Population EcologyPopulation EcologyPopulation EcologyPopulation Ecology

Chapter 9Chapter 9

G T Miller Jr.G T Miller Jr.

Chapter 9Chapter 9

G T Miller Jr.G T Miller Jr.

Shohail Motahir Choudhury

Sea Otters: Back from ExtinctionSea Otters: Back from Extinction

Population DynamicsPopulation Dynamics

What are the major characteristics of a population?

Population dynamics is the study of how populations change.

Populations change in size, density, and age distribution.

Three general patterns: Three general patterns: clumping, clumping, uniform distribution, and uniform distribution, and random dispersion.random dispersion.

Most species live in clumps or groups.Most species live in clumps or groups.

Population DistributionPopulation Distribution

Why Clumping?Why Clumping? • Availability of resources varies from

place to place.• Living in groups offers better protection

from predators.• Some predator species live in packs to

better have a chance to get a meal.• Temporary groups may form for mating

and caring for young.

Uniform pattern distribution may occur where a resource, such as water, is scarce.

Factors Governing Population SizeFactors Governing Population Size

Births and ImmigrationBirths and Immigration

Deaths and EmigrationDeaths and Emigration

Population ChangePopulation Change= (Births+Immigration)-= (Births+Immigration)-(Deaths+Emigration)(Deaths+Emigration)

Factors limiting population growthFactors limiting population growthNo Population can grow indefinitely because resources No Population can grow indefinitely because resources

Light Water Nutrients

Biotic Potential. Housefly: 5.6 trillion within 13 months. Within few years can cover the earth’s entire surface. (Intrinsic rate of increase (r).

Nature limits population growth. Environmental resistance.

Together biotic potential and environmental resistance determine the carrying capacity (K).

Growth factors(biotic potential)

Favorable lightFavorable temperatureFavorable chemical environment(optimal level of critical nutrients)

Abiotic

High reproductive rate

Generalized niche

Adequate food supply

Suitable habitat

Ability to compete for resources

Ability to hide from or defendagainst predatorsAbility to resist diseases and parasitesAbility to migrate and live in other habitatsAbility to adapt to environmentalchange

Too much or too little lightTemperature too high or too lowUnfavorable chemical environment(too much or too little of critical nutrients)

Abiotic

Low reproductive rate

Specialized niche

Inadequate food supply

Unsuitable or destroyed habitat

Too many competitorsInsufficient ability to hide from or defendagainst predatorsInability to resist diseases and parasitesInability to migrate and live in other habitatsInability to adapt to environmentalchange

Decrease factors(environmental resistance)

BioticBiotic

Population Size

Growth and Decrease Factors Growth and Decrease Factors

Exponential vs logistic growthExponential vs logistic growth

Reindeer introduction in south coast Reindeer introduction in south coast of Alaska. of Alaska.

268

Sheep introduction in Tasmania.Sheep introduction in Tasmania.

Types of population fluctuationsTypes of population fluctuations

Predation in Controlling Population SizePredation in Controlling Population Size

Top-down Bottom –up Interaction between predation and food supplies.

Human Impacts on EcosystemsHuman Impacts on Ecosystems

Habitat degradation and fragmentationHabitat degradation and fragmentation

Ecosystem simplificationEcosystem simplification

Genetic resistanceGenetic resistance

Predator eliminationPredator elimination

Introduction of non-native speciesIntroduction of non-native species

Overharvesting renewable resourcesOverharvesting renewable resources

Interference with ecological systemsInterference with ecological systems

Learning from NatureLearning from Nature

Principles of sustainabilityPrinciples of sustainability

Solar EnergySolar Energy

Nutrient Nutrient RecyclingRecycling

Population Population ControlControl

BiodiversityBiodiversity

Next ClassNext ClassNext ClassNext Class

Energy Efficiency and Renewable EnergyEnergy Efficiency and Renewable Energy

Chapter 18Chapter 18G T Miller Jr.G T Miller Jr.

Energy Efficiency and Renewable EnergyEnergy Efficiency and Renewable Energy

Chapter 18Chapter 18G T Miller Jr.G T Miller Jr.

Shohail Motahir Choudhury

Poster Presentation: February 21Poster Presentation: February 21