population ecology chapter 9. ch 9: population ecology how do populations change in structure in...

Population Population EcologyEcology

Population Population EcologyEcology

Chapter 9Chapter 9

Ch 9: Population EcologyCh 9: Population Ecology

How do populations change in How do populations change in structure in response to structure in response to environmental stress?environmental stress?

What reproductive patterns do What reproductive patterns do species use to enhance survival?species use to enhance survival?

What is conservation biology?What is conservation biology? How do humans impact populations, How do humans impact populations,

communities, and ecosystems?communities, and ecosystems?

Population DynamicsPopulation DynamicsPopulation DynamicsPopulation Dynamics

Population dynamics

Population dynamics Biotic potential

(intrinsic rate of increase [r])

Biotic potential (intrinsic rate of increase [r])

Environmental resistance Environmental resistance

Carrying Capacity Carrying Capacity

Exponential and Logistic Growth Exponential and Logistic Growth

Population Density Population Density

Study of how populations change in size, density, and age distribution

Rate at which a population would grow if it had unlimited resources

Consists of all factors that would limit population growth

Maximum number of individuals of a given specie that can be sustained indefinitely in given space

A population that grows at every increasing increments

Population growth that is steady and eventually levels off

Number of individuals in a population in a particular space

Population DispersionPopulation Dispersion

1. Clumped-groups of individuals living in a tight knit cluster-fish, birds

2. Uniform-constant distance between individuals- better access to scarce resources

a. Resources aren’t evenly spread outb. Better protection from predators

c. Better able to find food-packs

d. Temporary groups for mating

3. Random-Just that

Factors Affecting Population Factors Affecting Population SizeSize

1. Births

2. Deaths

3. Immigration

4. Emigration

POPULATION SIZE= Biotic Factors – Env. Resistence

Exponential and Logistic Exponential and Logistic GrowthGrowth

Population Density EffectsPopulation Density Effects

Density-independent controls Density-independent controls

Density-dependent controls Density-dependent controls

Controls the size of the population regardless of the density of the population-natural disasters: fire, floods, habitat destruction

Affects the population depending on its density-predation, parasitism

Types of Population Change Types of Population Change Curves in NatureCurves in Nature

Population sizes follow one of these Population sizes follow one of these patterns.patterns.– StableStable: fluctuates slightly : fluctuates slightly and and carrying carrying

capacity.capacity.


Population sizes follow one of these patterns.Population sizes follow one of these patterns.– IrruptiveIrruptive: explosion followed by crash to stable : explosion followed by crash to stable

level.level.


Population sizes follow one of these patterns.Population sizes follow one of these patterns.– CyclicCyclic: fluctuate w/reg pattern or boom-and-bust : fluctuate w/reg pattern or boom-and-bust

cycles.cycles.


Population sizes follow one of these Population sizes follow one of these patterns.patterns.– IrregularIrregular: erratic due to chaos or drastic : erratic due to chaos or drastic

change.change.

Role of Predation on Pop Role of Predation on Pop SizeSize

Role of Predation on Pop Role of Predation on Pop SizeSize

Predator-prey cycles Predator-prey cycles

Top-down control Top-down control

Bottom-up control Bottom-up control

predator controls the population size of the prey

prey controls the population size of the predator

Reproductive Patterns and Reproductive Patterns and SurvivalSurvival


Asexual reproduction Asexual reproduction

Sexual reproduction Sexual reproduction

Offspring are exact genetic copies of a single parent

Offspring are produced by combining sex cells from two parentsDisadvantages:

1. males do not give birth-females have to produce twice as many offspring to continue specie

2. increased chance of defects when recombining chromosomes

3. courtship and mating consumes time and energy, results in disease and injury(males)

Advantages:

1. greater genetic diversity

2. male can protect young



r-selected speciesr-selected species– High rate of pop High rate of pop , ,

small in sizesmall in size

K-selected speciesK-selected species– Low rate of pop Low rate of pop , ,

large in sizelarge in size

Many small offspring, small adults

Little/ no parental care or protection of offspring

Early reproductive age

Most offspring die before reaching reproductive age

Adapted to unstable climate and environmental conditions

High population growth rate (r)

Population size fluctuates wildly above and below carrying capacity (K)

Generalist niche

Low ability to compete

Early successional species



r-selected speciesr-selected species– High rate of pop High rate of pop , ,

small in sizesmall in size

K-selected speciesK-selected species– Low rate of pop Low rate of pop , ,

large in sizelarge in size

Fewer, larger offspring, large adults

High parental care and protection of offspring

Later reproductive age

Most offspring survive to reproductive age

Adapted to stable climate and environmental conditions

Lower population growth rate (r)

Population size fairly stable and usually close to carrying capacity (K)

Specialist niche

High ability to compete

Late successional species

K-Selected Species

Saguaro

Elephant

Survivorship Survivorship CurvesCurves

Shows % of species in a population surviving at different ages. Three types: late loss, early loss, and constant loss.

Life tables- show the numbers of individuals at each age on a survivorship curve.

Tonight’s HomeworkTonight’s Homework

Read p. 206-209Read p. 206-209

Answer the following:Answer the following:

1.1. How does conservation biology differ from How does conservation biology differ from environmental science and wildlife environmental science and wildlife management?management?

2.2. Describe 3 principles held by conservation Describe 3 principles held by conservation biologists, and 3 questions they seek to answer.biologists, and 3 questions they seek to answer.

3.3. Describe at least 7 general human habits that Describe at least 7 general human habits that have modified natural ecosystems.have modified natural ecosystems.

4.4. State and describe 5 principles for living more State and describe 5 principles for living more sustainably.sustainably.

Human Impacts on EcosystemsHuman Impacts on EcosystemsHuman Impacts on EcosystemsHuman Impacts on Ecosystems

Habitat degradation and fragmentation Habitat degradation and fragmentation

Ecosystem simplification Ecosystem simplification

Genetic resistance Genetic resistance

Building sub-divisions, filling in wetlands, and building new roads through wilderness areas

Loss of biodiversity, cropland, clear forests, and housing projects

Overuse of pesticides breeds strains that are resistant to these chemicals

Predator elimination Predator elimination

Introduction of non-native species Introduction of non-native species

Overharvesting renewable resources Overharvesting renewable resources

Interference with ecological systems Interference with ecological systems

Human Impacts on Human Impacts on EcosystemsEcosystems

Human Impacts on Human Impacts on EcosystemsEcosystems

Killing off of predators; wolves, eagles, that compete with humans

Food crops and livestock are beneficial; lamprey eels, zebra mussels, goby

Overgrazing, excessive farming, illegal hunting, overharvesting of fish

Increased emissions of carbon dioxide, CFCs, greenhouse gases disrupt normal processes: nutrient cycles, energy flow

Learning from NatureLearning from Nature

population ecology chapter 9. ch 9: population ecology how do populations change in structure in...

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