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30 Cards in this Set
- Front
- Back
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A population
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- smallest unit of life that can evolve
- a group of individuals of one species that live in a particular area |
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Density
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number per unit area
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Spacing
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uniform or clumped or random
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In a clumped dispersion
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- individuals aggregate in patches
- may be influenced by resource availability and behaviour |
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A uniform dispersion is one in which
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- individuals are evenly distributed
- may be influenced by social interaction such as territoriality |
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In a random dispersion
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- the position of each individual is independent of other individuals
- it occurs in the absence of strong attractions or repulsions |
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Demography
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- the study of the vital statistics of a population and how they change over time
- death rates and birth rates are the particular interest to demographers |
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Factors involving demography
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- birth rates
- death rates - growth rates - generation time - age structure |
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Birth rate
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the number of offspring produced during a certain period of time
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Death rate
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the number of the population that die during a certain period of time
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Growth rate
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the difference between birth and death rate
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Generation time
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The average time between the birth of individuals and the birth of their offspring
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Life tables
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- an age specific summary of the survival patter of a population
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Survivorship Curve
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- a graphic way of representing the data in a life table
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Three general types of survivorship curve
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- Type 1: low death rates during early and middle life, increases among older age groups
- Type 2: death rate is constant over the lifespan - Type 3: high death rates for the young, slower death rates for the survivors |
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Reproductive rates
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- often concentrate on the females in a population
- age specific - describes reproductive patterns of a population |
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A small population has the potential to
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Grow
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The extent and speed of growth depends on 2 major factors
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- The actual size of the population
- The biotic potential (the capacity of a population to increase); Rmax |
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Rmax
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The intrinsic rate of natural increase
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Rmax may only be apparent or measurable in
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uncrowded conditions
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After a natural disaster, the population with the highest R value will recover the...
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- Quickest
- R-selected species |
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R-selected species
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Grow exponentially
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If Immigration and emigration are ignored, a population's growth rate (per capita increase)
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equals birth rate minus death rate
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Zero population growth occurs when
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Birth rate = death rate
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Exponential population growth is
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- population increase under idealized conditions
- under these conditions, the rate of reproduction is at its maximum, called the intrisic rate of increase (Rmax) - represented by a J shaped curve on a graph |
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Rselected species
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- shows exponential rate of growth
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Biotic Potential
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- Number of offspring produced in a breeding season
- survival through reproductive stages - age at which reproduction begins - length of reproductive stage |
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Exponential population growth is not bological reality as it is not
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sustainable
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Density dependent and independent factors play a role in
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controlling population growth
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Another, truer type of population growth is called
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logistical or equilibrial growth
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