The Study of Individual Species in Relation to the Environment

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POPULATION DYNAMICS, CARRYING CAPACITY, AND CONSERVATION BIOLOGY The Walker School Environmental Science

Population Ecology




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?

Populations


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)

Celestichthys

WHAT IS BIOGEOGRAPHY?

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.

Giant Pandas

Factors Explaining Species Distributions
   



Speciation Extinction Continental drift Glaciations (associated variations in sea level, river routes) River capture

Speciation & Population Types
 Ranges

 Physical

Structures  Food Resources

Paleobiogeography




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?

Mark-Recapture Method


A method commonly used in ecology to estimate population size and population vital rates (i.e., survival, movement, and growth)

Lotek Wildlife GPS Monitors
http://www.lotek.com/

The Process
1.

2.

3.

4.

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.

Analysis

WHAT FACTORS GOVERN CHANGES IN POPULATION SIZE?

Demography


The study of the vital statistics that affect population size. •Size •Density •Age Distribution •Dispersion

Population Dispersion Patterns

Clumped (elephants)

Uniform (creosote bush)

Random (dandelions)

Factors Affecting Distribution
Density Dependant


Density Independent


  

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

Carrying Capacity

Population Growth Curves: J-Curve & S-Curve
© 2004 Brooks/Cole – Thomson Learning

K Population size (N) Population size (N) Time (t)

Time...
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