Human Population Issues Unit4:人口与环境 Size of Competition human for population resources Reproductive Social behavior Economic well-being decisions Political decisions
Human Population Issues Human Population Issues Unit 4: Unit 4: 人口与环境
Population Characteristics Population -Group of individuals inhabiting the same area simultaneously Natality and mortality Natality-Number of individuals added through reproduction Birth Rate(Humans born /1000) Mortality-Number of individuals removed via death Death Rate(Humans Died /1000)
Population Characteristics • Population - Group of individuals inhabiting the same area simultaneously. – Natality and Mortality Natality - Number of individuals added through reproduction. ¾ Birth Rate (Humans born / 1000) Mortality - Number of individuals removed via death. ¾ Death Rate (Humans Died / 1000)
Deaths per Costa Rica United States Hungary population 13 1100 1090 1088 1080 1070 1070 1052 1050 1040 1034 1030 1030 1024 1020H017 1018 1012 1010 Year 1000 997 Total population increase Total population increase Total population decrease 8.8% Births per thousand ulation +15 Effect of Birthrate and Death Rate on Population Size For a population to grow, the birthrate must exceed the death rate for a period of time. These three human populations illustrate how the combined effects of births and deaths would change population size if birthrates and death rates were maintained for a five-year period
Effect of Birthrate and Death Rate on Population Size Effect of Birthrate and Death Rate on Population Size For a population to grow, the birthrate must exceed the death rate for a period of time. These three human populations illustrate how the combined effects of births and deaths would change population size if birthrates and death rates were maintained for a five-year period
Types of Survivorship Curves 100 。 1000 10 (a) The Dall sheep is a 210,00 large mammal that 1000 produces relatively few 0123456785 young. Most of the young Age(years) survive. and more susceptible to predation (b) The curve shown for the white-crowned and disease 20 sparrow is typical of that Age (years) for many kinds of birds After a period of high (c) Many small animals mortality among the and plants produce enormous numbers of young the mortality rate is about equal fro all ages offspring. Mortality is very of adult birds high in the younger individuals and few dividuals reach old age
Types of Survivorship Curves Types of Survivorship Curves (a) The Dall sheep is a large mammal that produces relatively few young. Most of the young survive, and more susceptible to predation and disease. (b) The curve shown for the white-crowned crowned sparrow sparrow is typical of that for many kinds of birds. After a period of high mortality among the young the mortality rate is about equal fro all ages of adult birds. (c) Many small animals small animals and plants and plants produce enormous numbers of offspring. Mortality is very high in the younger individuals, and few individuals reach old age
Population Characteristics Sex Ratio- Age Distribution Sex Ratio- Relative number of males and females in a population Age Distribution-Number of individuals of each age in the population Greatly influences reproductive rate of a population
Population Characteristics • Sex Ratio - Age Distribution – Sex Ratio - Relative number of males and females in a population. – Age Distribution - Number of individuals of each age in the population. Greatly influences reproductive rate of a population
Rapid Growth Slow Growth Negative Growth (Kenya) (United States) Germany) Male Female Age Male Female Year of Birth Male Female Before 1915 915-1919 1920-1924 Postreproductive 1925-1929 1930-1934 50·54 1940-1944 45-49 1945-1949 40-44 1950-1954 35-39 1955-1959 Reproductive 1964-1969 1970-1974 Prereproductive 1985-1989 1990-1994 Percent of population Percent of population Percent of population in each of the three categories are good clues to the future growth of g viduals Age Distribution in Human Populations The relative numbers of ing population
Age Distribution in Human Populations Age Distribution in Human Populations The relative numbers of individuals in each of the three categories are good clues to the future growth of a population
Population Density and Spatial Distribution Population Density -Number of individuals per unit area Dispersal -Movement of individuals from densely populated locations to new areas Emigration -Out movement 今 mmigration- n Movement
Population Density and Spatial Distribution • Population Density - Number of individuals per unit area. – Dispersal - Movement of individuals from densely populated locations to new areas. Emigration - Out movement Immigration - In Movement
Population Growth Curve Biotic Potential -Inherent reproductive capacity Generally, biotic potential is much above replacement level Natural tendency for increase All living populations follow an exponential growth curve
Population Growth Curve • Biotic Potential - Inherent reproductive capacity. – Generally, biotic potential is much above replacement level. Natural tendency for increase. – All living populations follow an exponential growth curve
Geese Pi Biotic Potential The ability of a species to reproduce greatly exceeds the number necessary to replace those who die. Here are some examples of the prodigious reproductive abilities of some species
Biotic Potential Biotic Potential The ability of a species to reproduce greatly exceeds the number necessary to replace those who die. Here are some examples of the prodigious reproductive abilities of some species
Exponential Growth Curve Lag Phase-First portion of the curve-slow population growth EXponential Growth Phase -More organisms reproducing causing accelerated growth continues as long as birth rate exceeds death rate Stable Equilibrium Phase- Death rate and birth rate equilibrate -population stops growing
Exponential Growth Curve • Lag Phase - First portion of the curve - slow population growth. • Exponential Growth Phase - More organisms reproducing causing accelerated growth - continues as long as birth rate exceeds death rate. • Stable Equilibrium Phase - Death rate and birth rate equilibrate - population stops growing
