Population Biology?

種群∶一個區(qū)域內(nèi)的所有屬于同一物種的相同生物

Population density: the number of individuals of a population that inhabit a certain?area

種群變動∶

Change in population size (N)=(birth + immigration)-(death +immigration)

生物因素∶ food,?predators, competitors, parasites

非生物因素∶temperature, oxygen availability, light availability, toxins and pollutants

控制種群數(shù)量∶

1. Predators are eliminated?

2. More food

3. Nitrogen fertilizers and artificial light?

4. Predators

5. Anaerobic conditions or low temperatures?

6. Pesticides

影響種群變動的因素∶

1.Distribution

Types: random, clumped (most), and uniform

Reasons: gather around nutrients or resources; group together for protection, cooperative hunting, care the young

2. Age structure

Pre-reproductive & reproductive?→ grow

Post-reproductive → decrease

3. Reproductive strategies

Population growth model：?

Exponential(geometric) growth:

Populations that grow at their intrinsic rate of increase (r), not limited by resources.?

J-shaped curve

Logistic growth:

A population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment (K).

Carrying capacity (K): the upper limit of logistic growth.

S-shaped curve

Population cycle:

Boom-and-bust cycle

The rapid changes may be linked to predictable cycles in the environment.

Predator-prey cycle

The predator population changes after the prey population does.

Ecological footprint: the environmental impact of a population

IPAT model: I(the total impact)=P(population size)×A(affluence)×T(level of technology)

物種的瀕危和滅絕∶

Extinction > endangered > threatened

Background extinction rate: the natural rate of extinction

Destruction of animal and plant habitats:

1. Habitat fragmentation when building roads and cities

2. Habitat degradation when adding pollutants to the environment?

3. Invasive species

4. Direct hunting or overexploitation for animal products

Biodiversity hot spot: a highly diverse region that faces severe threats

相關(guān)法案∶

Marine Mammal Protection Act: protect marine mammals from falling below their optimum sustainable population levels

Endangered Species Act Program: prohibited the commerce of those species considered to be threatened?

CITES: bans the capture, exportation or sale of endangered and threatened species

HUMAN POPULATION

人口激增的原因∶

Agricultural revolution: more food becomes available

Industrial revolution: the development of machinery increases agricultural efficiency and improved housing conditions

Medical revolution: improvements in sanitation and the control of diseases reduce the mortality rate

人口變動的因素∶

Total fertility rate: the average number of children born to a woman during her lifetime

Replacement-level fertility: slightly higher than two children per couple

Infant mortality rate: the number of babies out of every 1000 births who die before 1 year old

Crude birth/death rate: the number of births/deaths per 1000 people in a population

Immigration: foreigners move into?

Emigration: residents more out

The Rule of 70: 70/ annual growth rate (%)= doubling time

注意如果題目中給的是 crude rate，先把干分率換為百分率，然后進行計算。

影響生育率的因素∶

The availability of birth control

The demand for children in the labor force?

The base level of education for women

The existence of public and/or private retirement systems?

The population's religious beliefs, culture, and traditions

Demographic transition 人口過渡

Pre-industrial∶高出生率，高死亡率，低自然增長率

Transitional∶ 高出生率，死亡率開始下降，自然增長率和總?cè)丝诖蟠笤黾?/p>

Industrial∶出生率開始下降，死亡率降到更低，自然增長率減慢但仍為正數(shù)，總?cè)丝诰徛黾?/p>

Post-industrial∶出生率繼續(xù)下降，死亡率保持較低水平，自然增長率下降，總?cè)丝诒３址€(wěn)定或負增長

Age-structure pyramids/diagrams 人口金字塔

人口金字塔通過對比不同年齡的人口數(shù)量，可以推出未來的人口發(fā)展趨勢和規(guī)律。

A∶增長型人口，金字塔底部人口數(shù)量最多，說明了高出生率，未來人口會不斷增加

B&D∶穩(wěn)定型人口，除最上部外各年齡層人口數(shù)量相似，自然增長率較低，未來人口會比較穩(wěn)定

C∶衰退型人口，底部人口數(shù)量少，老齡化嚴重，自然增長率為負，未來人口數(shù)量可能會減少

作用∶

Predict future changes to the population growth rate of the country or region Predict the social condition of the country or region

關(guān)于人口問題的計算公式∶

Birth rate= number of births during year/ original population at start of year×100%

Death rate = number of deaths during year/original population at start of year×100%

人口增長的影響∶

1. Food distribution: unevenly distributed?

2. Hunger: malnutrition

3. Resource use and habitat destruction

4.Infectious diseases: spread more quickly in densely populated areas?

Epidemic →limited to one area or region; pandemic → spread globally

e.g. influenza(most deadly), HIV(second-most deadly), malaria, diarrnheal diseases, tuberculosis, measles, SARS, West Nile virus