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Valen said:I'm tired of this place... I'm leaving there is no complete reasoning
Jet Black said:you didn't take into account the amount of available food, predators, diseases, weather and all the other things that are going to affect the monkey population. and you threw in a completely arbitrary growth rate.
Jet Black said:well it could be a number... but the problem I see is that it is too simplified. As Darwin points out, you just cannot assume geometrical growth of any population in a realistic environment. You might achieve it if you pu a breeding monkey pair in an infinitely large banana plantation devoid of predators, but in any real environment, there are too many things that will keep a check on populations.
Valen said:Your solution for the monkey breeding in 1,600,000 years...
Let's presume the following...
annual breeding rate is 1 for each pair:
m = 10
P = 1600000 of monkey breeding
no mortalities
Nathan David said:Okay, Valen, here's an equation for population growth:
G=b-d/t
where G is the rate of population growth b is number of births in a population, d is the number of deahts, and t is elapsed time.
lucaspa said:Now, why are there no mortalities? No disease? No predators? No limitations on food so that too many monkeys in an area starve?
It is that "no mortalities" that screws up your calculations.
Valen said:NO THAT CALCULATION (The Latter) IS NOT AN ASSUMPTION MY FRIEND I DEFINITELY DISAGREE WITH YOU!
Even if there are death rates the bigger the years the larger the number unless there was real worst catastrophes.
Valen said:What's the cause of it any way, before you can state an effect state a cause. The cause must be valid base on real evidences not possibility.
Linnæus has calculated that if an annual plant produced only two seedsand there is no plant so unproductive as thisand their seedlings next year produced two, and so on, then in twenty years there would be a million plants. The elephant is reckoned to be the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase: it will be under the mark to assume that it breeds when thirty years old, and goes on breeding till ninety years old, bringing forth three pair of young in this interval; if this be so, at the end of the fifth century there would be alive fifteen million elephants, descended from the first pair.
Seedlings, also, are destroyed in vast numbers by various enemies; for instance, on a piece of ground three feet long and two wide, dug and cleared, and where there could be no choking from other plants, I marked all the seedlings of our native weeds as they came up, and out of the 357 no less than 295 were destroyed, chiefly by slugs and insects.
Climate plays an important part in determining the average numbers of a species, and periodical seasons of extreme cold or drought, I believe to be the most effective of all checks. I estimated that the winter of 1854-55 destroyed four-fifths of the birds in my own grounds; and this is a tremendous destruction, when we remember that ten per cent. is an extraordinarily severe mortality from epidemics with man.
When I ascertained that these young trees had not been sown or planted, I was so much surprised at their numbers that I went to several points of view, whence I could examine hundreds of acres of the unenclosed heath, and literally I could not see a single Scotch fir, except the old planted clumps. But on looking closely between the stems of the heath, I found a multitude of seedlings and little trees, which had been perpetually browsed down by the cattle. In one square yard, at a point some hundred yards distant from one of the old clumps, I counted thirty-two little trees; and one of them, judging from the rings of growth, had during twenty-six years tried to raise its head above the stems of the heath, and had failed. No wonder that, as soon as the land was enclosed, it became thickly clothed with vigorously growing young firs. Yet the heath was so extremely barren and so extensive that no one would ever have imagined that cattle would have so closely and effectually searched it for food.
lucaspa said:Yes, the calculation was an assumption. The assumption was "no mortality". And what we are saying is that
assumption is wrong. There is mortality.
lucaspa said:Another assumption you didn't state but that is implicit is an unlimited food supply. We know that is wrong.
lucaspa said:Again, you don't need catastrophes.
lucaspa said:Just look at all the seeds produced by ANY of the trees in your yard. Look at the number of mosquitoe eggs laid by a SINGLE female and apply your calculations to it.
you are assuming it is better get raw facts.lucaspa said:IF ALL those offspring survive, your calculations would have the world filled with mosquitoes in less than 10 years and oak trees in less than 10,000.
lucaspa said:Apply your calculations to elephants today and their birth rates. As slow as they are -- one calf in two years -- if all of them survived and also reproduced at that rate the world would be full of elephants in 3,000 years. Yet we haven't had a major catastrophe within that time to stop them..
conclusions basing on assumptions are rather guessing or doubtslucaspa said:The conclusion is that the death rates equal the birth rates and the population is stable.
