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One plant becomes two, two become four… Can a population keep doubling for ever?
Population Dynamics lab · Last updated: 16 October 2026
One plant becomes two, two become four. Can a population keep doubling for ever? In this 3D lab, you watch numbers explode and then see limits such as food and space bring growth under control. It explains how bacteria spread, why pests boom and how ecologists predict populations.
What you'll discover
- Doubling grows numbers astonishingly fast: ten doublings turns one into over a thousand.
- Limited food, space and other resources slow growth as a population gets crowded.
- Many populations level off near the largest number their habitat can support, called the carrying capacity.
The science in plain words
When every individual can produce offspring, a population can grow by multiplying rather than adding. If it doubles each generation, one becomes 2, 4, 8, 16 and so on. After ten doublings there are 1,024, and after twenty there are more than a million. This is called exponential growth. Some bacteria, given warmth and food, can divide roughly every 20 minutes, so a single cell could in principle become billions in a day.
In the real world this never lasts. As numbers rise, individuals compete for food, water, light and space. Waste builds up, diseases spread more easily and predators find prey more often. Births slow and deaths rise, so growth gradually tails off. The population tends to level out near the carrying capacity, the largest population the environment can support over time. Plotted on a graph, this gives an S-shaped curve: slow start, rapid rise, then a plateau.
Populations can also overshoot the carrying capacity and then crash, especially if the food supply recovers slowly. Ecologists use these models to manage fisheries, control pests and protect endangered species, and similar mathematics describes how infections spread.
Where it fits
- India, NCERT: Population growth models go beyond the NCERT syllabus for classes 6 to 10; the lab builds on Class 10 Our Environment.
- United States: Grades 6 to 12
- Next Generation Science Standards: MS-LS2-1, HS-LS2-1
Common questions
What is exponential growth?
Exponential growth is when a quantity grows by multiplying by the same factor each time, such as doubling. It starts slowly and then shoots upwards. Ten doublings turn one into 1,024, and twenty doublings turn it into over a million.
What is carrying capacity?
Carrying capacity is the largest population of a species that a habitat can support over a long time, given its food, water, space and other resources. When a population is below it, numbers tend to rise; when above it, they tend to fall.
Why can't a population grow forever?
Resources such as food, water and space are limited. As a population grows, competition increases, disease spreads more easily and predators find more prey. Eventually births and deaths balance and growth stops, or the population crashes if it has used up its resources.
Related labs
- Predator-Prey Dynamics: Why do hare and lynx numbers boom and crash again and again?
- Natural Selection: Why do living things fit where they live so well? Watch hungry birds change a moth population.
- Fibonacci Spiral: Count the spirals in a sunflower and you find 21, 34, 55… Why does a flower know these numbers?
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Try it yourself
The Population Dynamics lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.