Biological Interactions

1. Biological Interactions Relationships Between Organisms

2. Types of Relationships • Predator – Prey • Competitive • Symbiotic • Mutual • Commensal • Parasitic

3. Growth • Populations can grow in 2 possible ways • Unrestrained growth and eventual crash (r-selected species) • Examples: mosquitoes, bacteria, mold, weeds • Initially fast growth that levels off to maintain a steady population (K-selected species) • Examples: Lions, elephants, bears, whales, trees

4. J – Curve Growth

5. S – Curve Growth

6. Carrying Capacity • A population’s carrying capacity is the point in a population’s growth where the environment can no longer sustain further growth • Carrying capacity keeps populations from getting too large • Carrying capacity is determined by the availability of food, water, space, and other resources

7. Predator – Prey Relationships • Predators and their prey affect each other in dramatic ways Rabbit population increases due to lack of predators Lynx population decreases due to lack of prey More food available for lynx Lynx population increases Rabbit population decreases Larger lynx population eats more rabbit

8. Competition • Organisms of the same species or different species often compete for the same resources • Every organism has a niche, which is basically their job or role in the ecosystem • Organisms with the same niche must compete for limited space, food, water, etc…

9. Symbiosis • Some organisms from different species form relationships that give at least one of them a survival advantage • There are 3 main types: • Mutualism: both organisms benefit from the relationship • Commensalism: one organism benefits from the relationship, but the other is neither harmed nor helped by the relationship • Parasitism: one organism benefits from the relationship at the expense of the other

10. Symbiosis