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I'm looking for a website that shows the population sizes of a species (doesn't matter which) as a function of time at a geographic coordinate. Is there a government website or other free database with such information?
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 here: http://onlinelibrary.wiley.com/doi/10.1111/j.1461-0248.2011.01702.x/abstract
Theoretical Population Biology
An interdisciplinary journal, Theoretical Population Biology presents articles on theoretical aspects of the biology of populations, particularly in the areas of demography, ecology, epidemiology, evolution, and genetics. Emphasis is on the development of mathematical theory and models that enhance the.
An interdisciplinary journal, Theoretical Population Biology presents articles on theoretical aspects of the biology of populations, particularly in the areas of demography, ecology, epidemiology, evolution, and genetics. Emphasis is on the development of mathematical theory and models that enhance the understanding of biological phenomena.
Articles highlight the motivation and significance of the work for advancing progress in biology, relying on a substantial mathematical effort to obtain biological insight. The journal also presents empirical results and computational and statistical methods directly impinging on theoretical problems in population biology.
Further elaboration on the aims and scope of the journal appears in an editorial.
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Population growth is defined as the percentage increase in a population over a given time period.
First, the initial population must be determined. For this example, the initial population size is estimated to be 10,000.
Next, you must calculate or estimate the growth rate. This is typically a growth rate per year in percent, but it can be any period length the problem calls for. For this problem, the growth rate is found to be 12% per year.
Next, you must determine the total number of years or periods that the growth occurs for. In this example, the growth occurs for 5 consecutive years.
Finally, the final population amount can be calculated using the formula above. Plugging in the information from the steps above, the final population is calculated to be 17958.56. Sometimes these numbers are rounded to the closest integer because you can have half a person.
In this next problem, we will look at a case in which the population grows on a shorter time scale of a month.
The initial population is given as 10,000. the growth rate is 15% per month, and the length of growth is 20 months.
Using the same formula as before, the growth of the population is found to be 163,666. In this problem, we can really see the effect of compound growth.
Population growth is the increasing growth of a population due to reproducing.
A population growth rate is a rate at which a population increase every year, or per time period that is being analyzed.
Typically population growth is exponential, however, at some point, all populations hit a tipping point where they cant support their growth rate any longer due to many factors including health and food supply.
Measure of the Total Population Structure and Size
Crude rates: A crude rate is used to describe the frequency of a demographic event across the total population, without regard to age or sex. The standard reference period is one year. Because the population is usually not the same at the beginning and end of the year, the denominator for crude rates is the average of the population at the beginning and end of the one year period. The numerator is the number of vital events (e.g., births, deaths) observed for the total population in the specified calendar year.
Crude Birth Rate (CBR): # of births per 1,000 persons in a population over a given period of time (i.e. 1 year). This rate is most often used when looking at fertility, though the crude measure does not account for important variations in population fertility such as sex ratios, age distributions, postponement or acceleration of marriage age, all of which can alter the way that the crude rate should be interpreted.
Example: In the town of Kolikouro, Mali, there were 5663 births. The total population was 149,442. The CBR is:
5663/149,442 * 1000 = 37.9
Ranges of CBR:
Crude Death Rate (CDR) : # of deaths per 1,000 persons in a population over a given period of time (i.e. 1 year). CDR is calculated in the same way as for CBR, but with deaths instead of births as the numerator.
Ranges of CDR:
crude r (rate of growth of a population) &ndash Among locales where an estimate of the total population is available each year, estimating the growth of a population requires little more than dividing the change in population at the end of the year by the population at the beginning of the year. However, for most settings, vital statistics are collected during censuses only every few years. For these cases, we can estimate the average yearly population growth using the following formula, and solving for r.
Pt = P0 * e rt where:
Pt is the population # at the last year for which there is data
P0 is the population # at the first year for which there is data
e is the natural logarithmic constant
r is the unknown annual rate of growth
t is the number of years between Pt and P0
Example: In 1950, the population in thousands for the Dominican Republic was 2,353. In 2000 (50 years later), it was 8,353. The rate of growth is estimated as follows:
8353 = 2353*e **r(50)
8353/2353 = e** r(50)
Take logs and re-arrange, to:
(ln 8353 &ndash ln 2353 ) /50 = r
r = 2.54
Ranges of r:
Crude net migration rate &ndash This rate illustrates the change in the population as it is affected by people moving in and out of a country or other specified locale. To calculate this rate, one would need to know both the number of people that immigrated to (moved into) a country or the designated district/subnational area and the number of people that emigrated from (moved out of) a country or the designated district/subnational area. Then the crude net migration rate can be calculated using the following formula:
Crude net migration rate = I &ndash E / P * 1,000
I is the number of immigrants or in-migrants
E is the number of emigrants or out-migrants
P is the total midyear population of the country or designated area.
