1. Population Dynamics, Carrying Capacity, and Conservation Biology

2. Population Dynamics - environmental stress
changes in populations as a result of
environmental stress
changes in environmental conditions.

3. A population
Is a group of individuals of a single species living in the same general area

4. Major characteristics of a population
Size – number of individuals
Density – number of individuals in a certain space
Dispersion – spatial pattern of a population
Age distribution – proportion of individuals of each age in a population

5. Generalized dispersion patterns
Most populations live in clumps although other patterns occur based on resource distribution.

6. A clumped dispersion Is one in which individuals aggregate in patches
May be influenced by resource availability and behavior
Figure 52.3a
(a) Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory.

7. A uniform dispersion
Is one in which individuals are evenly distributed
May be influenced by social interactions such as territoriality
Figure 52.3b
(b) Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors.

8. A random dispersion
Is one in which the position of each individual is independent of other individuals
Figure 52.3c
(c) Random. Dandelions grow from windblown seeds that land at random and later germinate.

9. Changes in Population Size: Entrances and Exits
Populations increase through births and immigration
Populations decrease through deaths and emigration

10. biotic potential – capacity for population growth
Intrinsic rate of increase (r)
rate with unlimited resources
organisms with a high biotic potential
reproduce early in life
have short generation times
can reproduce many times
have offspring each time they reproduce

11. environmental resistance - factors acting to limit population growth
No population can grow indefinitely.
There are always limits to population growth in nature.

12. Carrying Capacity (K)
the number of individuals of a given species that can be sustained indefinitely in a given space.

13. Population Growth Curves
© 2004 Brooks/Cole – Thomson Learning
Carrying capacity K
Population size (N)
Population size (N)
Time (t)
Time (t)
Exponential Growth
Logistic Growth

16. Exponential and Logistic Population Growth: J-Curves and S-Curves
Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off.

17. Exponential and Logistic Population Growth: J-Curves and S-Curves
As a population levels off, it often fluctuates slightly above and below the carrying capacity.

18. What Happens When Populations Exceed Carrying Capacity
Members of populations which exceed their resources will die unless they adapt or move to an area with more resources.

19. Black Death–the Plague Agricultural revolution16 15 ? 14 13 12 11 ? 10 9
Billions of people 8 ? 7 6 5
World Population Growth 4 3 2
Black Death–the Plague 1
2-5
Mil years
8000
6000
4000
2000
2000
2100
Time
B.C.
A.D.
Hunting and
gathering
Agricultural revolution
Industrial
revolution

20. Population density Density-independent population controls
Affect a population’s size regardless of its population density.
Floods, fires, hurricanes habitat destruction
Density-dependent population controls
Factors that have a greater effect as a population’s density grows
Competition of resources, predation, parasitism, disease

21. Types of Population Change Curves in Nature
Population sizes may stay the same, increase, decrease, vary in regular cycles, or change erratically.
Stable: fluctuates slightly above and below carrying capacity.
Irruptive: populations explode and then crash to a more stable level.
Irregular: erratic changes possibly due to chaos or drastic change.
Cyclic: populations fluctuate and regular cyclic or boom-and-bust cycles.

22. Simplified Population Change Curves
© 2004 Brooks/Cole – Thomson Learning
(3) Irregular
(1) Stable
Number of individuals
(4) Cyclic
(2) Irruptive
Time

23. Types of Population Change Curves in Nature
Population sizes often vary in regular cycles when the predator and prey populations are controlled by the scarcity of resources. (predator-prey oscillation)

24. Reproductive Patterns and Survival
Asexual reproduction
Offspring are exact copies of a single parent
Sexual reproduction
Organisms produce offspring by combining the gametes or sex cells from both parent
Disadvantages
Females must produce twice as many offspring
Chance of genetic errors increases
Mating entails costs
Advantages
Provides greater genetic diversity
Division of labor – males gather food and protect females and young