1. Zebra mussel reduces diversity
~2 months
ecological & economic damage
reduces diversity
loss of food & nesting sites for animals
economic damage

2. Purple loosestrife 1968 1978 reduces diversity
loss of food & nesting sites for animals

3. Logistic rate of growth
Can populations continue to grow exponentially?
Of course not!
no natural controls
K = carrying capacity
Decrease rate of growth as N reaches K
effect of natural controls
What happens as N approaches K?

4. Number of breeding male
Carrying capacity
Time (years)
1915
1925
1935
1945 10 8 6 4 2
Number of breeding male
fur seals (thousands)
Maximum population size that environment can support with no degradation of habitat
varies with changes in resources
500
400
300
200
100 20 10 30 50 40 60
Time (days)
Number of cladocerans
(per 200 ml)
What’s going on with the plankton?

5. Changes in Carrying Capacity
Population cycles
predator – prey interactions
At what population level is the carrying capacity? K K

6. Human population growth
Population of… China: 1.3 billion
India: 1.1 billion
Human population growth
adding 82 million/year
~ 200,000 per day!
Doubling times
250m  500m = y ()
500m  1b = y ()
1b  2b = 80y (1850–1930)
2b  4b = 75y (1930–1975)
20056 billion
Significant advances
in medicine through
science and technology
What factors have contributed to this exponential growth pattern?
Industrial Revolution
The population doubled to 1 billion within the next two centuries, doubled again to 2 billion between 1850 and 1930, and doubled still again by 1975 to more than 4 billion. The global population now numbers over 6 billion people and is increasing by about 73 million each year. The population grows by approximately 201,000 people each day, the equivalent of adding a city the size of Amarillo, Texas, or Madison, Wisconsin. Every week the population increases by the size of San Antonio, Milwaukee, or Indianapolis. It takes only four years for world population growth to add the equivalent of another United States. Population ecologists predict a population of 7.3–8.4 billion people on Earth by the year 2025.
Is the human population reaching carrying capacity?
Bubonic plague "Black Death"
1650500 million

7. Distribution of population growth
uneven distribution of population:
90% of births are in developing countries 11 10
high fertility
uneven distribution of resources:
wealthiest 20% consumes ~90% of resources increasing gap between rich & poor 9 8
There are choices as to which future path the world takes…
medium fertility 7
low fertility 6
World total
World population in billions
What is K for humans?
10-15 billion?
the effect of income & education 5 4
Developing countries 3 2 1
Developed countries
1900
1950
2000
2050
Time

8. individual at standard of living of population
Ecological Footprint
30.2
15.6
6.4
3.7
3.2
2.6
USA
Germany
Brazil
Indonesia
Nigeria
India
Amount of land required to support an
individual at standard of living of population 2 4 6 8 12 10 14 16 18 20 22 24 26 28 30 32 34
Acres
over-population or over-consumption?
uneven distribution:
wealthiest 20% of world:
86% consumption of resources
53% of CO2 emissions
A more comprehensive approach to estimating the carrying capacity of Earth is to recognize that humans have multiple constraints: We need food, water, fuel, building materials, and other requisites, such as clothing and transportation. The ecological footprint concept summarizes the aggregate land and water area appropriated by each nation to produce all the resources it consumes and to absorb all the waste it generates. Six types of ecologically productive areas are distinguished in calculating the ecological footprint: arable land (land suitable for crops), pasture, forest, ocean, built–up land, and fossil energy land. (Fossil energy land is calculated on the basis of the land required for vegetation to absorb the CO2 produced by burning fossil fuels.) All measures are converted to land area as hectares (ha) per person (1 ha = 2.47 acres). Adding up all the ecologically productive land on the planet yields about 2 ha per person. Reserving some land for parks and conservation means reducing this allotment to 1.7 ha per person—the benchmark for comparing actual ecological footprints.
The graph is the ecological footprints for 13 countries and for the whole world as of We can draw two key conclusions from the graph. First, countries vary greatly in their individual footprint size and in their available ecological capacity (the actual resource base of each country). The United States has an ecological footprint of 8.4 ha per person but has only 6.2 ha per person of available ecological capacity. In other words, the U.S. population is already above carrying capacity. By contrast, New Zealand has a larger ecological footprint of 9.8 ha per person but an available capacity of 14.3 ha per person, so it is below its carrying capacity.
The second conclusion is that, in general, the world was already in ecological deficit when the study was conducted. The overall analysis suggests that the world is now at or slightly above its carrying capacity.

9. Ecological Footprint deficit surplus
A more comprehensive approach to estimating the carrying capacity of Earth is to recognize that humans have multiple constraints: We need food, water, fuel, building materials, and other requisites, such as clothing and transportation. The ecological footprint concept summarizes the aggregate land and water area appropriated by each nation to produce all the resources it consumes and to absorb all the waste it generates. Six types of ecologically productive areas are distinguished in calculating the ecological footprint: arable land (land suitable for crops), pasture, forest, ocean, built–up land, and fossil energy land. (Fossil energy land is calculated on the basis of the land required for vegetation to absorb the CO2 produced by burning fossil fuels.) All measures are converted to land area as hectares (ha) per person (1 ha = 2.47 acres). Adding up all the ecologically productive land on the planet yields about 2 ha per person. Reserving some land for parks and conservation means reducing this allotment to 1.7 ha per person—the benchmark for comparing actual ecological footprints.
The graph is the ecological footprints for 13 countries and for the whole world as of We can draw two key conclusions from the graph. First, countries vary greatly in their individual footprint size and in their available ecological capacity (the actual resource base of each country). The United States has an ecological footprint of 8.4 ha per person but has only 6.2 ha per person of available ecological capacity. In other words, the U.S. population is already above carrying capacity. By contrast, New Zealand has a larger ecological footprint of 9.8 ha per person but an available capacity of 14.3 ha per person, so it is below its carrying capacity.
The second conclusion is that, in general, the world was already in ecological deficit when the study was conducted. The overall analysis suggests that the world is now at or slightly above its carrying capacity.
Based on land & water area used to produce all resources each country consumes & to absorb all wastes it generates

10. Any Questions?

11. Measuring population density
How do we measure how many individuals in a population?
number of individuals in an area
mark & recapture methods
Difficult to count a moving target
sampling populations

12. Evolutionary adaptations
Coping with environmental variation
regulators
endotherms
homeostasis
(“warm-blooded”)
conformers
ectotherms
(“cold-blooded”)

13. Bright blue marble spinning in space
Ecology

14. Studying organisms in their environment
biosphere
ecosystem
community
population
organism