Interaction between Environment and Biota

Biota and the Environment (Meaning)

The environment encompasses all elements that surround us.

Biota are the backbone of environmental stability, maintaining the functioning of ecosystems and keeping services like clean water and air "running". Biotic matter also releases nutrients, which can then be decomposed and used by other organisms.

When thinking about environmental stability, it is important to consider homeostasis. If you have a look at the previous lesson's Key takeaway (The Living Environment) you will probably get the gist of this chapter pretty quickly: "We are part of a distinct global ecosystem that is constantly trying to achieve homeostasis."

Let's dive further into a definition by S. K. Ernest (2008):

But why do we need to know this?

It's because the environment and the biota define each other. Below, you will see the most important factors determining these interactions that maintain stable living conditions.

Environmental Stability Definition

A stable and resilient ecosystem structure is less affected by the changing numbers of one species because there are other species that can fulfil the same or a similar role.

In an unstable ecosystem, there is a singular link in a process (e.g. x can only be pollinated by y) which makes that type of interaction (e.g. pollination) vulnerable to change because nothing else can replace it.

Perturbations can occur due to the change of seasons, ageing of organisms, migrations, or anthropogenic activities. Perturbations can be both biotic and abiotic.

Some changes may occur due to ecological succession.

Ecological Succession

Ecological succession is a natural process that happens when one ecosystem type is slowly colonized by different species. Succeeding species usually replace the species that had arrived first, called pioneer species. On Earth, this process is cyclical and helps balance ecosystems. We can distinguish between primary and secondary succession.

Primary succession happens when life is eliminated by abiotic factors such as volcanism or glaciation, due to which previously biotic environments cannot sustain the growth of organisms. It starts with barren environments.

Secondary succession refers to a partial extinction event where the environment is not entirely barren and can still host some life. Examples of events that generate this type of succession include wildfires and floods.

You can split ecological succession into four stages as follows:

• Nudation: the formation of an area devoid of life, for example, due to extreme events like volcanism.
• Invasion: the establishment or arrival of the first species.
• Competition and reaction: increased species numbers and food availability leading to competition and habitat change.
• Stabilization or climax: a relative state of equilibrium maintained by the terminal community.

Human activity can cause the ecological succession process within ecosystems to happen faster than nature intended. Examples include habitat fragmentation and introduced species. Extreme disturbances, which include natural or anthropogenic phenomena like sudden radiation bursts or emissions, can irreversibly alter ecosystems.

Disturbances can be an important part of ecosystems when natural, exactly because they can trigger or stimulate succession. A disturbance's size, frequency, intensity and timing can all affect the rate and direction of successional change (e.g., whether a community recovers its original composition).

Species succession

• Environments don't necessarily follow a linear pattern of succession, nor do they have to go through or complete all successional stages. Below we can distinguish three categories (pioneers, late-succession, ruderal) used for plant, bacteria and fungi species that succeed each other in an environment. Animal species are also affected by these cycles.

In a new environment, the first organisms to colonize barren or nutrient-poor mediums like barren sand or clear water are typically called pioneer species. When overall biodiversity is low, the pioneers, also known as early-successionals, don't have to compete for resources.

Climax or late-succession species follow up the pioneers and, being better competitors than colonizers, dominate a climax community. In a climax community, nutrient up-cycling and energy consumption may have reached a relative peak and will remain stable for large periods of time (on Earth, hundreds of years) until perturbations start to occur.

Ruderal species are those that colonize heavily disturbed habitats, such as contaminated sites. Ruderal species may be placed in the same category as the pioneers, or may be considered a subdivision of pioneer species, as their colonization strategies are similar. Both are succeeded by climax species.

In all these cases, animal species may be moving in and out of these systems due to their increased mobility when compared to plants.

Environmental Stability Factors

Biota are the great regulators of Earth's environmental stability because they occur in every habitat on the planet, from the coldest polar regions to the hottest deserts. Populations need to respond to changes and strive to achieve environmental stability thresholds, in order to pass on their genes.

Biotic factors that contribute to environmental stability include:

• Biogeochemical regulation: biota mediate the most important cycles on earth, such as the carbon, oxygen, nitrogen, water and phosphorus cycles. These cycles affect atmospheric, water and soil quality, among others.

• Nutrient cycling and dispersal: salt-eating organisms (e.g. elks, reindeer, humans) will seek and incorporate salt minerals into their diets. Excretion then spreads the obtained sodium and chloride in a variety of habitats.

• Pollutant levels control: microbial bioremediation.

Interaction Between Environment and Biota (examples)

Interactions between the environment and its biotic component can be both direct and indirect. A direct interaction can be represented by an organism directly using sunlight or consuming another organism. An indirect interaction can be that of an organism helping the growth of another by predating on its consumer (see the example below).

Below are a few examples of interactions.

• Respiration: the exchange of gases between organisms and their environment.

• Disease: organisms interacting with the abiotic factors in their environment influence disease processes.

• Decomposition: both biotic and abiotic elements help decompose carcasses which then become hummus, e.g. beetles and water.
• Carbon sequestration: When organisms such as plankton die, they fall to the bottom of the ocean, sequestering carbon away from the atmosphere.

• Trophic interactions: foraging and hunting - herbivores, omnivores and carnivores are interlocked in trophic interactions and provide nutrients from these interactions such as urine, faeces, honey, or carcasses.

• Sunlight usage: Autotrophs (primary producers) may use photosynthesis. Heterotrophs (organisms consuming others for energy) such as iguanas and humans use direct sunlight to synthesize vitamin D².

• Rain and moisture: Perspiration - plants transpire most of the water they absorb, aid cloud formation, and even influence wind patterns³. Water and moisture also influence organisms' rate of decomposition and the ability of an environment to sequester carbon⁴.

• Ambient temperature control: Shading - trees in a 2010 study⁵ significantly reduced soil (over 8 degrees C) and air temperature (over 2 degrees C) compared to unshaded areas during hot seasons.

Earth's biota plays an important role in the regulation of biogeochemical cycles and ecosystem services provision. Without them, our freshwater resources would be less clean, gaseous oxygen non-existent, and we'd have to eat molten rocks! Joking, we are part of the biota too, so we basically wouldn't be here either. I hope you enjoyed the article, and don't forget to check the following ones!