Environmental ScienceEnvironmental ScienceChapter 4:Chapter 4:

Population EcologyPopulation Ecology

February 3, 2014- February 3, 2014- SIGN SIGN ININ1. Get an environmental science book (FROG on it)

2. Do the following questions…DO NOT WRITE the question, only the answers

1. Page: 89 questions: 1,2,32. Page : 94 questions: 23,24,253. Page : 103 questions: 1,2,34. Page : 109 questions: 1,3,45. Page : 117 questions: 1,2,3

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 W

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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 W

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All Ecosystems are All Ecosystems are connectedconnected

How does your ecosystem impact the Atlantic Ocean?

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

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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

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Organizing Organizing Biotic PartsBiotic Parts

Smallest UnitSmallest Unit

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

Species are groups of Species are groups of organismsorganisms

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Species Species Species: Species: groups of groups of

organisms that resemble organisms that resemble each other in:each other in:

1.1. appearanceappearance2.2.BehaviorBehavior3.3.ChemistryChemistry4.4.genetic makeupgenetic makeup5.5.able to reproduce VIABLE able to reproduce VIABLE

offspringoffspring 3.6 to 100 million species 3.6 to 100 million species

(1.4 identified)(1.4 identified)

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PopulationPopulation

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

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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.

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EcosystemEcosystem

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

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BiosphereBiosphere

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

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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.

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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)?

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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 population size.estimate population size.

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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•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

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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

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Population DistributionPopulation Distribution

•Uniform distribution: Organisms evenly spaced

•Random distribution: Organisms arranged in no particular pattern

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

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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?

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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.

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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.

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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.

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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”

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Limiting FactorsLimiting FactorsLimiting Factor Limiting Factor

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

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Carrying CapacityCarrying Capacity

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

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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.

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Open Book to page Open Book to page 122122

Answer questionsAnswer questions

17-2317-23

25-2625-26

Class workClass work

Open Book to page Open Book to page 123123

Answer question Answer question number 32number 32

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