The Theory of The Theory of EvolutionEvolution

Charles Darwin and Charles Darwin and

The Origin The Origin ofof Species Species

What do you think of when you hear the wordWhat do you think of when you hear the word

Survival?Survival?Religion?Religion?

Fossils?Fossils?

Extinction?Extinction?

Humans?Humans?

Animals?Animals?Science?Science?

Charles Charles Darwin?Darwin?

Change?Change?

““EEVVOOLLUUTTIIOONN””

Evolution is a very complex and controversial issue. This lesson is just a basic introduction to the theory of evolution and natural selection as presented by Charles Darwin

Charles Darwin (1809-1882)Charles Darwin (1809-1882)►He was an English NaturalistHe was an English Naturalist►He traveled around the world on He traveled around the world on

his ship, the his ship, the BeagleBeagle► Studied species and fossils in the Studied species and fossils in the

Galapagos IslandsGalapagos Islands and around the and around the worldworld

►Why did some species survive Why did some species survive while others became extinct?while others became extinct?

►Natural selectionNatural selection► Published Published The Origin of SpeciesThe Origin of Species in in

18591859

Darwin’s TheoryDarwin’s Theory► Darwin's theory of evolution has four main parts: Darwin's theory of evolution has four main parts:

Organisms have changed over time, and the ones living Organisms have changed over time, and the ones living today are different from those that lived in the past. today are different from those that lived in the past. Furthermore, many organisms that once lived are now Furthermore, many organisms that once lived are now extinct. The world is not constant, but changing. extinct. The world is not constant, but changing.

All organisms come from common ancestors by a process of All organisms come from common ancestors by a process of branching. Over time, populations split into different species, branching. Over time, populations split into different species, which are related because they are descended from a common which are related because they are descended from a common ancestor. Thus, if one goes far enough back in time, any pair of ancestor. Thus, if one goes far enough back in time, any pair of organisms has a common ancestor. This explained the organisms has a common ancestor. This explained the similarities of organisms that were classified together -- they similarities of organisms that were classified together -- they were similar because of shared traits inherited from their were similar because of shared traits inherited from their common ancestor. It also explained why similar species tended common ancestor. It also explained why similar species tended to occur in the same geographic region. to occur in the same geographic region.

Change is gradual and slow, taking place over a long time. Change is gradual and slow, taking place over a long time. This was supported by the fossil record, and was consistent This was supported by the fossil record, and was consistent with the fact that no naturalist had observed the sudden with the fact that no naturalist had observed the sudden appearance of a new species. appearance of a new species.

The mechanism of evolutionary change was natural The mechanism of evolutionary change was natural selection. selection.

Natural SelectionNatural Selection

► ““I have called this principle, by which each I have called this principle, by which each slight variation, if useful, is preserved, by slight variation, if useful, is preserved, by the term of natural selection.” the term of natural selection.” – – Charles Darwin from “The Origin of Species”Charles Darwin from “The Origin of Species”

►Darwin's theory of Darwin's theory of natural selectionnatural selection holds holds that variation within species occurs that variation within species occurs randomly and that the survival or extinction randomly and that the survival or extinction of each organism is determined by that of each organism is determined by that organism's ability to adapt to its organism's ability to adapt to its environment. environment.

On The Galapagos IslandsOn The Galapagos Islands

► Darwin found Darwin found mockingbirdsmockingbirds that were similar to ones that that were similar to ones that were native to Chile, but differed slightly from island to islandwere native to Chile, but differed slightly from island to island

► He studied different species of He studied different species of finchesfinches and the slight and the slight variations in their beaksvariations in their beaks

► He noticed that the shapes of He noticed that the shapes of tortoisetortoise shells also varied shells also varied slightly from island to islandslightly from island to island

► He found He found fossils fossils of animals that had recently become extinctof animals that had recently become extinct► He kept a journal and collected fossils and specimens for He kept a journal and collected fossils and specimens for

further studyfurther study

Darwin’s FinchesDarwin’s Finches

► These are some of the These are some of the finches that Darwin studied finches that Darwin studied on his voyageon his voyage

