1. Population Ecology

2. Population Dynamics Population:
All the individuals of a species that live together in an area
Demography:
The statistical study of populations, allows predictions to be made about how a population will change
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

3. Population Dynamics Three Key Features of Populations Size Density
Dispersion
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

4. Three Key Features of Populations
Size: number of individuals in an area
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

5. Three Key Features of Populations
Growth Rate:
Birth Rate (natality) - Death Rate (mortality)
How many individuals are born vs. how many die
Birth rate (b) − death rate (d) = rate of natural increase (r)
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

7. Three Key Features of Populations
Density: measurement of population per unit area or unit volume
Pop. Density = # of individuals ÷ unit of space
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

8. How Do You Affect Density?
Immigration: movement of individuals into a population
Emigration: movement of individuals out of a population
Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites)
Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)

9. Factors That Affect Future Population Growth
Immigration + + -
Population
Mortality
Natality -
Emigration

10. Population Dispersion

11. Three Key Features of Populations
Dispersion: describes the spacing of organisms relative to each other
Clumped
Uniform
Random
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

12. How Are Populations Measured?
Population density = number of individuals in a given area or volume
Count all the individuals in a population
Estimate by sampling
Mark-Recapture Method

13. How Do Populations Grow?
Idealized models describe two kinds of population growth:
Exponential Growth
2. Logistic Growth

14. Logistic Growth Curve

15. Carrying Capacity Carrying Capacity (k):
The maximum population size that can be supported by the available resources
There can only be as many organisms as the environmental resources can support
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

16. The logistic population growth model and life histories.
This model predicts different growth rates for different populations, relative to carrying capacity.
Resource availability depends on the situation.
The life history traits that natural selection favors may vary with population density and environmental conditions.
In K-selection, organisms live and reproduce around K, and are sensitive to population density.
In r-selection, organisms exhibit high rates of reproduction and occur in variable environments in which population densities fluctuate well below K.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

17. K-Selected Species Poor colonizers Slow maturity Long-lived
Low fecundity
High investment in care for the young
Specialist
Good competitors

18. Exponential Growth Curve
Figure 35.3A

19. r-Selected Species Good colonizers Reach sexual maturity rapidly
Short-lived
High fecundity
Low investment in care for the young
Generalists
Poor competitors

20. Reproductive Strategies
K Strategists
Long life span
Large body size
Reproduce slowly
Have few young
Provides parental care
Ex: humans, elephants

21. Reproductive Strategies
R Strategists
Short life span
Small body size
Reproduce quickly
Have many young
Little parental care
Ex: cockroaches, weeds, bacteria

23. Introduction Why do all populations eventually stop growing?
What environmental factors stop a population from growing?
The first step to answering these questions is to examine the effects of increased population density.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

24. Factors Limiting Growth Rate
Declining birth rate or increasing death rate are caused by several factors including:
Limited food supply
The buildup of toxic wastes
Increased disease
Predation

25. Density-Dependent Factors
limiting resources (e.g., food & shelter)
production of toxic wastes
infectious diseases
predation
stress
emigration

26. Density-Independent Factors
severe storms and flooding
sudden unpredictable severe cold spells
earthquakes and volcanoes
catastrophic meteorite impacts

27. Density-dependent factors
increase their affect on a population as population density increases.
This is a type of negative feedback.
Density-independent factors are unrelated to population density, and there is no feedback to slow population growth.
Fig
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

28. Negative feedback prevents unlimited population growth
A variety of factors can cause negative feedback.
Resource limitation in crowded populations can stop population growth by reducing reproduction.

29. Population dynamics reflect a complex interaction of biotic and abiotic influences
Carrying capacity can vary.
Year-to-year data can be helpful in analyzing population growth.

30. Some populations fluctuate erratically, based on many factors.
Fig
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

31. Other populations have regular boom-and-bust cycles.
There are populations that fluctuate greatly.
A good example involves the lynx and snowshoe hare that cycle on a ten year basis.

32. “Booms” and “Busts”

33. Introduction Humans are not exempt from natural processes.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

34. The human population has been growing almost exponentially for three centuries but cannot do so indefinitely
The human population increased relatively slowly until about 1650 when the Plague took an untold number of lives.
Ever since, human population numbers have doubled twice
How might this population increase stop?

35. POPULATION CYCLES HUMAN POPULATION 1650 - 500,000,000
ONE BILLION
TWO BILLION
FOUR BILLION
2010 – SIX BILLION
EIGHT BILLION

36. Human Population Growth
J curve growth
Grows at a rate of about 80 million yearly
r =1.3%
Why doesn’t environmental resistance take effect?
Altering their environment
Technological advances
The cultural revolution
The agricultural revolution
The industrial-medical revolution

37. Fig
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

38. Human Growth Rate

39. The Demographic Transition.
A regional human population can exist in one of 2 configurations.
Zero population growth = high birth rates – high death rates.
Zero population growth = low birth rates – low death rates.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

40. Age structure is the relative number of individuals of each age.
Age structure diagrams can reveal a population’s growth trends, and can point to future social conditions.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

42. Age Distribution
Distribution of males and females in each age group of a population
Used to predict future population growth