Ecology Notes: Interspecific Interactions

Processes in Ecological Communities

Types of Interspecific Competition

• Community: Populations of organisms interacting in a habitat.
• Intraspecific Competition: Competition within the same species.
• Interspecific Competition: Competition between different species, including predation, symbiosis, and competition.

Predation

• One organism (predator) consumes another (prey).
• Essential for food chains/webs; energy and materials are transferred.
• Predators help maintain ecosystem balance.

Food Chains

Grazing Food Chain

• Starts with a producer (photosynthetic plant).
• Energy source: sunlight.

Detrital Food Chain

• Starts with detritus (decomposing material).
• Energy source: dead organic matter.
• Primary consumers: decomposers and detritivores (e.g., bacteria, fungi).

Key Differences

Predator-Prey Relationships

• Cyclical population dynamics: prey increase -> predator increase -> prey decline -> predator decline.
• Predator Adaptations: Speed, camouflage, group hunting.
• Prey Adaptations: Camouflage, nocturnal behavior, warning coloration, mimicry, chemical defenses.

Symbiosis

• Close relationships between two different living organisms.

Mutualism

• Both organisms benefit.
• Examples:
  • Sea anemone and hermit crab.
  • Honey bees and flowers.
  • Plover birds and Nile crocodiles.
  • Lichens (fungus and alga).

Commensalism

• One organism benefits, the other is unaffected.
• Examples:
  • Cattle egrets and grazing cattle.
  • Barnacles and whales.

Parasitism

• One organism (parasite) benefits, the other (host) is harmed.
• Ectoparasites: Live on the outer surface (e.g., leeches).
• Endoparasites: Live within the host (e.g., tapeworms).
• Obligate Parasites: Always live parasitically.
• Facultative Parasites: Can live as a parasite or independently.

Examples of Parasitic Plants

• Broomrape:
  • Lacks chlorophyll.
  • Has a swollen root organ.
  • Hooked haustoria penetrate host tissues.
• Dodder (Cuscuta):
  • Obligate parasite.
  • Twins around the host.
  • Rootless and leafless.
  • Haustoria absorb nutrients.

Haustoria

• Specialized structures for penetrating host tissues, enabling absorption of water, minerals, and sugars.

Tapeworm (Taenia solium)

• Endoparasite with primary (human) and secondary (pig) hosts.
• Adaptations:
  • Scolex with hooks and suckers.
  • No intestine.
  • Thick cuticle.
  • Flattened shape.
  • Hermaphrodite.
  • Large number of eggs.
  • Secretes anti-enzymes.

Amensalism

• One species is harmed, the other is unaffected.
• Examples:
  • Zebras trampling on plants.
  • Penicillium harming bacteria.

Interspecific Competition

• Competition between different species for the same resources.

Ecological Niche

• A species' role and position in its environment.
• Includes interactions with biotic and abiotic factors.
• Niche Breadth: Range of conditions a species can tolerate.

Generalists vs. Specialists