The scientific study of short- and long-term changes in the size and age composition of populations and the processes driving these changes.

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83 views

Start studying mathematical biology from basics

I am really passionate about theoretical and quantitative biology and I would like to build my future career around this topic. I've just got my bachelor's degree in biology (ecology) but scince I've ...
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1answer
67 views

What is the outcome of a human population starting with only 2 individuals? [closed]

Starting with a human population N = 2, is there any way the genetic variability seen today could have come about? I don't know that much about meiosis, but isn't there a very limited number of ...
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26 views

Effects on Bear Population [closed]

imagine in a given area or an ecosystem ,bear hunting is totally banned, but there is a scarcity of food for the bears. i want know what would be the future of the bear population?. and want to derive ...
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1answer
40 views

Does a top heavy population grow, decline or stabilize?

Imagine a population that has a larger proportion of older individuals than younger ones, what could possible happen to it in the future? I am guessing that if the older individuals reproduce, the ...
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1answer
32 views

$F_{ST}$ when considering a multi-allelic locus

Sewall Wright defined the $F_{ST}$ in a metapopulation as being: $$F_{ST} = \frac{\text{Var}(p)}{\bar p (1-\bar p)}$$ , where $p$ is a vector of frequencies of a given allele and $\bar p$ and ...
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37 views

$F_{ST}$ and the genetic variance in metapopulations

From this video (21'15''), the speaker gives the following formulae in order to calculate the between and among populations genetic variance from the $F_{ST}$: $$V_{Among Pop} = 2 F_{ST}V_G$$ ...
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1answer
39 views

Various Genetic Loads and their Definitions

In population genetics, we talk about several types of genetic loads (also called just loads). I am asking for a exhaustive list and a short definition. Here are for example some genetic loads that ...
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1answer
73 views

Coalescent theory - independence of coalescent times

Let $T_i$ be the time to coalesce from $n(t)=i+1$ to $n(t)=i$, where $n(t)$ is the number of sites that have not coalesced yet. In the below example the maximum $n(0)=6$. As I understand it, many ...
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35 views

Inbreeding depression and dominance

From this article, second paragraph of the second page A classic theoretical result is that the mean of a character controlled by a single locus $i$ with two alleles $A_{i1}$ and $A_{i2}$ is only ...
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1answer
52 views

Coefficient of relationship and path of coefficient

A path of coefficient of relationship is defined as $$\rho_{AO} = \left( \frac{1}{2}\right)^n \sqrt { \frac{1+f_A}{1+f_O}}$$ This SE post discusses this definition From this, the coefficient of ...
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0answers
26 views

How important is the womb's environment?

Background Talking about one particular phenotypic trait, the total phenotypic variance $V_p$ is decomposed into genetic and environmental variance for this trait, represented by the symbols $V_G$ ...
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22 views

Inbreeding Coefficient and Coefficient of Relationship

Wikipedia gives the following formula to calculate a "path of coefficient of relationship" between an ancestor $A$ and an offspring $O$: $$\rho_{AO} = 2^{-n} \left( \frac{1+f_A}{1+f_O} \right)^{1/2} ...
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1answer
41 views

Defining: Evolutionary (quantitative) Genetics and Population Genetics

How do we define the fields that are Evolutionary (quantitative) genetics and population genetics. What set these two fields apart? Can you try to provide definitions? To my intuitive understanding, ...
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1answer
31 views

Metapopulation structure - book recommendations

What book would you recommend me to study: the dynamics of metapopulations, the structure of metapopulations, the evolution in structured metapopulations? I am not looking for an introduction ...
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33 views

Effects of Genetic Drift on Linkage Disequilibrium

From what I understood of @Canadianer's answer here... Genetic drift randomly causes negative or positive linkage disequilibria, by changing allele frequencies through random sampling. Natural ...
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1answer
25 views

Definition of Linkage Desiquilibrium (LD)

According to [wiki][2], linkage disequilibrium $D$ equals $$D = x_{11} - p_1\cdot q_1$$ where: $$ \begin{matrix} \text{Haplotype} & \text{Frequency}\\ A_1B_1 & ...
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1answer
125 views

Heterozygosity and overdominance

Consider $m$ loci with heterozygote advantage (overdominance) such that the fitness of the two homozygotes is $1-\frac{s}{2}$ and the fitness of the heterozygotes is $1+\frac{s}{2}$, where $s>0$. ...
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1answer
28 views

Coalescent Theory - Probability for $k$ alleles that of one coalescence event occured $t+1$ generations ago

From this textbook Under the wright-Fisher model of genetic drift and under the assumption that all alleles are neutral, the probability that $k$ alleles had $k$ distinct parent alleles the previous ...
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2answers
83 views

Effect on fitness of mutations

What is the distribution/probability density function (PDF) of impacts on fitness of new mutations? I very welcome any partial answer that does not give the whole PDF but just some information ...
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1answer
35 views

Dominance/recessivity of new mutations

What is the distribution/probability density function (PDF) of recessivity/dominance of new mutations? I very welcome any partial answer that does not give the whole PDF but just some information ...
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1answer
49 views

Additive genetic variance with $n$ loci

The genetic variance of a quantitative trait (the quantitative trait in question is fitness) can be express as the sum of two components, the dominance and additive variance: $$\sigma_D^2 + ...
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1answer
81 views

Additive genetic variance with $n$ alleles

The genetic variance of a quantitative trait (the quantitative trait in question is fitness) can be express as the sum of two components, the dominance and additive variance: $$\sigma_D^2 + ...
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2answers
82 views

Initial population when i count backwards?

My question is dealing with how many ancestors it took to produce me: --> to produce me it took 2 people (my parents) = ($2^1$) people = 2 --> one generation further included = ($2^1 + 2^2$) people ...
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1answer
207 views

How do I calculate the change in allele frequency in a haploid population under selection?

