1. Interactions Within Ecosystems

2. Populations Made up of a group of organisms of the same species that live together in one place at one time and interbreed. (produce offspring) Understanding population growth is important – Populations of different species interact – Interactions can affect the number of individuals in a population

3. Population Growth How do populations grow and shrink? – Immigration Movement of individuals into a population – Emigration Movement of individuals out of a population Growth Rate – Affected when more individuals are born than die Population grows – Exponential growth Numbers increase by a certain factor over a period of time J-shaped curve graph (pg 104 in text)

4. Exponential Growth

5. Logistic Growth – Exponential Growth illustrates what the population would look like if there were no outside influences – Populations are affected by certain factors like availability of habitat, predators, and disease – Populations slow and stabilize – Carrying capacity Largest population that an environment can support

6. Logistic Growth – Population growth that starts with a minimum number of individuals and reaches a maximum depending on the carrying capacity of the habitat – S – shaped curve graph (pg 105) Population starts off small Growth rate increases due to the abundance of resources Population reaches carrying capacity as resources become scarce Competition for resources slows the growth rate of the population birthrate = deathrate, no growth in population

7. Logistical Growth

8. Factors that Affect Population Size Abiotic Factors Biotic Factors Human Activities Science and Technology Predator – Prey Interactions – Predation – Coevolution

9. Predator – Prey Interactions – Predation Act of one organism killing another for food – Coevolution Back and forth evolutionary adaptations as a result of interactions – Parasitism One organism feeds on the other (host) – Herbivory Plants adapt to protect themselves from being eaten

10. Herbivory – Monarch caterpillar and milkweed – Milkweed is toxic to deter herbivores but does not harm caterpillar instead it stores toxin to keep from getting eaten itself

11. Predation/Coevolution – Zebra has stripes to confuse predator, also long legs, stays in herds – Lion hunts in packs, camouflage with landscape

12. Symbiosis Species live in close association with each other – Mutualism both species benefit – Commensalism one species benefits other is neither harmed or helped

13. Parasitism – Tapeworm Mutualism – Clownfish and Sea Anemone

14. Commensalism – Orchid gets closer to the sun

15. Competition Competition determines the organism’s niche – Role that the organism plays in the community Carving a Niche – Affects other organisms in the community – Niche vs Habitat Habitat is where an organism lives Niche is the role that the organism plays in that habitat

16. Ecosystem Resiliency Interactions between organisms and the number of species (biodiversity) in an ecosystem add to the resiliency of an ecosystem. Resiliency – to withstand, resistant, tough, hardy, durable Keystone species – Species that is critical to an ecosystem because the species affects the survival and number of other species in its community – Examples (wolves in Yellowstone, Sea Otters off the Pacific Coast)