population ecology
DESCRIPTION
Population Ecology. Chapter 52. Population - group of individuals living in same area at same time. Population density - # of individuals per unit area. Population dispersion - arrangement of population in area. Dispersion patterns happen 3 ways. 1 Clumped dispersion - individuals in groups. - PowerPoint PPT PresentationTRANSCRIPT
Population Ecology
Chapter 52
• Population - group of individuals living in same area at same time.
• Population density - # of individuals per unit area.
• Population dispersion - arrangement of population in area.
• Dispersion patterns happen 3 ways.• 1Clumped dispersion - individuals in
groups.• 2Uniform dispersion – individuals
evenly spaced out.• 3Random dispersion - individuals
live regardless of where other individuals live.
CLUMPED
UNIFORM
RANDOM
• Demography - study of statistics of a population.
• Life tables - show summary of specific ages of population and survival rates.
• Survivorship curve - can see how many individuals are alive at specific ages.
• Reproductive tables - reproductive rates at various ages.
• Focus only on females and not males in these tables.
• Life history - traits that affect organism’s schedule of reproduction and survival.
• 1Big-bang reproduction (produce large number of offspring sometimes followed by the organism’s death)
• Known as semelparity.
The agave plant
• 2Repeated reproductive episode - organism produces smaller numbers of offspring.
• This is also known as iteroparity.
• Change in population - # of births minus # of deaths during that same time.
• Equation : N/t = r; r= difference between birth and death rates, N= change in population size, and t= change in time.
• Limitations on population growth due to resources.
• K = carrying capacity.• Carrying capacity – max # of
individuals an area can handle based on resources.
• Logistic population growth model - incorporates affect of population density on rate of increase.
• Carrying capacity cannot be exceeded - graph is S-shaped.
Carrying capacity equals change in population size
Cannot exceed carrying capacity
Carrying capacity
• Life histories - predict how population will reproduce.
• 1K-selection - live and reproduce around K.
• 2r-selection - high rates of reproduction, but live in environments where populations are well below K.
• 2 factors determine the growth of a population.
• 1Density-dependent factors increase their effect as density increases (negative feedback)
• 2Density-independent factors - not affected by density increase.
• Negative feedback - caused by several different factors.
• One - resources (force populations to stop reproducing if conditions are crowded)
As # of planted seeds increase,# reproducing decreases
• Competition for resources can force decreased reproduction rates.
• Need to defend space can reduce population size.
• Predation can decrease the size.
• Human population has been steadily growing since 1650.
• Zero transition growth # of births = # of deaths.
• Only way to steady out population growth.
• One of the difficulties with population growth is looking at the distribution of ages.
• The problem is that the carrying capacity of Earth has not been determined.
• http://www.youtube.com/watch?v=GECJcW2Ifm4