► Though they are all finches, Though they are all finches, their beaks distinguish them their beaks distinguish them from one anotherfrom one another

► Some finches developed Some finches developed short,short, strong beaksstrong beaks that that made it possible for them to made it possible for them to crack nutscrack nuts

► Some developed Some developed long, fine long, fine beaksbeaks to reach insect larvae to reach insect larvae in tiny holesin tiny holes

► This is an example of how This is an example of how these finches adapted to these finches adapted to their environment to survive their environment to survive ((natural selectionnatural selection))

Darwin’sDarwin’s FinchesFinches

Darwin believed that all of the different finches came from a common ancestor and that their differences were a result of natural selection

Example of Natural SelectionExample of Natural SelectionPeppered MothPeppered Moth

Moths can camouflage with trees to Moths can camouflage with trees to avoid being eaten by birds.avoid being eaten by birds.

► There were light moths and dark moths There were light moths and dark moths living near English industrial cities in the living near English industrial cities in the 1919thth century century The dark moths stood out on the light The dark moths stood out on the light

colored trees and were more likely to colored trees and were more likely to be seen and eaten by birdsbe seen and eaten by birds► Thus, there were many more light Thus, there were many more light

colored moths than dark colored colored moths than dark colored moths.moths.

► As English factories produced more and As English factories produced more and more soot, the trees turned a darker color. more soot, the trees turned a darker color. This was able to camouflage the dark This was able to camouflage the dark moths, but not the light mothsmoths, but not the light moths THEN, the light moths stood out on the THEN, the light moths stood out on the

dark trees and were more likely to be dark trees and were more likely to be seen and eaten by birds!seen and eaten by birds!► Thus, there were more dark colored Thus, there were more dark colored

moths than light colored moths.moths than light colored moths.

Because the dark moth was Because the dark moth was able to camouflage it was able able to camouflage it was able to avoid being eaten. to avoid being eaten.

If the light colored moth is not If the light colored moth is not able to adapt to its able to adapt to its environment then it will environment then it will eventually become extinct.eventually become extinct.

Camouflage Camouflage ► Many animals have evolved to resemble the environment around them.Many animals have evolved to resemble the environment around them.► This makes it very difficult for predators to find them and eat them, thus This makes it very difficult for predators to find them and eat them, thus

increasing their chance of survival.increasing their chance of survival.► Can you spot them?Can you spot them?

Brimstone Butterfly Stick Bug Large Fly Preying Mantis

Camo Moth SealLion

Patterns of EvolutionPatterns of Evolution

► Darwin believed that natural Darwin believed that natural selection can ultimately lead to the selection can ultimately lead to the formation of new species. formation of new species.

► Sometimes many species evolve Sometimes many species evolve from a single ancestral species. from a single ancestral species.

► Similarities in skeletal and muscular Similarities in skeletal and muscular structure of structure of Hawaiian honeycreepersHawaiian honeycreepers led scientists to conclude that the 23 led scientists to conclude that the 23 species of honeycreepers evolved species of honeycreepers evolved from one ancestral species. from one ancestral species.

► Such an evolutionary pattern, in Such an evolutionary pattern, in which many related species evolved which many related species evolved from a single ancestral species, is from a single ancestral species, is called called adaptive radiation.adaptive radiation.

Adaptive RadiationAdaptive Radiation

►Adaptive radiation Adaptive radiation most commonly occurs most commonly occurs when a species of when a species of organisms successfully organisms successfully invades an isolated invades an isolated region where few region where few competing species competing species exist. If new habitats exist. If new habitats are available, new are available, new species will evolve.species will evolve.

Divergent EvolutionDivergent Evolution

► Divergent evolutionDivergent evolution is the process of two is the process of two or more related species becoming more or more related species becoming more and more dissimilar. and more dissimilar.

