In order to better understand the role of an individual species within a larger system, we must first gain a basic understanding of that system. An ecological system can be broken down into smaller components. The list below outlines a general breakdown of a natural system in descending order (large to small).
Biosphere – the Earth and the atmosphere
Biome - large areas of the Earth that display similar climatic and geographical features. Typically these features determine what type of organisms inhabit these areas.
Ecosystem – a general term used to describe an area and its biotic (living) and abiotic (non-living) components.
Community – all of the living organisms that inhabit an ecosystem
Population - all members of a single species living in a community of organisms
Organism - a individual member of a population
Morphotype – any group of different types of individuals in any population
A species is a group of genetically similar individuals that can breed and produce viable offspring (capable of reproducing). All species have critical functional roles within their larger ecosystem. Sometimes this role is referred to as the species niche, and the area where the species lives is known as its habitat.
Although every species has a functional role within its habitat or ecosystem, some species are critically important to the overall health of the ecosystem. Such species are known as keystone species. The removal of a keystone species would cause a series of changes within the system and could eventually cause the system to collapse.
Relationships between species also are critical in the functioning of a healthy ecosystem. These are known as symbiotic relationships. Generally speaking, these relationships can be defined three ways:
Mutualism - a relationship between two species where both benefit from the relationship (+,+)
Parasitism - a relationship between two species where one species benefits and the other species is negatively affected (+,-)
Commensalism - a relationship between two species where one species benefits and the other species experiences neither positive or negative gain (=,0)
Niche vs. Habitat
A long time ago I had a science teacher who made this distinction incredibly clear. I will paraphrase him here: An organism’s niche is its occupation (what it does for a living, its job) and its habitat is its home or address.
Niche – job (functional role), Habitat - address
Plant species often play very important roles as providers of habitat in many ecosystems. Countless species rely on plants for food, protection, and homes. In general, we can divide the plant kingdom into two basic categories, gymnospermata and angiospermata.
Gymnospermata – Gymnosperms do not produce flowers. These plants release pollen from non-flowering male and female reproductive structures. The male structure is know as the strobili and the female structures are cones. Gymnosperms rely primarily on the wind to distribute pollen. The pollen released by male strobili fertilizes the egg cells found in cones which then develop into seeds. You may know these seeds as pine nuts (delicious in pesto). Evolutionarily speaking, gymnosperms are much older than angiosperms.
Angiospermata – Angiosperms produce flowers. Angiosperm species are pollinated by insects and other pollinators. Honeybees pick up sticky pollen as they visit flowers to consume nectar. The bees then deliver this pollen to neighboring flowers they visit instigating fertilization and seed formation. The flower may be the most important development in plant evolution!