Darwin’s Theory of Evolution Darwin Presents his Case

Darwin’s Theory of Evolution Darwin Presents his Case
Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006

Butterball turkeys have to do with EVOLUTION?
What do oranges and Butterball turkeys have to do with EVOLUTION? (Answers to come in this slide show!) THINK ABOUT IT

EVIDENCE OF EVOLUTION:
________________ 3. _______________ 4. _______________ 5. _______________ 6. _______________ 7. _______________ Artificial selection Fossil record Geographic Distribution Homologous structures Embryology DNA See Natural selection happen

Isn’t evolution just a theory?
A theory is a ____________, _______, explanation of phenomena that have occurred in the natural world, like the theory of __________________, ________, and _____________. well-supported testable gravitational attraction cell theory atomic theory

_________________ is found naturally in all populations
GENETIC VARIATION

copyright cmassengale
See Natural Selection Driving force for evolution Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable (genetic variation) During the struggle for resources, strongest survive & reproduce (natural selection) . copyright cmassengale

Darwins idea from Malthus …….. ______________________
means that members of each species must ________ for food, space, and other __________. STRUGGLE FOR EXISTANCE COMPETE RESOURCES

WHAT IS DARWIN’S THEORY?
Some organisms in a ________ are ________ to survive. Natural Selection population less likely

Darwin developed two main theories of natural selection: 1
Darwin developed two main theories of natural selection: 1. DESCENT WITH MODIFICATION 2. MODIFICATION BY NATURAL SELECTION Rd pgs in text book

____________________________
WHAT IS DARWIN’S THEORY? DESCENT WITH MODIFICATION ____________________________ suggests that each species has ___________, with ________, from other species over time. This idea suggests that all living species are ____________________, and that all species, living and extinct, share a _________________. DESCENDED CHANGES RELATED TO EACH OTHER COMMON ANCESTOR

Common Descent with Modification
Idea that organisms change with time, diverging from a common form This is what Caused evolution of new species

Descent With Modification
Takes Place Over Long Periods of Time Natural Selection Can Be Observed As Changes In Ecological Niches (their role in society) Body Structures Habitats (where they live) copyright cmassengale

Species Today Look Different From Their Ancestors Each Living Species Has Descended With Changes From Other Species Over Time copyright cmassengale

copyright cmassengale

Implies All Living Organisms Are Related Single Tree of Life DNA, Body Structures, Energy Sources Common Descent All Species, Living & Extinct, Were Derived From Common Ancestors copyright cmassengale

Natural Variation and Artificial Selection
Abandoned The Idea That Species Were Perfect & Unchanging Observed Significant Variation in All Species Observed Observed Farmers Use Variation To Improve Crops & Livestock Called Selective Breeding copyright cmassengale

mutation sexual reproduction
ARTIFICIAL SELECTION WORKS In artificial selection, ____________ provides the _________ through _________ and _________________ and ______________ those traits that they find ______. NATURE variation mutation sexual reproduction humans select useful EX: We have selected for and bred cows to produce more milk, turkeys with more breast meat, etc.

Breeds of Dogs Chihuahua – bred from Techichi of Mexico
by Mayans, had religious significance Saint Bernard – bred by monks around 1050 A.D. to rescue travelers of mountain passes in the Swiss Alps between Italy and Switzerland Irish Wolfhound – bred in Ireland to hunt wolves and elk Dachshund – bred in Germany as early as the 15th century to hunt badgers SLIDE FROM: BIOLOGY by Miller and Levine; Prentice Hall Publishing©2006

Butterball turkeys have to do with EVOLUTION?
What do oranges and Butterball turkeys have to do with EVOLUTION? THINK ABOUT IT

This is what a butterball turkey and a naval orange have in common
This is what a butterball turkey and a naval orange have in common. They have been artificially selected and sometimes genetically modified.