From this book For simplicity, let us consider a haploid organism and assume that the frequencies of alleles $A_1$ and $A_2$ are given by $x$ and $y=1-x$, respectively. We also assume that the ...
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0answers
49 views

Effective population size and overlapping generations

From this book; If generations overlap, then the effective population size $N_e$ does not equal the population size $N$. I know mathematical formulations in order to find the effective population ...
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1answer
37 views

Effective population size when the population sizes varies from season to season

Let's think of a species which has four generations per year and which population size changes from season to season so that the population size is 100 in summer, 200 in spring, 50 in autumn and 20 in ...
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27 views

Linkage disequilibrium with $n_l$ loci $n_a$ alleles

Linkage disequilibrium $\left(D\right)$ for two bi-allelic loci is defined as: $$D=X_{11}X_{22} - X_{12}X_{21}$$ , where $X_{11}$, $X_{12}$, $X_{21}$, X$_{22}$ are the frequencies of the haplotypes ...
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55 views

Selection on linked loci in a diploid population

Let’s consider two linked loci $A$ and $B$ that are both bi-allelic. In consequence, we have four different possible haplotypes $A_1B_1$, $A_1B_2$, $A_2B_1$, $A_2B_2$, which frequencies are $X_1$, ...
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4answers
182 views

What prevents predator overpopulation?

I've often heard that a population, human or otherwise, will continue to grow as long as there is food available (assuming nothing else is killing them off). It makes sense: if you have food you can ...
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1answer
48 views

Why will world population keep growing if all women have only 2.1 children

Why is it that, even if we were going to immediately agree that every women will not have more than 2.1 children on average, the world population would continue to grow for another 60 years? I've ...
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1answer
78 views

Hill-Roberston effects and effective population size

From this article, first page, middle of the second column: Even if harmful alleles do not become fixed, they can still reduce the efficacy of selection on neighbouring loci through a process ...
3
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1answer
66 views

Chaos theory and population cycles

I have just begun to read about Chaos theory and have come across the statement that "Period three implies chaos." My question: Does any odd period imply chaos or only 3? If so, how can populations ...
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1answer
120 views

Why do genetic drift generates negative linkage disequilibrium?

The very first sentence of the abstract of this article are: "In finite populations subject to selection, genetic drift generates negative linkage disequilibrium, on average, even if selection ...
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128 views

The Assumption of Weak Selection?

I was reading this question and I failed to fully understand the introductory part of it. The OP (@Artem Kaznatcheev) says: Most analytic models like to assume weak selection because it allows ...
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0answers
54 views

Why did the yeast rise?

Here are the notes I made for an experiment I was doing (I didn't put it here as it is too long) (please ignore the numbers at the end of the pdf file) The graph looks like this: As you see on ...
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1answer
184 views

Population Growth Rate Question?

A population of 600 birds faced a problem of biological magnification resulting in a large number of deaths reducing their population to 350. But 230 births also took place and 21 birds immigrated ...
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1answer
105 views

Population genetics and the fitness probability distribution. Why is the arithmetic mean all we need?

When recording change in allele frequency in diploid, bi-allelic, infinite and panmixic population we usually use this kind of equation: $\delta_p = \frac{p * q *( p (w11 - w12) + q * (w12 - ...
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1answer
111 views

How to classify equilibrium points [closed]

I have the two differential equations: $$\frac{dN_1}{dt} = N_1(2 - N_1 - 2N_2)$$ $$\frac{dN_2}{dt} = N_2(3 - N_2 - 3N_1).$$ I worked out the equilibrium points to be at $N_1 = 0, \frac{4}{5}$ and ...
9
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1answer
267 views

When does weak selection produce qualitatively different results from strong selection?

In evolutionary game theory, it is typical to model organisms as having a base fitness that is modified slightly by the game interaction. The ratio of the game effect versus the base fitness ...
2
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1answer
37 views

Range of feasible coefficients in an unlimited growth model

If you are given an unlimited growth model in the form: $\frac {dP(t)}{dt} = k P(t)$ Obviously the population growth would never be unlimited, but let's presume for the moment that we are ...
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2answers
2k views

How many organisms have ever lived on Earth?

I've looked for some information on this, but couldn't find anything useful. Has there been any noteworthy attempt to estimate the sum amount of individuals of all species that have ever lived on ...
9
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1answer
85 views

Vaccination and population dynamics of an epidemic

I'm trying to figure out how should a vaccination model be built to correlate with population density, and I'm having problems to understand meanings of the results I receive when I apply theory on ...
3
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2answers
544 views

Does finite rate of increase depend on mortality of individuals in a population?

As written in my lecture handouts, there two main factors in the Geometric Growth Model of populations: $R_{0}$ is the expected lifetime reproductive output. This way, for unicellulars, for example, ...
6
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1answer
123 views

Genetic Diversity and Adaptation

I am somewhat new to evolutionary biology, having studied it on my free time as a computer science student. There is one particular thing that has always bothered me for which I have not seen a good ...
9
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1answer
698 views

How does population stability evolve?

The number of individuals constituting a population is called population size. Over time population size does not remain constant, it fluctuates to different extent over generations because of ...
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3answers
218 views

When are population dynamics models useful?

When are population dynamics models useful? There seems to have been a lot of research about it, but how does it help? If I need data about how a population will evolve under what conditions, I need ...
9
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1answer
2k views

How many mice are on the Earth?

We are 7 billion human beings on the Earth. But how many mice are there? How would you estimate such a number?
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376 views

Smallest viable reproducing population

What is the smallest viable reproducing population, such as in a human population. By viable I mean a population which keeps genetic defects low (enough). A very strongly related question: what is ...