1. Inquiry into Life Twelfth Edition
Lecture PowerPoint to accompany
Inquiry into Life Twelfth Edition
Sylvia S. Mader
Chapter 33
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 33.1 The Scope of Ecology
Modern ecology focuses on developing testable hypotheses.
One goal of ecology is to develop models that explain and predict the abundance of populations.

4. Levels of Ecological Organization

5. 33.2 Patterns of Population Growth
Growth Rate = Per capita rate of increase
Example: A population has 1000 members
Birth rate = 30 / year
Death rate = 10 /year
The growth rate per year will be:
/ 1000 = 0.02 = 2.0% per year

6. 33.2 Patterns of Population Growth
Biotic potential is the highest per capita rate of increase for a population
Factors that influence biotic potential:
Average number of offspring per reproduction
Chances of survival until age of reproduction
Age at first reproduction
How often each individual reproduces

7. Patterns of Population Growth

8. 33.2 Patterns of Population Growth
J-shaped Curve
Lag phase: Growth is small because the population is small
Exponential growth phase: Growth is accelerating, and the population is exhibiting its biotic potential
S-shaped Curve
Deceleration phase: The rate of population growth slows down
Stable equilibrium phase: Little if any growth takes place because births and deaths are about equal.

9. 33.2 Patterns of Population Growth
Carrying Capacity:
The number of
individuals of a species
that a particular
environment can support

10. 33.2 Patterns of Population Growth
Survivorship
Growth curves assume all individuals are identical
In real life, individuals are in different life stages
Cohort-group of individuals born at the same time
Plotting the number surviving over time gives us a survivorship curve
Type I survivorship curve- most individuals survive until old age
Ex: humans
Type II- survivorship curve- decreases consistently over time
Ex: songbirds
Type III survivorship curve- most individuals die early
Ex: oysters

11. Survivorship Curves

12. 33.2 Patterns of Population Growth
Human Population Growth
Approximately 225,000 people are added to the world’s population every day.
Approximately 82 million people are added to the world’s population every year.
Current doubling time is 56 years
(length of time it takes for population size to double)

13. World Population Growth

14. 33.2 Patterns of Population Growth
Human Population Growth
More Developed Countries (MDC’s) versus Less Developed Countries (LDC’s)
MDC’s
Population growth is low and standard of living high
Increased rapidly between 1850 and 1950 due to decreased death rate
Then came a decrease in birth rate(demographic transition)
Population growth in MDC’s has stabilized at 0.1%
Germany, Hungary, Italy, Greece, Sweden are actually decreasing in size
The United States has a low yearly growth rate (0.6%), however many people immigrate to the United States each year.

15. 33.2 Patterns of Population Growth
Human Population Growth
More Developed Countries (MDC’s) versus Less Developed Countries (LDC’s)
LDC’s
Population growth is expanding rapidly and standard of living is low
Population of LDC’s could reach 11 billion by 2100
Most of this increase in Latin America, Africa, and Asia
Ways to decrease this expected growth are
Establish/strengthen family planning programs
Use social progress to reduce desire for large families
Delay onset of childbearing

16. Age Structure Diagram

17. 33.3 Regulation of Population Growth
Two Types of Life History Patterns
Opportunistic Pattern
Many offspring are produced
Short life spans
Weeds and insects are examples
Equilibrium Pattern
Few offspring are produced
Longer life spans
Birds and mammals are examples

18. Life History Patterns

19. 33.3 Regulation of Population Growth
Abiotic and Biotic Factors
Abiotic factors are called density-independent factors
Weather, natural disasters
Effects are the same for all sizes of populations
Biotic factors are called density-dependent factors
Competition, predation, parasitism
Effects depend on the size of the population

20. 33.3 Regulation of Population Growth
Competition
Occurs when members of two different species try to utilize the same resource
Competitive Exclusion Principle: no two species can occupy the same ecological niche at the same time
Ecological Niche: role organism plays in the community; includes habitat, resources used, and interactions
Resource Partitioning
Slight differences in the way a resource is utilized
Decreases competition

21. Competition Between Two Laboratory Populations of Paramecium

22. Competition Between Two Species of Barnacles

23. 33.3 Regulation of Population Growth
Predation
Predator-Prey Population Dynamics
Cycling of predator and prey populations
Occurs when either predators overkill prey, or when prey overuse resources and their numbers crash
In either case, predator numbers also decrease from a decrease in food source

24. Predatory-Prey Cycling of a Lynx and a Snowshoe Hare

25. 33.3 Regulation of Population Growth
Predation
Antipredator Defenses
Coevolution is present when each of two species adapts in response to selective pressures imposed by the others.

26. Antipredator Defenses

27. 33.3 Regulation of Population Growth
Predation
Antipredator Defenses
Mimicry: One species resembles another species
Can help capture food or avoid being preyed upon
Batesian Mimicry: A prey that is not harmful mimics another species that has a successful antipredator defense.
Warning colorations.
Mullerian mimicry: Species that resemble each other all have successful defenses.

28. Mimicry Among Insects

29. 33.3 Regulation of Population Growth
Symbiosis: Close interactions between members of two species.

30. 33.3 Regulation of Population Growth
Parasitism
Parasite derives nourishment from host
Parasite benefits and the host is harmed
Examples:
Disease-causing Bacteria
Ticks
Leeches

31. 33.3 Regulation of Population Growth
Symbiosis
Commensalism
One species benefits, the other is not effected
Examples:
Clownfish and sea anemones
Cattle egrets and cows

32. 33.3 Regulation of Population Growth
Symbiosis
Mutualism
Both members of the association benefit.
Plants and pollinators
Small fish and large organism

33. 33.3 Regulation of Population Growth
Ecological Succession
A change in a community’s composition that is directional and follows a continuous pattern of extinction and colonization by new species.
Primary Succession (land): Establishment of a plant community in a newly formed area where there is no soil formation
Secondary Succession: The return of a community to its natural vegetation following a disturbance
Pioneer Species: Plants that begin the process of secondary succession

34. Secondary Succession in a Forest

35. 33.3 Regulation of Population Growth
Ecological Succession
Models of Succession
Climax-pattern model: particular areas will always lead to a specific climax community
Based on the fact that climate determines what plants survive
Exact composition of climax community need be the same
For example, the climax community in an area may be deciduous forest, but the tree species may differ
Facilitation model: each successive community prepares the environment for the next
Grasses are necessary before shrubs, and then shrubs before trees

36. 33.3 Regulation of Population Growth
Ecological Succession
Models of Succession
Inhibition model: colonizing species hold on to space until they die or are damaged
Tolerance model: different species can colonize at the same time
Random chance determines which arrives first