announcements midterm exam: wednesday, nov 3 rd midterm exam: wednesday, nov 3 rd review this week...

AnnouncementsAnnouncements

• Midterm Exam: Wednesday, Nov 3Midterm Exam: Wednesday, Nov 3rdrd

• Review this week in section:Review this week in section:• Bring questions to sectionBring questions to section

Summary from FridaySummary from Friday• Building a model to show population Building a model to show population

interactionsinteractions• Age structure affects populationAge structure affects population• Life tablesLife tables

• static vs. cohort-basedstatic vs. cohort-based• Life strategiesLife strategies

• opportunists vs. competitorsopportunists vs. competitors• seasonal variation in life strategy within seasonal variation in life strategy within

a speciesa species• NicheNiche

What is a What is a nicheniche??

• A A nicheniche is the total of all biotic and is the total of all biotic and abiotic factors that determine how an abiotic factors that determine how an organism fits into its environment.organism fits into its environment.

• Where and how does an organism Where and how does an organism live and function?live and function?• habitathabitat• role in communityrole in community

Environmental variable (Temperature, for example)

Succ

ess

optimum

potential survival,

but stressed

potential survival,

but stressed

intolerant intolerant

Niche in n-variable hyperspace

Fundamental vs. Realized Niche

Fundamental niche: where a species could live

Realized niche: with competition from other species, where a species does live

Niche Partitioning in Animals

• Species divide up an apparent niche

annual grassesperennial grasses

Convergent EvolutionConvergent Evolution

• Organisms adapt to fill open nichesOrganisms adapt to fill open niches• Organisms in two different Organisms in two different

environments that are not closely environments that are not closely related may have the same “job” and related may have the same “job” and similar anatomysimilar anatomy

Selection minimizes competition

Two species living separately.

Two species living together.

Species interactionsSpecies interactions

• CompetitionCompetition• Mutualism Mutualism

• both species benefitboth species benefit

• Commensalism Commensalism • one benefits, other is unaffectedone benefits, other is unaffected

• Parasitism Parasitism • one benefits, one losesone benefits, one loses

• Predator-PreyPredator-Prey

ParasitismParasitism

• microparasites vs. macroparasitesmicroparasites vs. macroparasites• BiotropicBiotropic

• thrive on live hosts onlythrive on live hosts only

• NecrotropicNecrotropic• can benefit even if host diescan benefit even if host dies

• ParasitoidsParasitoids• always kill their hostalways kill their host

Predator-Prey RelationshipsPredator-Prey Relationships

• Prey defensesPrey defenses• coevolutioncoevolution

• as predator evolves, prey evolves to evade itas predator evolves, prey evolves to evade it




• warning coloration and mimicrywarning coloration and mimicry• aposematic “away signal” = bright red and aposematic “away signal” = bright red and

yellowyellow• some mimics very toxic, others harmlesssome mimics very toxic, others harmless






• camouflagecamouflage• blending inblending in






• camouflagecamouflage• blending inblending in

• moment-of-truth defensesmoment-of-truth defenses• large or startling displayslarge or startling displays


• Optimal Foraging Theory- describes Optimal Foraging Theory- describes how prey are chosenhow prey are chosen• small prey provide little food, but they small prey provide little food, but they

are easy to huntare easy to hunt• large prey provide a lot of food, but they large prey provide a lot of food, but they

are more difficult to huntare more difficult to hunt

• Trophic CascadesTrophic Cascades• Food webs can be complexFood webs can be complex

Prey Selection

Trophic CascadeTrophic Cascade

Eagles

Foxes

Mice

Plants 1st trophic level

2nd trophic level

3rd trophic level

4th trophic level

autotroph/ primary producer

herbivore/ primary

consumer

predator/ secondary consumer

predator/ tertiary consumer


Eagles

Foxes

Mice


2nd trophic level

3rd trophic level

4th trophic level

if eagles go extinct, what could happen to…

foxes?

mice?

plants?


Eagles

Foxes

Mice


2nd trophic level

3rd trophic level

4th trophic levelIf a new

predator on mice is introduced, what could happen to…

mice?

foxes?

plants?

eagles?


Eagles

Foxes

Mice


2nd trophic level

3rd trophic level

4th trophic levelIf drought

caused a dip in plant production, what would happen to…

mice?

foxes?

eagles?

