Biotic Interactions

Community

consists of all the populations of all the different species that live together in a particular area

Community Ecology

investigate the factors that influence biodiversity, community structure as well as the distribution and abundance of species

COMMUNITY

consists of all the populations of all the different species that live together in a particular area

GUILD

Collection of species that use similar resources (or have similar roles within a community)

TROPHIC LEVEL

Subset of species within a community that acquire energy in a similar way; a sequence of steps in a food chain or food pyramid (primary producer, primary consumer, secondary consumer, etc.)

Individualistic

all species present in the community share similar requirements

Gleason’s Individualistic Concept in ecology

It is the idea that a community is made up of individual species that coexist mainly because they have similar environmental needs, not because they strongly depend on each other.

Superorganism

are tightly bound together both now and throughout their evolutionary history

Clements' Superorganism Concept in ecology

It is the idea that a community functions as a tightly bound, highly organized unit—like a single organism—with species that are strongly connected and co-evolved.

Interspecific interactions

Different types of interspecific interactions have different effects on the two participants, which may be positive (+), negative (-), or neutral (0).

Competition (-/-)

It is an interaction where both species or individuals are harmed (-/-) because they compete for the same limited resource like food, space, or light.

intraspecific competition

Competition that occurs within the same species, where individuals fight for the same resources (e.g., food, mates, territory).

interspecific competition

Competition that occurs between different species that require similar resources in the same environment.

overlapping niches

Species compete when they have _______, that is, overlapping ecological roles and requirements for survival and reproduction.

interference competition

A type of competition where organisms directly interact or fight to limit the access of others to resources.
Example: Defending territory or food, killing competitors.

exploitation competition

A type of competition where organisms indirectly compete by using up resources, leaving less for others.
Example: Plants absorbing all available nitrogen in the soil.

resource partitioning

The process where species with overlapping niches adapt to use different resources, allowing them to coexist.

Competitive Exclusion Principle (Gause’s Law)

States that two species cannot coexist in the same community if they occupy exactly the same niche and compete for identical resources. One species will eventually outcompete the other.

Weaker Species in Competitive Exclusion

The weaker species in a competition will either go extinct or adapt to a different resource, leaving the competition over time.

Niche in Competitive Exclusion

According to the Competitive Exclusion Principle, only one species per niche can exist long-term if they compete for identical resources.

Predation (+/-)

An interaction where a predator species feeds on a prey species, resulting in a positive effect (+) for the predator and a negative effect (-) for the prey. It can involve animals, insects, or even plants in the case of herbivory.

Herbivory

A special case of predation, where animals (predators) consume part of a plant (the prey). This interaction is similar to predation but involves plant consumption.

Predator Adaptations

Adaptations that predators develop through natural selection to better capture and consume prey. These adaptations include features like claws, teeth, fangs, stingers, and poison.

Prey Defensive Adaptations

Features or behaviors that prey species develop to avoid being caught by predators. These can be behavioral, morphological, or physiological.

Behavioral Defenses

Defensive strategies that involve behavioral actions to avoid predation, such as hiding, fleeing, forming herds or schools, self-defense, or making alarm calls.

Cryptic Coloration (Camouflage)

A morphological adaptation where prey species develop camouflage to blend into their surroundings, making them harder for predators to spot.

Aposematic Coloration

A morphological adaptation where animals with toxic chemicals or poison develop bright, warning coloration to signal danger to predators, who become more cautious when encountering such prey.

Batesian Mimicry

A form of mimicry where a harmless species mimics the appearance of a harmful or unpalatable species to avoid predation. The harmless species is a "pretender".
Example: Hawkmoth larva mimics a Green parrot snake.

Müllerian Mimicry

A type of mimicry where two or more unpalatable species evolve to resemble each other, reinforcing the “yuck” signal to predators. Both species are genuinely unpalatable.
Example: Yellow jacket and Cuckoo bee.

Mimicry

A defensive strategy where a prey species mimics the appearance of another species to gain protection from predators. Mimics can either be harmless or unpalatable.

Secondary Compounds (Plant Defenses)

Chemical defenses produced by plants to protect themselves from herbivores. These include noxious odors, repellent tastes, or toxic effects when ingested.
Example: Foxgloves produce deadly chemicals like cardiac and steroidal glycosides, which can cause nausea, hallucinations, and even death when ingested.

Secondary Metabolites

Compounds produced by plants that are not directly involved in photosynthesis or necessary for growth or respiration. These metabolites often serve as defense mechanisms against herbivores or pathogens.

Mechanical Defenses (Plant Defenses)

Physical structures that act as an impenetrable barrier to herbivores, such as bark, waxy cuticle, thorns, and spines, which make it difficult for herbivores to access or consume the plant.

Mutualism (+/+)

A type of symbiosis where both species involved benefit from the interaction, resulting in a positive outcome (+) for each.
Example: Pollination between flowers and bees.

Obligate Mutualism

A type of mutualism where **both species cannot survive without each other. They are highly dependent on one another for survival.
Example: Lichens, where algae and fungi live together.

Facultative Mutualism

A type of mutualism where both species can survive independently, but still benefit from the interaction.
Example: Cleaner fish and host fish, where the cleaner fish eats parasites but the host fish doesn’t depend on them for survival.

Commensalism (+/0)

A type of symbiosis where one species benefits from the interaction, while the other is neither helped nor harmed. The interaction has a positive effect (+) on one species and no effect (0) on the other.
Example: Barnacles attaching to the shell of a turtle. The barnacles get access to food while the turtle is unaffected.

Parasitism (+/-)

A type of symbiosis where one species, the parasite, benefits at the expense of the other species, the host, which is harmed by the interaction.
Example: The isopod Cymothoa exigua, a fish parasite, replaces the tongue of the fish Lithognathus, feeding off the host.