Though taught at the college level, however, this is knowledge for knowledge sake, to ponder, and will not transfer for credits anywhere.
Okay, enough promoting, let’s dive in.
Ecology is the study of the interactions of organisms and their environment, which includes other organisms. A “good” ecosystem performs some major things: energy flows through it and nutrients are recycled by it. Ecosystems also perform what these days are called ecosystem services; these are beneficial things that ecosystems do for humans including cleaning water and air, decomposing waste, producing food and more.
Some Big Concepts in ecology:
Biodiversity and Functional diversity
A more biodiverse system is usually more functionally diverse. These systems are generally more resilient (resistant to change), and have higher levels of ecosystem functioning (more energy flow, nutrient cycling, ecosystem services).
Competition
If species compete, for a food resource for example, one may harm to other by outcompeting it (getting more food faster for example). Early on studies suggested that two organisms with completely overlapping niches (lifestyle, food source, etc) could not live in the same place. Lab studies showed two organisms competing over a food source only allowing one survivor. This was called the competitive exclusion principle. In a real ecosystem, not lab study, organisms living in the same place and eating nearly the same thing, appear to adjust behavior and/or food sources so avoid overlapping competition.
Cooperation
Organisms may compete but also cooperate. They do this on many levels, from living inside each other to one organism presence being enough for another organisms to also be present. Perhaps the presence of big predator that doesn’t feed on you, scares your predator away, thus you can chill in the sunlight without a care. Wait, its nature, chilling without a care probably doesn’t happen much, don’t let your guard down.
Ecological succession
Ecological succession might be considered a type of cooperation. Under a successive regimen the dominant organisms in a systems changes over time. The classic example is bare rock, with lichens coming in first, to old growth forest. Many steps occur in between, and many years go by as this occurs. Ecological succession also occur after a fire, which may have burnt down the large tree. Grasses come in first, then bushes…If you wait long enough the forest trees will again dominate. This type of succession is called secondary succession.
Keystone species
In some systems one species appears to hold such a dramatic hold on the systems that if removed the system comes tumbling down. Like the keystone in an archway. This was first studied on an intertidal zone and the keystone predator was a sea star. Upon removal the intertidal ecosystem changed dramatically. It’s biodiversity plummeted. Although it was not measured, I expect all those ecosystem functions dropped (energy flow, nutrient cycling etc).
Ecosystem Resilience
This is defined a few ways in the ecological literature but mostly it is the ability of the system to resist change. It can also be interpreted as the ability of the system to bounce back (or the time until it bounces back).
These ecosystem concepts overlap. Keystone species cause collapse of the biodiversity but higher biodiversity might have pushed up resilience and prevented collapse. The presence of the keystone species is a type of cooperation that allows other organisms to live in this intertidal zone. This change could be the start of a secondary succession process (but this one may be reaching a little). AND, secondary succession could be interpreted as a low resilience systems that just takes a long time to bounce back.
Our Microbiome
Our gut contains thousand and thousand of species of bacteria, and other microbes. Within this microbiome (because its several ecosystems including the stomach, the small intestine, and the large intestine) bacteria eat, compete, cooperate, go through changes (succession?), and may contain keystone species.
At first glance the biodiversity of our gut does not appear very biodiverse with most bacteria from two groups, both of which have gone through a recent name change: The Firmicutes (Now Bacillota) and the Bacteroidetes (now Bacteridota) groups make up most of our bacteria. The familiar Coliform bacteria (Escherichia coli), are a mear 0.1 percent of gut microbiota. However, this is not the whole picture as far as bacterial diversity. It’s hard /expensive to determine all the species present, it requires molecular techniques. Mostly these days they test for the presence of ribosomal RNAs. Studies that have dived in deeper keep finding more and more species, so the biodiversity appears to be very high. This is turn means we probably have resilient system.
Some bacteria feast on the same food source (the sugar groups in our intestinal lining) and compete for space amongst this region. Other bacterial groups feast on the metabolic end products of those bacteria. Thus within this system we have both cooperation and competition.
The level of cooperation goes deeper. It appears that a few bacterial species can metabolize metals.Their metabolic end products are critical for other bacteria. If, I say if, those metal eaters were to be removed, would this system come crashing down? If so, then those are keystone species.
When we are born we are first infused with the bacteria from mom. Other people and pets we encounter also add to our biota. At birth the Dominant species/groups are Bifidobacterium, Bacteroides, and Clostridium species. When we start our milk diet Bifidobacterium becomes more dominant. When we start eating solid food Bacteroides, Clostridium, and Ruminococcus increase, while Bifidobacterium and Enterobacter decrease. This primary is succession.
When humans go through disease, or even more so when we go through treatments for disease, the bacterial community is disrupted. For example, long-term antibiotic treatment may keep you alive, but your gut bacteria suffer. Long-term antibiotics make you more susceptible to C. Difficile the scourge of hospital infections. The resilience of the system has wained. Antibiotics are not the only thing that can mess our bacteria up, chemotherapy can, as can a germ free environment.
Once the treatment stops, our gut, which may be in bad shape, begins to rebuild. Given enough time, our gut is fully functional again. This is secondary succession.
Out microbiota can be manipulated in many ways. It seems pretty obvious that our diet influences our gut bacteria and what we eat can be harmful or beneficial. There is quite a bit of work on obesity and diet and However, be wary, be skeptical, silly claims like green tea will make everyones gut super healthy are simply not true. Could green tea be helpful? Perhaps. Do probiotics work? Maybe. Be skeptical. We still know less about these ecosystems than any other on earth.
Our gut is a biome within which several ecosystems are housed. It is a has highly Biodiverse resilient system. It contains competitors and cooperators, and goes through both primary and secondary succession.
Disturbances happens, adjustments occur. Goal a functional / healthy system. Ultimate gaol, can we manipulated our microbiota to the degree that it rids us of a disease?
Sources and Further Readings
Figueireo ART, and Kramer J. 2020. Cooperation and conflict within the Microbiota and their effects on animal hosts. Frontiers in Ecology and Evolution 8 (132).
Gause G. 1934. The struggle for existence. Baltimore: Williams & Wilkins.
The competitive exclusion principle idea came from Joseph Grinnel in 1904, but was tested by Gause in the lab. For an easier read, or one you can actually find, try Hardin G. 1960. The competitive exclusion principle. Science 131: 1292–1297
Ley RE, Peterson DA, and Gordon JI. (2006) Ecological and evolutionary forces shaping microbial diversity in the human intestine. Cell 124, 837–848.
Paine R. 1966. Food web complexity and species diversity. The American Naturalist 100: 65–75.
Rodriguez JM, et al. 2015. The composition of the gut microbiota throughout life, with an emphasis on early life. Microb. Ecol. Health Dis. 26, 26050
Selber-Hnatiw S, et al 2017. Human gut microbiota” Toward an ecology of disease. Frontiers in Microbiology 8 (1265).