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Lecture

Ecology 9.docx

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Department
Biology
Course
BIOL 121
Professor
Carol Pollock
Semester
Winter

Description
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 growingAGE STRUCTURE IN B.C. 2001, 2009 75+ 65-74 55-64 45-54 35-44 25-34 15-24 5-14 1-4 of pop. 18 16 14 12 10 8 6 4 0 2 4 6 8 10 12 14 16 18 Females Males. Blue 2009, black 2001 AGE STRUCTURE IN B.C. 2001, 2009 75+ 65-74 55-64 45-54 35-44 25-34 15-24 5-14 1-4 of pop. 18 16 14 12 10 8 6 4 0 2 4 6 8 10 12 14 16 18 Females Males. Blue 2009, black 2001 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 30Ecol9-3 Exponential population growth – growth is independent of density The population is going to keep on growing Very rare 65 60 55 50 45 Pop. size 40 35 30 25 20 15 10 5 0 1 2 3 4 5 6 No. of generations of Saccharomyces cer
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