Major Problem in Darwin’s Theory
No mechanism (the how) to explain natural selection How could favorable variations be transmitted to later generations? With the rediscovery of Mendel’s work in the first half of the 20th century, the missing link in evolutionary theory was found . copyright cmassengale

Evidence of Evolution Key Concept
Darwin Argued That Living Things Have Been Evolving On Earth For Millions of Years. Evidence For This Process Could Be Found In: 1.The Fossil Record 2.The Geographical Distribution of Living Species 3.Homologous Structures of Living Organisms 4.Similarities In Early Development

How Do We Know Evolution Happens?
The Fossil Record – ______ are the _______ _________________ found in layers of rock in the Earth. Fossils remains of ancient organisms

How Do We Know Evolution Happens?
The layers of rock tell the history of the _____, while the _____ found within the rock tell a history of ___. The fossils are thought to be the ________ as the rock they are found in. Earth fossils life same age

Movement of Earth’s Crust
Section 15-2 Earthquakes and volcanoes cause uplifting of the layers of the Earth, taking the fossils along Sea level Fossils of marine fish found on the mountain- sides of southwest Wyoming, which at one time was covered by an inland sea Fish die in the ocean and are covered in sediment. Over time and under increasing pressure, the remains becomes fossilized Sedimentary rocks form in horizontal layers. When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers. As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.

TRANSITIONAL FOSSILS HAVE BEEN FOUND
Scientific American; Dec 2005; Vol 293; p

Geographic distribution of Fossils of similar species
Fossils of similar species have been found in different areas. Body structure is similar enough to suggest they were related and could have once been the same species.

Figure 15–14 Geographic Distribution of Living Species
Section 15-3 Differences between _____________ muskrat and coypu show _________ evolution, while similarities ______________ capybara and coypu show ___________ evolution. Beaver NORTH AMERICA Muskrat Capybara SOUTH AMERICA Coypu Beaver and Muskrat Coypu and Capybara closely-related Beaver and capybara are ______________ _______ living in very ________ environments, while beaver and musk-rat are _______________ _______ living in a ______ environment. Differences between beaver and capybara show _________ evolution, while similarities between beaver and muskrat show __________ evolution. closely-related species divergent different distantly-related distantly-related species similar convergent divergent convergent

closely related different species
If Darwin’s theory is correct you would expect to find ____________ yet _______________ living in a Geographic region as they spread into nearby habitats and evolve. (development of traits suited to their particular environment) closely related different species That’s EXACTLY what we do see!

When a single species or small group of species has evolved through ___________________ into diverse forms that live in different ways = ____________________________________ natural selection adaptive radiation OR divergent evolution Ex: Galápagos finches It is called Divergent evolution because they all started with a common ancestor and diverged or radiated out into different species from there.

Tortoises adapted to different habitats as they
REMEMBER THE GALAPAGOS TORTOISES Intermediate vegetation Intermediate necks Little vegetation Long necks Image from: BIOLOGY by Miller and Levine; Prentice Hall Publisher©2006 Lots of vegetation Short necks Tortoises adapted to different habitats as they spread from the mainland to the different islands. = DIVERGENT EVOLUTION = ADAPTIVE RADIATION

The _____ of Galapagos finches have ______ to eating a _____ of _____.
GALAPAGOS FINCHES The _____ of Galapagos finches have ______ to eating a _____ of _____. beaks adapted variety foods

different species far apart more alike
If Darwin’s theory is correct you would also expect to find _______________ living in ________ geographic regions but similar habitats becoming ________ as they adapt to ______________. different species far apart more alike similar ecosystems That’s EXACTLY what we do see!

Sometimes different organisms evolve in different places or at different times but in ____________________ environments…and end up looking very similar. Process by which unrelated organisms come to resemble each other = _______________________ converge means come together or become more alike. ecologically similar convergent evolution

This is the opposite of divergent evolution
This is the opposite of divergent evolution. In divergent evolution, species were diverging and becoming more different from each other, BUT HERE, they are adapting to similar environments even though they are not living together and become more alike. They LOOK similar because their environments are similar even if they aren’t in the same place!

