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Questions tagged [population-biology]

Questions pertaining to populations of organisms.

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1answer
9 views

How to model species interactions on population size dynamic?

Here are two classical discrete time models of population size dynamic. The exponential growth model $$N_{t+1} = r\cdot N_t$$ and the logistic growth model $$N_{t+1} = r\cdot N_t \left(1 - \frac{...
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1answer
45 views

Growth rate oscillation in the a population of non-interacting bacteria

I have come across this theoretical paper claiming that if you start a batch culture from a single E. coli cell, the exponential growth rate of the population defined as $$k = \frac1N \frac{dN}{dt}$$ ...
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0answers
13 views

Finding genotype/allele frequencies of second generation in Hardy-Weinberg equilibrium given that the recessive allele is deleterious [duplicate]

A population in Hardy-Weinberg equilibrium has p=0.6 and q=0.4, and allele q (recessive) is deleterious. If 25% of heterozygous individuals and 50% of homozygous recessive individuals die before ...
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1answer
54 views

What proportion of the people who lived 1000 years ago have genetic descendants alive today?

For context, I've been wondering about this for a paper I'm writing (in philosophy). Really, I want to figure out the chances that someone alive today will end up still having descendants 1000 years ...
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1answer
25 views

Repopullation after a mass extinction [duplicate]

Is it possible to restart the whole human species with less than 10 individual. let say that the whole human species was wipe out of the surface of the earth by a catastrophe only 8 different couple ...
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1answer
36 views

What determines the duration of larval stage?

Why do insects have very long pre reproductive periods and very short reproductive periods? Is there a common characteristic that can indicate the duration of these stages or offer an explanation for ...
4
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1answer
62 views

How to check if a population density obeys replicator dynamics

Say we have a probability vector or population density $p = (p_1,...,p_n)$ with $p_i \geq 0$ and $\sum_i p_i =1$. Also assume we know the functions $g=(g_1,...,g_n)$ such that: $$p_i(t+1) = g_i(p(t))...
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0answers
28 views

How should should I run a yeast experiment where I measure population growth?

Soon I will conduct an experiment involving the population growth of yeast. Nonetheless, I am not sure how long should I let my experiment running for, nor do I know at which intervals should I ...
2
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1answer
47 views

Linkage between chromosomal loci and the Hardy-Weinberg principle

Referring to the Hardy-Weinberg principle, which is always stated with respect to a particular locus on the chromosome, if we observe that two different loci are either always together in Hardy-...
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0answers
87 views

Is there any example, where cooperative behaviour of predators induce fear in prey population?

I am basically from math background and doing Ph.D in mathematical biology. So I am not so efficient in biology. But my problem based on cooperative behaviour of animals during hunting which is ...
2
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0answers
21 views

Sampling of Species counting same member of species twice

As part of the biology class, we performed a sample on the number of red squirrels in a forest a few miles away from the classroom to estimate its population. When we returned to analyse our data, we ...
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1answer
105 views

Impact of Natural Selection on Population Size

I have conducted a lab with my IB Biology 11 class, regarding changes in allele frequencies within generations overseeing the natural selection of an advantageous phenotype. We were looking to ...
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0answers
358 views

Calculate growth rate of a population by Leslie matrix

We can calculate growth rate of a population by calculate the dominant eigen value of a Leslie matrix. What does this growth rate mean? I think that the growth rate N(t+1)/N(t) is depend on the age ...
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2answers
2k views

Can predator-prey relationship be an example of negative feedback?

Predators eat their prey, prey population decreases. This results in the predator population to decrease, so less prey are consumed which causes the prey population to increase. Therefore, if the ...
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1answer
149 views

Why hasn't evolution gotten rid of the appendix yet?

A figure I have recently stumbled upon suggests that about 7% of the world population will, or have, had appendicitis in their lifetime. Cutting out the appendix was impossible until very recently. ...
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1answer
180 views

How is (Insect) population control through male sterilization effective

This is no doubt a simple question. I was reading about Sterile Insect Technique where sterile males out-compete non-sterile ones to mate with females and thus reduce the population. My question ...
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0answers
29 views

How does one calculate Rx/a in population genetics?

