Warm-Up Questions 1.How old is the Earth? 2.How long ago did life originate on Earth? 3.What did the first life-forms look like? 4.How long ago did dinosaurs.

Warm-Up Questions

1. How old is the Earth?

2. How long ago did life originate on Earth?

3. What did the first life-forms look like?

4. How long ago did dinosaurs go extinct?

5. How long ago did human beings appear on Earth?

Warm-Up Questions

1. How did life emerge on Earth?

2. How do we know what organisms lived in the past?

3. What is the theory of evolution?

4. What is natural selection?

5. What is artificial selection?

6. What does “survival of the fittest” mean?

Evolution and Biodiversity:Origins, Niches, and Adaptations

What is Evolution?Chapter 5

Evolution and Biodiversity:Origins, Niches, and Adaptations

What is Evolution?Chapter 5

Key ConceptsKey Concepts

Origins of lifeOrigins of life

Evolutionary processesEvolutionary processes

Ecological nichesEcological niches

Species formationSpecies formation

Species extinctionSpecies extinction

Earth: The Just-Right, Adaptable Planet

Earth: The Just-Right, Adaptable Planet

• During the 3.7 billion During the 3.7 billion years since life years since life arose, the average arose, the average surface temperature surface temperature of the earth has of the earth has remained within the remained within the range of 10-20range of 10-20ooCC

• What other What other conditions make life conditions make life on Earth possible?on Earth possible?

Origins of LifeOrigins of Life• Evidence suggests that life on earth developed Evidence suggests that life on earth developed

in 2 phases: Chemical Evolution and Biological in 2 phases: Chemical Evolution and Biological EvolutionEvolution

• Chemical EvolutionChemical Evolution– formation of the Earth’s crust and atmosphereformation of the Earth’s crust and atmosphere– evolution of the biological molecules necessary evolution of the biological molecules necessary

for lifefor life– evolution of the systems of chemical reactions evolution of the systems of chemical reactions

needed to produce living cells needed to produce living cells ((protocells))

Electrical sparkssimulating lightingprovide energy tosynthesize organic compounds

Sample for chemical analysis

Cooled water containing organic compounds

Cold water

Condenser

ElectrodeWater vapor

H2O

CH4

CO2N2

NH3 H2

H2O

Origins of LifeOrigins of Life

• http://www.youtube.com/watch?v=iahBQolXQH8

• https://massasoit.instructure.com/courses/346438/wiki/video-the-primordial-soup-with-julia-child

Plants begininvadingland

Evolution and expansion of life

First fossilrecord ofanimals

Plants invade the land

Age of reptiles

Age of mammals

Insects and amphibians invade the land

Modern humans(Homo sapiens)appear about2 secondsbefore midnight

Recorded humanhistory begins¼ secondbefore midnight

Origin of life (3.6–3.8 billion years ago)

noon

midnight

History of the Earth CalendarHistory of the Earth Calendar

• First living cells - April 1st, 6pm• Algae & Marine Invertebrates - November 26th, 4:24am• Arthropods, Mollusks, first fish - December 1st, 6:36am• Many fish, trilobites, vascular plants - December 5th, 7:42am• Age of fishes, first amphibians, first insects - December 7th, 4:24am• Mosses, many amphibians, first reptiles - December 13th, 6pm• First mammals and dinosaurs - December 16th, 10:14pm• Age of Dinosaurs, first birds - December 19th, 1:03am• Flowering plants, mass extinction - December 23rd, 5:54am• Birds and mammals flourish - December 28th, 1:09am• Hominids, ice ages, giant mammals - December 31st, 9:09pm

How Do We Know Which Organisms Lived in the Past?

How Do We Know Which Organisms Lived in the Past?

