Chapter 53 Population Ecology. Population Dynamics… Changes that occur in: Population size...
-
Upload
toby-watts -
Category
Documents
-
view
214 -
download
1
Transcript of Chapter 53 Population Ecology. Population Dynamics… Changes that occur in: Population size...
Chapter 53 Population Ecology
Population Dynamics… Changes that occur in:
Population size Density Dispersion Age distribution
…due to environmental change or stress.
Population Size Limits to population growth: (births + immigration) – (deaths + emigration) Carrying capacity (k)-- # of individuals that an
environment can sustain indefinitely; determined by: Biotic potential (maximum capacity for pop. growth) Environmental resistance (all factors that limit growth)
G = r x N (growth over time) (rate of increase) (pop size)
Types of Growth Exponential growth
(J-shaped curve)
Logistic growth (S-shaped curve) – pop levels off around carrying capacity.
Types of Growth (cont) “Boom and Bust”
Population overshoots carrying capacity, then has dieback (death/emigration).
Reproductive Strategies r-selected species: “Opportunist”; insects and
rodents. Many, small young. Reproduce early and often. Little parental care; most
young die. High pop growth rate (r).
K-selected species: “Competitor”; large
mammals and birds. Few, larger young. Reproduce later and not as
often. Care of young; most
survive. Stable pop size near
carrying capacity (k).
Survivorship Curves Different reproductive
patterns lead to different age structures in the population.
Late loss (green): K-selected species.
Early loss (red): r-selected species.
Constant loss (black)
Human Population History
Factors affecting birth rates 1. Children needed to
work. 2. Living in urban
areas. 3. Cost of raising kids. 4. Opportunities for
women. 5. Infant mortality.
6. Ave age of marriage. 7. Pensions. 8. Legal abortions. 9. Birth control. 10. Religious beliefs.
Factors affecting death rates 1. Increased food supply. 2. Better nutrition. 3. Improved health care/technology. 4. Improved sanitation/hygiene. 5. Safer water supplies.
Age Structure Diagrams …shows the proportion of the population of each sex
at each age level. Looks at 3 age categories:
0 to 14 yrs (pre-reproductive) 15 to 44 yrs (reproductive) 45+ (post-reproductive) (number of women impacts fertility rates)
Can be used predict population growth and study economic impact.
Predicting Populations Rapid growth (Kenya) –
large numbers of younger people.
Slow growth (US) Zero or negative growth
(Sweden) – small numbers of young people.