Whales and sharks have a _____ body design
Whales and sharks have a _____ body design even though they are very _______ organisms (one is a fish; the other, a mammal) because they have _________________ to living in a _____ environment. similar different independently adapted similar = CONVERGENT EVOLUTION

Whales are closely related to wolves, but don’t look or act much like them
= divergent evolution Conclusion: The pressure of the environment drives evolution Whales are distantly related to sharks, but look and act more like them = convergent evolution

How fast does evolution operate?
Darwin believed evolution happened slowly over a long time If biological change is at a slow pace, it is called ____________. gradualism

bursts Fossil record shows evolution happens more in _____.
Pattern of a long stable period interrupted by a brief period of more rapid change =____________ bursts Punctuated Equilibrium

Punctuated equilibrium is any sudden, rapid change in a species and can be genetic (mutation) or the result of other causes, such as huge and sudden changes in the environment that result in more rapid changes in the organism

Gradualism and Punctuated Equilibrium
Gradualism and punctuated equilibrium are two ways in which the evolution of a species can occur. A species can evolve by only one of these, or by both. Scientists think that species with a shorter evolution evolved mostly by punctuated equilibrium, and those with a longer evolution evolved mostly by gradualism.

Evolutionary Time Scales
Macroevolution: Long time scale events that create and destroy species. copyright cmassengale

Evolutionary Time Scales
Microevolution: Short time scale events (generation-to-generation) that change the genotypes and phenotypes of populations copyright cmassengale

Homologous Body Structures –
Structures, like the limbs of vertebrates, look very _______, but are made from the __________, because they are made from the same clump of _____________ cells in the _______. different same bones undifferentiated embryo Image from:

4. _____________________
HOMOLOGOUS Structures Image from:

Homologous Body Structures
Scientists Noticed Animals With Backbones (Vertebrates) Had Similar Bone Structure May Differ In Form or Function Limb Bones Develop In Similar Patterns Arms, Wings, Legs, Flippers

If you look at these organisms DNA you will see structures That Have Different Mature Forms…. But Develop From The Same Embryonic Tissues Strong Evidence That All Four-Limbed Animals With Backbones Descended, With Modification, From A Common Ancestor Help Scientist Group Animals

Section 15-3 Turtle Alligator Bird Mammal Ancient lobe-finned fish

homologous body structures
Some _______________________ are _______ and have no useful function even though they are still present, like ________in whales and boa constrictors, or a ____ and ________________in humans. homologous body structures vestigial hipbones tail cecum (appendix)

Most mammals have a pouch between their small and large intestine that contains bacteria to digest plants called a _____. cecum In humans the cecum is shrunken and unused. It is our _________ appendix

Why grow a tail and then lose it?
HUMAN EMBRYO _________________ has a tail at 4 weeks Tail disappears at about 8 weeks tail

WHY DOES EVOLUTION MATTER NOW?
Can see Natural selection happen 7.____________________________ EX: Peppered Moths There is a natural variation in populations of peppered moths. ________________ ___________________ Typica Carbonaria Typica form - lighter Carbonaria form - darker

Why would an organism possess organs ___ ________________? with
Skinks are a type of lizard. In some species, legs have become so small they _______ ______ in walking. no longer function Why would an organism possess organs ___ ________________? with little or no function One explanation: The ________ is present to make the organ, but _________________ through ______________. If the organ is not vital to survival, then natural selection would cause its elimination. gene code function has been lost change over time

Not All Serve Important Functions Vestigial Organs Appendix In Man Legs On Skinks

Humans have many other nonfunctional vestigial genes called ________________.
EX: Humans have more than 99 different odor receptor genes, but more than 70% of them are ___________. PSEUDOGENES nonfunctional

Similarities In Early Development
Embryonic Structures Of Different Species Show Significant Similarities Embryo – early stages of vertebrate development

Similarities in Embryology
5. _____________________ ________ of many animals with backbones are very similar. Similarities in Embryology Embryos Image from:

It is clear that the same groups of _____________ cells develop in the same order to produce the same tissues and organs of all vertebrates, suggesting that they all _______ from a _______________. undifferentiated evolved common ancestor Image from:

