quiz 3

Growth rate r = b+i-d-e or r = b-d+i-e and calculation

(N) Population - total number of all the members of a single species living in a specific area at the same time. (r) Rate—This is the rate of growth; the number of individuals which can be produced per unit of time under ideal conditions (with no limits to the population's growth). - Population change of an area (r)= (births + immigration) - (deaths + emigration) r = (b - d) + (i - e) (t) Time—This is the unit of time upon which the rate is based.

Biotic and abiotic regulatory factors corresponding with density-independent and density-dependent

• Intrinsic factors - operate within or between individual organisms in the same species • Extrinsic factors - imposed from outside the population • Biotic factors - caused by living organisms. Tend to be density dependent. • Abiotic factors - caused by non-living environmental components. Tend to be density independent, and do not really regulate population, although they may be important in increasing or decreasing numbers. Example: Rainfall, storms.

Majority of nutrients and calories are relied by human?

• Iron deficiency is the most common dietary imbalance in the world. • Leads to anemia, insufficient hemoglobin in the blood • Increases risk of death from hemorrhage in childbirth and affects development • Lack of iodine leads to goiter as well as stunted growth and reduced mental capacity. • Lack of vitamin A affects as many as 140 million children and 350,000 go blind each year.

K-Adapted Species:

• K-Selected species have few offspring, slower growth as they near carrying capacity and exercise more parental care. • For example: an elephant produces one offspring every 4 or 5 years, but nurturing by a herd increases the likelihood of it surviving to maturity.

Vitamins and protein deficiencies coursed human health problems, e.g. vitamin A, Iron.... deficiencies, and marasmus and kwashiorkor problems?

• Kwashiorkor = diet lacks protein or essential amino acids • Occurs when children stop breast-feeding • Bloated stomach, mental and physical disabilities • Marasmus (thin)= protein deficiency and insufficient calories • Wasting or shriveling of the body

What are the logistic and exponential growth rates for population growth?

Exponential Growth - • Can only be maintained by a population as long as nothing limits its growth. • In the real world there are limits to growth that each population will encounter. • Eventually, shortages of food or other resources lead to a reduction in the population size. • Exponential Growth - growth at a constant rate of increase per unit time (geometric); has no limit. E.g. When growth proceeds at a rate similar to 2 4 8 16 32 64...etc., it is called.

Problems With Green Revolution

¥ From 1900 to 2000, cultivated area increased 33% Ð While energy inputs increased 80 times Ð Positive effects on the environment ¥ Prevented some deforestation and land conversion ¥ Preserved biodiversity and ecosystems Ð Negative effects on natural resources ¥ Pollution, erosion ¥ Salinization, desertification

Population Crash:

• A rapid dieback in the population to a level below the carrying capacity.

Demographic Transition -

• A stable pre-industrial state of high birth and death rates changes to a stable post-industrial state of low birth and death rates. • As mortality decreases, there is less need for large families - Parents invest in quality of life • Death rates fall before birth rates - Resulting in population growth

The age structure of a population

• Age structure diagrams (population pyramids) show age structure • Wide base = many young: - High reproduction - Rapid population growth • Even age distribution: - Remains stable - Births = deaths Or age distribution = relative numbers of individuals of each age or age class in a population.

Logistic Growth -

• As a population approaches its carrying capacity, the growth rate slows because of limiting resources. • Logistic Growth is density-dependent which means that the growth rate depends on the population density. • Many density-dependent factors can influence a population including: disease, physiological stress and predation. • Density-dependent factors intensify as population size increases.

The cultural carrying capacity?

• Cultural carrying capacity (Human species) is the maximum number of people who could live in reasonable freedom and comfort indefinitely, without decreasing the ability of the earth to sustain future generations.

Density-Independent:

• Density independent factors may also affect populations. These may include drought, fire, or other habitat destruction that affects an ecosystem. • Most are aspects of the external environment: Weather - Droughts, storms, floods. Physical disruptions - Fire, road construction.

Extinction Rates -

• Extinction rates are highest for islands with many species. • Extinction rates are highest on small islands (small populations). • Extinction rates are not affected.

