Population Size Analysis
Population Size Analysis - Related Videos
07:03
Analysis of Earthworm Populations in Soil
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2023
Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University Using mustard, Lumbricus terrestris earthworm populations can be sampled directly from soil depths without landscape disturbance or toxicity. Earthworms can then be counted for data and statistical analysis using a bar graph and student’s t-test. Monitoring earthworm populations is a vital technique for environmental scientists, as multiple species of earthworms (most notably those from the suborder Lumbricina) have...
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Population Growth - Student Protocol
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2019
Exponential Population Growth Model ExpandNOTE: In these experiments you will use computer software to simulate different types of growth models. HYPOTHESES: The experimental hypothesis might be that if we increase either R, the reproductive rate or the initial population size, NT, that this will increase the population size after 10 generations in an exponential growth model compared to unmanipulated control populations. The null hypothesis may be that populations of different R and initial...
04:45
Population Growth - Concepts
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2019
Population Models An ecological population is a group of individuals of a single species living in an area at the same time. To persist, a population must either grow or maintain its size. Population ecology is the study of how population size and age distribution change over time through interactions with other species and the environment as well as with individuals of their own species. A particularly important feature that is studied by ecologists is the rate at which a population grows or...
04:51
Size Exclusion Chromatography Based Separation of Bacterial Extracellular Vesicles: A Technique to Separate Heterogenous Population of Gram-Negative Bacterial Outer Membrane Vesicles Based on Their Size
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2025
In this video, we demonstrate a technique–size exclusion chromatography–to separate a heterogenous population of outer membrane vesicles or OMVs derived from bacteria. These vesicles are nanosized spherical structures and are separated into large and small subpopulations based on their size through Size Exclusion Chromatography.
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Conservation of Small Populations
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2019
Small population sizes put a species at extreme risk of extinction due to a lack of variation, and a consequent decrease in adaptability. This weakens the chances of survival under pressures such as climate change, competition from other species, or new diseases. Large populations are more likely to survive pressures such as these, as such populations are more likely to harbor individuals that have genetic variants that are adaptive under new stresses. Small populations are much less likely to...
FAQs
Detectability determines whether an observation reflects the actual population or only the individuals that were noticed. Researchers therefore use approaches such as repeated observations, distance sampling, or mark-recapture to account for members that remain unseen. Addressing detectability makes estimates more reliable and improves comparisons of population density or change across habitats and sampling periods.
Mark-recapture uses repeated observations and the proportion of marked individuals found during later sampling to estimate the number of unobserved members. A higher proportion of marked individuals among later observations indicates that a larger share of the population has been encountered, whereas a lower proportion suggests more individuals remain unseen. This supports estimates beyond a single count.
Different approaches provide complementary evidence about a population. Direct censuses can record observed individuals, while quadrat surveys and distance sampling organize observations within defined sampling contexts. Comparing these results helps researchers assess density and distribution while accounting for the difficulty of observing every member. The combination is useful when one observation strategy alone may not describe the population adequately.
Researchers first define the area or habitat being studied, then select a direct census or sampling approach suited to the population and observations available. They collect repeated observations when needed, apply the relevant information about marked or unseen individuals, and examine density, distribution, or change over time. This workflow produces evidence for interpreting population status and dynamics.
It is useful when researchers need to identify population declines, evaluate conservation interventions, or assess how habitat conditions may influence future populations. Estimates of density and distribution can guide habitat management, while measurements repeated over time reveal whether a population is changing. These results help connect management decisions with observed population responses rather than isolated counts.
Population estimates provide information about how many individuals occupy a defined habitat and how that number changes over time. In disease-transmission studies, this supports examination of population patterns relevant to spread. For sustainable harvesting, estimates help characterize population status and trends, providing evidence for judging whether continued removal may be compatible with maintaining the population.