Example: In 2002, a central African nation had 8,320 immigrants and 7249 emigrants, according to their international arrivals and departure statistics. The total population (June 2002) was estimated as 1,258,000. The NMR is (8,320-7249)/1258000 * 1000 = 0.85
Accurate and complete data on immigrants and emigrants is very difficult to obtain. Immigrants may be incompletely observed because countries may keep track of airplane arrivals, but seldom of all arrivals. Further, they may only note permanent resident visas, and not the conversion of visitors to residents. Forced immigrants may only include those requesting asylum, and not all forced migrants. There also are problems with the reporting of emigrants. Few governments know when people have left permanently, and they may only track departures by mode of transport (air, bus, car). Even these reports are likely to be grossly underestimated, particularly for settings with significant forced refugee movements when people cross at unregulated borders or times. Interpretation of the NMR is also problematic, as a low figure can result from low levels of movement or from high counterbalanced in and out flows. For this reason, it is generally preferred to calculate two separate crude migration rates: Crude In-migration rate (I/P * 1000) and Crude Out-Migration rate (E/P * 1000).
Ranges of NMR:
Specific Rates: As noted above, population events, particularly vital events such as births or deaths, do not affect people in all age groups in the same way. Age-specific rates are used to show the different probabilities of demographic events for each age group. Age specific rates are typically calculated for 5 year age groups, but as noted above in the discussion of age structure, these may be aggregated for several age groups where the rates do not vary much between age groups. The numerators for specific rates are the numbers of events observed in a one year period for the denominator population, namely the total population in the requisite five year age group at the beginning of the observation year. For example, the ASFR for women 20-24 would be the total number of births recorded in the given calendar year for women 20-24 divided by the total number of women 20-24 at the beginning of the calendar year.
Specific Mortality Rates &ndash Mortality rates that distinguish between different age groups help to inform public health practitioners about different kinds of health concerns. Very high death rates among children under 1 year of age may require a very different intervention than would very high death rates among adults over 70 years of age. If unfavorable changes in the crude mortality rate alone is used to gauge the health of a population, than important differentiations and programmatic responses would be impossible.
Age Specific Death Rates (ASDRs)- In describing population phenomenon like mortality, rates are often calculated for specific age groups of the population to gain a more sophisticated picture of how the population is changing over time. This is especially important for gauging the efficacy of health interventions that are targeted at specific segments of the population such as children or the elderly. They are usually expressed per 1000 persons.
Age Specific Death Rates are the number of deaths experienced in a single year by the specific age and sex group at risk for those deaths. The population at risk is assessed as the mid-year population. The formula is as follows:
D = deaths
P = population
i = age group
j = sex
Example: In 1997-99, in a neighborhood in Dar es Salaam, Tanzania, there were an average of 29 deaths for males 5-9 years of age and 39 for females 5-9 years of age. At this time there were 11,525 males and 11,657 females. The ASDR for the 5-9 year old cohort are calculated as follows:
ASDR 5-9, M = 29/11525 * 1000 = 2.5
ASDR 5-9, F = 39/11657 * 1000 = 3.3
Examples of Directional Selection
Also known as Galapagos finches, these little birds where of particular interest to Darwin while he was on his famous discovery expedition. Darwin noticed that the species on different islands where remarkably varied, while undeniably coming from the same source. In recent years, scientist Peter and Rosemary Grant have been studying the finches. In the past thirty years, they have witness all sorts of selection on the finches and the evolution that ensued. In one very drastic example of directional selection the Grants observed as birds with larger beaks were selected for, after only one season of an extremely drastic form of directional selection.
Industrial Revolution as a Directional Selection
While many only know the Industrial Revolution from history books, it became an important part of biology when scientists started studying the changes that humans create in the environment. In 1811, during the earliest years of the industrial revolution, the first black peppered moth was found. Typically, peppered moths were lightly colored. The two varieties can be seen together in the image below, with the lightly colored moth on the right.
However, as the industrial revolution progressed, more and more of the dark moths were seen. The reason for this increase has been traced to a directional selection applied by the industrial revolution. During the industrial revolution, dust, soot, and pollution increased drastically in large cities. In these cities, almost no lightly colored moths were found. In forests far from large cities, the lightly colored moths were predominant. Many experiments on the evolution and ecology of these moths has shown than an increase in the number of dark moths is due to their increased success in avoiding predators. Lightly colored moths on sooty, dirty buildings are easy to spot, and predators quickly eat the lightest moths. The directional selection exists both ways, as industry selects for dark moths in cities and white moths in the woods. Therefore, if the entire population of moths is considered, this could also be an example of disruptive selection. At the level of each city, it is a directional selection, because only the dark variety of moths are selected for.
How do you calculate population growth?
We calculate population growth by looking at the change in population over time.
We calculate population growth by looking at the change in population over time. The formula for population growth is below:
Learn about Euler's number here or here.
For example, if we have a population of zebras in 1990 that had 100 individuals, we know the population is growing at a rate of 5%, and we want to know what the population is in the year 2020, we would do the following to solve:
#=100*e^(.05*30yrs) # **note that this is .05 multiplied by 30
We multiply .05 by 30 years. Then we raise e by that result (1.5). Our last step is to then multiply 4.48 by our original population, which is 100 individuals.
