Population Cycles
Population Cycles - 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...
09:32
Cell Cycle Analysis
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2023
Cell cycle refers to the set of events through which a cell grows, replicates its genome, and ultimately divides into two daughter cells through the process of mitosis. Because the amount of DNA in a cell shows characteristic changes throughout the cycle, techniques known as cell cycle analysis can be used to separate a population of cells according to the different phases of cell cycle they are in, based on their varying DNA content.This video will cover the principles behind cell cycle...
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...
01:30
Lytic Cycle of Bacteriophages
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2019
Bacteriophages, also known as phages, are specialized viruses that infect bacteria. A key characteristic of phages is their distinctive “head-tail” morphology. A phage begins the infection process (i.e., lytic cycle) by attaching to the outside of a bacterial cell. Attachment is accomplished via proteins in the phage tail that bind to specific receptor proteins on the outer surface of the bacterium. The tail injects the phage’s DNA genome into the bacterial cytoplasm. In the lytic replication...
FAQs
Delayed effects of reproduction can turn population growth into a repeating pattern. When reproduction increases population size, the resulting demand for resources or exposure to predators, competitors, or disease may affect the population later rather than immediately. That lag can allow numbers to continue rising before limiting pressures dominate, producing alternating growth and decline instead of a steady approach to a fixed level.
Resource limitation, competition, predation, and disease can each strengthen or weaken population feedback. Their relative influence affects how rapidly a population increases, when decline begins, and how large the change becomes. Environmental conditions can modify these pressures as well, so the timing and amplitude of cycles may vary across populations or change as climate and other conditions shift.
Predator–prey relationships provide a biological feedback through which changes in one population can influence another. Predation can contribute to rises and falls in population size, making these interactions central to interpreting fluctuations within biological communities. Examining such dynamics helps biologists connect changes observed in wildlife populations with broader questions about regulation, community change, and ecosystem stability.
Biologists examine wildlife survey data collected across time to identify recurring changes in population size or density. They can compare when increases and declines occur, estimate the timing and amplitude of fluctuations, and evaluate whether patterns are seasonal or multi-year. Relating these observations to environmental change helps reveal how conditions influence population regulation.
Comparing cycle timing and amplitude across species shows whether populations respond similarly or differently to environmental conditions. These comparisons can reveal changes in population regulation associated with climate or other environmental shifts. They also help place individual population trends in a broader biological context, supporting interpretation of community change rather than treating each fluctuation as an isolated event.
Population-cycle studies help conservationists distinguish recurring fluctuations from broader changes that may require attention. The same information can support pest-management decisions by clarifying when populations tend to increase or decline. Because cycles also inform understanding of ecosystem stability and predator–prey dynamics, they connect monitoring results with practical strategies for managing biological communities.