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## Biology library

### Course: Biology library>Unit 28

Lesson 3: Population growth & regulation

# Exponential and logistic growth in populations

AP.BIO:
SYI‑1 (EU)
,
SYI‑1.H (LO)
,
SYI‑1.H.1 (EK)
,
SYI‑1.H.2 (EK)
AP.ENVSCI:
ERT‑3 (EU)
,
ERT‑3.D (LO)
,
ERT‑3.D.1 (EK)
,
ERT‑3.F (LO)
,
ERT‑3.F.1 (EK)
NGSS.HS:
HS‑LS2‑1
,
HS‑LS2‑2
,
HS‑LS2.A.1
Learn about population growth rates and how they can be modeled by exponential and logistic equations.

## Want to join the conversation?

• Uhh, there are no questions I see. But (this will be about exponential growth) what if a community of 30 rabbits doesn't reproduce at all but rabbits from all over the world join this community and there's a pattern: the first 5 years the community grows 29% a year for 5 years, the next five years, the population grows only 5% per year, next 2 years population decreases 2% a month then it restarts that cycle. (remember all of the additions are not reproductions). Would this still be considered exponential growth if the whole population dies off in 400 years
• Whether the change in population is caused by reproduction or rabbits from elsewhere joining, the mathematical relationship is the same. The 29% a year for five years and so on definitely indicate an exponential pattern.

I made a computer program that calculates the number of rabbits in a given year according to the pattern you provided, if you'd like to see that: https://www.khanacademy.org/computer-programming/bio-problem/4647796705640448

It appears that the population would not reach zero after 400 years, if that was what you were thinking.
• what is or mean the carrying capacity
• The limit to the number of organisms a region can support.
• Is ❝Malthusian Limit❞ fluctuated by many man made cases like war, unemployment and so on? Are these right that impose to maintain family planing and sterilization both male and female, contribute to reduce high population growth?
• Are density and disperal close to the same thing?
• Do you mean...Dispersal?
Dispersal: the action or process of distributing things or people over a wide area
Density: the degree of compactness of a substance:
• The video said it's multiplying by 10% or 1+0.1, but why add 1? Why not use 10% of 1000?
• Does the population stay the same after they reach compacity?
• If you mean capacity (you typed compacity), then no. The population cycles, meaning it goes above then below the capacity, like a sine function cycling around its midline. This is mainly due to resource availability.
• is it still times 1.1 if you did a 100 instead of 1000