Population Size
Population Size - Related Videos
14:47
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...
02:04
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...
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.
01:25
The Anchoring-and-Adjustment Heuristic
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2020
In order to make good decisions, we use our knowledge and our reasoning. Often, this knowledge and reasoning is sound and solid. However, sometimes, we are swayed by biases or by others manipulating a situation. For example, let’s say you and three friends wanted to rent a house and had a combined target budget of $1,600. The realtor shows you only very run-down houses for $1,600 and then shows you a very nice house for $2,000. Might you ask each person to pay more in rent to get the $2,000...
FAQs
Population size changes through four demographic flows: births and immigration add individuals, whereas deaths and emigration remove them. The balance among these processes determines whether a population grows, declines, or remains relatively stable over a given period. Tracking all four is important because an increase may reflect movement into the area rather than reproduction within it.
Density-dependent and density-independent effects represent two broad ways environmental factors can regulate growth. Competition, predation, disease, and resource availability are examples of regulating influences, while environmental conditions more generally can also affect populations. Distinguishing these effects helps biologists interpret why growth changes and whether regulation is associated with population density or external conditions.
Population-size data help estimate carrying capacity and assess extinction risk, linking observed numbers to habitat constraints and persistence concerns. Resource availability and environmental conditions influence how many individuals an area can support, while sustained declines may signal greater vulnerability. Considering both measures allows biologists to evaluate population status rather than relying on a single count.
A population-size value is meaningful only in relation to the area, habitat, and time period being studied. Changing any of these reference conditions can alter the number observed without indicating a true biological change. Consistent sampling contexts therefore improve comparisons of growth, decline, environmental responses, and ecosystem change across observations.
Wildlife managers and conservation planners use population-size data to evaluate growth rates, estimate carrying capacity, and assess extinction risk. These measurements help identify whether a population is increasing, declining, or approaching limits associated with its habitat. The same information supports decisions about wildlife management and the planning of conservation actions.
Population size provides context for studying evolution, species interactions, and ecosystem change. Shifts in abundance can indicate changing relationships among organisms or responses to environmental conditions, while comparisons across populations can reveal broader biological patterns. Consequently, population-size data connect demographic observations with research on how species and ecosystems change over time.