I'm trying to remember two terms that define sexually reproducing species: one term is for species that breed continually until their environment can't sustain them, then a bunch die off, then the process starts all over again. The other term is for species that only breed continually until their population reaches a healthy level, then breeding slows down so that their population plateaus out. Does that sound familiar?
I don't believe there is a term for the second example, because those types of organisms don't really exist. All organisms will try to reproduce as much as possible until they reach a stabilization point determined by predation and resource consumption. Fluctuations in those factors (and others) can cause the species' in question numbers to rise or fall.
No organism self-regulates below its carrying capacity (K) that I'm aware of. All organisms to my knowledge (I'm a plant scientist and ecologist grad student) will continue to grow in population until either:
A) there is a massive overburdening of the ecosystem, followed by population collapse (a boom-bust cycle), or
B) grow slowly until nearing the hypothetical K, maybe barely exceeding it and losing a few members.
Perhaps you're thinking of R vs. K theory or R vs. K vs. S theory?
Wayfinder, PaizoCon Founder
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Yes, this sounds like the r/K selection theory
Your first example is of an r-strategist. Your 2nd is not quite a K-strategist, but I think you were going there, with the stabilizing population bit.
(Part of my thesis had to deal with r-strategists...a estuarine amphipod invading and colonizing a freshwater reservoir 100s of miles upstream)
Now that I think about it, one of these sounds like the logistic growth model. The other model's name I can't remember, how embarassing.
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Wayfinder, PaizoCon Founder
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There is the logistic growth model and the exponential growth model.
Links give a very good explanation, btw. The logistic growth model has the parameters of r and K.
There is the logistic growth model and the exponential growth model.
Links give a very good explanation, btw. The logistic growth model has the parameters of r and K.
Thanks for the reminder. I kept thinking that there was a better name than the exponential growth model. I don't need a reminder about r and K; those I have down pat, along with s.
You'd think I was a freshman bio student instead of a Master's student soon to defend, forgetting stuff like that. Yeesh. It's been a longer week than I thought.
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Wayfinder, PaizoCon Founder
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You'd think I was a freshman bio student instead of a Master's student soon to defend, forgetting stuff like that. Yeesh. It's been a longer week than I thought.
LOL. I know where you are coming from, Lathiira. I defended back in 1998. You are never completely ready for it, though. I got waylaid by my major prof, when he asked me a stat question...out of left field. WHAM! Explain "Coefficients of Variation".
You'd think I was a freshman bio student instead of a Master's student soon to defend, forgetting stuff like that. Yeesh. It's been a longer week than I thought.LOL. I know where you are coming from, Lathiira. I defended back in 1998. You are never completely ready for it, though. I got waylaid by my major prof, when he asked me a stat question...out of left field. WHAM! Explain "Coefficients of Variation".
Lucky me, I kept my notes from Biostatistics. Guess I'll be rereading those too.
To the OP, have we answered your question?
It's as good as any other answer; still ties back to r vs. K too.
And people say that these games rot your mind. Instead, they can promote scientific discussions. ha ha ha. The world's great minds will not come from its universities, its goverments, or its businesses (at least directly). No, they will come from the belittled and trod-upon geeks, nerds, and part-time players of fantasy games, who breed new ideas as easy as (or more easily than) breathing
Ok r vs k so what is S?
Stress.
R-selected species are good pioneers. They aren't great at competing with other creatures in general. Their life history strategy involves propagating quickly, get in, then move on.
K-selected species are great competitors. They tend to breed more slowly, moving into an area only after it's been colonized a while.
S-selected species can handle stressful environments real well. They don't grow fast and don't handle competition with other species well, but they can deal with environments other creatures can't.
Examples (mind you, no species is a perfect fit for any of these descriptions):
r-selected species: black cherry, eastern red cedar
k-selected species: white oak
s-selected species: cacti, saltwater mangroves
I'm using plants because I'm studying plants, but this applies regardless of what kingdom a critter is in.