► Example: The red fox and the kit fox Example: The red fox and the kit fox The red fox lives in mixed farmlands and The red fox lives in mixed farmlands and

forests, where its red color helps it blend forests, where its red color helps it blend in with surrounding trees. in with surrounding trees.

The kit fox lives on the plains and in the The kit fox lives on the plains and in the deserts, where its sandy color helps deserts, where its sandy color helps conceal it from prey and predators. The conceal it from prey and predators. The ears of the kit fox are larger than those of ears of the kit fox are larger than those of the red fox. The kit fox's large ears are an the red fox. The kit fox's large ears are an adaptation to its desert environmentadaptation to its desert environment

► Similarities in structure indicate that the Similarities in structure indicate that the red fox and the kit fox had a common red fox and the kit fox had a common ancestor. As they adapted to different ancestor. As they adapted to different environments, the appearance of the environments, the appearance of the two species diverged, or became more two species diverged, or became more and more different. and more different.

Red Fox

Kit Fox

Convergent EvolutionConvergent Evolution► ConvergentConvergent evolutionevolution is the opposite of divergent is the opposite of divergent

evolutionevolution► In In convergent evolutionconvergent evolution, unrelated species , unrelated species

become more and more similar in appearance as become more and more similar in appearance as they adapt to the same kind of environment. they adapt to the same kind of environment.

► Frogs Frogs andand Chameleons Chameleons are examples of are examples of convergent evolutionconvergent evolution because although they are because although they are different amphibians, they have both developed different amphibians, they have both developed harpoon-like tongues to catch insectsharpoon-like tongues to catch insects

Co-evolutionCo-evolution► Co-evolutionCo-evolution is the joint change of two or more is the joint change of two or more

species in close interaction. Predators and their species in close interaction. Predators and their prey sometimes prey sometimes co-evolveco-evolve; parasites and their ; parasites and their hosts often hosts often co-evolveco-evolve; plant-eating animals and ; plant-eating animals and the plants upon which they feed also the plants upon which they feed also co-evolve. co-evolve.

► One example of One example of co-evolutionco-evolution is pollination of is pollination of orchids by African moths. orchids by African moths.

These species These species co-evolveco-evolve because the moths because the moths depend on the flowers for nectar, and the flowers depend on the flowers for nectar, and the flowers depend on the moths to spread their pollen so depend on the moths to spread their pollen so that they can reproduce.that they can reproduce.

► The relationship between the moth and the The relationship between the moth and the orchids is mutually beneficial because they help orchids is mutually beneficial because they help each other survive.each other survive.

Why is This Important?Why is This Important?

►DivergentDivergent, , convergentconvergent and and co-co-evolutionevolution are different ways organisms are different ways organisms adapt to the environment. These are adapt to the environment. These are examples of how the diversity of life examples of how the diversity of life on earth is due to the ever-changing on earth is due to the ever-changing interaction between a species and its interaction between a species and its environment.environment.

ExtinctionExtinction► Extinction is the disappearance of an entire speciesExtinction is the disappearance of an entire species► If a species does not have the genetic traits to survive in its If a species does not have the genetic traits to survive in its

environment, then the species will eventually become environment, then the species will eventually become extinct foreverextinct forever

► Some examples of extinct animals are:Some examples of extinct animals are:

Thylacine Quagga Dodo Bird

Galapagos Tortoise

Bali Tiger

Dinosaurs Steller’s Sea Cow

Laughing Owl

Reasons for ExtinctionReasons for Extinction► RarityRarity- when there are very few animals of a species left (Galapagos tortoise)- when there are very few animals of a species left (Galapagos tortoise)► InbreedingInbreeding- when animals mate too much within their own group the offspring - when animals mate too much within their own group the offspring

become less able to survive and adapt in a healthy way become less able to survive and adapt in a healthy way ► HybridizationHybridization-When two animals from different sub-species mate, they might -When two animals from different sub-species mate, they might

