华南农业大学：《农业生态学》课程教学课件（讲稿）Chapter 5 Population Regulation

Chapter 5 Population regulation

1 Chapter 5 Population Regulation

Contents Why and how does a population change in size? Exponential vs.Logistic growth >Density independent density dependent forces 2

2 Why and how does a population change in size? ¾ Exponential vs. Logistic growth ¾ Density independent / density dependent forces Contents

Some invasive plants in China Eive-fingered Morn oomoea cairica Castooav SiescestntE pes.(Mart

3 Five-fingered Morning Glory Ipomoea cairica (L.) Sweet Water Hyacinth Eichhornia crassipes (Mart.) Solms Castorbean Ricinus communis L. Mile-a-minute Weed Mikania micrantha H.B.K. Some invasive plants in China Water hyacinth (Eichhornia crassipes)

Patterns of Population Growth All populations have a particular pattern of growth Biotic potential-The highest possible per capita rate of increase for a population The factors that determine whether the biotic potential is high or low are: 1.The usual number of offspring per reproduction 2.The chances of survival until age of reproduction 3.How often each individual reproduces 4.The age at which reproduction begins 4

4 Patterns of Population Growth All populations have a particular pattern of growth Biotic potential – The highest possible per capita rate of increase for a population The factors that determine whether the biotic potential is high or low are: 1. The usual number of offspring per reproduction 2. The chances of survival until age of reproduction 3. How often each individual reproduces 4. The age at which reproduction begins

5.1 Exponential growth-the J-shaped curve(指数增长模型，J型增长)

5 5.1 Exponential growth – the J-shaped curve（指数增长模型， J型增长）

Exponential growth-the J-shaped curve (指数增长模型，J型增长) Exponential growth formula(公式) ·Nt=Noet where r is the exponential growth parameter (自然增长率) No is the starting population ·t is the time elapsed r is the maximum rate of increase of the population内禀增长率 r=0 if the population is constant, r>0 if population is increasing, 6 r<0 if the population is decreasing

6 Exponential growth formula（公式）： • N t =N 0 ert • where r is the exponential growth parameter (自然增长率 ) • N 0 is the starting population • t is the time elapsed • r is the maximum rate of increase of the population 内禀增长率 • r=0 if the population is constant, r>0 if population is increasing, r<0 if the population is decreasing. Exponential growth – the J-shaped curve （指数增长模型， J型增长）

The intrinsic rate of increase内禀增长率(rm Definition The rate at which a population increases in size if there are no density-dependent forces regulating the population is known as the intrinsic rate of increase. 种群在不受空间、食物的限制并排除了天敌、疾 病、他种生物危害以及温度、湿度等物理因素的不 利影响，具有最适密度和稳定年龄分布时表现出的 最大增殖速度。 I是物种固有的，由遗传特性所决定，是表明种群 谓袋潜力的一个固定参数 ◆I是在理想环境条件下获得的指标，把它和实际值 相比较，可以探讨环境因素对种群增长的影响。 7

7 Definition ：The rate at which a population increases in size if there are no density-dependent forces regulating the population is known as the intrinsic rate of increase. 种群在不受空间、食物的限制并排除了天敌、疾 病、他种生物危害以及温度、湿度等物理因素的不 利影响，具有最适密度和稳定年龄分布时表现出的 最大增殖速度。 ‹rm是物种固有的，由遗传特性所决定，是表明种群 增长潜力的一个固定参数 ‹rm是在理想环境条件下获得的指标，把它和实际值 相比较，可以探讨环境因素对种群增长的影响。 The intrinsic rate of increase 内禀增长率（rm)

The J-shaped curve has The LGraw-Hill Companies,Inc.Permission required tor reproduction two phases: Patterns of population growth Lag phase停滞阶段 growth is slow due to small population size exponential- growth Exponential growth phase指数增长期- -growth is 6 accelerating the population is exhibiting its biotic lag potential Time之

8 The J-shaped curve has two phases: • Lag phase停滞阶段 ––– growth is slow due to small population size • Exponential growth phase 指数增长期 – ––growth is accelerating & the population is exhibiting its biotic potential

Exponential growth-the J-shaped curve This is probably the best,simple,model of population growth.it predicts the rate of growth,or decay,of any population where the per capita rates of growth and death are constant over time. In exponential growth models,births deaths, emigration and immigration take place continuously This is a good approximation for the growth of most biological populations -i.e.,human populations grow exponentially when resources are plentiful 9

9 Exponential growth – the J-shaped curve • This is probably the best, simple, model of population growth .it predicts the rate of growth, or decay, of any population where the per capita rates of growth and death are constant over time. – In exponential growth models, births deaths, emigration and immigration take place continuously – This is a good approximation for the growth of most biological populations – i.e., human populations grow exponentially when resources are plentiful

Under what conditions would a population experience this exponential growth? 10

10 Under what conditions would a population experience this exponential growth?