EvolutionEvolutionChapter 15Chapter 15

EvolutionEvolution

EvolutionEvolution, or change over time, is , or change over time, is the process by which modern the process by which modern organisms have descended from organisms have descended from ancient organisms.ancient organisms.

Voyage of the BeagleVoyage of the Beagle

Charles Darwin – born in EnglandCharles Darwin – born in EnglandJoined the crew of the Joined the crew of the

H.M.S. BeagleH.M.S. Beagle Sailed around the worldSailed around the worldMade numerous observationsMade numerous observations and collected evidence that and collected evidence that led him to propose his led him to propose his hypothesis.hypothesis.

Darwin’s ObservationsDarwin’s Observations

Patterns of Diversity:Patterns of Diversity:

• Puzzled by where different species lived and Puzzled by where different species lived and did not livedid not live

• AskedAsked: :

Why were there no rabbits in Australia, Why were there no rabbits in Australia,

despite the presence of habitats thatdespite the presence of habitats that

seemed perfect for them?seemed perfect for them?

Why were there no kangaroos in England?Why were there no kangaroos in England?

Darwin’s ObservationsDarwin’s ObservationsLiving Organisms and FossilsLiving Organisms and Fossils

• Darwin collected and preserved fossilsDarwin collected and preserved fossils

• FossilsFossils resembled organisms that were still resembled organisms that were still alive – other looked completely unlike any alive – other looked completely unlike any creature he had ever seen.creature he had ever seen.

He Asked: Why had so many of these species He Asked: Why had so many of these species

disappeared?disappeared?

Darwin’s ObservationsDarwin’s Observations The Galapagos IslandsThe Galapagos Islands

• Most influenced DarwinMost influenced Darwin

• Although islands were so close together, the Although islands were so close together, the islands had very different climates.islands had very different climates.

• Fascinated by the land tortoises and marine Fascinated by the land tortoises and marine iguanas.iguanas.

Darwin’s ObservationsDarwin’s ObservationsGalapagos Islands continuedGalapagos Islands continued

• Saw that giant tortoises varied in predictable Saw that giant tortoises varied in predictable ways from one island to another.ways from one island to another.

• The shape of a tortoise’s shell could be used to The shape of a tortoise’s shell could be used to identify which island a particular tortoise lived.identify which island a particular tortoise lived.

Natural Selection QuestionsNatural Selection Questions(Bill Nye)(Bill Nye)

1.1. A young man that walked out was __ ___.A young man that walked out was __ ___.2.2. He quit medical school to become a ___.He quit medical school to become a ___.3.3. How long did the Beagle stay in the Galapagos How long did the Beagle stay in the Galapagos

Islands? __ daysIslands? __ days4.4. Finches had different shaped ___: varied by Finches had different shaped ___: varied by

the environment they inhabited.the environment they inhabited.5.5. What was the mechanism that made evolution What was the mechanism that made evolution

occur? ___ ____occur? ___ ____6.6. When did he publish his book?When did he publish his book?7.7. Now, every where we look at today, we see Now, every where we look at today, we see

something that came from ___.something that came from ___.

Natural Selection Clip Natural Selection Clip (Bill Nye)(Bill Nye)

An Ancient, Changing EarthAn Ancient, Changing Earth

James Hutton and Charles Lyell James Hutton and Charles Lyell

Recognized that Earth is Recognized that Earth is many millionsmany millions of years of years old.old.

And the processes that changed Earth in the And the processes that changed Earth in the past are the same processes that operate in the past are the same processes that operate in the present.present.

Hutton and LyellHutton and Lyell Volcanoes release hot lava and gases now, just as Volcanoes release hot lava and gases now, just as

they did on an ancient Earth.they did on an ancient Earth.

Erosion continues to carve out canyons, just as it did Erosion continues to carve out canyons, just as it did in the past.in the past.

Also said that awesome geological features could be Also said that awesome geological features could be built up or torn down over long periods of time.built up or torn down over long periods of time.

(examples: earthquakes and volcanoes)(examples: earthquakes and volcanoes)

Darwin then askedDarwin then asked: : If the Earth could change over time, If the Earth could change over time, might life change as well? might life change as well?

Lamarck’s Theory of EvolutionLamarck’s Theory of Evolution

Proposed that by selective use or disuse of Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits organs, organisms acquired or lost certain traits during their lifetime.during their lifetime.

