1. Chapter 8 – Understanding Populations

2. Organization Remember that ecosystems are organized like:
Organism species population community ecosystem
A group of the same species living in the same place at the same time.

3. Properties of Populations
Density – the number of individuals in a population
Dispersion - how individuals are spread out in the population.
Three Types:
EVEN
CLUMPED
RANDOM

4. Population Growth Measured by Growth Rate
Change in population Size
Births
Deaths
Growth Rate can be positive, negative, or Zero growth.
Depending on the organism, growth rate can be rapid or slow.

5. Population Growth Growth rate can depend on
Reproductive potential - maximum number of individuals a population can produce.
For example: bacteria produce far more offspring than humans
Generation time - the average amount of time it takes to mature and reproduce.
For example: bacteria reproduce much faster than humans
reproduction at an early age has the greatest influence on population growth.
Shorter Generation Time = Higher Reproductive Potential

6. Population Growth
As resources become scarce (based on most limited of resources, usually water), populations will eventually “level out” to the population level that the area can support. This is the environment’s carrying capacity. (Represented by an S-shaped Curve)
All populations experience exponential growth initially, however, limiting factors eventually causes change. (Represented by J-Shaped Curve)

7. Limiting Factors of Populations
Density – independent factors – are limiting factors that influence the population without regard to the number of individuals present.
Density – dependent factors - are more severe when populations are extremely large (or small in some cases).
Human Disturbance
Climate
Natural Disasters
Population
Size
Predation
Competition for resources like: food, water, and territory (Intraspecific Competition)
Disease
Parasitism
Like dysentery spreading through public H2O sources

8. Species Interactions
Remember habitat is where an organism lives and gets its resources, but niche is how a species lives (its role in its ecosystem)
Niche of one species is affected by its interactions with other species.
1. Competition - a relationship where both species are harmed (through less access to shared resources)
can be direct or indirect
can lead to competitive exclusion (one population becomes extinct due to direct competition) if two species try to share the same resource

9. Adaptations to Competition
Niche Restriction occurs when one species uses less of the niche than they are capable of using.
Realized Niche of Species A
Species A
Fundamental Niche of Species A
Species B
Fundamental & Realized Niche of Species B

10. Species Interactions
2. Predation – one species benefits (predator) and one species is killed and eaten (prey)
For example : Lynx and snowshoe hare

12. Combating Predation
Aposematic Coloration
Mimicry
Protective Covering

13. Species Interactions
3. Symbiosis - interactions between two species living in very close association with each other.
Three Types to Know :
1. Parasitism – interaction where one benefits (parasite) and the other is harmed (host). Parasite actually lives off bodily fluids of host.

14. Parasites and Humans

16. Species Interactions 3. Symbiosis (cont.)
2. Commensalism – an interaction in which one species is helped and one species is not affected positively or negatively.

18. Species Interactions 3. Symbiosis (cont.)
3. Mutualism – an interaction in which both species benefit.
Ants and Acacia tree

19. Species Interactions
Coevolution - process in which two species evolve in response to one another.

20. THE END