Question

Which statement about carrying capacity is false?

	A.	Per capita growth rate is negative when the population is below the carrying capacity.
	B.	At carrying capacity, r = 0 and populations stop growing.
	C.	Carrying capacity is the number of individuals that the environment can support indefinitely.
	D.	Technology has increased Earth's carrying capacity for humans.
	E.	The carrying capacity of a particular environment can fluctuate over time.

Answer 1

In an ecosystem, with the presence of many other species and many abiotic conditions, a given population will have an upper limit that cannot be exceeded. Such a limit is called the carrying capacity of the environment for the population. It can be defined as the maximum number of individuals an environment can sustain indefinitely provided there is enough food, water, and other necessities in the environment.

During logistic growth, the intrinsic rate of natural increase (r) is progressively reduced as population size increases towards the carrying capacity. Hence, during this, unlike exponential growth, population growth is not constant and r decreases as population increases until r = 0 at carrying capacity.

Hence, the statement “at carrying capacity, r = 0 and populations stop growing” is true.

Thus, option b is incorrect.

As stated earlier, carrying capacity is the number of individuals that the environment can support indefinitely.

Statement c is thus true.

Hence, option c is not correct.

Carrying capacity of the environment has increased due to development in technology. Invention of agriculture, use of fossil fuels, alternative fuels, fertilizers, greenhouses, etc. have artificially increased the carrying capacity of the planet.

Hence, statement d is true.

Thus, option d is incorrect.

Carrying capacity of an environment can change due to changes in food availability, availability of water, changes in habitat, and other environmental conditions. Thus, the carrying capacity of a particular environment can fluctuate over time.

Statement e is true as well.

Hence, option e is not correct.

During exponential growth, per capita rate stays the same irrespective of the size of population. But during logistic growth, per capita growth rate decreases when the size of the population increases and reaches a point when resources become limited.

Thus, per capita growth rate is not negative when the population size is below the carrying capacity, but becomes negative when it reaches the carrying capacity.    

Hence, statement a is false.

Therefore, the correct answer is option a.