POPULATIONS

SC STANDARD B-6. 2: Students will demonstrate an understanding of the way populations are affected by density-dependent factors & density-independent factors.

CN page

Topic: Populations

EQ: What factors affect population size?

How do Populations Grow?

3 important characteristics of a population are its :

geographic distribution density growth rate

Geographic Distribution

is the range or area where the organism is found

Hooker’s Manzanita

found in maritime chaparrel (threatened habitat due to development)

Central California (Monterrey County)

Franklin’s Bumble Bee

Most restricted geographic distribution of any known bee

Between Pacific coast & Sierra Nevada in Oregon & northern California

Density

population density: the # of individuals per unit area

Density is one of the main characteristics that describes a natural population.

Growth Rate

3 factors affect population growth:

1. # of births 2. # of deaths 3. # of

individuals that immigrate or emmigrate

Immigration: movement of individuals into an area

Emmigration: movement of individuals out of an area

EXPONENTIAL GROWTH

growth pattern in which the individuals in a population reproduce at a constant rate

Under ideal conditions with unlimited resources, a population will grow exponentially

LOGISITIC GROWTH

growth pattern in which a population’s growth rate slows or stops following a period of exponential growth

carrying capacity: largest # of individuals of a population that a given environment can support

Carrying Capacity Graph

Limiting Factors to Growth

In respect to populations a limiting factor is anything that causes population growth to decrease.

Limiting factors are either:

Density-Dependent

Density-Independent

Density-Dependent Limiting Factors limiting factor

that depends on population size

become limiting only when population density reaches a certain level

Include: 1. competition 2. predation 3. parasitism &

disease

1. Competition

When populations become crowded members of same or different species compete for food, shelter, mates, space, sunlight

2. Predation

Predator-Prey relationships mechanism of population control

3. Parasitism & Disease

Parasites take nourishment from their host host weakens does not usually die

Density-Independent Factors

affect all the populations in similar ways, regardless of #’s Forest fires Floods Seasonal cycles Human

interference (clear-cutting, damming river)

Human Population Growth

Population of humans on Earth increases with time

Patterns of Population Growth Birth rates,

death rates, & the age structure of a population help predict why some countries have high growth rates while other countries grow slowly.

The Demographic Transition

the change in a population from high birth & death rates to low birth & death rates

Complete concept map from page 134 of book on page of notebook (landscape)