Population of the United States

on

September 23, 2008 @ 8:02 pm EST

POPClock Projection

305,232,977

• One birth 7 sec

• One death 13 sec

• One international migrant (net) 29 sec

• NET GAIN OF ONE PERSON 9 sec

U.S. Population

The statistical study of the size and structure of a population

Demography

Objectives:

1. Relate population size and density

2. Describe how physical environment limits the geographic range of species

3. Identify population distributions in a landscape

4. Describe what rare (and other associated terms) mean

Population Distribution and Abundance - Chapter 9

A quantitative description of the population

Four different Characters

1. Population Density

2. Dispersion

3. Age Structure

4. Sex Ratio

Demography

Define: Population

A group of conspecifics inhabiting a specific place at a specific time, capable of reproducing with each other.

Population

Most fundamental characteristic:

The Density

Expressed as:

Number of individuals/unit area (volume)

Population Density

All individuals in a study area without regard to habitat type

Crude Density All individuals in a study area of similar or

appropriate habitat

Ecological Density

Population Density

LakeBass = 2000

TreesSquirrels = 100

Clover FieldFoxtail = 10000

Census:

1. Easy to identify: Elephants, deer, trees, sessile organisms

2. Less conspicuous:

A. Nocturnal, difficult habitat, moving, too darn many to count, too much area to cover, etc,

Determining Population Density

B. What parts do we count? e.g., plants (flowers), animals (colonial)

Determining Population Density

Absolute Density:

Determining the absolute number/spatial unit.

5016 fish/hectare

3 deer/kilometer2

17898 stems of bluegrass/m2

0.15 pheasants/hectare

HOW: count every organism, mark-recapture, quadrat sampling, etc.

Determining Population Density

Relative Density-

Determining relative no. for comparison e.g.,

fish/trap/night

number of deer/car accidents

% of bluegrass in a field

number of pheasant calls/mile road

HOW: Different sampling questions with different answers

Determining Population Density

Fig. 9-20

Environmental Limitations

Two most important abiotic features of distributions:

• Moisture

• Temperature

Macropus rufus

Fig. 9.2

Environmental Limitations

Two most important abiotic features of distributions:

Moisture, Temperature

Can also be distributed due to biotic interactions

e.g., Competition, Predation

OR COMBINATIONS OF THE ABOVE!!

Fig. 9.8

Balanusbalanoides

Dispersion: Spatial distribution of organisms within a given area - :

Distribution of Organisms

Small Scale – small distances over which there is little environmental change

Distribution of Organisms

Fig. 9-10

What Do We Know So Far?

1. The study of populations is called demography

2. Populations can be measured in absolute or relative abundances

3. Features that control distributions can be abiotic (e.g., moisture, temp.) or biotic (e.g., competition, predation)

4. Distributions are classified as random, clumped or regular.

The Question

You are trying to establish the population density of the ant eating fire bush in the Zippity Nature Preserve in southern Do Da County. Your sampling design requires that you know how the organism is distributed across the nature preserve (clumped, random, or regular). How do you determine the dispersion type?

Dispersion: Spatial distribution of organisms within a given area - :

Note: Scale may determine dispersion type, particularly on a small scale:

Distribution of Organisms

Population Dispersion

• Effect of Quadrat Size:

Clumped

Population Dispersion

• Effect of Quadrat Size:Random

Population Dispersion

• Effect of Quadrat Size:

Clumped

Population Dispersion

• Effect of Quadrat Size:

Regular

Population Dispersion

• Effect of Quadrat Size:

Clumped

Fig. 9-13

Fig. 9-14

Distribution

Large Scale:

• Usually clumped distribution

• May relate to environmental gradients (e.g., moisture and temperature)

Fig. 9.15

Rarity and Distribution

1. Extensive vs. restricted geographical range

2. Broad vs. narrow habitat tolerance

3. Small vs. large population size

Fig. 7.22

Finished for today!!

Question of the Day