14
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 actual data:
Does not look very normally distributed. In fact, the shapiro test confirms this impression:
Shapiro-Wilk normality test
data: df$life_expectancy
...
9
You can access the Imperial College global population dynamics database. They will have time series data at specific locations. http://www3.imperial.ac.uk/cpb/databases/gpdd
There is a sister database as well that might be useful. http://lits.bio.ic.ac.uk:8080/litsproject/
These contain several hundred time series, and you can see a paper that used them ...
9
Are you looking for 'Home range' (see also the definition in Encyclopaedia Britannica)? Generally, 'home range' is defined as the entire area an individual animal uses, while the 'territory' is the subset of the home range that is actually defended from conspecifics (in animals that show territoriality). 'Home range' is often delimited by the types of ...
9
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-functional.
In fact, it is important that the sperm are functional and simply contain dominant-lethal mutations at a sufficient probability (Robinson, 2005 ...
8
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 genetic drift will occur.
"...the smaller number of males still contributes half of the genes in the next generation..."
In other words, assuming the male ...
7
There are a number of things to clarify here; Fecundity is the number of offspring that is produced by an individual, and this can be separated into potential fecundity (maximum reproductive capacity) and realized fecundity (number of offspring actually produced). Realized fecundity is very similar to fertility, which is defined as the number of viable ...
7
Here is my full derivation to the book example you gave, hopefully it'll help you clear up what went wrong:
You need to remember that after there is selection acting on the population, you no longer have a total of 1 after selection. Think of selection as "killing" individuals, which means the total is now 1 minus what has been "selected out". sy is what is ...
6
Your calculations are the following. Assuming non-overlapping generations, the number of ancestors you have in the last $t$ generation is given by:
$$\sum_{i=1}^t 2^t$$
This sounds correct. But there are some very strong assumptions:
Generations are non-overlapping. A more realistic model would need to consider $t$ as a continuous variable a give a ...
6
To me, there are two issues that are mixed up here (if I understand you correctly). First, do you want to estimate the mean and variance for a statistical population (i.e. to characterize a larger population by independent samples), or do you want to calculate the actual density for a particular area, where you have counted all occurences in that entire area ...
6
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 a number of hours (more-or-less true in a real
culture)
In your original model you are using discrete states and fixed time steps. So, if 30 min is one time ...
6
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 $i$) x (breeding probability given that survival).
Making this continuous converts the equation to
$$
\begin{split}
& \int_0^\infty bp \cdot S^i \, di \\
= \...
6
I think your explanation is correct. The expected value of the exponential distribution is:
$$t \sim \text{e}^{-\lambda t} \implies \langle t \rangle = \int_0^\infty t \ \text{e}^{-\lambda t} \; \text{d}t = 1/\lambda.$$
For the exponential survival function, we have to identify the parameter $S$. Since $S$ is the number of survived individuals after one year,...
6
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 this sort of information over the next few years.
We do know the history and evolution of a limited number of viruses. Included in this are some of the common-...
5
According to Hartl & Clark on population genetics:
"Population genetics deals with Mendel's laws and other genetic
principles as they apply to entire populations of organisms.... also
includes the study of the various forces that result in evolutionary
changes in species through time."
According to Conner & Hartl also on population genetics:...
5
The genetic load is a population construct, a way of quantifying the fitness reduction in a population due deviations from the optimal genotype.
One type of load comprises all the others, namely genetic load.
Genetic load is just the loss of mean fitness relative to the ideal fitness.
You forgot to include substitution load in your list, but ...
5
To avoid confusion I just want to add to fileunderwater's answer the equivalent words we use to describe the "area size a population/species lives in".
The spatial range a single individual occupies is generally called home range or territory (as fileunderwater said before me).
The spatial range a single species (or population) occupies is called ...
5
A Poisson process follows these postulates:
$\lim\limits_{h\to0+}\frac{P(N_h=1)}h=\lambda$ i.e. the probability of occurrence one event in a very small interval of time is equal to the macroscopic rate or intensity ($\lambda\,$).
$P(N_h\geqslant2)=o(h)$ i.e. the probability of occurrence of more than one events in an infinitesimal interval is essentially ...
5
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 about in interpreting this:
each species has a negative effect on the other (i.e., increasing the density of either species lowers the other's population growth ...
4
It is certainly possible as yes, rapid population growth will reduce LD. From Slatkin, 1994:
In a rapidly growing population, however, there will be little chance of finding significant nonrandom associations even between completely linked loci if the growth has been sufficiently rapid.
Or Nature Reviews, 2002
Przeworski... showed that population ...
4
Genetic drift is the change of allele frequencies in a population due to random sampling during reproduction. This can cause some allele combinations to become more or less common than would be expected without drift, thus creating a disequilibrium. However, it's the combination of genetic drift AND selection that generates negative (instead of positive) ...
4
An easy way to visualize the mistake in your thought experiment is to consider a bottleneck event, when the ancestral population was very small, maybe just a few individuals. This would mean that the entire current population is descending from just a few individuals. Your thought experiment is assuming that the "pyramid" of your ancentors is expanding all ...
4
As long as members of a generation "randomly choose" their ancestor in the previous generation the law of independent probability (your equation) will hold.
Any study of coalescent theory begins with the Wright-Fisher model. The assumptions are:
finite diploid population of constant size N,
non-overlapping generations (simultaneous reproduction),
...
4
Recap of the question:
Looking at a single locus trait ($A$) controlled by two alleles, $A_1$ and $A_2$, the phenotypic mean is only affected by inbreeding depression, $f$ (Wright's inbreeding coefficient), if there is some degree of dominance, $d$. Why?
Answer:
If we take inbreeding as a higher than expected frequency of homozygotes, such that if the ...
4
Could not fit in a comment....
To make sure we all understand your question...
Is your question how many (eukaryote) species are currently living? or How many (eukaryote) cells are currently living??
Just a hint to answer the question
Micheal Lynch, in his book (On the Origin of Genome Architecture) at page 3, Box 1.1 tries to answer the question How ...
4
Note: This is not an area where I know the litterature well
Where are many counteracting processes to consider for this question. For instance, the rate of evolution will be affected by the rate of mutation, the distribution of positive and deleterious mutations, strength of selection, whether the fitness effects are small or large, if fitness effects ...
4
First of all, the $\mu$ is not expected time for a mutation to occur and get fixed; it is the rate at which mutations are fixed in the population. The basic result states that if neutral mutations arise at a locus at rate $\mu$ within individuals, mutations at this locus will be fixed in the population at rate $\mu$ as well.
The expected time for a given ...
4
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 $d$ is the number of islands ($d$ stands for "deme"). As $d \rightarrow \infty$, $\left( \frac {d}{d-1} \right) ^2 \rightarrow 1$ and Slatkin equation becomes the ...
4
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/lancet/article/PIIS0140-6736(16)30054-X/abstract
4
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 data, but it's probably fairly reflective of the world overall) and plotted the number of deaths per 100,000 at each age.
This looks like it makes sense - the ...
4
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 decline without unmanaged forests, can reach 4-10 bats per hectare, and the world population might normally be in 10s of billions, save for the use of pesticides ...
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