Lecture Notes: Predation, Herbivory, and Parasitism

Important Dates

• Due Dates:
  • Quiz 14, 15 due Friday, March 28th, 11:59 PM
  • Phenology 1st draft due April 11

Chapter 14: Predation and Herbivory

Learning Objectives

• Understand how predators and herbivores limit species abundance.
• Recognize the cyclical fluctuations in consumer and consumed populations.
• Identify the evolutionary defenses favored by predation and herbivory.

Defense Mechanisms

How to Avoid Being Eaten

• Crypsis: Camouflage matching the environment or breaking up the outline (e.g., katydids, horned lizards).
• Structural Defenses: Reduce predator's ability to capture/attack prey.
  • Example: Crucian carp grow muscle mass to swim faster when detecting predatory fish.

Chemical Defenses

• Aposematism: Warning coloration associated with distastefulness.
• Mimicry: Exploiting coevolutionary interactions.
  • Mullerian Mimicry: Similar warning patterns among unpalatable species.
  • Batesian Mimicry: Palatable species mimicking unpalatable ones (e.g., hover flies mimic wasps).

Costs of Defenses

• Defenses can impact growth, development, and reproduction (e.g., ladybugs need high food intake to produce alkaloids).

Evolution of Herbivory

• Plant Chemical Defenses: Alkaloids, terpenoids, phenolics.
  • Trade-offs: Investment in growth/reproduction vs. defense.
  • Example: Tobacco plants produce nicotine in response to herbivores.

Coevolution and Trade-offs

• Chemical coevolution between plants and herbivores.

Chapter 15: Parasitism and Infectious Diseases

Learning Objectives

• Understand parasite-host interactions and their impact on host abundance.
• Recognize cyclical population fluctuations of parasites and hosts.
• Identify evolutionary strategies of parasites and hosts.

Types of Parasites

• Ectoparasites: Live on the outside, e.g., ticks, lice.
• Endoparasites: Live inside host cells or between cells, e.g., viruses, bacteria.

Parasite and Host Dynamics

• Dynamics are similar to predator-prey but parasites often reproduce faster without killing hosts.

Transmission Mechanisms

• Vertical Transmission: Parent to offspring.
• Horizontal Transmission: Between individuals, not parent-offspring.
  • Factors Influencing Infection: Mode of entry, vector reliance, ability to jump species.

Host and Parasite Adaptations

• Parasite Offenses: Manipulating host behavior, counterattacking immune systems.
• Host Defenses: Behavioral changes, chemical defenses, genetic recombination.

Examples of Host Adaptations

• Self-Medication: Chimpanzees consuming specific plants to combat parasites.

Modeling Parasite-Host Populations

• Infection Resistance: Preventing infections through immune responses.
• Infection Tolerance: Minimizing harm from infections.
• S-I-R Model: Models disease transmission and includes immunity.
  • Reproductive Ratio (R0): Determines if an infection will spread.

Importance of Vaccinations

• Vaccinations play a critical role in controlling infection resistance and tolerance.
  • S-I-R Models: Used to understand infectious disease spread, applicable to COVID-19.

Key References

• Research literature on insect mouthparts and plant chemical defenses.
• Notable scientists like Dr. May Berenbaum for studies on chemical coevolution and insect-plant interactions.

These notes overview the complex interactions between species, focusing on predation, herbivory, and parasitism, highlighting evolutionary strategies and adaptations that reflect the ongoing evolutionary arms race between species.