Environmental ScienceEnvironmental ScienceChapter 4:Chapter 4:

Population EcologyPopulation Ecology

Mr. ManskopfMr. Manskopf

Notes also available at Notes also available at http://www.manskopf.com

Population Ecology Big IdeasPopulation Ecology Big Ideas

In an ecosystem, the biotic and In an ecosystem, the biotic and abiotic components interact to abiotic components interact to form an interconnected system.form an interconnected system.

Humans classify the diversity of Humans classify the diversity of life on Earth in order to better life on Earth in order to better understand their relationships.understand their relationships.

Population sizes change Population sizes change according to changes in the according to changes in the environment. environment.

Section 1: Studying EcologySection 1: Studying Ecology

GOALSGOALS Distinguish between biotic and Distinguish between biotic and

abiotic factors in an ecosystemabiotic factors in an ecosystem Describe how a population, Describe how a population,

community differ from a speciescommunity differ from a species Explain the importance of habitatsExplain the importance of habitats

What is ecology?What is ecology?

The study of The study of how organisms how organisms interact with interact with each other and each other and with their with their environmentsenvironments

What is an ecosystem?What is an ecosystem?

Defining an ecosystemDefining an ecosystem

Ecosystem: all the Ecosystem: all the organisms living organisms living in an area in an area togethertogether

Forest EcosystemForest Ecosystem Pond EcosystemPond Ecosystem Vacant Lot Vacant Lot

EcosystemEcosystem Desert EcosystemDesert Ecosystem

All Ecosystems are All Ecosystems are connectedconnected

How does your ecosystem impact the Atlantic Ocean?

Parts of an ecosystemParts of an ecosystem

Parts of an ecosystem Parts of an ecosystem

In order for an In order for an ecosystem to ecosystem to survive there must survive there must be certain basic be certain basic partsparts

EnergyEnergy Mineral nutrientsMineral nutrients Carbon dioxideCarbon dioxide WaterWater Oxygen and moreOxygen and more

What are some parts of this What are some parts of this ecosystem?ecosystem?

You will be conducting a You will be conducting a study of the interactions of study of the interactions of

vegetation, animals, mineral vegetation, animals, mineral composition of the soil, and composition of the soil, and water levels in a saltmarsh. water levels in a saltmarsh.

You are studying the You are studying the saltmarsh ___.saltmarsh ___.

ECOSYSTEM

Biotic vs. AbioticBiotic vs. Abiotic

Biotic: living parts Biotic: living parts of the ecosystemof the ecosystem

Plants, animals, Plants, animals, bacteria, etc.bacteria, etc.

Abiotic: nonliving Abiotic: nonliving parts of the parts of the ecosystemecosystem

Sunlight, soil, air, Sunlight, soil, air, temperaturetemperature

What are some biotic AND abiotic parts of this ecosystem?

Organizing Organizing Biotic PartsBiotic Parts

Smallest UnitSmallest Unit

Organism: an Organism: an individual living individual living thingthing like you, a like you, a tree, a fox, a rosetree, a fox, a rose

Species are groups of Species are groups of organismsorganisms like red like red foxes or black foxes or black widow spiders, or widow spiders, or grizzly bearsgrizzly bears

Species Species Species: Species: groups of groups of

organisms that organisms that resemble each other resemble each other in appearance, in appearance, behavior, chemistry behavior, chemistry and genetic and genetic makeup…able to makeup…able to reproducereproduce

3.6 to 100 million 3.6 to 100 million species (1.4 species (1.4 identified)identified)

Mostly insects/microMostly insects/micro Tropical forestsTropical forests

Known species1,412,000

Insects751,000

Plants248,400

PopulationPopulation

Population: all the Population: all the members of the same members of the same species that live in species that live in the same place at the the same place at the same timesame time

Field mice living in a Field mice living in a corn field, grizzly corn field, grizzly bears of Yellowstone bears of Yellowstone Park areaPark area

CommunityCommunity

Community: a group Community: a group of various species of various species that live in the that live in the same place and same place and interact with each interact with each other. other.

