evolution and biodiversity: origins, niches, and adaptations what is evolution? chapter 5 evolution...
TRANSCRIPT
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))
Fig. 5-2 p. 93Fig. 5-2 p. 93
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
Animation on CD
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 begins1/4 secondbefore midnight
Origin of life(3.6–3.8 billionyears ago)
noon
midnight
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 analysis.DNA analysis.
Comparing Anatomy and EmbryologyComparing Anatomy and EmbryologyComparing Anatomy and EmbryologyComparing Anatomy and Embryology• Homologous StructuresHomologous Structures
– 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
• Similar EmbryosSimilar Embryos– Embryos of different
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 (I.e. tailbone and appendix in humans)
• Analogous Structures– Parts that are
similar in function but not structure
– i.e. Wing of bee, bird, bat
Fossilsmineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such itemsprovide physical evidence of organismsFossil record is INCOMPETE – only found and 1% of the species that are believed to have lived
Fossilsmineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such itemsprovide physical evidence of organismsFossil record is INCOMPETE – only found and 1% of the species that are believed to have lived
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.
Evolution and AdaptationEvolution and Adaptation
• MicroevolutionMicroevolution - small genetic changes - small genetic changes that occur that occur in a population. Genes in a population. Genes mutate, individuals are selected and mutate, individuals are selected and populations evolve.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 number number of DNA molecules in a cellof 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
Evolution and AdaptationEvolution and Adaptation
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 animal.or 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• This is CaraThis is Cara
Natural SelectionNatural Selection
Conditions necessary for natural Conditions necessary for natural selection:selection:– Variability – phenotypic differences in a Variability – phenotypic differences in a
traittrait– Heritability – trait must have a genetic Heritability – trait must have a genetic
basis to evolvebasis to evolve– Differential Reproductive Success – Differential Reproductive Success –
phenotypic traits determine individual phenotypic traits determine individual survival and successsurvival 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
1)1) Directional Selection Directional Selection (peppered moth example)(peppered moth example)
2)2) Stabilizing SelectionStabilizing Selection
3)3) Diversifying SelectionDiversifying Selection
Evolution as Genetic Change in PopulationsEvolution as Genetic Change in Populations
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
Disruptive 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)
How Natural Selection Works – 3 Types
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
Coloration of snails
Average shifts
Stabilizing Natural SelectionStabilizing Natural Selection
Coloration of snails
Light snailseliminated
Dark snailseliminated
Num
ber
of in
divi
dual
s
Coloration of snails
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
Coloration of snails
Num
ber
of in
divi
dual
s Snails with light and darkcolors dominate
Diversifying Natural SelectionDiversifying Natural Selection
Coloration of snails
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 limited by its gene poolgene pool and and how fast it can how fast it can reproducereproduce..– Humans have a relatively slow Humans have a relatively slow
generation time (decades) and output generation time (decades) and output (# of young) versus some other species.(# of young) versus some other species.
Common Myths about Evolution through Natural
Selection
Common Myths about Evolution through Natural
Selection• Evolution through natural selection is Evolution through natural selection is
about the most descendants.about the most descendants.• Misconception 1: survival of the fittest Misconception 1: survival of the fittest
does not mean survival of the strongest – does not mean survival of the strongest – it is referring to it is referring to REPRODUCTIVE SUCCESSREPRODUCTIVE SUCCESS
• Misconception 2: Evolution involves some Misconception 2: Evolution involves some grand plan of nature in which species grand plan of nature in which species become progressively more perfectbecome progressively more perfect– Organisms do not develop certain traits Organisms do not develop certain traits
because they need them.because they need them.– There is no such thing as genetic perfection.There is no such thing as genetic perfection.
Evolution and AdaptationEvolution and Adaptation
• Co-EvolutionCo-Evolution– Populations of two Populations of two differentdifferent species species
interactinginteracting over a long period of time over a long period of time
– Changes in the gene pool of one Changes in the gene pool of one species can lead to changes the gene species can lead to changes the gene pool of another speciespool of another species
• Predator-Prey Relationships (salamander Predator-Prey Relationships (salamander and snake – the coffee pot incident)and snake – the coffee pot incident)
• Plant defense mechanisms (mistletoe plant)Plant defense mechanisms (mistletoe plant)
Ecological Niches and AdaptationEcological Niches and Adaptation
• Ecological nicheEcological niche– Total way of life or functional role Total way of life or functional role
of a species in an ecosystem.of 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 physical, Full potential range of the physical,
chemical, and biological factors a chemical, and biological factors a species can use if there were species can use if there were nono directdirect competitioncompetition from other species. from other species.
• Realized nicheRealized niche– Part of a species fundamental niche Part of a species fundamental niche
that are actually used.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 places.Live in many different places.• Eat a variety of food.Eat a variety of food.• Tolerate a wide range of environmental Tolerate a wide range of environmental
conditions.conditions.(flies, mice, deer, catfish, humans)(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 conditions.other environmental conditions.(tiger salamander, red-cockaded woodpecker, (tiger salamander, red-cockaded woodpecker, spotted owls, pandas)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 conditions.conditions.
• Specialist Specialist species can species can only tolerate only tolerate a narrow a narrow range of range of conditions.conditions.
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, 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.
Speciation, Extinction, and Biodiversity
Speciation, Extinction, and Biodiversity
2)2) Reproductive IsolationReproductive Isolation – – isolated populations become isolated populations become so genetically different they so genetically different they cannot . . . cannot . . .
Interbreed, orInterbreed, orproduce live, fertile produce live, fertile
offspringoffspring
Extinction: Lights OutExtinction: Lights Out
• Extinction occurs when the population cannot adapt to changing environmental conditions.The 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 climate.climate.
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 species as of various species as
a result of changes in local a result of changes in local environmental conditionsenvironmental conditions
• Mass extinctionMass extinction– extinction resulting from extinction resulting from catastrophic, catastrophic,
wide-spread eventwide-spread event in which large in which large groups of existing species are wiped outgroups of existing species are wiped out
• Adaptive radiationAdaptive radiation– Process in which numerous new species Process in which numerous new species
evolve to evolve to fill vacant and new ecological fill vacant and new ecological nichesniches in changed environments in changed environments
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..