These traits could then be passed on to their These traits could then be passed on to their offspring.offspring.

Over time, this process led to change in a speciesOver time, this process led to change in a species

Lamarck ContinuedLamarck ContinuedFiddler Crabs: An ExampleFiddler Crabs: An Example

1. The male crab uses its small front 1. The male crab uses its small front claw to attract mates and ward off claw to attract mates and ward off predatorspredators

2. Because the front claw has been 2. Because the front claw has been used repeatedly, it becomes used repeatedly, it becomes larger.larger.

3. A larger claw, is then passed on to 3. A larger claw, is then passed on to the crab’s offspring.the crab’s offspring.

He was WRONG! He did not realize He was WRONG! He did not realize that the large claw traits were that the large claw traits were inheritedinherited

Lamark’s TheoryLamark’s Theory

According to Lamarck's According to Lamarck's theory, a given giraffe could, theory, a given giraffe could, over a lifetime of straining to over a lifetime of straining to reach high branches, reach high branches, develop an elongated neck. develop an elongated neck.

The long neck is The long neck is ACQUIREDACQUIRED

Population GrowthPopulation Growth

Malthus (an economist) – observed that babies Malthus (an economist) – observed that babies were being born faster than people were dying.were being born faster than people were dying.

He reasoned that if the He reasoned that if the

human population continued human population continued to grow unchecked, sooner to grow unchecked, sooner or later there would be or later there would be insufficient living space and insufficient living space and food for everyone.food for everyone.

Carrying CapacityCarrying Capacity

The largest number of individuals The largest number of individuals of a population that a given of a population that a given environment can support.environment can support.

The Origin of SpeciesThe Origin of Species

The actual title is:The actual title is:

The Origin of Species by Means of Natural SelectionThe Origin of Species by Means of Natural Selection

• The book proposed a mechanism for The book proposed a mechanism for evolution that he called evolution that he called natural selectionnatural selection..

• Presented evidence that demonstrating Presented evidence that demonstrating the process of evolution has been taking the process of evolution has been taking place for millions of year.place for millions of year.

Darwin’s ArgumentsDarwin’s Arguments

Natural Variation and Artificial SelectionNatural Variation and Artificial Selection

• Argued that species were not perfect and Argued that species were not perfect and unchanging.unchanging.

• Natural VariationNatural Variation: There are differences: There are differences

among individuals of a species.among individuals of a species.

ExamplesExamples: :

Some cows gave more milk than others & some Some cows gave more milk than others & some plants bore larger fruit than others.plants bore larger fruit than others.

Darwin’s ArgumentsDarwin’s Arguments

Natural Variation and Artificial SelectionNatural Variation and Artificial Selection

Artificial SelectionArtificial Selection: Nature provided the : Nature provided the variation among different organisms, and variation among different organisms, and humans selected those variations that they humans selected those variations that they found useful.found useful.

* Only the largest hogs, fastest horses, and the * Only the largest hogs, fastest horses, and the cows that gave the most milk were selected to cows that gave the most milk were selected to breed and produce offspring.breed and produce offspring.

Evolution by Natural SelectionEvolution by Natural SelectionThe Struggle for ExistenceThe Struggle for Existence: Means that : Means that

members of each species compete regularly to members of each species compete regularly to obtain food, living space, and other necessities obtain food, living space, and other necessities of life.of life.

A predator that is the fastest or has a particular A predator that is the fastest or has a particular way of catching prey can catch more prey.way of catching prey can catch more prey.

Prey that are faster, better Prey that are faster, better

camouflaged, or better protected camouflaged, or better protected

avoid being caught.avoid being caught.

Evolution by Natural SelectionEvolution by Natural Selection

Survival of the FittestSurvival of the Fittest: Process by which : Process by which individuals that are better suited to their individuals that are better suited to their environment survive and reproduce most environment survive and reproduce most successfully; also called successfully; also called Natural SelectionNatural Selection..

Darwin called the ability of an individual to Darwin called the ability of an individual to survive and reproduce in its specific survive and reproduce in its specific environment environment fitnessfitness..

An An adaptationadaptation is any inherited characteristic is any inherited characteristic that increases an organism’s chance of that increases an organism’s chance of survival.survival.

Darwin’s Discoveries Video ClipDarwin’s Discoveries Video Clip

Survival of the Fittest Survival of the Fittest

The concept of The concept of fitnessfitness, Darwin argued, was , Darwin argued, was central to the process of evolution by natural central to the process of evolution by natural selection.selection.