Pond CommunityPond CommunityPineland ForestPineland Forest

BiosphereBiosphere

All parts of All parts of the Earth the Earth where life is where life is foundfound

Giraffes, lions, zebras, Giraffes, lions, zebras, hyenas, and all the other hyenas, and all the other

living things of the living things of the Serengeti make up a(n) ___Serengeti make up a(n) ___

COMMUNITY

HabitatHabitatHabitat: a place Habitat: a place

where an where an organism lives organism lives Organisms are Organisms are well suited for well suited for their habitattheir habitat

HabitatHabitat Habitats provide Habitats provide

an organism with an organism with resources—resources—anything an anything an organism needs organism needs to survive and to survive and reproduce, reproduce, including food, including food, shelter, and shelter, and mates.mates.

Section 1 ReviewSection 1 Review

Distinguish between biotic and Distinguish between biotic and abiotic factors in an ecosystemabiotic factors in an ecosystem

Describe how a population, Describe how a population, community differ from a speciescommunity differ from a species

Explain the importance of Explain the importance of habitatshabitats

Section 2: Describing Section 2: Describing PopulationsPopulations

Explain the usefulness of Explain the usefulness of tracking population sizestracking population sizes

Define population densityDefine population density Describe three ways populations Describe three ways populations

can be distributedcan be distributed

The Decline of the The Decline of the Passenger PigeonPassenger Pigeon

How does a species How does a species go from having go from having billions to extinct in billions to extinct in just one century…just one century…TheThe Passenger Passenger Pigeon Story.Pigeon Story.

Extinct in the wild Extinct in the wild since 1900 and last since 1900 and last died in the died in the Cincinnati Zoo Cincinnati Zoo 1914. 1914.

Review: What is a Review: What is a population?population?

Population: all the Population: all the members of the members of the same species that same species that live in the same live in the same place at the same place at the same timetime

Field mice living in a Field mice living in a corn field, grizzly corn field, grizzly bears of Yellowstone bears of Yellowstone Park areaPark area

Wolves in Yellowstone NP

Population SizePopulation Size

Why care about Why care about the size of the the size of the population?population?

How can How can scientists scientists estimate the estimate the population (say population (say of Elephant Seals of Elephant Seals on a beach in on a beach in CA)?CA)?

Population SizePopulation Size• The number of The number of

individuals in a individuals in a population at a given population at a given timetime

• Sudden and dramatic Sudden and dramatic decreases in population decreases in population size can indicate an size can indicate an unhealthy population unhealthy population headed toward headed toward extinction. extinction.

• Ecologists often use Ecologists often use sampling techniques to sampling techniques to estimate estimate population size.population size.

Did You Know? The passenger pigeon was once North America’s most abundant bird. Hunting drove them to extinction in less than 100 years.

Did You Know? The passenger pigeon was once North America’s most abundant bird. Hunting drove them to extinction in less than 100 years.

Mark and RecaptureMark and Recapture

Common way of Common way of estimating estimating population sizepopulation size

Estimating PopulationEstimating PopulationHow can you estimate the population of trees in this valley?

WHY NOT COUNT THEM ALL?

WHY IS SAMPLING NEEDED?

Population DensityPopulation Density

What is population density?

What are advantages and disadvantages of high and low density?

Population DensityPopulation Density•Measure of how crowded a population is

•Larger organisms generally have lower population densities.

•Low population density: More space, resources; finding mates can be difficult

•High population density: Finding mates is easier; tends to be more competition; more infectious disease; more vulnerability to predators

Population DistributionPopulation DistributionHow organisms are arranged within an area:

UNIFORM

RANDMOM

CLUMPEDOccurs where

resources needed are found throughout, wildflowers in meadow

Occurs when individuals hold territory or compete for space. Plants in desert

Most Common. Occurs where resources are together. Water hole in desert, humans in cities

Many bird species are Many bird species are territorial. In territorial birds territorial. In territorial birds

species, what kind of species, what kind of population structure would population structure would

you expect?you expect?

UNIFORM

Population DistributionPopulation Distribution

•Random distribution: Organisms arranged in no particular pattern

•Uniform distribution: Organisms evenly spaced

•Clumped distribution: Organisms grouped near resources; most common distribution in nature

What type of distribution? What type of distribution?

CLUMPED

WHY?

Age StructureAge Structure

• Relative number Relative number of organisms of of organisms of each age group each age group within populationwithin population

• Can be used to Can be used to predict future predict future population growth population growth of a population of a population

• HOW?HOW?

