The study of individual species in relation to the environment. The field is concerned with conservation and focuses on Population and Population Viability Analysis (PVA)
Population Viability Analysis
A species-specific method of risk assessment. Brings together species characteristics and environmental variability to forecast population health and extinction risk. Begins with the question: “Is this species at risk of becoming endangered? If so, why?”. A research example may include: “What are the effects of industrial forestry on biodiversity.”
WHAT ARE THE MAJOR CHARACTERISTICS OF A POPULATION?
A group of individuals of a single species that simultaneously occupy the same general area.
Populations Under Study
Diseases (prions, viruses, bacteria) Vegetation (crops, orchards, forests) Terrestrial Animals (cattle, sheep, pigs, chickens) Aquatic Organisms (fish, shrimp) Humans
HIV Population in South Africa Arcview GIS
Characteristics of Populations
Distribution Numbers (size) Age Structure Density (#/area)
WHAT IS BIOGEOGRAPHY?
The study of the size and distribution of biodiversity over space and time. It aims to reveal where organisms live, and at what abundance.
Factors Explaining Species Distributions
Speciation Extinction Continental drift Glaciations (associated variations in sea level, river routes) River capture
Speciation & Population Types
Structures Food Resources
goes one step further to include paleogeographic data and considerations of plate tectonics. Uses molecular analyses and fossils to determine the change in a species over millions of years. Hominid Evolution
HOW ARE POPULATIONS TRACKED?
A method commonly used in ecology to estimate population size and population vital rates (i.e., survival, movement, and growth)
Lotek Wildlife GPS Monitors
Researcher visits a study area and uses traps to capture a group of individuals alive. Captured animals are marked with tags, collars, bands, or spots of dye and then is released unharmed back into the environment. Sufficient time is allowed to pass for the marked individuals to redistribute themselves among the unmarked population. Next, the researcher returns and captures another sample of individuals.
WHAT FACTORS GOVERN CHANGES IN POPULATION SIZE?
The study of the vital statistics that affect population size. •Size •Density •Age Distribution •Dispersion
Population Dispersion Patterns
Uniform (creosote bush)
Factors Affecting Distribution
Competition for Resources Predation Parasitism Infectious Disease
Floods Hurricanes Unseasonable Weather Fire Clear Cutting Pesticide Spraying
Changing and Clumping
Availability and variation of resources Provide protection in numbers Packs have a better chance of obtaining food Temporary groups for mating
Factors that Govern Population Size
Crude Birth Rate (CBR) Crude Death Rate (CDR) Immigration Emigration
Population Change = (births + immigration) – (deaths + emigration)
Population Age Structures
WHAT LIMITS POPULATION GROWTH?
Resources and Competitors
Biotic Potential (r) Ecosystem Carrying Capacity (K) Rate of Increase Environmental Resistance
Population Growth Curves: J-Curve & S-Curve
© 2004 Brooks/Cole – Thomson Learning
K Population size (N) Population size (N) Time (t)