Chapter 10 - Population Dynamics

Population Dynamics

Area of ecology concerned with factors influencing expansion, decline, and maintenance of populations

Importance of understanding population dynamics

• invasive species control

• protection of endangered/threatened species

• pest control (parasites/pathogens)

• maintain economically important spp.

Dispersal

Movement of individuals away from population they were born

Dispersal in Eurasian collared doves

Eurasian collared doves were purposefully introduced to North America and began to expand in small jumps. Juveniles might disperse however adults are generally stationary.

Range changes in response to climate change?

after the ice age the range of organisms expanded.

Numerical response

Change in the density of a predator population in response to increased prey density.

Immigration vs. Emigration

• immigration - movement in a population

• emigration - movement out of a population

Survivorship

Proportion of offspring produced by a population or species that survive to a certain age class

What are the 3 main methods for estimating patterns of survival?

1. Cohort method

2. Age at death method

3. Age distribution method

Cohort Method

involves identifying individuals born at same time and keeping records form birth.

Age at Death Method

Involves record age of death for a number of individuals.

Age Distribution Method

Involves calculating differences in proportion of individuals in each age class

Why is understanding age distribution important to estimating patterns of survival?

Age distribution reflects a population’s history of survival, reproduction, and potential future for future growth. 

What kind of life table does the Age of Distribution and Age at Death method form?

Static life table

What is a survivorship curve?

A graph that illustrates the number of individuals in a population that survive over time and at different ages. 

Type 1 survivorship curve

Survival is high among young individuals and mortality is higher among older individuals.

Type 2 survivorship curve

Constant rate of survival throughout lifetime.

Type 3 survivorship curve

High mortality among young individuals followed by high survivorship.

Examples of type 1 survivorship

• humans

• elephants

• gorillas

• hippos

Examples of type 2 survivorship

• birds

• rodents (squirrels)

• butterflies

Examples of type 3 survivorship

• fish

• sea turtles

• frogs

• most insects

What kind of survivorship curve is this?

type 1 survivorship curve

What kind of survivorship curve is this?

type 2 survivorship curve

What kind of survivorship curve is this?

type 3 survivorship curve

fecundity schedule

a table of birthrates for females of different ages in a population.

Geometric rate of increase (lamba)

ratio of the population size at two points in time.

Net reproductive rate (N₀)

Average number of offspring produced by an individual in a population during its lifetime.

Generation time (T)

average age of reproduction

Per capita rate of increase (r)

Measurement of population growth in species with continuous or overlapping reproduction.