1. Population Ecology Chapter 55

2. Environmental Challenge
Ecology: the study of how organisms interact with one another and their environments.
Populations: groups of individuals of the same species in one place

3. Populations Range: area throughout which a population occurs
Most species have limited geographic range
Devil’s hole pupfish lives in a single spring in southern Nevada

4. Range expansion of the cattle egret
Populations
Humans alter the environment and some species have altered their range in reponse.
Range expansion of the cattle egret

5. Populations
Dispersion: how individuals in a population are spread out within their range
Random: individuals do not interact strongly with one another.
Uniform: behavioral interactions, resource competition
Clumped: uneven distribution of resources.

7. Biotic Potential The rate of growth for a population if every individual survived and reproduced.
Under such ideal conditions, a population would have exponential growth

8. Exponential growth = J-curve

9. Growth levels off as population approaches carrying capacity
b = d
Growth levels off as population approaches carrying capacity
Exponential growth
initially
Population
Logistic Growth
S-Curve
Lag phase

10. Many populations exhibit logistic growth
Growth and Limits
Many populations exhibit logistic growth

11. Carrying capacity (K): the maximum number of individuals in a species that an environment can support
Determined by the amount of resources available (food, water, nutrients, etc)
Results in logistic growth
Hunting brings pop to Winter K

12. Demography and Dynamics
Demography: the quantitative study of populations
How size changes through time

13. Population Changes
Calculating growth rates: (Births + I) - (Deaths + E) Immigrants (I) - Individuals moving into a population
Emigrants (E) - Individuals moving out of a population (exiting)

14. Limiting Factors: situations that prevent a population from increasing
Density-Independent Factors --do not depend on the number of individuals in the population.
--Usually abiotic factors such as pollution, weather events and natural disasters

15. Density-Dependent Factors -become limiting only when population reaches a certain size -strongest when population is large and dense -usually biotic factors such as food, predators, disease, and competition

16. Sawtooth Curve: Shows periodic fluctuations (rise and fall) of populations. --Can show density-dependant factors at work (predator-prey) --Can show density-independent factors at work (seasonal changes)

17. -showing seasonal population fluctuations
Sawtooth Graph
-showing seasonal population fluctuations
summer
winter

18. Fluctuations in the number of pupae of four moth species in Germany

19. North American snowshoe hare 10 year cycle
Two factors generate this cycle:
Food plants
Predators

20. Reproductive patterns
r-strategist:
produce many offspring in a short period of time (mice, flies)
take advantage of a temporarily abundant resource
k-strategist:
produce a few offspring that have a better chance of surviving with intense parental care (humans, elephants)
Limited resources, pop near carrying capacity

22. Human Population Growth
K-selected life history traits
Small brood size
Late reproduction
High degree of parental care
Human populations have grown exponentially
Last 300 years birth rate has remained same
Death rate has fallen dramatically

23. Human population growth:. Year. Estimated population. (in millions)
Human population growth: Year Estimated population (in millions) 0 A.D ,000 (1 billion) , ,000 (4 billion) /3/10 6,817,237, U.S. 309,191,081

24. A. The graph of human population is a J curve
A.The graph of human population is a J curve. It shows exponential growth
Agriculture
begins
Plowing
and
irrigation
Bubonic
plague
Industrial
Revolution

25. Number of years to add each billion (year)
All of Human History
(1800)
123 (1930)
33 (1960)
15 (1975)
12 (1987)
12 (1999)
13 (2012)
16 (2028)
26 (2054)
Sources: First and second billion: Population Reference Bureau. Third through ninth billion: United Nations, World Population in 2300 (medium scenario), 2003.

26. What has allowed human populations to grow exponentially. 1. )medicine
What has allowed human populations to grow exponentially? 1.)medicine 2.)plenty of food(agriculture) 3.) sanitation * medical advances allow people to live longer and decreases infant mortality (Child death)

27. What is Earths’ carrying capacity?
Unknown
J curve will continue until some resource becomes limiting
Some countries have exceeded their carrying capacities: China, Ethiopia, Somalia, India

28. Sex and age distributions show that less developed countries have significantly younger populations than more developed countries.
Roughly one-third of the population in less developed countries is under age 15. In many sub-Saharan African countries, this proportion rises to nearly one-half of the population. In contrast, less than one-fifth of the population in more developed countries is under 15.
Today there are more than 2 billion young people below age 20 in less developed regions—the age cohort that will soon become the world’s newest group of parents.
Young age structures in the less developed countries are due mainly to higher levels of childbearing in recent decades.

30. World Population Clock
Natural Increase per
World
More Developed Countries
Less Developed Countries
Less Developed Countries (less China)
Year
80,224,198
912,053
79,312,145
71,498,784
Day
219,792
2,499
217,294
195,887
Minute
153 2
151
136
Source: Population Reference Bureau, 2004 World Population Data Sheet.

31. Human Population Growth
Distribution of population growth

32. Human Population Growth
Consumption in the developed world further depletes resources
Wealthiest 20% of the world’s population accounts for 86% consumption of resources and produces 53% of CO2 emissions
Poorest countries: 20% is responsible for 1.3% consumption and 3% CO2 emissions

33. Human Population Growth
Ecological Footprint: amount of productive land required to support an individual at the standard of living of a particular population through the course of his/her life