Our answer is 448 individuals. So, from a population of 100 individuals in 1990, if that population is growing at a rate of 5%, we will have 448 individuals in the year 2020.
Explore the Beetle Dissection
The outside of beetles can be shiny, dull, or extremely colorful. But what is going on inside of beetles? Take a virtual look inside the body of a beetle with this Beetle Dissection Tool.
Explore on your own or follow our Beetle Dissection Activity. Visit Beetle Dissection Central for more.
Difference Between Population and Community
Population and community are two different levels of biotic assemblages in any ecosystem. These are terms used in ecology, to understand the different ecologically important levels. There are difference characteristics about the two levels and the two should be understood separately in order to identify the difference between those.
Population is a widely used term in many disciplines to refer a closely associated group of one kind. The biological definition for the term population is a group of individuals of the same species living in the same place at a certain time. Since these individuals are of the same species, they usually occupy the same niche in the ecosystem with similar habits and habitats. Usually, the individuals in a certain population do interbreed in order to maintain the population size that ensures successful future generations, and their kind is saved. When it is considered in large-scale, a population could be defined as all the individuals of a particular species living in a large geographical area such as a country.
Populations are subjected to change with time according to the environmental changes. These changes take place in terms of the size of the population, which is the same as the number of individuals in the population. When the conditions favour the organisms, the population size increases and goes down otherwise. The success of a particular population could be determined via studying the change of population sizes over a timescale, which could be weeks, months, seasons, years, or decades. Instead of counting each individual in a population, scientists perform sampling techniques to estimate the population sizes. A population consists of all the genes of a particular species, which means the gene pool is represented in the entity of population.
According to the definition, community is the ecological unit that is composed of a group of organisms in different populations of different species that occupy a particular place at a particular period while interacting with both biotic and abiotic environment. It would be easy to understand when it is introduced as a collection of populations living in a particular place at a given time. A community may consist of different species of animals, plants, and microorganisms. The composition of species in a community differs in different ecosystems a particular community in a tropical rainforest shows a higher diversity than community in a desert would.
Since it consists of many different populations, there are many habitats as well as many ecological niches. One particular community is composed of thousands of interactions and relationships within and among populations. When two populations live together in a relationship, it could be mutualism, commensalism, parasitism, or synergism. Those basic ecological relationships or associations result in many ways such as both populations are benefitted, one is benefitted and other is suffered, or one benefits while other has no effect. Predation is another very important ecological relationship taken place in a community that results in a death for one party (prey) while the other party (predator) gets food. There are many food chains functioning inside a community those are important for the energy flow inside the entire ecosystem, which is formed as a collection of communities.
What is the difference between Population and Community?
• A population is composed of a single species while a community has more than one population.
• The number of individuals is higher in a community than in a population of the same ecosystem.
• Individuals in a population can breed to produce fertile offspring but not all the individuals in a community.
• Different populations make a community while few communities would make an ecosystem.
Conditions Leading to Directional Selection
The directional selection phenomenon is usually seen in environments that have changed over time. Changes in weather, climate, or food availability can lead to directional selection. In a very timely example connected to climate change, sockeye salmon have recently been observed shifting the timing of their spawn run in Alaska, likely due to rising water temperatures.
In a statistical analysis of natural selection, directional selection shows a population bell curve for a particular trait that shifts either further left or further right. However, unlike stabilizing selection, the height of the bell curve does not change. There are far fewer "average" individuals in a population that has undergone directional selection.
Human interaction can also speed up directional selection. For example, human hunters or fishermen pursuing quarry most often kill the bigger individuals of the population for their meat or other large ornamental or useful parts. Over time, this causes the population to skew toward the smaller individuals. A directional selection bell curve for size will show a shift to the left in this example of directional selection. Animal predators can also create directional selection. Because slower individuals in a prey population are more likely to be killed and eaten, directional selection will gradually skew the population toward faster individuals. A bell curve plotting species size will skew toward the right when documenting this form of directional selection.
Balantidium (=Neobalantidium) (=Balantioides) coli, a large ciliated protozoan, is the only ciliate known to be capable of infecting humans. It is often associated with swine, the primary reservoir host. Recent molecular analyses have suggested the need for taxonomic revision, and it is now sometimes referred to as Neobalantidium coli or Balantioides coli, although this nomenclature has neither been resolved nor widely adopted in the medical community.
Cysts are the stage responsible for transmission of balantidiasis . The host most often acquires the cyst through ingestion of contaminated food or water . Following ingestion, excystation occurs in the small intestine, and the trophozoites colonize the large intestine . The trophozoites reside in the lumen of the large intestine and appendix of humans and animals, where they replicate by binary fission, during which conjugation may occur . Trophozoites undergo encystation to produce infective cysts . Some trophozoites invade the wall of the colon and multiply, causing ulcerative pathology in the colon wall. Some return to the lumen and disintegrate. Mature cysts are passed with feces.