• Our knowledge Our knowledge about past life about past life comes from fossils, comes from fossils, chemical analysis, chemical analysis, cores drilled out of cores drilled out of buried ice, and buried ice, and DNA analysisDNA analysis

Comparing Anatomy and Comparing Anatomy and EmbryologyEmbryology

Comparing Anatomy and Comparing Anatomy and EmbryologyEmbryology

• Homologous Homologous StructuresStructures– Parts that are similar

in structure but different in function

– Humans, penguins, alligators, bats all have the same bones in their arms but they are used for different things

Comparing Anatomy and Embryology


• Analogous Structures– Parts that are similar in

function but not structure

– Ex: wings of bee, bird, bat



• Similar EmbryosSimilar Embryos– Embryos of different

(but related) organisms are very similar and have similar structures early on

– Must have similar proteins at work



• Vestigial StructuresVestigial Structures– Structures that are

so reduced in size of function that they are merely traces of similar organs in other species

– Ex: tailbone and appendix in humans

FossilsFossils

• Mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items provide physical evidence of organisms

• Fossil record is INCOMPETE

FossilsFossils"It isn't easy to become a fossil… Only about one bone in a billion, it is thought, becomes fossilized. If that is so, it means that the complete fossil legacy of all the Americans alive today – that's about 310 million people with 206 bones each – will only be about 50 bones, one-quarter of a complete skeleton. That's not to say, of course, that any of these bones will ever actually be found. Bearing in mind that they can be buried anywhere within an area of slightly over 9.3 million square kilometers, little of which will ever be turned over, much less examined, it would be something of a miracle if they ever were”~ Bill Bryson

Origins of LifeOrigins of Life

• Biological evolutionBiological evolution– change in the genetic makeup of a population of

a species in successive generations, if continued long enough it can lead to the formation of a new species

– How do new genes get into the population?• mutations, genetic drift (organisms coming in and

out of the population)

– Populations – NOT INDIVIDUALS – evolvePopulations – NOT INDIVIDUALS – evolve

Evolution and AdaptationEvolution and Adaptation

Theory of Evolution – all species descended Theory of Evolution – all species descended from earlier, ancestral species. from earlier, ancestral species. HOMER

• MacroevolutionMacroevolution - long-term, large-scale - long-term, large-scale evolutionary changes through whichevolutionary changes through which

• new species are formednew species are formed from ancestral from ancestral species andspecies and

• other species are lostother species are lost through extinction through extinction


• MicroevolutionMicroevolution - small genetic - small genetic changes that occur changes that occur in a populationin a population

• Genes mutate, individuals are selected Genes mutate, individuals are selected and populations evolveand populations evolve

• Gene poolGene pool – set of all genes in the – set of all genes in the individuals of the population of a speciesindividuals of the population of a species

• MutationMutation – changes in the – changes in the structurestructure or or numbernumber of DNA molecules in a cell of DNA molecules in a cell

– Mutations are random, rare, Mutations are random, rare, only only source of totally new allelessource of totally new alleles

» Exposure to mutagensExposure to mutagens» Mistakes during replicationMistakes during replication


Natural selectionNatural selection• Process in by which individuals of a Process in by which individuals of a

population acquire population acquire genetically based traitsgenetically based traits that that increaseincrease their their chances of survivalchances of survival and and their their ability to produce offspringability to produce offspring

Adaptation (n.)Adaptation (n.)– A heritable trait that enables an A heritable trait that enables an

organism to better survive and organism to better survive and reproduce under a given set of reproduce under a given set of environmental conditionsenvironmental conditions

Artificial selectionArtificial selection• Humans select one or more desirable Humans select one or more desirable

genetic traits in the population of a plant genetic traits in the population of a plant or animalor animal

Artificial SelectionArtificial Selection

• The selective breedingselective breeding of domesticated plants and animals by man.

• Question:Question:What’s the ancestor of the domesticated dog?

• Answer:Answer: WOLFWOLF

Natural SelectionNatural Selection

Conditions necessary for natural Conditions necessary for natural selection:selection:– VariabilityVariability – phenotypic differences – phenotypic differences

in a traitin a trait– HeritabilityHeritability – trait must have a – trait must have a

genetic basis to evolvegenetic basis to evolve– Differential Reproductive SuccessDifferential Reproductive Success

– phenotypic traits determine – phenotypic traits determine individual survival and successindividual survival and success• Combination of survival and reproduction Combination of survival and reproduction

is called “fitness”is called “fitness”

Fig. 5-4 p. 96

CD ANIMATION 4

Fig. 5-4 p. 96

CD ANIMATION 4

3 Types of Natural Selection3 Types of Natural Selection

Stabilizing SelectionIndividuals with the average form of a trait have the highest fitnessRepresents the optimum for most traitsResults in a similar morphology between most members of the species

Directional SelectionIndividuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the traitA shift in one directionPeppered moth

Diversifying SelectionIndividuals with either extreme variation of a trait have greater fitness than individuals with the average form of the traitA shift in both direction, away from the centerShell color (dark rocks and light sand)

Warm-UpWarm-Up

• What is the difference between stabilizing, directional, and diversifying natural selection?

