Negative Interactions in Biology

Negative Interactions in Biology

• Parasitism (Exploitation): One species harms another by directly or indirectly using it for support, shelter, or food. Two types include social parasitism and parasitism.

Social Parasitism

• Exploitation of one species by another for benefit. Examples include egg parasitism (like cuckoos), brood parasitism (like Indian Koels), and ants stealing food or nesting materials from others.

Parasitism (Specific)

• Harmful interaction between two species: host and parasite. Primarily a food relationship but parasites also gain shelter and protection. Typically, the parasite is smaller than the host.

Parasite Classification

• Viruses, microbes, plants (phytoparasites), animals (zooparasites), internal (endoparasites), external (ectoparasites), permanent, and temporary parasites.

Parasitic Adaptations

• Reduction in sensory organs, nervous system, and movement.
• Development of clinging structures (hooks, suckers) for attachment.
• Often anaerobic respiration, high reproduction rate, parthenogenesis (growth from unfertilized sex cell), hermaphroditism, polyembryony (many embryos from one egg), and complex life cycles.

Host-Parasite Interactions and Effects

• Parasites don't always cause immediate death but can damage host structures and lead to death.
• Diseases can be caused by parasites, stress, nutritional deficiencies, or toxins.
• Potential causes of disease and mortality in animals include viruses, bacteria (producing toxins), fungi (aspergillosis), protozoans, internal worms (tapeworms, nematodes), and external parasites (ticks, fleas, lice).
• External parasites often act as vectors for other diseases.
• Nutritional deficiencies in diet can contribute to diseases or death.
• Food poisoning can result from contaminated food.

Predation

• One species (predator) eats another (prey).

Predation Types

• Herbivores (plant eaters)
• Carnivores (meat eaters)
• Insect parasitism
• Cannibalism

Predation Characteristics

• Predators have developed hunting abilities, either specialized or generalized.
• Prey age, size, and strength influence predation.
• Predators only hunt when necessary.
• Overlapping habitats or territories increase predator-prey contact.
• Predators may switch prey depending on availability.

Prey Defensive Mechanisms

• Aposematic Coloration: Bright colors warning of noxiousness (toxins).
• Group Living: Easier predator detection, deterrence, distraction.
• Camouflage: Blending with the environment (e.g., chameleon).

Amensalism

• One species negatively affects another without being harmed itself. Often a chemical interaction.
• Allelopathy: One organism inhibiting the growth of another through chemical release (e.g., plants releasing oils).
• Antibiosis: Complete or partial inhibition or death of one organism by another through substance release (e.g., microorganism secretions). Examples include red tides in marine waters.

Competition

• Individuals compete for resources insufficient to support all.

Competition Types

• Intraspecific Competition: Competition within the same species.
• Interspecific Competition: Competition between different species.

Interspecific Competition Outcomes

• One species survives: The species with a greater negative effect on the other.
• Both species coexist: Interspecific competition less intense than intraspecific in both. Neither reaches carrying capacity without the other.
• Higher density species persists: Equal negative effects, but interspecific competition stronger.