---
title: "Population Growth Curves and Carrying Capacity"
description: "In a logistic growth model, population growth slows as resources become limited. Carrying capacity is estimated from a sustained population level. Density-dependent and density-independent effects are"
canonical: https://lightmysky.com/learn/science/population-growth-curves-and-carrying-capacity-mt_KX6rhHF5kj
source: https://lightmysky.com/learn/science/population-growth-curves-and-carrying-capacity-mt_KX6rhHF5kj.md
retrieved: 2026-11-12
---

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# Population Growth Curves and Carrying Capacity

In a logistic growth model, population growth slows as resources become limited. Carrying capacity is estimated from a sustained population level. Density-dependent and density-independent effects are distinguished by how their effect per individual changes with crowding.

Subject: Science · Area: Organisms & Life Processes · Ages 17 to 18
Page: https://lightmysky.com/learn/science/population-growth-curves-and-carrying-capacity-mt_KX6rhHF5kj

## Ready when they can

- Labels the phases of a growth curve and explains what limits each one.
- Distinguishes a density-dependent factor from a density-independent one with an example of each.
- Estimates carrying capacity from a plotted curve.

## Lesson: Boom, Brake, Balance

*(drawing: Culture phases at equal intervals. Nutrient shortages or waste limit growth; new cells roughly balance deaths at stationarity. Wild populations may lack lag.)*

Carrying capacity K is the largest population a habitat's resources support over time. Closed cultures may decline after nutrients run out. Without migration, stable numbers mean births roughly equal deaths.

**Example.** In a separate stable woodland, annual rabbit counts settle at 498, 502, 500 and 501, suggesting K near 500. Use the sustained level, not the start or fastest rise. The culture's brief plateau alone cannot establish K.

Density is individuals per area or volume. Density-dependent effects change with density, measured per individual or fraction affected. Crowding can intensify competition for food, space or nitrates, disease, predation and waste, reducing survival or reproduction.

Density-independent effects do not change with density when measured per individual. This covers survival and reproduction. Unchanged death risk from a flood is one example. Compare equal-sized areas at different densities; total deaths alone cannot classify effects. Weather and crowding can interact.

**Example.** Exponential models are J-shaped without resource limits. Hourly bacterial doubling in rich broth lasts only while nutrients remain. Logistic growth from well below K slows toward K in an S-shape. Yeast can show this pattern temporarily; real populations may differ.

**Example.** A deer herd can stop growing in grass-covered fields. Grass cover does not establish suitable food. Food quality, disease or predators may limit growth; counts cannot identify causes. Seasons, habitat damage and competitors can change K.

**Recap.** Logistic growth slows toward carrying capacity K. Classify limiting effects by how they change with density. Real populations can grow, level off or decline.

*Original lesson, questions, worked solutions and flashcards written for this dataset.*

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [The Nitrogen Cycle and the Microbes That Drive It](https://lightmysky.com/learn/science/the-nitrogen-cycle-and-the-microbes-that-drive-it-mt__K1J47NhWj)

## Opens up

- [Succession from Pioneer to Climax Community](https://lightmysky.com/learn/science/succession-from-pioneer-to-climax-community-mt_3s3dVLP0Lf)
- [Life-History Trade-offs and How Reproduction Is Allocated](https://lightmysky.com/learn/science/life-history-trade-offs-and-how-reproduction-is-allocated-mt_eGwlydfDWO)
- [Microbial growth: generation time, growth curves and continuous culture](https://lightmysky.com/learn/science/microbial-growth-generation-time-growth-curves-and-continuous-culture-mt_ltzgjIBytk)
- [Demography: life tables, age structure and what they predict](https://lightmysky.com/learn/science/demography-life-tables-age-structure-and-what-they-predict-mt_raWfdLLACU)
- [Competition, Niches and What Allows Coexistence](https://lightmysky.com/learn/science/competition-niches-and-what-allows-coexistence-mt_VS9Yud3rCQ)