1. Chapter 20 Lab Biology Chapter 26 Honors Biology
Populations
Chapter 20
Lab Biology
Chapter 26
Honors Biology

2. Anticipatory Set: Count the number of dolphins in this picture…
Does this represent a population of dolphins?

3. Properties of Populations
Grp. Of organisms of the same species in a particular place at the same time.
Population Size no. of individuals it contains (how do we measure it?)
Population Density measures how crowded a population is (indiv. Per unit of area or volume)
Dispersion spatial distribution of individuals within the population
Clumped
Even
random

4. Population Dispersion

5. FIGURE 26-13a Population distributions
(a) Clumped: a gathering of caterpillars.

6. FIGURE 26-13b Population distributions
(b) Uniform: creosote bushes in the desert.

7. FIGURE 26-13c Population distributions
(c) Random: trees and other plants in a rain forest.

8. Population Dynamics (change over time)
Birth rate – no. of births occurring in a period of time Death rate – number of deaths in a period of time Life expectancy –how long on average an individual is expected to live

9. Continue…
Age Structure the distribution of individuals among different ages in a population Patterns of Mortality tends to conform to one of three curves on a graph called survivorship curves they show the likelihood of survival at different ages throughout the lifetime of the organism.

10. Population Growth Rate
Growth rate the amount by which a population’s size changes in a given time This depends on 4 processes: Birth Death Emigration immigration

11. Formulas for growth rate!!
Loss… Birth rate – death rate = growth rate (per capita use 1,000) Gain… To find the no. of new indiv. That will be added to the population in a yr. Multiply the per capita growth rate by the no. of indiv. In the popul.

12. Exponential Model
Exponential Model describes a population that increase rapidly after only a few generations Exponential Growth the larger the population gets the faster it grows

13. Predictions Based on the Exponential Model
View population growth over time Represented by a J – shaped curve

14. Limitations of the Exponential Model
Exponential growth occurs only under rare conditions and for short periods of time Why: resource get depleted and waste builds up Limiting factor – a factor that restrains the growth of a population

15. Logistic Model
A population growth builds on the exponential model but accounts for the influence of limiting factors Carrying capacity: the no. of indiv. The environment can support over a long period of time. Logistic growth

16. Environmental Resistance
Environmental resistance can be classified into two broad categories Density-independent factors Density-dependent factors

17. Population Regulation
2 Kinds of limiting factors control population size: 1. Density-independent factors: limit populations regardless of their density Examples: climate, weather, floods, fires, pesticide use, pollutant release, and overhunting 2. Density-dependent factors: can cause birth rates to drop and/or death rates to increase Population growth slows resulting in an S-shaped growth curve (or S-curve)

18. Density- Independent Factors
Some species have evolved means of limiting their losses Examples: seasonally migrating to a better climate or entering a period of dormancy when conditions deteriorate

19. Density-Dependent Factors
Density-dependent factors can cause birth rates to drop and/or death rates to increase Population growth slows resulting in an S-shaped growth curve (or S-curve)

20. FIGURE 26-6a The S-curve of logistic population growth
(a) During logistic growth, the population will remain small for a time, then will expand increasingly rapidly for a time. Then the growth rate slows and growth eventually ceases at or near the carrying capacity (K). The result is a curve shaped like a "lazy s."

21. Density-Dependent Factors
Carrying capacity is determined by the continuous availability of resources

22. Density-Dependent Factors
Include community interactions Predation Parasitism Competition

23. History of Human Population Growth
1. Development of Agriculture – “agricultural revolution” stabilized and increase available food supply 2. Population Explosion – 3. Population Growth today – - developed countries - developing countries