In recent years, the burning of cleaner fuels and Clean Air
The ___________ form was the predominant form in England _____________________________. Around the middle of the 19th century the ______ form began to appear. It was first reported in By % of the moths in Manchester were the ____ variety. In recent years, the burning of cleaner fuels and Clean Air regulations has reduced the pollution there and the ______ colored moths have increased in numbers. light colored prior to the Industrial Revolution darker dark lighter

____________________________
EX: Changes in disease-causing microbes that produce new organisms and __________. _______ ___ __________________________ You Can see Natural selection happen new diseases Bird flu HIV Antibiotic-resistant tuberculosis

Evolution of pesticide resistance in response to selection

Evidence for Evolution – Evolution Observed
Evolution of drug-resistance in HIV

Types of Selection Disruptive-P:\PLC Biology\Unit 8 - Evolution\Video, Web, and PPT Supplements\Disruptive Selection.wmv Stabilizing-P:\PLC Biology\Unit 8 - Evolution\Video, Web, and PPT Supplements\Stabilizing Selection.wmv Directional-P:\PLC Biology\Unit 8 - Evolution\Video, Web, and PPT Supplements\Directional Selection.wmv

____________ and ________
TODAY we can understand how evolution works better than Darwin ever could because of our knowledge about ____________ and ________ genes DNA

Because members of a population interbreed, they share a common group of genes called a ___________
A gene pool consists of ____________ present in a population, including all the different _________. GENE POOL ALL the genes alleles

The ____________________ is the number of times that an allele occurs in the gene pool compared to the occurrence of other alleles in the gene pool. relative frequency Sample Population 48% heterozygous black 36% homozygous brown 16% homozygous black Frequency of Alleles allele for brown fur allele for black fur Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing ©2006

RELATIVE FREQUENCY is often expressed as a __________________.
EX: In this population Dominant B allele (black) = 40% Recessive b allele (brown) = 60% percentage Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing ©2006

NOTHING DOMINANT RECESSIVE
RELATIVE FREQUENCY has _________ to do with whether an allele is ______________ or _____________ In this population, the recessive allele is more frequent. DOMINANT RECESSIVE Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing ©2006

EVOLUTION IN GENETIC TERMS __________________
is any change in the relative frequency of alleles in a population If the relative frequency of the B allele in this mouse population changed over time to %, the population is evolving. EVOLUTION Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing ©2006

change the __________________ of alleles in population!
SEXUAL REPRODUCTION _______________________IS THE MAJOR SOURCE OF VARIATION IN POPULATIONS, but it does _______ change the __________________ of alleles in population! NOT relative frequency Shuffling a deck of cards can shuffle to produce many different hands, but doesn’t change the number of kings or queens in the deck.

____________________ on
NATURAL SELECTION ____________________ on single-gene frequencies can lead to changes in ____________________ and thus to EVOLUTON ALLELE FREQUENCIES EX: A population of normally brown lizards. Mutations produce new color choices. If red lizards are more visible to predators, they might be less likely to survive. Bird image from: Chart from BIOLOGY by Miller and Levine; Prentice Hall Publishing ©2006

Natural selection can affect the
distribution of phenotypes in 3 ways: ______________________ DIRECTIONAL selection STABILIZING selection DISRUPTIVE selection

DIRECTIONAL SELECTION
Graph from BIOLOGY by Miller and Levine; Prentice Hall Publshing©2006 DIRECTIONAL SELECTION KEY Low mortality, high fitness High mortality, low fitness Food becomes scarce. Individuals at _____________ of the curve have higher fitness than individuals in middle or at other end. Graph shifts as some individuals fail to survive at one end and succeed and reproduce at other ONE END

EXAMPLE OF DIRECTIONAL SELECTION
Beak size varies in a population Birds with bigger beaks can feed more easily on harder, thicker shelled seeds. Suppose a food shortage causes small and medium size seeds to run low. Birds with bigger beaks would be selected for and increase in numbers in population.