The ratio of sex-linked to autosome mutation frequencies (R) is Rx/a =(2/3)(2+ α)/(1+ α) for X-linked genes and Ry/a = 2 α /(1+ α) for Y-linked genes. How does one calculate Rx/a, in order to find α?
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2answers
84 views

Spread of a benign virus in a population over time

This is a somewhat difficult (for me) population dynamics question and I wonder if someone with experience in this area could suggest a reasonable approach? My simplifying assumptions: As a gross ...
3
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1answer
134 views

How to give a biological interpretation to this phase portrait?

Consider the following system and analyze its behavior. $$\begin{array}{rl} \frac{dA}{dt} &= A \left( 2-\frac{A}{5000}-\frac{L}{100} \right)\\ \frac{dL}{dt} &= L \left(-\frac{1}{2}+\frac{...
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1answer
117 views

Mathematical model about the relationship between two animal species

I'd like to relate a mathematical model with two animal species. This is the model: $$ \begin{split} \frac{dN}{dt} & =rN-\frac{rN(N+M)}{k} \\ \frac{dM}{dt} & =r'M-\frac{r'M(N+M)}{k'} \end{...
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1answer
2k views

What does 'per capita births and deaths' mean?

My book says, If in a pond there are 20 lotus plants last year and through reproduction 8 new plants are added, taking the current population to 28, we calculate the birth rate as 8/20 = 0.4 ...
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4answers
10k views

Value of r (intrinsic rate of natural increase)

What is the current value of 'r' (instrinsic rate of natural increase) in India? How do we calculate it? My book says that In 1981, the r value for human population in India was 0.0205. But this ...
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2answers
130 views

Have there ever been as many mammals as there are now?

I apologize for the weird question, but based on a Google search it looks like this topic hasn't been discussed before. I'm hoping that enough information about population biology is stored in the ...
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1answer
635 views

Do death rate and birth rate become equal at replacement fertility rate?

A population transitions from stage 3 to stage 4 when the fertility rate reaches the population replacement level of 2.1. My question is that if the population replacement level reached, shouldn't ...
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0answers
23 views

Could there be latent infections in the human population that we don't know of?

Herpes simplex 1 virus and toxoplasmosis are common infections that that many of use have (65% and 10% of americans, respectively). Both of these are chronic, latent infections that can occasionally ...
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0answers
24 views

Population-biology, migration-patterns, & ethology of the Big Five (elephants, rhinos, lions, leopards, & buffalo) in S. Africa's winter months?

I know that animals are unpredictable, but I also know that there are seasons in which the wildlife are more active. Now, August in South Africa is still their winter season, which is emerging into ...
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2answers
134 views

Is it mostly true that predators or parasites traverse wider spatial areas than their prey or hosts?

Does it tend to be true that as you go up the food chain, the species tend to cover wider areas? I am basically asking whether a population's prey varies spatially more than a population's predators ...
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2answers
568 views

Is there a reliable estimate of the number of cells on Earth?

A quick Google search didn't turn up any reliable sources. An awkward Cosmoquest thread gives a rough estimate of 10^25 to 10^32, but this is just a bad extrapolation of the number of cells in a human ...
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1answer
78 views

How can DNA profiling be used to determine the number of organisms from a specific species that is within a certain area?

Here is the tedious exam question that asks this: question 8(b). https://drive.google.com/drive/folders/0B23NLD5L6099VWJya3dfLVJpbmc The question states: In 2007, the brown bear was a threatened ...
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1answer
1k views

How can I measure bee and wasp population?

Bees and wasps in our garden disappeared suddenly last year - I asked a question about it at Why our bees might have suddenly disappeared. This year, I see that some bumblebees are active now. I'd ...
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0answers
36 views

How many animals inhabit the United States?

How many animals inhabit the United States and its waters? Not the number of species, but the number of individual animals. And since animals are diverse, maybe we can limit the estimate to just ...
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1answer
68 views

Accurate surveys of urban pigeon and bird populations

I've been working on an assignment to develop mathematical models of urban pigeon populations. (As a disclaimer, this is part of a math course, not a biology course). I already understand the ...
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1answer
97 views

Calculation of Malthusian fertility and mortality from birth and death rates

In a simple Malthusian model, the population $p$ grows according to $p = p_0e^{rt}$, where $r = \beta - \mu$, $\beta$ is the "fertility" parameter and $\mu$ the "mortality" parameter. In the case of $\...
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1answer
61 views

What are the migratory patterns of Orcas in the Pacific Northwest? Do they pass by Vancouver in the Fall?

