FW 491 – Online Ecological Module

By: Jessica Caton

Introduction to Population Ecology • What is a population?

– A group of individuals of a single species inhabiting a specific area (Molles 2010, p. 202)

• Areas of study involved – Population genetics– Population dynamics

Population Dynamics

An area of population ecology concerned with the factors influencing the expansion, decline, or maintenance of populations (Molles 2010, p. 222)

• Increases = Birth and Immigration• Decreases = Death and Emigration

Population Dynamics (con’t)

Important for ecology to understand/prevent decline and extinction of endangered species

Antarctic Species of Interest:Adélie Penguin

(Pygoscelis adeliae) • Physical appearance:

– Medium-sized (2 feet tall), black and white – Angular head and tiny bill– White eyering – Longest feather on body is the tail

• Smallest penguin in Antarctica

• One of the pack ice Antarctic penguins

• Most numerous bird in Antarctica

Adélie Penguins and Climate Change

• One of the best studied birds

• Changing population of species: numbers dropped a third

• Sea-ice decline, Adélie penguin populations decline

• Evolution of environmental instability?

Life Tables • A table that uses age specific information to estimate important population dynamic traits on a population

• Types of life tables:– a table based on individuals born (or beginning life in some other way) at same time (Molles 2010, p. 230)

– Static life table: a life table constructed by recording the age at death of a large number of individuals; a snapshot of survival within a population during a short interval of time

(Molles 2010, p. 231)

Life Table Summary Time

Cohort (horizontal)

Composite

Time-specific (static, vertical)

Data Collection for Life Table

Variables in Life Tables

• nx

• lx

• mx

• lxmx

• R0

• R0 = ∑lxmx

Survival and Mortality in a Population of Adélie Penguins

(Ainley & DeMaster 1980)

Survivorship Curve

• A graphical summary of patterns of survival in a population (Molles 2010, p. 231)

• Three types:– Type 1 = High mortality in

older individuals– Type 2 =Constant mortality rate– Type 3 =High mortality in juveniles