Sex RatiosSex Ratios• Proportion of Proportion of

males to femalesmales to females

• Age structure Age structure diagrams give diagrams give information about information about sex ratios.sex ratios.

• For a For a monogamous monogamous species, the ideal species, the ideal sex ratio is 50:50.sex ratio is 50:50.

Why is 50/50 not as important in non-monogamous populations?

Section 2: Describing Section 2: Describing Populations ReviewPopulations Review

Explain the usefulness of tracking Explain the usefulness of tracking population sizespopulation sizes

Define population densityDefine population density Describe three ways populations can Describe three ways populations can

be distributedbe distributed TERMS: TERMS: Population Size, Population Population Size, Population

Density, Population Distribution, Age Density, Population Distribution, Age Structure, Sex RatiosStructure, Sex Ratios

Section 3: Population Section 3: Population GrowthGrowth

Describe the factors that influence Describe the factors that influence population’s growth ratepopulation’s growth rate

Explain exponential and logistic growthExplain exponential and logistic growth Explain how limiting factors and biotic Explain how limiting factors and biotic

potential affect population growthpotential affect population growth TERMS: TERMS: survivorship curve, survivorship curve,

immigration, emigration, exponential immigration, emigration, exponential growth, carrying capacity, logistic growth, carrying capacity, logistic growth, biotic potentialgrowth, biotic potential

What does this graph show?What does this graph show?

Population Growth?Population Growth?

Why are there so few whales, but so Why are there so few whales, but so many bacteria?many bacteria?

Factors the Determine Factors the Determine Population GrowthPopulation Growth

A population’s relative A population’s relative birth and death rates birth and death rates ((mortality and mortality and natalitynatality) affect how it ) affect how it grows.grows.

More births than More births than deaths = population deaths = population increaseincrease

More deaths than More deaths than births = population births = population decreasedecrease

SurvivorshipSurvivorship

Individuals of Individuals of different ages different ages have different have different probabilities of probabilities of dyingdying

Survivorship Survivorship curves show how curves show how the likelihood of the likelihood of death varies with death varies with age.age.

Type I survivorship curves are for species that have a high survival rate of the young, live out most of their expected life span and die in old age. Humans are a good example of a species with a Type I survivorship curve

Type II survivorship curves are for species that have a relatively constant death rate throughout their life span. Death could be due to hunting or diseases. Examples of species exhibiting a Type II survivorship curve are coral, squirrels, honey bees and many reptiles.

Type III survivorship curves are found in species that have many young, most of which die very early in their life. Plants, oysters and sea urchins are examples of species that have Type III survivorship curves.

If a tree wants to successfully reproduce, how many seeds should it spread?

If a couple in India knows for sure there child will survive to adulthood, will they decide to have more or less children do you think?

Immigration/Emigration Immigration/Emigration • In addition to births and deaths, In addition to births and deaths,

population growth is affected by population growth is affected by immigration and emigration—individuals immigration and emigration—individuals moving into and out of a population.moving into and out of a population.

• MigrationMigration, seasonal movement into and , seasonal movement into and out of an area, can temporarily out of an area, can temporarily change population change population size.size.

Population CalculationsPopulation Calculations

Net population Change = (births + immigration) – (deaths + emigration) There are 300 people living in a village, 50 children are born, 20 people die, 10 immigrate and 2 emigrate. What is the new population?

Calculating Growth RateCalculating Growth Rate• Determined by the following equation: Determined by the following equation:

(birthrate + immigration rate) – (death (birthrate + immigration rate) – (death rate + emigration rate)rate + emigration rate)

• Growing populations have a positive Growing populations have a positive growth rate; shrinking populations have a growth rate; shrinking populations have a negative growth rate.negative growth rate.

• Usually expressed in terms of individuals Usually expressed in terms of individuals per 1000per 1000

Current human growth rate 1.25% down from 2.2% in 1963

Every spring, many species Every spring, many species of bird travel north to the of bird travel north to the Arctic to breed, and in the Arctic to breed, and in the fall travel south again for fall travel south again for

the winter. This is an the winter. This is an example of _____example of _____

MIGRATION

How Populations GrowHow Populations Grow

What What resources resources are are available available to the to the populationpopulation??

Patterns of GrowthPatterns of GrowthEXPONETIAL GROWTHEXPONETIAL GROWTH

•Population increases by Population increases by a fixed percentage a fixed percentage every year.every year.

