Intro to Environmental Science Chapter Ch 4, Sect 4-6
more factors affecting birth rates
availability of private and public pensions; infant deaths; urbanization; educational and employment opportunities for women
Decrease factors (environmental resistance) - biotic
low reproductive rate specialized niche inadequate food supply unsuitable or destroyed habitat too many competitors insufficient ability to hide from or defend against predators inability to resist diseases and parasites inability to migrate and live in other habitats inability to adapt to environmental change
Are species one or the other?
no, most organisms have a reproductive pattern somewhere between the two extremes
Fertility rate
number of children born to a mother in her lifetime
2 types of fertility rate
replacement level (FR): average number of children needed to replace parents (not always 2) total fertility rate (TFR): average number of children born to women in a population during their reproductive years
What is Environmental Resistance?
the combination of all factors that limit population growth create environmental resistance
third factor in rapid human population growth
the development of sanitation systems, antibiotics, & vaccines helped to control infectious disease agents, & death rates then dropped sharply below birth rates
Second factor in rapid human population growth
the emergence of early & modern agriculture allowed more people to be fed
what is migration?
the movement of people into (immigration) and out of (emigration) specific geographic areas
additional factors affecting birth rates
availability of legal abortions and reliable birth control; religious beliefs, traditions, and cultural norms
In the UN Conference on Population and Development, what are some of the goals of their 2015 population plan?
- access to family planning - improve health care for infants, children, pregnant women - implement national population policies
(reproductive patterns): Explain opportunist species patterns
- disperse rapidly when conditions are favorable or when a disturbance opens up a new habitat or niche for invasion. - they often crash due to more competitive species or unfavorable environmental conditions - most opportunist species go through irregular & unstable boom-and-bust cycles
Stats about today's human population
- geographically unevenly distributed - underdeveloped countries growing about 14% faster than developed countries - 2012: 2% of the year's 84 million people were added to developed countries; other 98% born into developing countries - unequipped to handle population pressures
Goals of the UN 2015 population plan, continued
- improve status of women with education and job opportunities - increase roles of men in child rearing - reduce poverty levels - reduce unsustainable patterns of production and consumption
How does the empowerment of women help to slow human population growth?
- leads to a decrease of total fertility rates (via education opportunities, good paying jobs, support of Women's Rights)
(reproductive patterns): Explain competitor species patterns
- mature slowly; cared for and protected - reproduce later in life with few offspring; long life spans - do well in competitive situations when approaching carrying capacity
population 10,000 years ago, and now
10,000 years ago, about 5 million humans now, there are 7.1 billion humans
What is our growth rate and projected growth?
1920s - 2 billion 1970s - 4 billion 1990s - 6 billion 2012 - 230,000 new people every day, 1 every 3 seconds growing at 1.2% a year 2050 Projection Median Value is 9,600,000,000
What countries have the highest population?
2013: China had 1.35 billion, 1 out of every 5 India had 1.21 billion, 1 out of every 6 U.S. had 316 million China + India have 37% of global population
Population growth (environmental resistance)
a/now more individuals, less resources; b/environmental resistance at work; c/pushback on population growth; d/population will stabilize around the carrying capacity; 3/S-curve
Additional info (2) on empowerment of women helping to slow human population growth
Changes in less-developed countries (bottom up changes; could stabilize populations, reduce poverty and environmental degradation, give more access to basic human rights)
Crude birth rate / crude death rate
Crude birth rate: number of live births per 1000 people in a year Crude death rate: number of deaths per 1000 people in a year
Do developing countries show slower or more rapid population growth rates?
Developing countries show slower population growth rates.
Principles of Sustainability govern populations (3)
Disruptions of normal pathways can lead to degradation
Case studies of China and India (Page 88) China:
Due to its one-child policy, China cut its crude birth rate in half and trimmed its TFR from 5.7 to 1.5, compared to 1.9 in U.S. China's population will increase to about 1.4 billion by 2026 then begin a slow decline to about 750 million by end of century (see more on page 88)
Principles of Sustainability govern populations (2)
Each population plays a part in nutrient recycling
Is the world overpopulated? Yes?
Earth not currently providing adequate necessities for 1 out of every 5 people; VHEM; Population regulation proponents: death rates are going to increase due to declining health; resource use & enviro degradation will intensify, ecological footprints increasing in size
Name some examples of opportunist species
Examples include algae, bacteria, and most insects.
Rate of human population growth
For most of history, human population grew slowly; past 200 years, grew rapidly
According to the 2005 Millennium Ecosystem Assessment, what percentage of earth's ecosystem services has been degraded by humans?
