population ecology - staff portal camas school...
TRANSCRIPT
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 atommoleculeorganellecells*tissues
organsorgan systemsorganisms
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 more-developed countries (MDC) and less-developed 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.