•Normally occurs only Normally occurs only when small populations when small populations are introduced to an are introduced to an area with ideal area with ideal environmental environmental conditionsconditions

•Rarely lasts longRarely lasts long

WHAT SHAPE DOES EXPONENTIAL GROWTH LOOK LIKE?

Starts slowly, then takes off – “J-Shaped Curve”

Why doesn’t exponential Why doesn’t exponential growth last long?growth last long?

Limiting FactorsLimiting FactorsLimiting Factor Limiting Factor

Principle:Principle: too much too much or too little of any or too little of any abiotic factor can limit abiotic factor can limit or prevent growth of a or prevent growth of a population, even if all population, even if all other factors are near other factors are near or above optimum.or above optimum.

Why are there no Why are there no citrus fruit growing in citrus fruit growing in NJ?NJ?

Why do trees grow Why do trees grow toward the sky? toward the sky?

What Might Be Some What Might Be Some Limiting Factors in the Limiting Factors in the

Ocean? Ocean? Limiting factors Limiting factors

may include:may include:

• SalinitySalinity

• PhPh

• SunlightSunlight

• Dissolved oxygenDissolved oxygen

• TemperatureTemperature

Carrying CapacityCarrying CapacityLimiting Factors lead Limiting Factors lead to to Carrying Carrying Capacity: the Capacity: the largest population largest population an environment an environment can sustain.can sustain.

What is the What is the maximum amount maximum amount of wolves that can of wolves that can be sustained in be sustained in Yellowstone?Yellowstone?

Logistic GrowthLogistic Growth

Carrying Capacities are NOT fixed

A population of wolves is A population of wolves is reintroduced into Yellowstone reintroduced into Yellowstone

National Park. For the first decade, National Park. For the first decade, the wolf population grows the wolf population grows exponentially. Then, the exponentially. Then, the

population growth slows. The new population growth slows. The new pattern is known as ___pattern is known as ___

LOGISTIC GROWTHIn the example above, where wolves are reintroduced to Yellowstone National Park, the number of elk and other prey species within the park are _____Limiting Factors

Biotic PotentialBiotic Potential•An organism’s maximum ability to produce offspring in ideal conditions

•Many factors influence biotic potential, including gestation time and generation time.

•Organisms with high biotic potential can recover more quickly from population declines than organisms with low biotic potential.

Biotic PotentialBiotic Potential

Scorpion FishScorpion FishMature 3-5 yearsMature 3-5 yearsRelease 50,000 to Release 50,000 to 100,000 eggs100,000 eggsOnce fertilized Once fertilized take 12-16 days to take 12-16 days to hatchhatchHIGH BIOTIC HIGH BIOTIC POTENTIALPOTENTIAL

OrangutansOrangutansFemales Mature Females Mature 10 years10 yearsBirth to single Birth to single babies once every babies once every eight yearseight yearsLOW BIOTIC LOW BIOTIC POTENTIAL POTENTIAL

Section 3 Population Growth Section 3 Population Growth ReviewReview

Describe the factors that influence Describe the factors that influence population’s growth ratepopulation’s growth rate

Explain exponential and logistic growthExplain exponential and logistic growth Explain how limiting factors and biotic Explain how limiting factors and biotic

potential affect population growthpotential affect population growth TERMS: survivorship curve, TERMS: survivorship curve,

immigration, emigration, exponential immigration, emigration, exponential growth, carrying capacity, logistic growth, carrying capacity, logistic growth, biotic potentialgrowth, biotic potential

Chapter 4 Big IdeasChapter 4 Big Ideas

In an ecosystem, the biotic and In an ecosystem, the biotic and abiotic components interact to abiotic components interact to form an interconnected system.form an interconnected system.

Humans classify the diversity of Humans classify the diversity of life on Earth in order to better life on Earth in order to better understand their relationships.understand their relationships.

Population sizes change Population sizes change according to changes in the according to changes in the environment. environment.

Think About: EssaysThink About: Essays

Explain how limiting factors and Explain how limiting factors and biotic potential interact to regulate biotic potential interact to regulate the population growth of a species.the population growth of a species.

What are some of the benefits for What are some of the benefits for humans of keeping track of the humans of keeping track of the population sizes of wild species?population sizes of wild species?