Human activities have degraded about 60% of the earth's ecosystem services shift from exponential growth to logistical growth curve
3rd stage of demographic transition
Industrial: steady, but slow, low birth rates
Is carrying capacity fixed or variable?
It is not fixed. There are seasonal variations; also depends on the presence or absence of predators
What did the potato famine in Ireland, where a million people died in 1845, & 3 million more migrated, prove?
It proves that humans are not exempt from overshoot and dieback.
Case studies of China and India (page 88) India:
Just a few things: Started "family planning" in 1952, when population was about 400 million. 2012 (60 years of control efforts) 1.26 billion people, the world's 2nd largest population (due in part to life expectancy rising from 38 to 65, mostly from declining death rates.) UN projects will be most populous nation by 2050 with 1.69 billion. (see more on page 88)
Names some examples of competitor species
Most large mammals (elephants, whales, humans); birds of prey; tropical rain forest trees; orange roughy, swordfish, are some examples
Is it natural or not natural to have unlimited resources and growth?
NOT natural
What limits the growth of population?
No population can continue to grow indefinitely because of limitations on resources & because of competition among species for those resources.
Principles of Sustainability govern populations (1)
Plants and animals are dependent on Solar Energy
4 factors affect population size
Population = (Births + Immigration) - (Deaths + Emigration)
What factors influence the size of the human population? (concept 4-5A)
Population size increases because of births and immigration and decreases through deaths and emigration.
4th stage of demographic transition
Postindustrial: equal birth and death rates
1st stage of demographic transition
Pre-industrial: high birth rates, but high death rates
What are reproductive patterns?
Species use different reproductive patterns to help ensure their long-term survival. Some have many, usually small, offspring & give them little or no care or protection. They overcome large losses by having many so a few will survive.
Is the world overpopulated? No?
Technological advances can help to overcome any environmental resistance; opposition to population control - religious/moral issues, invasion of privacy and personal freedom
What factors influence the size of the human population? (concept 4-5B)
The average number of children born to women in a population (total fertility rate) is the key factor that determines population size.
What factors influence the size of the human population? (concept 4-5C)
The numbers of males and females in young, middle, and older age groups determine how fast a population grows or declines.
What else can happen when overshoot occurs?
The population suffers a 'dieback' or population crash, unless the excess individuals can switch to new resources or move to an area with more resources. Damage can allow replacement of resources with competitors/unfavorable conditions
Principles of Sustainability govern populations (4)
There are limits to population growth in nature
Decrease factors (environmental resistance) - abiotic
Too much or too little light Temperature too high or too low Unfavorable chemical environment (too much or too little of critical nutrients)
2nd stage of demographic transition
Transitional: rapid growth, low death rates
How can we slow human population growth?
We can slow human population growth by reducing poverty, elevating the status of women, and encouraging family planning.
What is "Overshoot"?
When you exceed carrying capacity - equals population crash - usually due to lack of resources (example to check is the reindeer in the powerpoint for chapter 4, p.76)
Population growth (biotic potential)
a/few species at first; b/population grows exponentially at its intrinsic rate of increase; c/nears carrying capacity, logistical growth
Biotic Potential
capacity for population growth under IDEAL conditions - it varies by species; for example, elephants versus bacteria
Factors affecting birth rates
children in the workforce (many poor couples have large numbers of children to help them daily tasks - hauling daily drink water, getting wood , tending crops, etc)
other factors affecting birth rates
cost of raising and educating children (in U.S. it costs more than $235,000 to raise a middle-class child)
reasons for movement
economic/job seeking; religious reasons; ethnic conflicts; political oppression; wars; environmental refugees (forced to leave due to food/water shortages, soil erosion, other forms of environmental degradation or depletion)
What are some benefits family planning can provide?
educational and clinical services
Growth factors (biotic potential) - abiotic
favorable light, favorable temperature, favorable chemical environment (optimal level of critical nutrients)
Additional info (1) on empowerment of women helping to slow human population growth
globally, women do 66% of the work and get paid 10% of the world's income
Growth factors (biotic potential) - biotic
high reproductive rate, generalized niche, adequate food supply, suitable habitat, ability to compete for resources, ability to hide from or defend against predators, ability to resist diseases and parasites
First factor in rapid human population growth
humans developed the ability to expand into diverse new habitats & different climate zones.
Carrying capacity
is determined by species biotic potential and amount of environmental resistance in a particular ecosystem; maximum population of a species that can be sustained indefinitely;
Intrinsic rate of increase
is the rate at which the population of a species would grow if it had unlimited resources (individuals in populations with a high intrinsic rate of growth typically reproduce early in life, have short generation times [the time between successive generations], can reproduce many times, & have many offspring each time they reproduce.)
factors affecting death rates
life expectancy; infant mortality rates
