Niches
A Niche is a particular role that an organism can play in an ecosystem to be able to successfully and consistently survive and reproduce there. By their nature, all organisms will want to find and fill all the available niches of an ecosystem, so that they may survive and procreate. This will lead to constant competition and evolution, with only the best adapted species managing to fill each niche. If a species is particularly well adapted, it may even fill several niches at once.
A niche can also be thought of as a combination of resources consumed by an organism.
Overview
Niches can be highly variable, as they depend on both the ecosystem's biome, and the species present in that ecosystem. Furthermore, environmental events could temporarily or permanently alter the biome and species present in the ecosystem, which can drastically change the available niches.
Two important terms in niches are the Fundamental Niche and the Realized Niche. A species' fundamental niche is the range of resources and habitats they can exploit based off of their traits (their anatomy, physiology, and behaviour). However, species do not exist in a vacuum, and there may be other species that are much better suited to exploit some of those same resources or habitats than you. So a species' realized niche is the actual, more limited range of resources and habitats that they actually exploit, because of competitive pressure from other species. If those competitor species were to be removed, a species would expand its exploitation to include all resources and habitats in its full fundamental niche.
Characteristics
Though it is hard to define a specific list of niches, there are many characteristics that can be used to define niches.
By Adaptability
Generalist: A species that is well adapted to live in a wide variety of environments. Because it is not specialized, it will have a hard time dominating any one environment in particular. However, in return, it is much more resistant to extinction, since if a natural event afflicts one biome it still has remaining members in others. This causes generalist species to be the most successful immediately after extinction events.
Specialist: A species that is highly adapted to living in a particular environment, at the cost of being less adapted to living in all other environments. Such a lifestyle will make it easy for a specialist species to outcompete all generalist species in that environment, but at the cost of making the species highly dependent on the stability of that environment. If a natural event were to occur in that environment killing many organisms or permanently altering its conditions, this could spell disaster for a specialist species.
By Diet
There are many different combinations of diets organisms can have, as such, there are many different ways of classifying them.
By Energy Source
All organisms must use energy (or ATP if microbes) to build the biomolecules (sugars, fats, proteins, DNA) they need to survive and reproduce. Depending on the source of this energy, the organism may be classified in different ways:
Phototroph: Receives their energy from light.
Thermotroph: Receives their energy from temperature gradients.
Chemotroph: Receives their energy from energy rich molecules (ex. glucose)
By Nutrient Type
Organotroph: Uses organic compounds (most carbon containing molecules) for nutrition. Ex. Glucose. On Earth, all animals are organotrophs.
Lithotroph: Uses inorganic compounds for nutrition. Ex. Iron, hydrogen sulfide, etc. On Earth, all plants and some bacteria are lithotrophs.
By Nutrient Source
Autotroph: Generates their own nutrients (AKA plants). Also referred to as a "Primary Producer".
Heterotroph: Obtains their nutrients from other organisms. Also referred to as a "Consumer". Will be referred to as a "Primary", "Secondary", "Tertiary" consumer based on how many degrees of separation there is between it and the eating of plants.
Types of Heterotrophs
Herbivore: Eats autotrophs (AKA plants). Also referred to as a "Primary Consumer".
- Browser: Eats plant matter off of high-growing plants such as trees.
- Grazer: Eats low-growing plants such as grasses or other multicellular organisms, such as algae.
- Exudativore: Eating autotroph excretions (ex. gum, sap, lerp, mucilage).
- Folivore: Eats leaves.
- Florivore: Eats flowers.
- Frugivore: Eats fruit.
- Graminivore: Eats grasses.
- Granivore: Eats seeds.
- Nectarivore: Eats nectar.
- Palynivore: Eats pollen.
- Algivores: Eats algae.
- Xylophage: Eats wood.
Carnivore: Eats other heterotrophs. Also referred to as a "Secondary Consumer" if it eats Herbivores, or a "Tertiary Consumer" if it eats other carnivores as well.
- Hypocarnivore: Eats less than 30% meat in its diet.
- Mesocarnivore: Eats between 30-70% meat in its diet.
- Hypercarnivore: Eats over 70% meat in its diet.
- Corallivore: Eats coral.
- Durophage / Osteophage: Eats bone.
- Ovivore / Egg Predator: Eats eggs.
- Haematophage / Sanguivore: Eats blood.
- Invertivore: Eats invertebrates.
- Keratophage: Eats skin, horns, wool, or other keratinous material.
- Lepidophage: Eats scales.
- Mucophage: Eats mucus.
- Zooplanktonivore: Eats zooplankton.
Omnivore: Eats both autotrophs and heterotrophs.
Coprophage: Eats feces.
Detrivore / Saprophage: Eats decomposing material. Also referred to as a "Scavenger".
Geophage: Eating inorganic soil.
By Trophic Level
Primary Producer: An organism that relies on producing its own energy through biosynthesis. The exact biosynthesis used can vary; it can be anoxygenic photosynthesis (used by bacteria), oxygenic photosynthesis (used by bacteria and plants), hydrogen sulfide chemosynthesis (used by bacteria), thermosynthesis (theoretical), and more. All life depends on primary producers and their metabolism (which is referred to as primary production). Primary producers are necessary to turn the inorganic molecules of nature into sugars, proteins, fats, and other biomolecules, that other life can then feed off of.
Primary Consumer: Consumers are organisms that feed on other organisms for survival (as opposed to producers). A primary consumer is an organism that feeds on primary producers only. As such, it can be considered as the first tier of consumers (hence "Primary"). Another word for Primary Consumer is "Herbivore". Because of the inefficiency of ingestion and digestion which causes energy to be lost from a prey when eaten by a predator (estimates place it at 90% of the energy being lost), a certain amount of primary producers in a habitat can typically only support a smaller number of primary consumers feeding off of them.
Secondary Consumer: Secondary consumers feed on primary consumers (and potentially primary producers as well). A secondary consumer can also be called a "Carnivore", since it feeds on other mobile organisms. Because of the energy loss in predation, a certain number of primary consumers in a patch can typically support only a smaller number of secondary consumers in the patch feeding off of them.
Tertiary Consumer:
By Predatory Nature
Mesopredator:
Apex Predator:
Ambush Predator:
Pursuit Predator:
Endurance Predator:
Pack Hunter:
By Habitat
Aquatic: Also known as Natatorial. A species that spends the majority of its time living in water.
Semi-Aquatic: Also referred
Terrestrial:
- Cursorial:
Aerial:
- Jumping:
- Gliding:
- Soaring:
- Flying:
- Ballooning
Arboreal:
Scansorial:
Fossorial:
By Circadian Rhythm
Diurnal
Nocturnal
Crepuscular
By Domestication Status
Wild
Domesticated