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Lecture 24

01:119:115 Lecture Notes - Lecture 24: Semelparity And Iteroparity, Exponential Growth, Paramecium

3 pages92 viewsFall 2013

Biological Science
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Concept 53.1: Dynamic biological processes influence population density,
dispersion, and demographics
Population ecology is the study of a population in relation to its environment,
including: density (number of individuals per unit area or volume) dispersion, age
structure, and population size
- Population density is the result of an interplay between processes that add
individuals to a population (birth, immigration) and those that remove
individuals (death, emigration)
Patterns of Dispersion
Environmental and social factors influence the spacing of individuals in a population
- Fig 53.4a clumped dispersion: individuals aggregate in patches
o a clumped dispersion may be influenced by resource availability
- A uniform dispersion is one in which individuals are evenly distributed (Fig
o It may be influenced by social interaction such as territoriality, e.g. the
defense of a bounded space against other individuals during nesting
(sometimes aggressive)
- In a random dispersion, the position of each individual is independent of
other individuals
o it occurs in the absence of strong attractions…
Demography: study of vital statistics of a population and how they change over
time, especially birth and death
- Utilizes a life table; an age-specific summary of the survival pattern of a
- Made by following of cohort of individuals of same age
o TBL 53.1 life table of Belding’s ground squirrels:
Provides data on proportions of males and females alive at
each age
while death rate is fairly constant, females…
A survivorship curve is a way of representing the same data in a life table
- Survivorship curves can be classified into three general types ( Fig 53.6)
o Type 1: low death rates during early and middle life and an increase in
death rates among older age groups (ex. humans!)
o Type 2: a constant death rate over the organism’s life span (ex.
o Type 3: high death rates for the young, those that survive have a lower
death rate (ex. oysters)
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