Population Ecology Chapter 44
Stages of Biology O Ecology is the interactions of organisms with other organisms and with their environments O These interactions occur in different hierarchies O The simplest level is the atom. O atom molecule organelle cells* tissues organs organ systems organisms O *Cells are the simplest hierarchy that is recognized as living
Stages of Biology O Organism: any individual living being O Population: group of organisms sharing the same area and gene pool O Community: group of interacting populations. O Ecosystem: group of communities as well as abiotic (non-living) factors O Biome: area of the planet that shares similar ecosystems O Biosphere: Region of planet Earth where life is found
Populations O Nearly all biologists are somehow concerned with populations O Environmentalist: are there enough resources to support the population? O Virologist: how long before a disease can spread throughout a population? O Naturalist: Is the population of prey enough to support a population of endangered predators? O Zoologist: Which animals are spreading into human territory, or humans into which animal s territory?
Populations O Populations are governed by mathematical principles O Density: The number of individuals per unit of area O Distribution: The pattern of dispersal O Limiting Factor: Environmental factors that are necessary for a population s survival O Carrying Capacity: The maximum number of individuals the environment can support
Population Growth models O Most organisms follow one of two population models O Discrete breeding: organisms reproduce only once in their lives O Insects, annual plants O Continuous breeding: multiple reproductive events in a lifetime O Vertebrates, trees and bushes O Knowing how a population reproduces is important because all population growth is calculated by the frequency of births minus frequency of deaths
Population growth model O Populations, when graphed, show similar tendencies no matter the species. O These tendencies can be monitored mathematically to look for patterns O These patterns can then be monitored in real-time to predict trends in current populations
Carrying Capacity
Regulation of Population Size O Density-Independent Factors O Abiotic factors, such as weather, presence of light, ph, natural disasters. O Density-Dependent Factors O Biotic factors, such as presence of predators, disease, or other same-specie competitors. O Any of these factors can be the limiting factor of a population.
Life History O There are seemingly two ways of increasing a population. Organisms follow each method to some degree O R-selection (High rates of birth): Organisms have a short lifespan, so they reproduce early and in great numbers. Almost no parental care occurs. O The larger the litter, the higher the number of survivors O K-selection (Maintain carrying capacity): Organisms live long lives and are subject to environmental fluctuations. Lots of parental care for offspring means even though fewer offspring are born, they have a better chance of survival
Human Population Growth O One method of measuring population growth is calculating doubling time the time for a population to double. O Currently, for humans, that time worldwide is only 53 years. O In 53 years, to maintain the same population growth, we would need to double the food, habitats, jobs, and all other resources as well. O Can it be done?
Human population growth O HPG is an ethically tricky subject. Reasons for reproduction differ between moredeveloped countries (MDC) and lessdeveloped countries (LDC) O MDC s, such as America, Europe, Japan, have lower population growths and high standards of living O LDC s, such as South America, Africa, and East Asia, have high population growths and low standards of living
Human Population Growth O Because the majority of growth on our planet occurs in LDC s, the majority of changes toward growth must occur here as well. O There are ethical issues, though, to a country of wealth telling a country of poverty that they need to change their way for the greater good. O Average numbers of children in LDC s are 5-7, and this is unlikely to change due to social and economical necessity.