1. How populations grow Ch 15 B3.5

2. What is a population Population – consists of all the individuals of a species that live together in one place at one time. Population – consists of all the individuals of a species that live together in one place at one time. Demography – the statistical study of all populations. Demography – the statistical study of all populations. Demographer - Study the composition of a population and try to predict how the size of the population will change. Demographer - Study the composition of a population and try to predict how the size of the population will change.

3. Three features of a population 1. Population size – the number of individuals in a population Can affect the population’s ability to survive. Can affect the population’s ability to survive. Natural disturbances (fires and flood) are more of a danger to a small population than a large population. Natural disturbances (fires and flood) are more of a danger to a small population than a large population. Small populations tend have more inbreeding Small populations tend have more inbreeding Example … Example …

4. Cheetah (Acinonyx jubatus) Very small population Very small population Genetically identical Genetically identical A disaster (new disease) could cause their extinction A disaster (new disease) could cause their extinction

5. Three features of a population 2. Population density – is the number of individuals that live in a given area. Spread out population (dispersed widely) won’t interact and breed. Spread out population (dispersed widely) won’t interact and breed. 3. Dispersion – is the way the individuals of the population are arranged in space. Spacing of populations affect how they interact with each other and the environment. Spacing of populations affect how they interact with each other and the environment.

7. Modeling population growth Population model – is the hypothetical population that attempts to exhibit the key characteristic of a real population. Population model – is the hypothetical population that attempts to exhibit the key characteristic of a real population. Growth rate – simple model describes the rate of population growth as the difference between the birthrate and the death rate. Growth rate – simple model describes the rate of population growth as the difference between the birthrate and the death rate.

8. Growth rate and population size Exponential growth curve – is a curve in which the rate of a population stays the same, as a result the population size increasing steadily. Exponential growth curve – is a curve in which the rate of a population stays the same, as a result the population size increasing steadily. Carrying capacity – the population size that an environment can sustain. Carrying capacity – the population size that an environment can sustain.

13. Resources and population size Density dependent resources – resources that are depleted at a rate that depends on the population density of the population that use them. Density dependent resources – resources that are depleted at a rate that depends on the population density of the population that use them. Limited resources, food and water Limited resources, food and water Logistic model – is a population model in which exponential growth is limited by a density dependent factor. Logistic model – is a population model in which exponential growth is limited by a density dependent factor. Excellent estimate of population growth in nature. Excellent estimate of population growth in nature. Competition for food, shelter, mates and limited resources tends to increase as a population approaches it carrying capacity. Competition for food, shelter, mates and limited resources tends to increase as a population approaches it carrying capacity.

14. Logistic model

15. Growth patterns in real populations Density independent factors – growth of an organism that is limited by environmental conditions. Density independent factors – growth of an organism that is limited by environmental conditions. Weather and climate Weather and climate Example, mosquito populations increase in the summer when it is warn and decrease in the winter. Example, mosquito populations increase in the summer when it is warn and decrease in the winter. R-strategies – grow exponentially when environmental conditions allow them to reproduce. R-strategies – grow exponentially when environmental conditions allow them to reproduce.

16. R-strategies R-strategies Short life span Short life span Reproduce and mature early and have many offspring with little or no parental care. Reproduce and mature early and have many offspring with little or no parental care. Example cockroaches (American cockroach, Periplaneta americana, ) Example cockroaches (American cockroach, Periplaneta americana, )American cockroachAmerican cockroach

17. K-strategies – organisms that grow slowly with long life span, fewer offspring, slow maturing process and reproduction late in life. K-strategies – organisms that grow slowly with long life span, fewer offspring, slow maturing process and reproduction late in life. Example Fin Whale (Balaenoptera physalus) Example Fin Whale (Balaenoptera physalus)