Population Growth and Limiting Factors

Explain what is going on in the cartoon below:

*KEY CONCEPT*As the human population grows, the demand for Earth’s resources increases.

I. Population GrowthA. An increase in the number of individuals in a

populationB. Unlimited resources and reproduction lead

to population growth (G)

1. Growth = Births – Deaths

(G = B – D)

But are our resources unlimited?

According to this bar graph, is the global population increasing or decreasing?

II. When births exceed deaths you see population growth.

A. Exponential Growth

1. Exponential growth means that as a population gets larger, it also grows at a faster rate.

III. When deaths exceed births the population falls

A. This S-shaped curve is known as logistic growth and depend on the population’s limiting factors.

IV. Types of limiting factors

A. Abiotic factors- those physical and chemical factors which affect the ability of organisms to survive and reproduce

1. Types of abiotic factorsa. intensity of light b. range of temperatures c. amount of moisture d. type of substrate (soil or rock

type) e. availability of inorganic

substances such as minerals f. supply of gases such as oxygen, carbon dioxide, and nitrogen g. pH

2. These are usually our density independent factorsB. Biotic factors-all the living things that directly or indirectly affect the environment ** Thus, the organisms, their presence, parts, interaction, and wastes are all biotic factors.

V. Carrying Capacity

A. the maximum number of organisms the resources of an area can supportB. The carrying capacity of the environment is limited by the available abiotic and biotic resources, as well as the ability of ecosystems to recycle the residue of dead organisms through the activities of bacteria and fungi.

C. Carrying Capacity is different for each population.

D. We don’t know earth’s carrying capacity for the human population (but we think it’s getting close)

1. Many of our environmental issues are considered a sign that we are reaching the planet’s carrying capacity