Chapter 20Lab BiologyChapter 26

Honors Biology

Does this represent a population of dolphins?

Anticipatory Set: Count the number of

dolphins in this picture…

Grp. Of organisms of the same species in a particular place at the same time.

Population Size no. of individuals it contains (how do we measure it?)

Population Density measures how crowded a population is (indiv. Per unit of area or volume)Dispersion spatial distribution of individuals

within the populationClumped

Evenrandom

Properties of Populations

Population Dispersion

Birth rate – no. of births occurring in a period of time

Death rate – number of deaths in a period of time

Life expectancy –how long on average an individual is expected to

live

Population Dynamics

(change over time)

Age Structure the distribution of individuals among different ages in a population

Patterns of Mortality tends to conform to one of three curves on a graph called survivorship curves they show the likelihood of survival at

different ages throughout the lifetime of the organism.

Continue…

Growth rate the amount by which a population’s size changes in a given time

This depends on 4 processes:

Birth

Death

Emigration

immigration

Population Growth Rate

Loss…Birth rate – death rate = growth rate

(per capita use 1,000)

Gain…To find the no. of new indiv. That will be added to

the population in a yr. Multiply the per capita growth rate by the no. of indiv. In the popul.

Formulas for growth rate!!

Exponential Model describes a population that increase rapidly after only a few generations

Exponential Growth the larger the population gets the faster it grows

Exponential Model

View population growth over time

Represented by a J – shaped curve

Predictions Based on the Exponential

Model

Exponential growth occurs only under rare conditions and for short periods of time

Why: resource get depleted and waste

builds up

Limiting factor – a factor that restrains the growth of a population

Limitations of the Exponential Model

A population growth builds on the exponential model but accounts for the influence of limiting factors

Carrying capacity: the no. of indiv. The environment can support over a long period of time.

Logistic growth

Logistic Model

Environmental resistance can be classified into two broad categories

Density-independent factors

Density-dependent factors

Environmental Resistance

2 Kinds of limiting factors control population size:

1. Density-independent factors: limit populations regardless of their density

Examples: climate, weather, floods, fires, pesticide use, pollutant release, and overhunting

2. Density-dependent factors: can cause birth rates to drop and/or death rates to increase

Population growth slows resulting in an S-shaped growth curve (or S-curve)

Population Regulation

Some species have evolved means of limiting their losses

Examples: seasonally migrating to a better climate or entering a period of dormancy when conditions

deteriorate

Density-Independent Factors

Density-dependent factors can cause birth rates to drop and/or death rates to increase

Population growth slows resulting in an S-shaped growth curve (or S-curve)

Density-Dependent Factors

Carrying capacity is determined by the continuous availability of resources

Density-Dependent Factors

Include community interactions

Predation

Parasitism

Competition

Density-Dependent Factors

1. Development of Agriculture – “agricultural revolution” stabilized and increase available food

supply

2. Population Explosion –

3. Population Growth today –

- developed countries

- developing countries

History of Human Population Growth