PREDATION

Introduction

• Predation and Herbivory

  • Discussion on the concepts of predation and herbivory.

  • Predation:

  • Definition: One organism gains a food resource, while the other sustains a loss.

  • Example: Predator gaining resources contributes to growth and reproduction, thereby increasing fitness, whereas the prey's fitness diminishes when captured.

  • Herbivory:

  • Definition: Comparison to predation; in many instances, herbivores do not kill the plants they consume.

  • Parasitism:

  • Similar to herbivory; parasites extract resources from their hosts without necessarily killing them, leading to a net gain for parasites and a loss for hosts.

  • Commensalism:

  • One organism benefits without affecting the other significantly.

  • Examples:

    • Epiphytes: Plants that live on other plants, causing negligible harm.

    • Barnacles on whales or Spanish moss on oak trees provide benefits without major detriment.

  • Mutualism:

  • Future discussion topic; involves two organisms benefiting from the relationship (+,+).

  • Overview of class focus on predation, herbivory, and parasitism, as entities involved exhibit plus-minus fitness interactions.

Predator-Prey Interactions

• Introduction to predator-prey dynamics.

• Key themes: adaptations of predators and prey in the context of survival.

  • Evolutionary Pressure:

  • Strong selection pressure shapes traits to enhance survival due to the risks of being consumed or failing to find food.

  • Important to the understanding of ecology’s influence on organism distribution and abundance.

• Types of Predators:

  • Carnivores (animal consumers), Herbivores (plant consumers), Omnivores (both plants and animals).

  • Most animals are facultative omnivores; they will consume whatever is available when needed.

  • Example: Chickens (descendant of dinosaurs) demonstrate omnivorous behavior, consuming both grains and small animals when available.

Feeding Strategies and Adaptations

• Obligate vs. Facultative Omnivores:

  • Obligate: Must consume specific resources.

  • Facultative: Consume various types but prefer specific categories based on availability.

• Nutrition Considerations:

  • Carbon, Nitrogen, and Phosphorus: Essential nutrients for building body tissues and growth.

  • Herbivorous diets typically require higher quantities of low-nitrogen plant resources compared to carnivores who consume nutrient-dense meat.

Specific Examples in Feeding Behaviors

• Pandas:

  • Evolutionary loss of detection for meat leads to eating bamboo, which is low in energy and requires extensive foraging.

  • Few natural competitors and predators aid survival despite the unnutritious diet.

• Koalas:

  • Consume toxic eucalyptus leaves, detoxifying their food, thereby dedicating significant energy to survival despite having few natural predators.

Predator Adaptations

• Overview of adaptations predators have developed to effectively capture prey.

• Group Feeding:

  • Example: Whales creating bubble nets to trap fish by blending and compressing groups of prey.

• Physical Adaptations:

  • Examples include claws, jaws, teeth tailored to capture and consume prey.

  • Examples of evolutionary structures:

  • Snakes: Adapt to feed on larger prey by unhinging jaws.

  • Velvet worms: Use glue to immobilize prey.

• Venom as Predatory Tool:

  • Venom serves to immobilize or digest prey.

  • Noting the difference between venomous (inflicting harm on others) and poisonous (causing harm upon consumption).

• Persistence Hunting:

  • Adaptation where predators exhaust prey through extended pursuit.

  • Human physiological traits suggest adaptation for efficient long-distance hunting over aggression.

Prey Defense Adaptations

• Protective adaptations discussed include:

  • Group Behavior:

  • Living in groups to minimize predation risk due to shared vigilance.

• Physical Armor:

  • Structures that deter predators; poses resource expenditure and energy needs directly affecting fitness.

Camouflage and Aposematism

• Cryptic Coloration:

  • Camouflage aids in predator avoidance by blending into the environment, allowing survival and reproduction.

• Aposematic Coloring:

  • Bright coloration to signal toxicity or danger to potential prey, deterring attacks.

  • Examples described include common toxic creatures like poison dart frogs and venomous insects.

• Mimicry:

  • Organisms mimic toxic counterparts to evade predation effectively.

  • Example: The monarch and viceroy butterflies.

Hunt Specific Prey

• Nitrogen as Diet Requirement:

  • Importance of nitrogen in building proteins; typically higher in animal tissues compared to plants.

• Specialization in Predation:

  • Some predators develop specialized adaptations for specific prey, such as anteaters for termites.

• Group Feeding:

  • Example: Whales' bubble net feeding illustrating effective group capture techniques.

Predator and Prey Mathematical Models

• Modeling Interactions:

  • Equations describing prey population growth, based on natural growth rates impacted by predation.

  • Functional responses (Type 1, Type 2, and Type 3) determine how predators respond to varying prey densities.