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MIT 2017 and 2016. These were hard, well-written and you had to know the material very well to medal.

whats the difference between R and K

ThiccleRick wrote:whats the difference between R and K

R-selected species have lots of young at once, don't tend to raise their young, reproduce often, and usually have a quick maturation. They excel in high change environments by just pumping out tons of babies and hoping that some survive. Examples include insects, fish, and rodents.

K-selected species tend to only give birth to one or two young at a time, have a long maturation period with parental rearing, and reproduce infrequently. Unlike r-selected species, they have much higher survival rates for young and they are strong competitors.

One way I remember the difference is "r" for "rabbit" (infamous for having tons of babies very often) and "K" for "King Kong" (big, one of a kind). Or "Kangaroo" if you want your example to make more sense.

gneissisnice wrote:

ThiccleRick wrote:whats the difference between R and K

R-selected species have lots of young at once, don't tend to raise their young, reproduce often, and usually have a quick maturation. They excel in high change environments by just pumping out tons of babies and hoping that some survive. Examples include insects, fish, and rodents.

K-selected species tend to only give birth to one or two young at a time, have a long maturation period with parental rearing, and reproduce infrequently. Unlike r-selected species, they have much higher survival rates for young and they are strong competitors.

One way I remember the difference is "r" for "rabbit" (infamous for having tons of babies very often) and "K" for "King Kong" (big, one of a kind). Or "Kangaroo" if you want your example to make more sense.

I always remembered r and k selected species based on logistic growth - in logistic growth, r is the maximum rate of growth of the population while k is the carrying capacity. When a population is small and there are Abundance resources, it grows fast, close to the theoretical maximum rate of growth, and species that live in these environments are r selected, with the characteristics described above to allow them to reproduce quickly. When a population is close to being the maximum possible for the environment it's in, (where k, the carrying capacity, is the maximum number of organisms the environment can support, so when the population size is close to k), then it grows much more slowly, and organisms have to compete for resources much more so they develop, again, the characteristics outlined above to maximize the chances of each offspring surviving. (Also, was the original question about r and k strategists or r and k terms in logistic growth, it could be either right, more likely the former but...?

Basically the difference between these two types of strategies is that one maximizes the chances of each offspring surviving to reproduce and the other maximizes the chance of some of the offspring surviving to reproduce, but you have to remember that this is a continuum, not 2 separate entirely unrelated types of animals and plants. One classic example is an oak tree - it's mostly like a k-strategist because it grows slowly in stable environments with significant competition, but it also produces lots and lots of acorns in the hopes that a few acorns will avoid being eaten, land on a new patch of soil, get enough water and sunlight, so it's maximizing the number of offspring, rather than the chances of each offspring.

Yes i suggest using the wiki for info.

how to "calculate" trophic level of a certain organism??

CaTaStRoPhY wrote:how to "calculate" trophic level of a certain organism??

Basically, just multiply the trophic level of everything it consumes by what percent of its diet it makes up, and then add all of it together.
Ex: Organism A eats Organism B and Organism C, which make up 60% and 40% of its diet, respectively. Organism B has trophic level 2, organism C has trophic level 3. Organism A's trophic level is 2.4.
2 * 0.6 + 3 * 0.4 = 2.4

Fridaychimp wrote:

CaTaStRoPhY wrote:how to "calculate" trophic level of a certain organism??

Basically, just multiply the trophic level of everything it consumes by what percent of its diet it makes up, and then add all of it together.
Ex: Organism A eats Organism B and Organism C, which make up 60% and 40% of its diet, respectively. Organism B has trophic level 2, organism C has trophic level 3. Organism A's trophic level is 2.4.
2 * 0.6 + 3 * 0.4 = 2.4

Taking the weighted average of the trophic levels as Fridaychimp wrote is shown correctly, but you also have to add 1 to the result to get Organism A's trophic level. An organism is always going to be 1 trophic level higher than what it eats, whether working with fractional trophic levels or counting up in integral levels from the bottom of a trophic pyramid. If what it eats has an average trophic level of 2.4, the organism's trophic level is 3.4

Fridaychimp wrote:

CaTaStRoPhY wrote:how to "calculate" trophic level of a certain organism??

Basically, just multiply the trophic level of everything it consumes by what percent of its diet it makes up, and then add all of it together.
Ex: Organism A eats Organism B and Organism C, which make up 60% and 40% of its diet, respectively. Organism B has trophic level 2, organism C has trophic level 3. Organism A's trophic level is 2.4.
2 * 0.6 + 3 * 0.4 = 2.4

Thanks!

knottingpurple wrote:

Fridaychimp wrote:

CaTaStRoPhY wrote:how to "calculate" trophic level of a certain organism??

Basically, just multiply the trophic level of everything it consumes by what percent of its diet it makes up, and then add all of it together.
Ex: Organism A eats Organism B and Organism C, which make up 60% and 40% of its diet, respectively. Organism B has trophic level 2, organism C has trophic level 3. Organism A's trophic level is 2.4.
2 * 0.6 + 3 * 0.4 = 2.4

Taking the weighted average of the trophic levels as Fridaychimp wrote is shown correctly, but you also have to add 1 to the result to get Organism A's trophic level. An organism is always going to be 1 trophic level higher than what it eats, whether working with fractional trophic levels or counting up in integral levels from the bottom of a trophic pyramid. If what it eats has an average trophic level of 2.4, the organism's trophic level is 3.4

Got it, thx!