STABILIZING SELECTION
Graph from BIOLOGY by Miller and Levine; Prentice Hall Publshing©2006 STABILIZING SELECTION Individuals in _____________ of the curve have higher fitness than individuals at either end Graph stays in same place but narrows as more organisms in middle are produced. CENTER

STABILIZING SELECTION
Section 16-2 Stabilizing Selection Male birds with showier, brightly- colored plumage also attract predators, and are less likely to live long enough to find a mate. The most fit, then, is the male bird in the middle-- showy, but not too showy. Male birds use their plumage to attract mates. Male birds in the population with less brilliant and showy plumage are less likely to attract a mate, while male birds with showy plumage are more likely to attract a mate. Key Low mortality, high fitness High mortality, low fitness Selection against both extremes keep curve narrow and in same place. Percentage of Population Brightness of Feather Color Graph from BIOLOGY by Miller and Levine; Prentice Hall Publshing©2006

EXAMPLE OF STABILIZING SELECTION
Human babies born with low birth weight are less likely to survive. Babies born too large have difficulty being born. Average size babies are selected for.

DISRUPTIVE SELECTION Individuals at _____________ of the curve
Graph from BIOLOGY by Miller and Levine; Prentice Hall Publshing©2006 DISRUPTIVE SELECTION Individuals at _____________ of the curve have higher fitness than individuals in middle. Can cause graph to split into two. Selection creates __________________PHENOTYPES EXTREMES TWO DISTINCT

EXAMPLE OF DISRUPTIVE SELECTION
Suppose bird population lives in area where climate change causes medium size seeds become scarce while large and small seeds are still plentiful. Birds with bigger or smaller beaks would have greater fitness and the population may split into TWO GROUPS. One that eats small seeds and one that eats large seeds.

In a small population this random change in allele frequency based on chance is called _________________ GENETIC DRIFT Genetic drift can occur when a _______ group of individuals colonizes a _____habitat. small new

Individuals may carry alleles in ______________ relative frequencies than in the larger population.
The population they “found” will be different from the parent population . . . not through natural selection but by _________ different chance

A situation in which allele frequencies change as a result of the
migration of a small subgroup of the population = _________________ FOUNDER EFFECT Graph from BIOLOGY by Miller and Levine; Prentice Hall Publshing©2006

In a situation in which allele frequencies remain constant
HARDY-WEINBERG PRINCIPLE states that allele frequency in a population will remain __________ unless one or more ________ cause the frequency to __________. In a situation in which allele frequencies remain constant ( = _________________ ) populations will NOT EVOLVE! constant factors change Genetic equilibrium

Population must be large
5 CONDITIONS REQUIRED TO MAINTAIN GENETIC EQUILIBRIUM FROM GENERATION TO GENERATION 1. _________________________ 2. _________________________ 3. _________________________ 4. _________________________ 5. _________________________ Must be random mating Population must be large No movement in or out No mutations No natural selection

Review copyright cmassengale

Darwin's Theory Individual Organisms In Nature Differ From One Another. Some Of This Variation Is Inherited Organisms In Nature Produce More Offspring Than Can Survive, And Many Of These Offspring Do No Reproduce copyright cmassengale

Darwin's Theory Because More Organisms Are Produced Than Can Survive, Members Of Each Species Must Compete For Limited Resources Because Each Organism Is Unique, Each Has Different Advantages & Disadvantages In The Struggle For Existence copyright cmassengale

Darwin's Theory Individuals Best Suited To Their Environment Survive & Reproduce Successfully – Passing Their Traits To Their Offspring, maximizing their fitness. Species Change Over Time and become increasingly adapted over long periods. Natural Selection Causes Changes That May Eventually Lead To New Species copyright cmassengale

Darwin's Theory Species Alive Today Have Descended With Modifications From Species That Lived In The Past All Organisms On Earth Are United Into A Single Tree Of Life By Common Descent copyright cmassengale

Concept Map Section 15-3 Evidence of Evolution includes
The fossil record Geographic distribution of living species Homologous body structures Similarities in early development which is composed of which indicates which implies which implies Physical remains of organisms Common ancestral species Similar genes

PBS EVOLUTION VIDEO CLIPS
Isn’t Evolution Just a Theory? QuickTime Who was Charles Darwin? How Do we Know Evolution Happens? How Does Evolution Really Work? QuickTime | Why Does Evolution Matter Now? Why is Evolution Controversial Anyway?

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