrate to the U.S. each year because of the yearly growth of the U.S. population.
The baby boom of 1946 and 1964 resulted in a large number of women still of reproductive age.
The majority of the world's population now lives in LDCs.
The death rate began to decline steeply in the LDCs after World War II, but the birthrate remained high.
Between 1960 and 1965, the yearly growth of the LDCs was 2.5%.
The death rate and birthrate have fallen since that time.
Many countries in sub-Saharan Africa have not participated in the decline of the collective growth rate for the LDCs.
Women average more than five children each.
The population of the LDCs is expected to explode to over 8 billion by the year 2050.
The Asian population is four times the size of the African population, which will lead to an increase in this area.
Asia has 60 percent of the world's population, living on 31% of the world's arable land.
Acute water scarcity, a significant loss of biodiversity, and increased urban pollution are expected to occur in Asia.
Twelve of the world's most polluted cities are in Asia.
There are suggestions to reduce the population increase in the LDCs.
A decline in growth can be seen in countries with good family planning programs.
Social progress can be used to reduce the desire for large families.
Raising the status of women, reducing child mortality, and providing education are some of the social improvements that could reduce this desire.
Delay the birth of children.
Birthrate decline could be helped by this and wider spacing of births.
The LDCs have more young women entering the reproductive years than older women leaving them.
Increased contraceptive use and improved women's rights could change this scenario.
A community health worker is teaching women in India how to use contraceptives.
If each couple has two children, there will be no increase in population size.
Most countries will continue to grow because of the age structure of the population.
Population growth will still occur if more young women enter the reproductive years than older women leave them.
A large proportion of the population is younger than 15 years old in most LDCs.
In Nigeria, 40.9% of the population is under the age of 15.
Nigerian women have a fertility rate of approximately 5.67 per woman.
The population of Nigeria is expected to increase by over 400 million by the year 2050.
Even after replacement reproduction is attained, the LDC populations will still expand.
Zero population growth can be achieved sooner if replacement reproduction is achieved quickly.
Population growth is putting extreme pressure on the Earth's resources.
Because the population of the LDCs is still growing at a significant rate, it might seem that their population increase will be the greater cause of future environmental degradation.
The LDCs consume less of the Earth's resources than the MDCs.
Environmental degradation is a major concern.
The environmental impact of a population is measured in terms of population size but also in terms of resource consumption per capita and the pollution produced by this consumption.
The first type of overpopulation is due to population growth, and the second is due to increased resource consumption.
The first type of overpopulation is more obvious in LDCs, and the second type is more obvious in the MDCs.
In terms of per-capita resource consumption and waste production, an average family in the United States is the equivalent of 30 people in India.
Only a limited number of people can be sustained at any given time in the MDCs.
Figure 44.17 shows the current environmental impact caused by LDCs.
The MDCs consume more oil and coal than the rest of the country.
China leads the world in CO2 emissions, but they also have the largest percentage of the human population, making their impact smaller than that of MDCs.
The environmental impact is caused by some people.
LDCs have larger populations.
In the United States, per-person oil consumption is 7.7 times greater than in China.
In India per person coal consumption is less than in the United States.
CO2 production in the United States is five times greater than in Mexico.
As the LDCs become more industrialized, their per-capita Page 844 consumption will also rise and, in some LDCs, it may nearly equal that of a more-developed country.
China is competing with the United States for oil and metals on the world markets because of its large population.
People in the United States will have no choice but to consume less as developing countries consume more.
The environment is negatively affected by the consumption of resources.
In Section 45.4, you'll learn how resource consumption leads to various pollution problems, and in Section 47.3, you'll learn how our increasing environmental impact may cause a mass extinction of wildlife.
Ecologists are interested in the distribution, abundance, and life history strategies of organisms.
The distribution of individuals can be random or uniform.
Population growth is dependent on a number of things.
Two models are used to describe population growth.
Growth cannot continue indefinitely in most environments.
The population stops growing when the carrying capacity is reached.
Some populations have other ways of regulating population growth.
Territoriality is a possible means of population regulation.
Other populations do not seem to be regulated.
Adults don't invest in parental care of their offspring.
Population size is affected by density- dependent factors.
Energy is given to survival and reproductive events.
The adults invest in their offspring.
The trade-offs between the two patterns are subject to natural selection.
The human population is still growing, but at a slower rate.
The growth rate of a country is slowed by this.
It is not known when the world population size will go down.
The majority of population increase will come from the LDCs, but we also need to consider the significant environmental impact thatMDCs have on the planet as we look to address future concerns.
Pick the best answer for the question.
The bloom of the algal populations occurs when the community has access to phosphorus.
This shows that phosphorus is a regulating factor.
The largest group is the prereproductive group.
A J-shaped growth curve is associated with exponential growth.
Population growth can correlate to changes in the environment.
A species that has many relatively small offspring, lives for a short period of time, and provides minimal parental care is an example.
The U.S. population can never level off because of the postwar baby boom.
parasites are a less important cause of death in the winter than cold winter weather.
Give an explanation for the inefficiency of parasites.
Populations will often overshoot the carrying capacity of their environment and eventually crash.
Finding a way to curb the rapid population growth of less-developed countries is the answer to how to curb the expected increase in the world's population.
Family planning leads to healthier women and children.
Women don't need to have many babies to survive.
Bettereducated people are more interested in promoting women's rights and postponing childbearing.
Women with equal rights have fewer children.
Beverly Winikoff at the Population Council in New York City says that women have no choice but to have fewer children.
Bangladesh is a case in point.
In 1990, the birthrate was 4.9 children per woman, in 2016 it was 2.2.
Some of the less developed countries have cut back on family planning programs due to economic crises, while the more developed countries have not taken up the slack.
The United States has been cut back on aid by some foreign donors.