PACKET #31CHAPTER #14

Population Ecology

Introduction & Review

Population Group consisting of

members of the same species that live together in a prescribed area at the same time.

Population Ecology The study of numbers of

individuals of a particular species, at a given time and location, and the interactions of that population with other populations and the environment

Population dynamics Study of changes in

populations

IMPORTANT FEATURES OF POPULATIONS

Population Ecology

Population Density

Population Density This is how population size is expressed The number of individuals of a species per unit space

Dispersion

Dispersion Describes the spacing

of individuals and there are three types.

Types of Dispersion

Uniform Dispersion Individuals are evenly distributed

Clumped (Aggregated) Dispersion Most common type Individuals are concentrated in specific parts of the habitat

Patchiness Occurs as a result of distribution of resources or by

asexual reproductionRandom dispersion

Occurs when individuals of a population are spaced throughout an area in a manner that is unrelated to the presence of others

Least common; hardest to observe Results from a lack of interaction between individuals or a

homogenous environment

MATHEMATICAL MODELS

Population Ecology

TYPES OF GROWTH RATES

Population Ecology

Exponential Growth

Exponential Growth Population growth is at

a rapid pace Humans have

exhibited this growth pattern for centuries—but can it last?

Exponential Growth & The Human Population II

Not all countries have the same growth rate Higher in developing

countries India South Asia Africa

Age structure of a country can be used to predict future population growth Shows the percentages of

population at different ages

A broader base to the age structure indicates a growing population while a narrower base indicates a stable or shrinking population.

Logistic Growth

Logistic Growth Exponential growth

with environmental resistance (carry capacity of the environment = K) incorporated into the equation

Exhibited by most natural populations.

FACTORS INFLUENCING POPULATION SIZE

Population Ecology

Dispersal

Dispersal Movement of

individuals among populations

Immigration Migration of

individuals into the population

Emigration Migration of

individuals out of the population

Density Dependent Factors II

PredationDisease

Increases when contact with toxic waste, produced by population itself, increases with population size.

Competition Intraspecific

Competition between members of the same species

Interspecific Competition between

members of different species

Density Independent Factors

Climatic factors Sunlight Rainfall Temperature

All have impacts no matter what the population size Climatic and seasonal factors, monsoon season for

example, can severely decrease populations

LIFE “HISTORY” TRAITS OF POPULATIONS

Population Ecology

Introduction

Life history traits, products of natural selection, are traits that affect an organism’s schedule of reproduction and survival. Birth Reproduction Death

Semelparous vs. Iteroparous Species

Semelparous Species Expend their energy in

a single, immense reproductive effort Pacific salmon Agave

Iteroparous Species Exhibit repeated

reproductive cycles Most vertebrates Most shrubs Most trees

r Strategists

r strategists Have traits that

contribute to a high population growth rate. High r Small size Large numbers of

offspring May live in

unpredictable habitats Weeds Pests

• Roaches

K Strategists

K strategists Maximize the chance of

surviving in an environment where the number of individuals (N) is near the carrying capacity (K) of the environment. Population size near K Larger body size Long life span Late reproduction and

slow development Have fewer offspring May care for their young

African elephants Humans

Review

Review

Students are encouraged to place their own questions and charts on following slides.