Human Population Growth

• Human population is increasing at a fixed percentage (exponential model) so that we are experiencing doubling of larger and larger populations. • Human population in 2009 was about 6.8 billion, 7.1 billion was n 2011 • Based on the current increase rate there will be 9.6 billion people by 2050. • Every second 4 or 5 children are born while only 2 people die. • There is a net gain of 2.3 persons per second. • Current world population is greater than 7 billion and growing at 1.4% per year. • Global population will double in 62 years if conditions remain unchanged. • Ecologists are concerned that overpopulation will cause environmental degradation that will threaten the ecological life-support systems on which we depend.

Immigration Rates -

• Immigration rates are highest for islands with few species. • Immigration rates are highest on large islands (big targets). • Immigration rates are highest for islands near the mainland.

Density-Dependent:

• Intraspecific Interactions - competition for resources by individuals within a population. • As population density approaches the carrying capacity, one or more resources becomes limiting. • Control of access to resources by territoriality; owners of territory defend it and its resources against rivals. • Stress-related diseases occur in some species when conditions become overcrowded.

Malnutrition?

• Malnourishment - nutritional imbalance caused by a lack of specific dietary components or an inability to absorb or utilize essential nutrients. • Undernourishment = too few calories (especially developing world. • 3 billion people suffer from vitamin, mineral or protein deficiency. • Results in illness and death

What is the total fertility rate (TFR)?

• Total fertility rate (TFR) = the average number of children born to each female • Replacement fertility = the TFR that keeps the size of a population stable (about 2.1) • Causes of decreasing TFR: - Medical care reduces infant mortality - Urbanization increases childcare costs - Children go to school instead of working - Social Security supports the elderly - Educated women enter the labor force

Boom & Bust:

• When a population undergoes repeated cycles of overshoots followed by crashes.

Life Span and Life Expectancy

• Maximum Life span - the longest period of life reached by a given type of organism - Bristlecone pines can live up to 4,600 years. - Humans may live up to 120 years. - Microbes may live only a few hours. • Differences in relative longevity among species are shown as survivorship curves. • Life expectancy = average number of years that an individual is likely to continue to live (increase lifespan) • Increases with reduced rates of infant mortality • Urbanization, industrialization, and personal wealth reduce infant mortality rates Survivorship Curves - ¥ Type I: survival rates are high when organisms are young and decrease sharply when organisms are old. ¥ Type II: survival rates are equivalent regardless of an organism's age. ¥ Type III: most mortality takes place at young ages, and survival rates are greater at older ages.

Green Revolution Strategies/Results:

• Most major improvements in farm production have come from technological advances and modification of a few well-known species. - Average corn yields jumped from 25 bushels per acre to 160 per acre in the past century. • Green Revolution started over 50 years ago with the production of tropical, semi-dwarf, wheat and rice strains which are now grown in developing countries around the world. • Green revolution plants are "high responders" which only show increased yields if they have fertilizers and protection from pests. • If these are lacking, they may not produce as well as traditional crops. • Poor farmers who cannot afford the costs of fertilizer, pesticides and hybrid seeds may be left out of the green revolution.

Carrying capacity?

• No matter how fast populations grow, they eventually reach a limit. This is improvised by shortages of important environmental factors. • The carrying capacity is the maximum number of individuals that an area can support. It is symbolized by "K."

R-Adapted Species:

• R-Selected species rely upon a high reproductive rate to overcome the high mortality of offspring with little or no parental care. • For example: a clam can release a million eggs in a lifetime, with few surviving to maturity.

Demographic Bottleneck Effect:

• The bottleneck effect is a sudden change in the environment that may drastically reduce the size of a population. • The resulting gene pool may no longer be reflective of the original population's gene pool. Founder effects and demographic bottlenecks reduce genetic diversity. Each may also result in inbreeding due to small population size. Inbreeding may lead to the expression of recessive genes that may have a deleterious effect on the population.

Founder Effect

• The founder effect occurs when a few individuals become isolated from a larger population or colonizes a new area. • It can affect allele frequencies in a population. • Small group of individuals establishes a population in a new location

Population Terminology - Overshoot:

• When a population exceeds the carrying capacity of the environment and deaths result from a lack of resources.