Population Dynamics

1. Chapter 4 Population Dynamics

2. Let’s talk about how population size change helps humans preserve healthy ecosystems.

3. Abiotic Factors • All the nonliving components of an ecosystem. • Sunlight • Temperature • Precipitation • Soil type • Salinity • Materials: Water, Nitrogen, and Oxygen

4. Biotic Factors • All the living things in an environment. • All the organisms with which an organism may interacts: Bacteria, plants, animals, fungi, and protists.

5. biotic factors continued… • May include: Other organisms that the organism eats or tries to eat • organisms that compete against one another • any other organism with which the organism has a symbiotic relationship.

6. Recall that…. A population is made up of all the organisms of a species that live in an area at the same time.

7. The size of a population is affected by: births, deaths, immigration, and emigration

8. Immigration • The movement of organisms into an area. • Births and immigration increase population size.

9. Emigration • Moving out of an area. • Deaths and emigration decrease population size.

10. Birth and death rates of humans are affected by many factors: • For example: Birth rates in underdeveloped nations tend to be much higher than those in developed nations. • This higher birth rate is due to a need for more people to do work such as farming.

11. At the same time, • death rates in many developing nations are higher than those in developed nations. • This is due to a lack of food and water, medical care, and sanitary conditions (clean water).

12. “Overall, changes in either abiotic or biotic factors can greatly affect population sizes. If a population cannotadapt to changes in its environment, some members will die or move away and the population will decrease. Likewise, if organisms are welladapted for a changed environment, their numbers may increase.” • -Biology Guru’s

13. Limiting Factors • Anything in the environment that can “limit” the size of a population.

14. A large population of • lions needs more food than • a small population. If there are not • enough resources, some lions • will move out or die. Therefore, their • food supply is limited. For Example:

15. Limiting Factors also include the following in addition to food… • Water • Oxygen • Sunlight • Relationships with other organisms

16. There are 2 main types of limiting factors: • Density-Dependent Factors • Density-Independent Factors

17. Density-Dependent Limiting Factor • A limiting factor that DEPENDS on the size of a population living in a certain amount of space.

18. Density Dependent Limiting factors include: • Competition- competing for the same resource • Predation-One kills and eats another • Parasitism- One organism benefits at the expense of another • Diseases- Spread by pathogens

19. All of these limiting factors can have a greater effect in a dense population in which organisms are crowded together! This is called Population Density.

20. Example of DD Limiting factor: • Dutch Elm Disease • Caused by fungus • Beetles spread the fungus • Because the trees were so close together, the disease spread rapidly and killed almost half the elm trees in the northern U.S.

21. Another example of DD limiting factor: • Tuberculosis (TB) • caused by bacteria that affects lungs • spread through the air when coughing, sneezing, or exhaling while talking. • Can spread rapidly in dense populations

22. Density-independent limiting factor • limits the growth of a population regardless of its density.

23. Examples of Density-Independent factors include: • Abiotic factors such as: weather, natural disasters such as forest fires, droughts, tsunamis, and pollution produced by humans.

24. these events can reduce population sizes or even wipe out populations!