Directional Natural SelectionDirectional Natural Selection

Natural selection

New average Previous average

Num

ber

of in

divi

dual

s

Coloration of snails

Proportion of light-coloredsnails in population increases

Num

ber

of in

divi

dual

s

Snail colorationbest adaptedto conditions

Average


Average shifts

Stabilizing Natural SelectionStabilizing Natural Selection


Light snailseliminated

Dark snailseliminated

Num

ber

of in

divi

dual

s


Snails withextreme

coloration areeliminated

Num

ber

of in

divi

dual

s

Average remains the same,but the number of individuals withintermediate coloration increases

Natural selection

Number of individuals with light and dark coloration

increases, and the number with intermediate coloration decreases


Num

ber

of in

divi

dual

s Snails with light and darkcolors dominate

Diversifying Natural SelectionDiversifying Natural Selection


Num

ber

of in

divi

dual

s

Light colorationis favored

Darkcolorationis favored

Intermediate-colored snails are selected against

Natural selection

Evolution PrimersEvolution Primers

• Isn't Evolution Just a Theory???

• How Does Evolution Really Work?

• How Do We Know Evolution Happens?

Limits on Adaptation Through

Natural Selection

Limits on Adaptation Through

Natural Selection

• A population’s ability to adapt to new A population’s ability to adapt to new environmental conditions through environmental conditions through natural selection is natural selection is limited by its gene limited by its gene poolpool and and how fast it can reproducehow fast it can reproduce– Humans have a relatively slow generation Humans have a relatively slow generation

time (decades) and output (number of time (decades) and output (number of offspring) versus some other speciesoffspring) versus some other species

Common Myths about Evolution through Natural

Selection

Common Myths about Evolution through Natural

Selection

• Misconception #1: Survival of the fittest Misconception #1: Survival of the fittest means survival of the strongestmeans survival of the strongest– It is referring to It is referring to REPRODUCTIVE SUCCESSREPRODUCTIVE SUCCESS

• Misconception #2: Evolution involves Misconception #2: Evolution involves some grand plan of nature in which some grand plan of nature in which species become progressively more species become progressively more perfectperfect– Organisms do not develop certain traits Organisms do not develop certain traits

because they need thembecause they need them– There is no such thing as “genetic perfection”There is no such thing as “genetic perfection”


• Co-EvolutionCo-Evolution– Populations of two Populations of two

differentdifferent species species interactinginteracting over a long over a long period of timeperiod of time

– Changes in the gene pool Changes in the gene pool of one species can lead of one species can lead to changes the gene pool to changes the gene pool of another speciesof another species• Predator-prey relationships Predator-prey relationships • Plant defense mechanisms Plant defense mechanisms

Ecological Niches and HabitatsEcological Niches and Habitats

• Ecological nicheEcological niche– Total way of life or functional role Total way of life or functional role

of a species in an ecosystemof a species in an ecosystem

• HabitatHabitat– Physical location of a speciesPhysical location of a species

Occupation

Address

Ecological Niches and AdaptationEcological Niches and Adaptation

• Fundamental nicheFundamental niche– Full potential range of the Full potential range of the

physical, chemical, and biological physical, chemical, and biological factors a species can use if there factors a species can use if there were were no directno direct competitioncompetition from from other speciesother species

• Realized nicheRealized niche– Parts of a species’ fundamental Parts of a species’ fundamental

niche that are actually usedniche that are actually used

Broad and Narrow NichesBroad and Narrow Niches

• Generalist speciesGeneralist species– Species with a Species with a broadbroad ecological niche ecological niche

• Live in many different placesLive in many different places• Eat a variety of foodEat a variety of food• Tolerate a wide range of environmental Tolerate a wide range of environmental

conditionsconditions• Ex: flies, mice, deer, catfish, humansEx: flies, mice, deer, catfish, humans

• Specialist speciesSpecialist species– Species with a Species with a narrownarrow ecological niche ecological niche

