Intraspecific population growth CHARPTER 11 Can a population continue to grow indefinitely in the real world?

Intraspecific population growth CHARPTER 11 Intraspecific Population Growth

Intraspecific population growth CHARPTER 11 What do we have to know in the chapter? 1. How to regulate? 2. What properties is influenced when regulations happen?

Intraspecific population growth CHARPTER 11 Outline 11.1The Environment Functions to Limit Population Growth 11.2Population Regulation Involves Density Dependence 11.3Competition Results When Resources Are Limited 11.4Intraspecific Competition Affects Growth and Development 11.5Intraspecific Competition Can Influence Mortality Rates 11.6Intraspecific Competition Can Reduce Reproduction 11.7High Density Is Stressful to Individuals 11.8Dispersal Can Be Density-Dependant 11.9Social Behavior May Function to Limit Populations 11.10Territoriality Can Function to Regulate Population Growth 11.11Plants Preempt Space and Resources 11.12Density-Independent Factors Can Influence Population Growth

Intraspecific population growth CHARPTER 11 Limited resources will result in increased mortality, decreased fecundity, birth, death or all. environment 11.1 The Environment Functions to Limit Population Growth

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth The population growth in real world

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth 1/k 1 r Carrying Capacity Logistic Model of Population The K suggests the per capita effect on the rate of population growth is 1/K inhibition. For example: K=100 The value of K varies when the environment (resources) is changed.

Intraspecific population growth CHARPTER 11

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth The significant of the term (1-N/K) (1) The term (1-N/K) represents unoccupied space. (2) When the population is close to 0, (1-N/K) is close to 1, that is to say the space is free, and population growth follows the exponential model rN. (3) As N approaches K, (1-N/K) is close to 0, the space is completely occupied, population growth is zero. (4) When population exceed K, population growth becomes negative and population declines back toward carrying capacity K. (5) The space becomes smaller and smaller as the size becomes bigger and bigger, the inhibition effect becomes stronger continuously, which is termed environmental inhibition.

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth Five stages (1)The begin stage: initially (low value of N) the population grows exponentially (2)Accelerating stage: the rate of population growth increases because of the bigger size. (3)Inflection point: the rate of population growth reaches a maximum value at a population size of K/2. (4)Decreasing stage: the rate of population growth decreases. (5)Saturate stage: the rate of population growth reaches zero as the N = K.

Intraspecific population growth CHARPTER 11

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth This is in contrast to the exponential model.

Intraspecific population growth CHARPTER 11 Human Population Growth 11.1 The Environment Functions to Limit Population Growth Krebs, 2001 (Figure 28.1) A.D.

Intraspecific population growth CHARPTER 11 Doubling times 11.1 The Environment Functions to Limit Population Growth

Intraspecific population growth CHARPTER 11 In 1924, Pearl and Reed fit U.S. population data for using the logistic equation. Joel E. Cohen, How Many People Can the Earth Support? Norton The Environment Functions to Limit Population Growth

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth In 1990, the population of the U.S. was 250 million Joel E. Cohen, How Many People Can the Earth Support? Norton 1995 year

Intraspecific population growth CHARPTER 11 Estimates of Earth’s Carrying Capacity Krebs, 2001 (Figure 28.5)

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth Ecological Footprint Krebs, 2001 (Figure 28.6)

Intraspecific population growth CHARPTER The Environment Functions to Limit Population Growth Adapted from: WWF, UNEP World Conservation Monitoring Centre, et al Living Planet Report Gland, Switzerland: WWF. Ecological footprint by region, 1996

Intraspecific population growth CHARPTER Density Dependence Regulation K suggests a negative feedback between population increase and resources available in the environment. As population density increases, the per capita availability of resources declines. The decline in per capita resources eventually reaches some crucial level at which it functions to regulate population. Implicit on this model of population regulation is density dependence.

Intraspecific population growth CHARPTER 11 Fig 11.4 Regulation of population size in three situations 11.2 Density Dependence Regulation b is independent of population density d is independent of population density full density- dependent regulation

Intraspecific population growth CHARPTER Density Dependence Regulation Density-dependent mechanisms have also been identified that reduce rates of birth and survival at low population densities. Allee effect

Intraspecific population growth CHARPTER Density Dependence Regulation Fig 11.5 Allee effect resultes in a inverse density dependence.

Intraspecific population growth CHARPTER Competition Results When Resources Are Limited competition Scramble competition Depressing equally across individuals in a population as the intensity of competition increases. contest competition Some individuals claim enough resources while denying others a share. When N(t)>K, what happens ? Local extinction Some survive and sustain the population According to interaction or not, compertition is termed exploitation or interference.

Intraspecific population growth CHARPTER Competition Affects Growth,Development and mortality rates What properties can be affected when competition occurs because of limited resource? Fig 11.7 effects of intraspecific competition on growth and photosynthesis of Atriplex prostrata

Intraspecific population growth CHARPTER Competition Affects Growth,Development and mortality rates and reproduction Fig 11.9 mean (growth rate, activity and relative body length) of larval wood frogs when density increases. Fig changes in the number of surviving individuals and average plant through time for an experimental population of horseweed.

Intraspecific population growth CHARPTER 11 Self thinning The progressive decline in density and increase in biomass (growth) of remaining individuals caused by the combined effects of density-dependent mortality and growth within a population Competition Affects Growth, Development and mortality rates and reproduction Yoda –3/2 law

Intraspecific population growth CHARPTER Competition Affects Growth, Development and mortality rates and reproduction Fig patterns of mortality and growth of juvenile steelhead trout in stream channels over an 8-week experimental period.

Intraspecific population growth CHARPTER Competition Affects Growth, Development and mortality rates and reproduction reproduction Density-dependent growth is a potentially powerful mechanism of population regulation, because fecundity is typically related to body size.

Intraspecific population growth CHARPTER 11 So high density is stressful to individual, and has the influence on many properties of a population. How to regulate by itself to a population?

Intraspecific population growth CHARPTER Dispersal Can Be Density Dependent Dispersal occurs in response to the overexploitation of resources, or crowding. And, is the reverse true? Does dispersal actually regulate a population? How to identify? And give some examples!

Intraspecific population growth CHARPTER Territoriality Can Function to Regulate Population Growth Home range: The area that an animal normally uses during a year. Territoriality: The animal defends any part of its home range.

Intraspecific population growth CHARPTER Territoriality Can Function to Regulate Population Growth The size of a home range is influenced by body size. Fig Relationship between the size of home range and body weight of North American mammals

Intraspecific population growth CHARPTER Territoriality Can Function to Regulate Population Growth How to defend a territory?

Intraspecific population growth CHARPTER 11 Plant can not move, and how do they hold on to space? Plant Preempt Space and Resource Fig the “territoriality” of Plant

Intraspecific population growth CHARPTER 11 All of the above are density-independent regulation. What are density-independent factors? And how about their influence on grow growth? Density-Independent Factors Can Influence Population Growth

Intraspecific population growth CHARPTER Density-Independent Factors Can Influence Population Growth Density-Independent Factors Natural disaster, sharp fluctuation of environmental factors. Can they regulate the population growth?

Intraspecific population growth CHARPTER 11 summary Limited resources Exponential growth Logistic growth How to reguate? When N>K Properties are infulenced Dispersal, social behavior, terrioriality

Intraspecific population growth CHARPTER 11 Study Questions How to use the logistic model to control the population number and get the maximal population grow rate in practice? Further Reading Thomas M. Smith and Robert Leo Smith. Elements of Ecology. pp:

Intraspecific population growth CHARPTER 11 Next class metapopulation and interspecific competition interspecific predation