lucaspa said:Causes of the recent population growth of humans and why extrapolating this backwards is invalid:
http://www.ecology.com/ecology-public-health-deborah-glik/population/population1.htm
In a finite world with limited resources, no population can grow forever.1. Population Growth (See 4 Handouts) -Population increases by birth (+ immigration) -Population decreases by death (+ emigration) -(r)Intrinsic or Instantaneous rate of increase or Malthusian parameter(r) = Instantaneous rate of change in population size per individual (r) = species specific (r) = average per capita birth rate (b) - average per capita death rate(d)
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(r) = b d (assume immigration and emigration cancel each other out)a. Exponential Growth Type of Explosive population growth -Mathematical Formula: ?N/?T = rN-Shows J-shaped curve. -Occurs when : 1. b > d, 2. Unlimited resources 3. No population regulation factors 4. Unrestricted growth under ideal conditions 5. We rarely see this type of growth for long in the real world. Popualtion growth rates eventually slow down. b. Logistic Growth -Mathematical Formula: ?N/?T = r(K-N/K)N -Type of population growth seen in most populations -Shows a S (Sigmoidal)shaped curve -Accounts for population. density via (K) Carrying Capacity which is the maximum # (N) of individuals the environment will hold. -Carrying capacity is determined by the amount of resources and other limiting factors in the environment. Populations usually fluctuate around K. -Each individual reduces the intrinsic rate of increase. -What happens to r when N=K ? Zero population growth -Some problems with the logistic model: 1. Populations usually fluctuate around K due to time delays or delayed responses to each added individual (e.g., effect of competition on birthrate may not be immediate) 2. K can change when available resources (food , shelter) and limiting factors (predators, disease, competition) change 2. Population Regulation -Population growth is influenced by a combination of density dependent and density independent factors. These factors keep population growth in check. a. Density Dependent Factors:- External factors which limit population growth in a density dependent way.
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-Recognize density dependence if birth rates, death rates or both are affected by population density -In other words, the proportion of individuals influenced by these factors changes with population density-Here are some density-dependent factors: 1. Competition and Food supply e.g., When food supply (e.g., plants) decrease, herbivores decrease, then plants recover, herbivores increase and compete for food, plant populations decreases, and the cycle continues (The more individuals, the less food to go around to each) (Remember my example of the reindeer introduced to St. Paul Island, Alaska. They overgrazed their food supply and this led a population crash).2. Predators e.g., When predator population is low, prey populations, then predator populations increase (as there is more food to go around grow and prey are at a greater risk of being captured) ,this is followed by prey populations decreasing, leading to predator populations decreasing (they starve), etc.(predator-prey oscillations)3. Disease As populations increase, disease causing microorganisms increase, and the cycle continues Disease is spread more easily in larger populations. 4. Waste As populations increase, waste increases. Even wine producing yeast (yeast ferment sugar for energy and make ethanol as a byproduct) can only tolerate 14% ethanol. Waste is a limiting factor. b. Density Independent Factors: -External Factors that limit population growth in a density independent way. -Birth and/or death rates are independent of changes in population density-Same proportion of individuals are affected at any population density -Some density-independent factors: Natural disaster (fire, hurricane), bad weather (i.e., cold spell)
www.esb.utexas.edu/engler/bio304/lectures/lect19.pdf+population+check+ecology+&hl=en&ie=UTF-8
Valen said:The problem about this is a constant at different productivity years this doesn't count valid all the time
Ok lets say the first fishes for example
(fish don't die easily unless of pollution or human interferences)
t = 500,000,000 years ago
d = base on events like catastrophes or being eaten by a fish (but nature balance creates few casualties without man)
good thing for fishes is they normally hatch eggs (Goody goody)
b = what do you mean per day, month or year?
Valen said:A calculation is more currect if all 'real effects' are concerned. Science is better if it eliminate all mistakes and remove assumptions. Possibilities are just like a doubt. What we need is hard-core evidences of 2 agreements.
"If catastrophes are real and true in must be included as a data"
you sound vague and must show necessary data
Originally Posted By: lucaspa
IF ALL those offspring survive, your calculations would have the world filled with mosquitoes in less than 10 years and oak trees in less than 10,000.
you are assuming it is better get raw facts.
Originally Posted By: lucaspa
Apply your calculations to elephants today and their birth rates. As slow as they are -- one calf in two years -- if all of them survived and also reproduced at that rate the world would be full of elephants in 3,000 years. Yet we haven't had a major catastrophe within that time to stop them..
discarding other informations..
Originally Posted By: lucaspa
The conclusion is that the death rates equal the birth rates and the population is stable.
conclusions basing on assumptions are rather guessing or doubts
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