Example: Example:

Baby birds compete for food in the nest. The Baby birds compete for food in the nest. The stronger bird may take food from the weaker stronger bird may take food from the weaker siblings. siblings.

Evolution by Natural SelectionEvolution by Natural Selection

Descent with ModificationDescent with Modification: Principle that each : Principle that each living species has descended, with changes, living species has descended, with changes, from other species over time.from other species over time.

• Implies that all living organisms are related to Implies that all living organisms are related to one another.one another.

Common DescentCommon Descent: The principle that says all : The principle that says all species – living and extinct – were derived from species – living and extinct – were derived from common ancestors.common ancestors.

Evidence of EvolutionEvidence of Evolution

Fossil RecordFossil Record

Fossils that had formed in Fossils that had formed in the different layers of rock the different layers of rock were evidence of gradual were evidence of gradual change over time.change over time.

One could view how a One could view how a species had changed and species had changed and produced different species produced different species over time.over time.

Evidence of EvolutionEvidence of EvolutionGeographic Distribution of Living SpeciesGeographic Distribution of Living Species

• Species now living on different continents had each descended from different ancestors.

• However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressures of natural selection.

• They ended up evolving certain striking features in common.

• This is called Convergent Evolution

Evidence of EvolutionEvidence of EvolutionSimilarities in Early DevelopmentSimilarities in Early Development

In their early stages of development, chickens, In their early stages of development, chickens, turtles, and rats look similar, providing evidence turtles, and rats look similar, providing evidence that they shared a common ancestry.that they shared a common ancestry.

Evidence of EvolutionEvidence of Evolution

Homologous StructuresHomologous Structures: Structures that have : Structures that have different mature forms in different organisms different mature forms in different organisms but develop from the same embryonic tissues.but develop from the same embryonic tissues.

Evidence for EvolutionEvidence for Evolution

• Vestigial StructuresVestigial Structures are structures that are the are structures that are the reduced forms of functional structures in reduced forms of functional structures in different species.different species.

ExamplesExamples: :

1. 1. Snake PelvisSnake Pelvis: The pelvis is the attachment : The pelvis is the attachment point for legs and is therefore nonfunctional in point for legs and is therefore nonfunctional in an animal without legsan animal without legs

Evidence of EvolutionEvidence of Evolution2. Kiwi Wing: The wings of kiwis are too small to 2. Kiwi Wing: The wings of kiwis are too small to

be of any use in flightbe of any use in flight

3. Human Appendix: Important for digestion in 3. Human Appendix: Important for digestion in many mammals, but of limited use in humans & many mammals, but of limited use in humans & some apessome apes

Analogous StructuresAnalogous Structures

• Analogous structuresAnalogous structures can be superficially can be superficially similar in construction, but are NOT inherited similar in construction, but are NOT inherited from a common ancestor. from a common ancestor.

• ExampleExample: The wing of an eagle & the wing of a : The wing of an eagle & the wing of a insect have the same function (both enable the insect have the same function (both enable the organism to fly) – but are constructed in organism to fly) – but are constructed in different ways & from different materials.different ways & from different materials.

Analogous StructuresAnalogous Structures

* While analogous structures do not indicate * While analogous structures do not indicate close evolutionary relationships, they do show close evolutionary relationships, they do show that functionally similar features can evolve that functionally similar features can evolve independently in similar environments.independently in similar environments.

Evidence of EvolutionEvidence of Evolution

Comparative Biochemistry- the more Comparative Biochemistry- the more closely related species are the greater the closely related species are the greater the number of amino acid sequences will be number of amino acid sequences will be shared.shared.

Geographic distribution-distributions of Geographic distribution-distributions of fossils and living organisms found around fossils and living organisms found around the world.the world.

AdaptationsAdaptations

MimicryMimicry: Adaptation in which one species : Adaptation in which one species evolves to resemble another species for evolves to resemble another species for protection or other advantages.protection or other advantages.

Adaptations:Adaptations:

CamouflageCamouflage: Adaptation : Adaptation

that allows organisms to blend that allows organisms to blend

into their surrounds.into their surrounds.

AdaptationsAdaptations

Bacterial resistance: species of bacteria Bacterial resistance: species of bacteria have developed drug resistance. have developed drug resistance.

The The EndEnd