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Population Growth Chapter 5 Population Remember a population is a group of a particular species living in a defined area Populations grow and they decline Important Characteristics of a Population Its geographic distribution – How far it is spread out Density – The number of individuals per unit area Growth rate – How fast it is growing or declining Factors That Affect a Population Size The number of births The number of deaths The number of individuals leaving or entering the population – Immigration- movement INTO an area – Emigration- movement out of an area Exponential Growth If a population has abundant resources and has no predators or diseases the population will multiply and the population will increase This can lead to Exponential Growthwhich occurs when individuals reproduce at a constant rate If conditions are ideal growth will happen exponentially Exponential Growth Logistic Growth When resources are unlimited it grows exponentially, however, resources are limited so growth will slow down after a certain point Logistic Growth- occurs when a population’s growth slows or stops Figure 5-4 Logistic Growth of Yeast Population Section 5-1 Logistic Growth Carrying capacity Time (hours) Carrying Capacity Carrying Capacity- largest number of individuals that an environment can support The growth rate at this point is zero Concept Map Section 5-1 Population Growth Population Growth can be Logistic growth Exponential growth characterized by No limits on growth Unlimited resources represented by Constant growth rate J-shaped curve characterized by Limits on growth which cause a Falling growth rate represented by S-shaped curve Limiting Factors A factor that causes population growth to decrease Can be …. – Density- Dependent – Density- Independent Density Dependent Competition – When it becomes crowded they compete for resources Predation – When a predator population increases, prey populations will decrease, and then the predators will decrease and the prey will increase Parasitism & Disease Density Independent Does not depend on the size of the population at all Unusual weather, natural disasters, human activities, etc Any Questions? “Information democracy.” is the currency of --Ralph Nader is an old saying that the course of civilization is a race between catastrophe and education. In a democracy such as ours, we must make sure that education wins the race.” --JFK “There
