Age structure is the relative number of individuals of each age in the population

Age structure diagrams are commonly graphed in the shape of a pyramids

For example, the age structure for the US is relativley even until older, post reproductive ages, except for a bulge that corresponds to the baby boom that lasted for about two decades after WW2

What/How size can tell us about a population:

Answers:

Size is the number of individual organisms in a population

Mark recapture method

Clumped random uniform

A survivor ship curve is a plot of the proportion or numbers in a cohort still alive at each age

pyramid

Quiz Time!

What is Size?

What is a method ecologists use to estimate size and density?

Name 2 of the 3 types of dispersion?

What is/are survivor ship curve(s)?

What shape are age structure diagrams commonly graphed in?

**Name five properties of populations and explain what they tell us about a population.**

What/How can dispersion tell us about a population:

Dispersion is the pattern of spacing among individuals within the boundaries of the population

There are three different kinds of dispersion: Clumped Dispersion, Uniform Dispersion, and Random Dispersion

Clumped dispersion is the tendency for populations to be found in tight clusters across their habitat.

Uniform Dispersion is where populations to be found evenly distributed about their habitat.

Random dispersion is what it sounds like, populations randomly distributed about their habitat.

What/How survivor ship curves can tell us about populations:

A survivor ship curve is a plot of the proportion or numbers in a cohort still alive at each age

Generally survivor ship curves begins with cohort of a convenient size- i.e. 1,000

to find the other points on the curve, we multiply the proportion alive at the start of each year by 1,000

The results is the number alive at the start of each year

A straight line indicates a relatively constant rate of death, and vise versa.

The five properties of a population are as follows:

size

density

dispersion

survivor ship curves

Age structure diagrams

What/How can Density tell us about a population:

Density is the number of individuals per unit area or volume

it also can tell us the resources required to support that population

In some cases population size and density can be determined by counting all individuals within the boundaries of the population

In most cases, however, ecologists use other methods such as the mar-recapture method, in which ecologists mark a certain number of animals, let them go, recapture them, and repeat in order to estimate the size and density of a population.

**Key words/topics**

Size

Density

Dispersion

Survivor ship curves

Age structure diagrams

Size

Density

Dispersion

Survivor ship curves

Age structure diagrams

Size is the number of individual organisms in a population

A small population size results in increased genetic drift.

Population bottlenecks are when population size reduces for a time, often due to natural disasters.

Overpopulation may indicate that the population of any species of animal may exceed the carrying capacity of its ecological niche.

END