What are the migratory patterns of Orcas in the Pacific Northwest? Do the pass by Vancouver in the Fall? I know you can never predict the sightings of a wild creature, but I was wondering what the ...
1
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1answer
291 views

Parasite - host equations

The Lotka–Volterra equations describe how predator–prey interactions affect population growth. Do these equations describe parasite-host interactions? If not, how would they change by adding these ...
2
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1answer
65 views

Confusion over equations for population's heterozygosity vs. heterozygous individuals

On page 24 of Gillespie's Population Genetics, 2nd ed, an equation for $H$, the probability that two randomly drawn alleles are different by state, is given. $H$ is stated to be similar to the ...
5
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3answers
209 views

Human Demography - Where can I find this statistic?

In "An Introduction to Genetics" by David J. Merrell, copyright 1975 by W.W. Norton + Co., p. 742, in the Chapter "Genetic Counseling and Eugenics," the author states: "... 50% of the women produce 85%...
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2answers
368 views

Predator prey interaction [closed]

I went through a line in my textbook which read: "But for predators, prey species could achieve very high population densities and cause ecosystem instability." I was not able to understand the ...
3
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0answers
110 views

What is the effective population size of a simple two deme metapopulation?

I am confused as to how to compute the effective population size $N_e$ of a theoretical structured population. Let's consider here a simple case study. Imagine a 2-deme metapopulation. Each deme is ...
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2answers
215 views

doubt with a multiple choice question [closed]

Permanent decrease in population would occur due to- A) Migration B) Natality C) Emigration D) Mortality E) Territoriality . It's obvious that C) & D) options are possible . But I'm confused ...
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0answers
59 views

Ecological specialization and relative abundance

I am reading Evolution in Changing Environments by R. Levin but have a hard time. Claim At page 25, Levin says as a conclusion The more efficient a caste at meeting the contingency for which it ...
2
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1answer
293 views

Relationship between genetic diversity within and between species

Here is a quote from Wagner (2008) A second line of evidence [against neutralism] comes from the relationship between the mean number of polymorphic differences between alleles within a species, $\...
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3answers
1k views

Exponential growth equation and bacteria

I'm a microbiologist, but I'm teaching some ecology in my intro-level course, so when we got to population growth, I thought I'd use the example of a microbial population. But, I hit a strange problem ...
4
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1answer
184 views

Guide to learning about Population biology / ecology / dynamics for a non-Biologist

I'm an applied mathematician who works in the field of feedback control systems but has been becoming interested in looking at population biology (e.g. Lotka-Volterra, Mathusian growth,etc.) from a ...
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0answers
39 views

Effective population size of a metapopulation structured on a grid

Scenario Consider a rectangular metapopulation consisting of $x \cdot y$ demes, where $x$ is the number of deme horizontally and $y$ is the number of demes vertically. The population size per deme is ...
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1answer
238 views

Hardy-Weinberg equilibrium generalized to add inbreeding (non-random mating)

Background Quoting from Gillespie's book The level of inbreeding is measured by the inbreeding coefficient, $F_I$, which is the probability that two alleles in an individual are identity by ...
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0answers
71 views

Evolution of parasite into ideal parasite [duplicate]

An ideal parasite is a parasite which thrives within a host without harming it (according to my NCERT textbook). Then, quite obviously, why hasn't that happened yet? I mean, natural selection can ...
3
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1answer
966 views

What type of Interspecific relationship does this graph depict?

The other day in class, our AP Biology teacher presented us with the following graph and asked us to determine which of the following interspecific relationships it represents: (A) ...
8
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1answer
2k views

Effect of sex-ratio on the effective population size

As stated on this wikipedia article, the effective population size $N_e$ when the sex ratio differs from $\frac{1}{2}$ is $$N_e = \frac{4N_mN_f}{N_m+N_f}$$ I understand the biased sex-ratio ...
3
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1answer
134 views

Parametric Bootstrap Capture Recapture

I am using the (one sample) capture recapture for estimating hidden human population. One sample method uses purely frequencies of capture to estimate population. One of my colleague suggested ...