BIOL 121 Lecture Notes - Saccharomyces Cerevisiae, Survivorship Curve, Logistic Function

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6 Apr 2012
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30Ecol9-1
ECOLOGY 9: DEMOGRPAHY AND POPULATION GROWTH
Objectives:
By the end of this lecture you should be able to:
Compare different ways of representing demographic information.
Identify factors that affect population growth.
Explain population growth using mathematical models.
Compare the logistic model of population growth to real populations.
Text Readings: Chapter 52 continued.
DEMOGRAPHY
The study of the factors statistics that determine the size and structure of
populations
The number of individual’s in a population depends on
- Births
-Deaths
-Etc.
Description of a population
1) Life tables Table 52.1(In text)
2) Survivorship curve Fig. 52.2
Log of no. of survivors vs. age
Three General Types
1. High survivorship from birth (Number of individuals are born are likely to live to
an old age and eventually die)
2. Steady survivorship (Ex. Birds)
3. Very low survivorship initially (Huge numbers are born and many die but those
that do survive live have a high survivorship)
3) Reproductive rates
e.g., fecundity (female offspring/female)
Why is this important? Females are the ones that have offspring so females are
required to keep the population going. Therefore if there is a low number of
females, there is less likely chance that the population will continue to keep
growing
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30Ecol9-2
e.g., female fertility rate
Ex. As human females age, probability that child born with be still born increases
and fertility decreases = reproductive health of a population. Therefore if there is
many females but fertility rate is negative = not a healthy populations
4) Role of life history
All aspects such as when is maturity reached, when do the individuals begin to
reproduce.
Fig. 52.4
5) Age pyramid
- Often used in human populations
POPULATION GROWTH
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