• Live only in one type of habitatLive only in one type of habitat• Use only a few types of foodUse only a few types of food• Tolerate only a narrow range of climatic and Tolerate only a narrow range of climatic and

other environmental conditionsother environmental conditions• Ex: tiger salamander, spotted owls, pandasEx: tiger salamander, spotted owls, pandas

Generalist and Specialist Species:

Broad and Narrow Niches

Generalist and Specialist Species:

Broad and Narrow Niches• Generalist Generalist

species species tolerate a tolerate a wide range of wide range of conditionsconditions

• Specialist Specialist species can species can only tolerate only tolerate a narrow a narrow range of range of conditionsconditions

Is it better to be a Generalist or a Specialist?

Is it better to be a Generalist or a Specialist?

Answer: It depends

Speciation, Extinction, and Biodiversity


Speciation - Speciation - formation of formation of two species two species from onefrom one species because of species because of divergent divergent natural selectionnatural selection

1)1)Geographic isolation – Geographic isolation – groups groups of the same species become of the same species become physically separatedphysically separated

Geographic IsolationGeographic Isolation

…can lead to reproductive isolation, divergence of gene pools and speciation.



2)2) Reproductive IsolationReproductive Isolation – – isolated populations become isolated populations become so genetically different they so genetically different they cannot . . . cannot . . .

InterbreedInterbreedProduce live, fertile Produce live, fertile

offspringoffspring

Extinction: Lights OutExtinction: Lights Out

• Extinction occurs when the population cannot adapt to changing environmental conditionsThe golden toad of Costa The golden toad of Costa

Rica’s Monteverde cloud Rica’s Monteverde cloud forest has become extinct forest has become extinct because of changes in because of changes in climateclimate

Extinction: Lights OutExtinction: Lights Out

•99.9 % of all species that ever existed are now extinct

Tertiary

Bar width represents relative number of living speciesEra Period

Species and families experiencing

mass extinction

Millions ofyears ago

Ordovician: 50% of animal families, including many trilobites.

Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.

500

345

Cambrian

Ordovician

Silurian

Devonian

Extinction

Extinction

Pal

eozo

icM

eso

zoic

Cen

ozo

ic

Triassic: 35% of animal families, including many reptiles and marine mollusks.

Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.Carboniferous

Permian

Current extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including manyforaminiferans and mollusks.

Extinction

Extinction

Triassic

Jurassic

Cretaceous

250

180

65Extinction

ExtinctionQuaternary Today

ExtinctionExtinction

• Background extinctionBackground extinction– Normal extinctionNormal extinction of various of various

species as a result of changes in species as a result of changes in local environmental conditionslocal environmental conditions

• Mass extinctionMass extinction– Extinction resulting from Extinction resulting from

catastrophic, wide-spread eventcatastrophic, wide-spread event in which large groups of existing in which large groups of existing species are wiped outspecies are wiped out

Period of Recovery Following ExtinctionPeriod of Recovery

Following Extinction

Adaptive radiation -Adaptive radiation -

Process in which numerous Process in which numerous new species evolve to new species evolve to fill fill vacant and new ecological vacant and new ecological nichesniches in changed in changed environmentsenvironments

How do speciation and extinction affect

biodiversity?

How do speciation and extinction affect

biodiversity?

Speciation – Extinction = Speciation – Extinction = BiodiversityBiodiversity

Extinctions and depletions temporarily Extinctions and depletions temporarily reduce biodiversity YET create reduce biodiversity YET create

evolutionary opportunitiesevolutionary opportunities for surviving for surviving species to undergo species to undergo adaptive radiationsadaptive radiations

to fill unoccupied and new biological to fill unoccupied and new biological nichesniches

Effects of Humans on Biodiversity

Effects of Humans on Biodiversity

• The scientific consensus is that The scientific consensus is that human activities human activities are decreasing the earth’s biodiversityare decreasing the earth’s biodiversity

Warm-Up Questions 1.How old is the Earth? 2.How long ago did life originate on Earth? 3.What did the first life-forms look like? 4.How long ago did dinosaurs.

Documents

land evolution

atmosphere evolution

expansion of life

theory of evolution

origins of life evidence

earth possible

origins of life http

earth calendar