Interactions Within Ecosystems

1. Interactions Within Ecosystems CH5

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)