Simplified Temperate Forest Food Simplified Temperate Forest Food WebWeb

To which trophic level do these organisms To which trophic level do these organisms belong?belong?

Oak seedling

Deer

Wolf

Fox

Rabbit

Grasses Herbs

Caterpillars

Shrews

Eagle

Optimal ForagingOptimal Foraging• Predators tend to target dominant Predators tend to target dominant

preyprey• enhancement of diversityenhancement of diversity

• What about herbivores?What about herbivores?• don’t necessarily eat dominant plantsdon’t necessarily eat dominant plants• plants have secondary compounds and plants have secondary compounds and

chemical toxins that taste badchemical toxins that taste bad herbivores may target tasty rare plants

Community EcologyCommunity Ecology

A A communitycommunity is a group of living is a group of living organisms that organisms that occupy a certain areaoccupy a certain area and and interact with one another.interact with one another.

• Niche partitioningNiche partitioning• Species interactionsSpecies interactions• Food web dynamicsFood web dynamics• Environmental variation/disturbanceEnvironmental variation/disturbance

• driver of diversitydriver of diversity

Do communities change?Do communities change?

• What we see now wasn’t always hereWhat we see now wasn’t always here• communities do changecommunities do change

• Spatial scale is importantSpatial scale is important• global vs. local changeglobal vs. local change

• Time scale is importantTime scale is important• long term changelong term change

• measured in 10’s of thousands of years or moremeasured in 10’s of thousands of years or more

• short term changeshort term change• measure on a decadal time scalemeasure on a decadal time scale

AnnouncementsAnnouncements

• Look at course webpage for Look at course webpage for study guidestudy guide• Read Enserink Read Enserink et al.et al. articles “Biological articles “Biological

Invasions Invasions Sweep In…” for section next Sweep In…” for section next week (after week (after midterm)midterm)

• Please let know today if you have special Please let know today if you have special needs needs for the examfor the exam

• Note on syllabus: problem set will be Note on syllabus: problem set will be handed out handed out Nov. 10Nov. 10thth

• Office hours: Monday after classOffice hours: Monday after class

http://www.es.ucsb.edu/classes/envs100/

Summary from WednesdaySummary from Wednesday

• Niche partitioning Niche partitioning • Convergent evolutionConvergent evolution• Community ecologyCommunity ecology

• Species interactionsSpecies interactions• Optimal foraging theory and prey Optimal foraging theory and prey

selectionselection• Herbivory and plant selectionHerbivory and plant selection• Trophic cascades and food web dynamicsTrophic cascades and food web dynamics• Change over timeChange over time

How do we detect long-term How do we detect long-term change?change?

• Sediment coresSediment cores• Ice coresIce cores• Pollen recordsPollen records• Fossil recordsFossil records• Packrat middensPackrat middens• Tree ringsTree rings

IsotopesIsotopes• Isotope: Isotope: element where atoms have a different # element where atoms have a different #

of neutronsof neutrons

= proton

= neutron

O18O16

Lighter and common Heavy and rare


of neutronsof neutrons• Can be used to detect global-scale long-term Can be used to detect global-scale long-term

changechange


of neutronsof neutrons• Can be used to detect global-scale long-term Can be used to detect global-scale long-term

changechange• Total oxygen pool is composed of: Total oxygen pool is composed of:

• Mix ofMix of OO1616 and and OO1818

• Fractionation during seawater evaporationFractionation during seawater evaporation• OO1616 evaporates easilyevaporates easily

• OO1818 gets left behindgets left behind

Isotopes in Sediment CoresIsotopes in Sediment Cores• Sediment contains foraminiferansSediment contains foraminiferans

• microscopic sea creaturesmicroscopic sea creatures• OO1616//OO1818 in tests reflects that of seawater in tests reflects that of seawater• live on sediment or sink to bottom when deadlive on sediment or sink to bottom when dead

Isotopes in Sediment CoresIsotopes in Sediment Cores• Sediment contains foraminiferansSediment contains foraminiferans

• microscopic sea creaturesmicroscopic sea creatures• OO1616//OO1818 in tests reflects that of seawater in tests reflects that of seawater• live on sediment or sink to bottom when deadlive on sediment or sink to bottom when dead

