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1. Chapter 8 Human Population I
Population dynamics, carrying capacity, and conservation
3. What are the characteristics of a population? Populations change in:
4. Population Size the number of individual species
4 variables that govern changes in size
Birth rate - gain (Natality)
Death rate - loss (mortality)
Immigration - gain
Emigration - loss
Population change = (B + I) - (D+E)
5. Population Density - the number of individuals in a certain space
Mass per volume
6. How does density affect population growth? Density-dependent factors will limit growth as the density gets too high; biotic factors
Examples: diseases, competition, predation, parasitism
7. Density-independent factors limit growth regardless of the density of the population, abiotic factors
Examples: hurricanes, floods, drought, fire, habitat destruction (these are usually natural disasters)
8. Population Dispersion spatial pattern, how the individual are set in relationship to each other
3 types of spatial patterns
10. Age Distribution Age structures will show how stable a population is and the number of individuals in certain age groups. We will take a look at this in more detail in the next chapter.
11. Other Elements that affect Population Carrying Capacity
Predator- prey interactions
12. NO population can grow indefinitely If we go above carrying capacity (k) the population may die out
What is carrying capacity?
Maximum number of organisms that an area can support over a period of time.
It is an unknown quantity. K is not a fixed number. It can fluctuate. But we know that if there are more people than resources the area can provide that people will die.
How does k compare to sustainable yield?
13. What is carrying capacity? Maximum number of organisms that an area can support over a period of time
14. What happens if a population exceeds the carrying capacity? Death of individuals in the population called a DIE BACK (usually due to density-dependent factors)
The more steep the angle of population over the k, the more drastic the die back
1845, 1 million Irish
Died b/c of the potato
Famine. 3 million
Migrated to the US
Leaving 1 million behind
15. Carrying Capacity K is affected by
Competition within and among species
Immigration and emigration
Natural and human causing catastrophic events
Seasonal fluctuations - floods
16. The Role of Predation in Controlling Population Size
17. Predator – Prey Interactions Species that interact as predator-prey often undergo cyclic changes in their numbers
With the hare and lynx, it was thought that the lynx was controlling the hare population; now researchers are suggesting that changes in the hare population due to food depletion control the size of the lynx population!
More research needs to be done to understand these interactions. Read case study on p. 186 which shows wolves (predators) controlling the moose (prey) population.
18. Role of Reproductive Strategies in Controlling Population Size .r - strategies species
* produce many offspring, provide little care for the offspring
* small adults
* high intrinstic rate
* population fluctuates above and below k
* low ability to compete
* cockroaches, weeds, fish, turtles
19. Reproductive Strategies .K- strategist
* many of the characteristics are opposite from r- strategist
* population fluctuates little above/below k
* much parental care
20. Survivorship % of population that will be alive at the end of a period of time
3 types of survivorship curves
Type I - high % lives a long time, produce fewer offspring
Type II - constant mortality, + = -
Type III - produce a lot & hope for the best, many die young