14
votes
Accepted
Is global life expectancy normally distributed?
Let's see!
I took the most recent WHO data from here and did a quick an dirty analysis in R. Here is the histogram as well as a normal distribution with the same mean and standard deviation as the ...
- 1,244
9
votes
How is (Insect) population control through male sterilization effective
Sterile insects are typically produced by radiation. A sufficient dose is used to cause substantial DNA damage in the gametes of the males. However, this doesn't mean the sperm are completely non-...
- 44k
8
votes
Effect of sex-ratio on the effective population size
The reason that an unequal sex ratio affects the effective population size is because offspring are produced by one male and one female parent, and an unequal sex ratio increases the rate at which ...
- 16k
7
votes
Exponential growth equation and bacteria
Considering your assumption:
I'm just looking at the exponential part, where the simple exponential
equation works. If we assume there's sufficient nutrients for bacteria
to grow unchecked for ...
- 35.2k
7
votes
Accepted
Understanding expected mean number of breeding seasons
It's just a continuous version of the discrete calculation. The discrete version is the (infinite series) sum
$$
\sum_{i = 0}^\infty S^i \cdot bp
$$
adding up every (chance of survival to season $i$) ...
- 1,709
7
votes
Understanding expected mean number of breeding seasons
I think your explanation is correct. The expected value of the exponential distribution is:
$$t \sim \text{e}^{-\lambda t} \implies \langle t \rangle = \int_0^\infty t \ \text{e}^{-\lambda t} \; \text{...
- 1,923
6
votes
Accepted
Viruses in human history
We don't know a whole lot about the direct evolution of the genomes of many viruses yet, though as methods for recovery of ancient nucleic-acid sequences improve, I would expect to see increases in ...
- 11.2k
5
votes
Accepted
Mathematical model about the relationship between two animal species
The model you present here is a special case of the Lotka-Volterra competition equations, where the two species have the same effect on each other (i.e., symmetric competition). Some things to think ...
- 5,324
5
votes
What happens to male turkeys?
This article from the humane society suggests that the male-female ratio in wild turkeys is generally 1:1 1.
It's likely that nothing 'happens' to the male turkeys. Possibly you and your family may be ...
- 337
5
votes
Accepted
Can SARS-COV2 strain competition be modelled by inter-species lotka volterra equations?
Presumably by "interspecies Lotka-Volterra equations" you mean the L-V competition equations (the predator-prey version is much better known).
Let's start with a two-strain epidemiological ...
- 5,324
4
votes
How could one calculate the gene flow between two populations?
Theoretical Background
From Slatkin 1991, at equilibrium
$$F_{ST} = \frac{1}{1+4Nm\left( \frac {d}{d-1} \right) ^2}$$
, where $N$ is the per island population size, $m$ is the migration rate and $d$...
- 68k
4
votes
Accepted
What is the global average BMI?
The answer might be a little late, but it was published after you asked the question. See the following publication for estimated global BMI averages from 1975 to 2014: http://thelancet.com/journals/...
4
votes
Is global life expectancy normally distributed?
A few people thought it would be interesting to see what the distribution looked like if we plotted the number of people dying at each age, so I took data from the SSA (which admittedly isn't global ...
- 470
4
votes
Accepted
What are the migratory patterns of Orcas in the Pacific Northwest? Do they pass by Vancouver in the Fall?
There are three ecotypes of orcas which are all members of the same species but tend to display different behaviours, communicate differently and have different prey preference. The most common ...
- 911
4
votes
Have there ever been as many mammals as there are now?
There can be perhaps 10 trillion rodents and bats on the planet, so the humans and livestock probably are small compared to a rainforest rodents and bats. The biggest bat colony is 40 million, they ...
- 10.3k
4
votes
Value of r (intrinsic rate of natural increase)
NCERT shows per capita value is divided by 1000, not hundred (%). So the data you see is 22.50 per thousand! So, the per capita rate is 22.50/1000 = 0.02250 that is almost equal to 0.0205 given in ...
- 41
4
votes
What proportion of the people who lived 1000 years ago have genetic descendants alive today?
Expanding on @heracho's answer and Wikipedia, assume pi denotes the probability of having (exactly) i children, and that dm denotes the probability of extinction by the mth generation (note that this ...
- 141
4
votes
Accepted
What are the long term consequences of settling an isolated territory with an extremely limited gene pool?
Minimum number of individuals needed to start a population
But could just one woman be the progenitor of a healthy nation? And,
if not, what is the minimum number of distantly-related individuals
...
- 2,351
4
votes
Is it possible to determine the initial population given the final one?
For the logistic equation,
$$\frac{\mathrm{d}N(t)}{\mathrm{d}t} = rN(t)\left(\frac{K - N(t)}{K}\right)$$ the solution that allows you to calculate population population size at any time is:
$$N(t) = \...
- 393
4
votes
Accepted
Which approach is the common one in the literature for determining the bacterial growth rate?
The simple logistic function that you are using here is a fine first-order approximation for modeling microbial growth. Both logarithmic and linear scales are reasonable, with different tradeoffs as ...
- 6,977
3
votes
How has the use and subsequent ban of DDT affected insect populations?
The most thorough study on the matter appears to be entitled "Anthropogenic impacts on mosquito populations in North America over the past century". Their broad conclusion is that various mosquito ...
- 535
3
votes
Accepted
What type of Interspecific relationship does this graph depict?
Competition makes the most sense, IMO.
For every other type of relationship, A and B should be dependent and roughly proportional: If parasites kill their host, they die in proportion. If predators ...
- 8,101
3
votes
Guide to learning about Population biology / ecology / dynamics for a non-Biologist
There are three seminal works that will give you an excellent grounding in the study of dynamical systems in population biology.
The first details the foundations of population genetics:
Crow, ...
3
votes
What is the global average BMI?
World Health Organization data
World Health Organization (WHO) is your friend for this kind of question. You can find loads of data on BMI per country, per region, per sex and even see the individual ...
- 68k
3
votes
Was the recent "conservation hunt" of a black rhino supported by science?
Yes it is. Besides Dr. Knights article which is very focused on the issue and describes numerous benefits, there are other sources of research that show this can be good not only for the animals but ...
- 1,152
3
votes
doubt with a multiple choice question
I don't know if this is just me, but I'd consider this a pretty badly worded question. For models of population dynamics, the rate at which the size of a population changes over time is normally ...
- 3,346
3
votes
Accepted
Predator prey interaction
I disagree with GForce's explanation; the meaning is not that growth of prey populations causes instability in predator species.
The sentence is merely saying that without predation, prey population ...
- 16k
3
votes
Accepted
Accurate surveys of urban pigeon and bird populations
You can find population data for lots of species at The Global Population Dynamics Database, which can be used to test and fit population models. When searching for Columbidae (the dove family) I find ...
- 16.7k
3
votes
Accepted
Value of r (intrinsic rate of natural increase)
From the UN database (this info is also reported on wikipedia), the growth rate in India in 2016 was $r=1.019$.
It is computed as $r = \frac{N_{2017}}{N_{2016}}$, where $N_{y}$ is the population size ...
- 68k
3
votes
Accepted
How many giant kelp are there per square meter?
The density of Macrocystis pyrifera is pretty variable. According to Dayton et al. 1984 off of the Southern California coast it can range from less than 0.1 to to 1.0 $individuals/m^2$. The variation ...
- 425
Only top scored, non community-wiki answers of a minimum length are eligible