Ok r vs k so what is S?Stress.
R-selected species are good pioneers. They aren't great at competing with other creatures in general. Their life history strategy involves propagating quickly, get in, then move on.
K-selected species are great competitors. They tend to breed more slowly, moving into an area only after it's been colonized a while.
S-selected species can handle stressful environments real well. They don't grow fast and don't handle competition with other species well, but they can deal with environments other creatures can't.
Examples (mind you, no species is a perfect fit for any of these descriptions):
r-selected species: black cherry, eastern red cedar
k-selected species: white oak
s-selected species: cacti, saltwater mangrovesI'm using plants because I'm studying plants, but this applies regardless of what kingdom a critter is in.
Would a black walnut be (generally speaking) a k-selected species?
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Ok r vs k so what is S?Stress.
R-selected species are good pioneers. They aren't great at competing with other creatures in general. Their life history strategy involves propagating quickly, get in, then move on.
K-selected species are great competitors. They tend to breed more slowly, moving into an area only after it's been colonized a while.
S-selected species can handle stressful environments real well. They don't grow fast and don't handle competition with other species well, but they can deal with environments other creatures can't.
Examples (mind you, no species is a perfect fit for any of these descriptions):
r-selected species: black cherry, eastern red cedar
k-selected species: white oak
s-selected species: cacti, saltwater mangrovesI'm using plants because I'm studying plants, but this applies regardless of what kingdom a critter is in.
Thank you...I dabble in a bit of everything but truth be told Biology is very low on my list. I know some of the basics and was tryign to follow along... but got lost. :D
Would a black walnut be (generally speaking) a k-selected species?
This one would probably be k-selected. Fairly long lifespan (though for a tree, nothing special), late successional, low number of propagules (compared to, say, a pine tree or milkweed). Not great as competitors go from my experience, but as I said earlier no species matches all the traits. I'm also speaking for my own region (eastern deciduous forest, oak-hickory now moving to beech-red maple, Piedmont region).
As a note, black cherry can be somewhat more of a k-selected species in some locales. Where I live, typical secondary succession places black cherry and eastern red cedar as early trees, along with Virginia pine and red maple, with later trees including tulip poplar, the taller oaks, and hickory. Late-successional species, broadly speaking, are k-selected.
Thank you...I dabble in a bit of everything but truth be told Biology is very low on my list. I know some of the basics and was tryign to follow along... but got lost. :D
Actually, we're talking about some fundamental ecological concepts. The s-aspect isn't always taught; I learned of it in my Plant Ecology class and that's the only class where I remember it coming up; I don't remember who wrote the seminal paper on the topic, it might be buried in my Plant Ecology notes. Thoreau? Tilman? Ehrlich? Clements? Gleason? I just don't remember.
I think there is some confusion here about r-selected and k-selected. These are relative terms, not absolute classificatory terms. Rats are k-selected compared to bees, but r-selected compared to elephants. Bees are k-selected compared to bacteria, but r-selected compared to dogs.
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Actually, we're talking about some fundamental ecological concepts. The s-aspect isn't always taught; I learned of it in my Plant Ecology class and that's the only class where I remember it coming up; I don't remember who wrote the seminal paper on the topic, it might be buried in my Plant Ecology notes. Thoreau? Tilman? Ehrlich? Clements? Gleason? I just don't remember.
Thank you...I dabble in a bit of everything but truth be told Biology is very low on my list. I know some of the basics and was tryign to follow along... but got lost. :D
Oh I had heard about R and K before, but since I have not delved far at all into biology I just had no clue. Thank you once again.
I think there is some confusion here about r-selected and k-selected. These are relative terms, not absolute classificatory terms. Rats are k-selected compared to bees, but r-selected compared to elephants. Bees are k-selected compared to bacteria, but r-selected compared to dogs.
Well-said. This is what I was implying when I mentioned that no species is entirely r-selected or k-selected.