Golden Key Points – Chapter 11 – Organisms and Populations

Golden Key Points

1. Population Growth Patterns:

   • Exponential Growth: Rapid increase in population when resources are abundant.
   • Logistic Growth: Population growth levels off due to limited resources (carrying capacity).
   • Real-world populations often follow logistic growth due to resource constraints.

2. Life History Variation:

   • Organisms evolve reproductive strategies based on their habitat’s conditions.
   • Strategies include single breeding events (Pacific salmon) or multiple breeding events (most birds, mammals).
   • Some species produce many small offspring (oysters) while others produce fewer large offspring (birds, mammals).

3. Population Interactions:

   • No habitat is inhabited by a single species; interactions among species are essential.
   • Interspecific interactions include predation, competition, parasitism, commensalism, and mutualism.
   • These interactions influence population dynamics, energy flow, and ecosystem stability.

4. Predation:

   • Predators transfer energy across trophic levels by consuming prey.
   • Predation controls prey populations and maintains species diversity.
   • Adaptations such as camouflage, toxins, and defenses evolve in prey species.

5. Competition:

   • Occurs when species compete for limited resources (food, space).
   • Strong competition can lead to competitive exclusion or resource partitioning.
   • Coexistence strategies include niche differentiation and behavioral adaptations.

6. Parasitism:

   • Parasites benefit at the expense of hosts, harming host fitness and survival.
   • Parasites exhibit host specificity and often have complex life cycles.
   • Hosts evolve defenses against parasites, such as immune responses and behavioral adaptations.

7. Commensalism:

   • One species benefits while the other is unaffected.
   • Examples include epiphytic orchids on trees and cattle egrets foraging near grazing cattle.

8. Mutualism:

   • Both species benefit from the interaction.
   • Examples include lichens (fungus-algae), mycorrhizae (fungi-plants), and plant-animal mutualisms (pollination, seed dispersal).
   • Co-evolution ensures mutualistic relationships remain beneficial and prevent exploitation.