• If the climate cools…If the climate cools…• ice sheets will expandice sheets will expand• ice comes from rain from evaporated seawaterice comes from rain from evaporated seawater• evaporated seawater is high in Oevaporated seawater is high in O1616

• seawater left behind high in Oseawater left behind high in O1818

• therefore, high Otherefore, high O1818 in ocean = cold conditions in ocean = cold conditions

Variation in Ocean O18

more negative values: less O18 and warmer conditions

less negative values: more O18 and colder conditions

Ice core Ice core measurements:measurements:

• thickness of layersthickness of layers• physical propertiesphysical properties• dust and siltdust and silt• conductivityconductivity• trapped air (COtrapped air (CO22, ,

NONOxx, and O, and O22))

• ions (Kions (K++, Ca, Ca2+2+, NO, NO33--))

• isotopesisotopes

Pollen records can be used to detect long term change on a regional scale.

Trees can migrate 200-300 miles in 1000 years.

J. G. Ogden III, 1966.

Fossil Pollen – Silver Lake, OH

Dendrochronology:Dendrochronology:• exact calendar dating exact calendar dating

using annual growth using annual growth rings in woodrings in wood

Dendroclimatology:Dendroclimatology:• using tree rings to using tree rings to

look at past climatelook at past climate• very old trees can be very old trees can be

used to get the used to get the longest historylongest history

• Bristlecone pine Bristlecone pine (Pinus longaeva)(Pinus longaeva)

White Mountains, CA White Mountains, CA

~5000 years old~5000 years old

Soil Soil developmentdevelopment

• Weathering of Weathering of primary mineralsprimary minerals• nutrients become nutrients become

more availablemore available• in old soils, the in old soils, the

nutrients get nutrients get leached outleached out

• Formation of Formation of claysclays

• Accumulation of Accumulation of organic matterorganic matter

Long-Term ChangeLong-Term Change

Shifts in climateShifts in climate

Change in vegetation

Change in soil development

Change in animal populations

Long-Term ChangeLong-Term Change

Shifts in climateShifts in climate

Change in vegetation

Change in soil development

Change in animal populations

Community change

Short-Term ChangeShort-Term Change

SuccessionSuccessionTextbook definition: Textbook definition:

““a change in species that occupy a given a change in species that occupy a given area, with some species invading and area, with some species invading and becoming more numerous while others becoming more numerous while others decline in population and disappear”decline in population and disappear”

Can be thought of as the Can be thought of as the replacement replacement of one community by anotherof one community by another

Primary vs. Secondary Primary vs. Secondary SuccessionSuccession

• Primary:Primary:• Community gets established on a Community gets established on a new new

surfacesurface• Lava flowLava flow• River sandbarRiver sandbar• Glacial moraineGlacial moraine

• Secondary:Secondary:• Recovery following disturbanceRecovery following disturbance

• FireFire• FloodFlood• Post-agriculturePost-agriculture

• Primary SuccessionPrimary Succession• Can take Can take

hundreds to hundreds to thousands of thousands of yearsyears

• Soil must developSoil must develop• New species New species

must come from must come from somewhere elsesomewhere else

• Secondary Secondary SuccessionSuccession• FasterFaster

EarlyEarly vs.vs. Late Late Succession Succession SpeciesSpecies

EarlyEarly• shade intolerantshade intolerant• nutrient nutrient

demandingdemanding• short-livedshort-lived• poor competitorspoor competitors

LateLate• shade tolerantshade tolerant• adapted to lower adapted to lower

nutrient nutrient conditionsconditions

• long-livedlong-lived• good good

competitorscompetitors

Classic SuccessionClassic Succession

Clements’ idea of “climax community” Clements’ idea of “climax community” • eventually, a given system reaches eventually, a given system reaches

a predictable steady-state a predictable steady-state • independent of the early independent of the early

succession communitysuccession community

Mixed Beech-Maple Forest

Oak-Hickory

Willow shrub

Cattail marsh

Aquatic plants

Swamp

Oak woodland

Sumac-Pine

Broomsedge

Aster-Goldenrod

Annual weeds

Old field

Oak forest

Pine forest

Poplars

Dune grass

Sand dune

Bird succession

announcements midterm exam: wednesday, nov 3 rd midterm exam: wednesday, nov 3 rd review this week...

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