BIO 181 Lecture Notes - Lecture 7: Ecological Study, Parasitism, Logistic Function

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11 Nov 2016
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Lecture 6 & 7: Chapter 55 Lecture Guide
Population Ecology
What is ecology?
- Ecology is the study of how organisms interact with each other and their
environment
Areas of ecological study:
Organismal- the study of a single organism
Population- a group of individuals of the same species inhabiting the same area
Community- all given populations living in an area
Ecosystem- an area and all of the organisms that live in it
Landscape- how human alteration of a geographical region can affect its organisms
The Environment
Biotic components
oLiving portion
Abiotic components
oNon-living portion
Sunlight, temperature, rainfall (water), soil conditions, geography
What is a population?
- A group of individuals of the same species inhabiting the same area
Key characteristics
oRange
oSpacing pattern
oChanges in size over time
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Lecture 6 & 7: Chapter 55 Lecture Guide
Checks on Populations
Density independent factors:
Drought, freezes, floods, forest fires, storms, etc.
Pollution
Rapid habitat loss
Density dependent factors:
Disease
Competition for resources
Intraspecific- within a species
Interspecific- between species
Predation
Parasitism
Population Ecology Defined
How populations interact with their environment
How and why the number of individuals changes over time
The proportion of males to females
How old the individuals are
How likely they are to reproduce or die
How to Study Populations
Demography—the study of factors that determine the size & structure of
populations through time
Population Growth—the change in the number of individuals in the population
(∆N) per unit time (∆t)
Population Dynamics—Interaction of all of the above factors
Demography
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Lecture 6 & 7: Chapter 55 Lecture Guide
The number of individuals that are present in a population depends on:
Age structure, or the relative number of individuals of each age.
How likely individuals are to survive the following year
How many offspring are produced by females of different ages
How many individuals of different ages immigrate and emigrate each generation
Population Growth Rate
The change in the number of individuals in the population (∆N) per unit time (∆t)
(appropriate time interval given the species like life span or generation time).
∆N/∆t=Births – Deaths or the per capita rate of increase, r
oIf r is positive, the population is growing
oIf r is negative, the population is decreasing
oIf r is zero, there is no population growth (ZPG)
Exponential Growth Model (J-Curve Model)
Population increase under ideal conditions
Per capita rate of increase may reach the maximum for the species
Cannot continue indefinitely, would eventually fill all breeding habitat.
Happens when populations are:
oColonizing new habitats
oRecovering
- The higher the r (slope), the steeper the curve will be
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Document Summary

Ecology is the study of how organisms interact with each other and their environment. Population- a group of individuals of the same species inhabiting the same area. Community- all given populations living in an area. Ecosystem- an area and all of the organisms that live in it. Landscape- how human alteration of a geographical region can affect its organisms. The environment: biotic components, living portion, abiotic components, non-living portion. Sunlight, temperature, rainfall (water), soil conditions, geography. A group of individuals of the same species inhabiting the same area. Key characteristics: range, spacing pattern, changes in size over time. Checks on populations: density independent factors, drought, freezes, floods, forest fires, storms, etc, rapid habitat loss. Pollution: density dependent factors, disease, competition for resources. How and why the number of individuals changes over time. How likely they are to reproduce or die. Demography the study of factors that determine the size & structure of populations through time.

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