pass on genes that are less healthy (Quagga-half horse half zebra)pass on genes that are less healthy (Quagga-half horse half zebra)► Gradual loss of habitatGradual loss of habitat- When an animal's habitat is slowly destroyed and they - When an animal's habitat is slowly destroyed and they

have nowhere to live. (Bali Tiger)have nowhere to live. (Bali Tiger)► Long-term environmental trends-Long-term environmental trends- Scientists think that dinosaurs became Scientists think that dinosaurs became

extinct because of a slow cooling of the earthextinct because of a slow cooling of the earth► CatastropheCatastrophe- Volcanic eruption, dramatic change in climate, tsunami, etc.- Volcanic eruption, dramatic change in climate, tsunami, etc.► Extinction or reduction of mutualistic population-Extinction or reduction of mutualistic population- If two species are dependent If two species are dependent

on each other, then the endangering of one also endangers the otheron each other, then the endangering of one also endangers the other► CompetitionCompetition- When a new species is introduced to a habitat, then the stronger - When a new species is introduced to a habitat, then the stronger

of the two species will be more likely to survive.of the two species will be more likely to survive.► PredatorsPredators-When the population of a species of predator in a habitat suddenly -When the population of a species of predator in a habitat suddenly

increases, the population of their prey decreases increases, the population of their prey decreases ► DiseaseDisease-- If a particular sickness spreads quickly throughout a particular If a particular sickness spreads quickly throughout a particular

species, then many may die before they can reproducespecies, then many may die before they can reproduce► Hunting and collectingHunting and collecting-- Hunters have been largely responsible for the Hunters have been largely responsible for the

endangerment of many animal species.endangerment of many animal species.

ApplicationsApplications► Knowledge about evolution and natural selection has Knowledge about evolution and natural selection has

benefited our society in many ways, and has helped make benefited our society in many ways, and has helped make numerous technological advances, especially in the field of numerous technological advances, especially in the field of biology and medicinebiology and medicine Using Darwin’s theory of natural selection, scientists have been Using Darwin’s theory of natural selection, scientists have been

able to identify the desirable traits which would improve the able to identify the desirable traits which would improve the probability of survival in certain speciesprobability of survival in certain species

It has helped scientists and doctors in treating viruses and It has helped scientists and doctors in treating viruses and diseases. diseases. ► For example: Did you know that when a doctor gives you antibiotics, For example: Did you know that when a doctor gives you antibiotics,

you need to continue taking them until all of the pills are gone, even if you need to continue taking them until all of the pills are gone, even if you start to feel better? When a doctor gives you antibiotics, they you start to feel better? When a doctor gives you antibiotics, they start to fight of the bacteria in your body, little by little. It starts with start to fight of the bacteria in your body, little by little. It starts with the weak bacteria, and eventually kills the strongest bacteria. the weak bacteria, and eventually kills the strongest bacteria.

► BUT, if you stop taking your medicine, then it is only the STRONG BUT, if you stop taking your medicine, then it is only the STRONG bacteria that are left in your body. That means that they will continue bacteria that are left in your body. That means that they will continue to reproduce and become stronger and stronger, and it will be much to reproduce and become stronger and stronger, and it will be much harder for the medicine to kill them. This is an example of natural harder for the medicine to kill them. This is an example of natural selection because the strong bacteria survives and grows.selection because the strong bacteria survives and grows.

ConclusionConclusion

► Darwin’s observations have Darwin’s observations have made a great impact in the made a great impact in the scientific community. scientific community. Because of his observations, Because of his observations, we are better able to we are better able to understand why some species understand why some species survive and some die. survive and some die.

► We are also better able to We are also better able to take precautions to protect take precautions to protect species that are endangered. species that are endangered.

► Lastly, we can understand the Lastly, we can understand the diversity in the world around diversity in the world around us and learn to appreciate itus and learn to appreciate it..

ReferencesReferences► http://www.lucidcafe.com/library/96feb/darwin.htmlhttp://www.lucidcafe.com/library/96feb/darwin.html

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