6-1 Darwin’s Discovery6-1 Darwin’s Discovery6-1 Darwin’s Discovery6-1 Darwin’s Discovery

Charles DarwinCharles DarwinCharles DarwinCharles Darwin◊ Charles Darwin was a naturalist (a Charles Darwin was a naturalist (a

person who studied the natural world) person who studied the natural world) who in 1831, sailed on the ship, the who in 1831, sailed on the ship, the BeagleBeagle, around the world., around the world.

◊ During this voyage, he observed plants During this voyage, he observed plants and animals he never saw before and and animals he never saw before and wondered why they were so different wondered why they were so different from those in England.from those in England.

◊ Charles Darwin was a naturalist (a Charles Darwin was a naturalist (a person who studied the natural world) person who studied the natural world) who in 1831, sailed on the ship, the who in 1831, sailed on the ship, the BeagleBeagle, around the world., around the world.

◊ During this voyage, he observed plants During this voyage, he observed plants and animals he never saw before and and animals he never saw before and wondered why they were so different wondered why they were so different from those in England.from those in England.

Charles Darwin (cont.)Charles Darwin (cont.)Charles Darwin (cont.)Charles Darwin (cont.)◊ He stopped in South America and was He stopped in South America and was

amazed at the amazed at the diversitydiversity (variety) of (variety) of speciesspecies he observed.he observed.

◊ A A speciesspecies is a group of similar organisms is a group of similar organisms that can mate with each other and produce that can mate with each other and produce fertile offspring.fertile offspring.

◊ He also found the bones of extinct animals He also found the bones of extinct animals that resembled animals he knew like giant that resembled animals he knew like giant sloths similar to the small sloths alive todaysloths similar to the small sloths alive today

◊ He stopped in South America and was He stopped in South America and was amazed at the amazed at the diversitydiversity (variety) of (variety) of speciesspecies he observed.he observed.

◊ A A speciesspecies is a group of similar organisms is a group of similar organisms that can mate with each other and produce that can mate with each other and produce fertile offspring.fertile offspring.

◊ He also found the bones of extinct animals He also found the bones of extinct animals that resembled animals he knew like giant that resembled animals he knew like giant sloths similar to the small sloths alive todaysloths similar to the small sloths alive today

Charles Darwin (cont.)Charles Darwin (cont.)Charles Darwin (cont.)Charles Darwin (cont.)◊ In 1835, he reached the Galapagos Islands In 1835, he reached the Galapagos Islands

off the coast of South America and was off the coast of South America and was surprised to see there were many animals surprised to see there were many animals and plants similar to the ones found on the and plants similar to the ones found on the mainland. But, he observed there were mainland. But, he observed there were important differences too. Like iguanas that important differences too. Like iguanas that fed on seaweed or cormorants (water birds) fed on seaweed or cormorants (water birds) that had such small wings they couldn’t fly.that had such small wings they couldn’t fly.

◊ From these observations, he inferred that From these observations, he inferred that these animals had originally came from the these animals had originally came from the mainland and over time they became mainland and over time they became different from their ancestors.different from their ancestors.

◊ In 1835, he reached the Galapagos Islands In 1835, he reached the Galapagos Islands off the coast of South America and was off the coast of South America and was surprised to see there were many animals surprised to see there were many animals and plants similar to the ones found on the and plants similar to the ones found on the mainland. But, he observed there were mainland. But, he observed there were important differences too. Like iguanas that important differences too. Like iguanas that fed on seaweed or cormorants (water birds) fed on seaweed or cormorants (water birds) that had such small wings they couldn’t fly.that had such small wings they couldn’t fly.

◊ From these observations, he inferred that From these observations, he inferred that these animals had originally came from the these animals had originally came from the mainland and over time they became mainland and over time they became different from their ancestors.different from their ancestors.

Mainland Animals vs Galapagos Mainland Animals vs Galapagos SpeciesSpecies

Mainland Animals vs Galapagos Mainland Animals vs Galapagos SpeciesSpecies

AdaptationsAdaptationsAdaptationsAdaptations◊ Darwin noticed the finches on the island while Darwin noticed the finches on the island while

similar to ones on the mainland but that many similar to ones on the mainland but that many had differences (like beak shapes) that made had differences (like beak shapes) that made them suited to the life they led.them suited to the life they led.

◊ For example, some that fed on insects had For example, some that fed on insects had thin, needlelike beaks. Ones feeding on seeds thin, needlelike beaks. Ones feeding on seeds had short, thick beaks.had short, thick beaks.

◊ He called these differencesHe called these differences like beak shape Adaptations.Adaptations.

◊ AdaptationsAdaptations are traits that help an organism are traits that help an organism survive in a particular environment and survive in a particular environment and reproduce.reproduce.

◊ Darwin noticed the finches on the island while Darwin noticed the finches on the island while similar to ones on the mainland but that many similar to ones on the mainland but that many had differences (like beak shapes) that made had differences (like beak shapes) that made them suited to the life they led.them suited to the life they led.

◊ For example, some that fed on insects had For example, some that fed on insects had thin, needlelike beaks. Ones feeding on seeds thin, needlelike beaks. Ones feeding on seeds had short, thick beaks.had short, thick beaks.

◊ He called these differencesHe called these differences like beak shape Adaptations.Adaptations.

◊ AdaptationsAdaptations are traits that help an organism are traits that help an organism survive in a particular environment and survive in a particular environment and reproduce.reproduce.

Galapagos FinchesGalapagos FinchesGalapagos FinchesGalapagos Finches

EvolutionEvolutionEvolutionEvolution◊ After Darwin returned home he continued to think After Darwin returned home he continued to think

about his observations and how the animals with about his observations and how the animals with different adaptations arose on the Galapagos.different adaptations arose on the Galapagos.

◊ He reasoned that when the animals arrived on the He reasoned that when the animals arrived on the Islands they found living conditions different then Islands they found living conditions different then those on the mainland. He thought that over time, those on the mainland. He thought that over time, each species changed and became better adapted each species changed and became better adapted to the new conditions.to the new conditions.

◊ The gradual change in a species over time is called The gradual change in a species over time is called evolution.evolution.

◊ His ideas are referred to as the His ideas are referred to as the theory of evolution.theory of evolution.

◊ A A scientific theoryscientific theory is a well tested concept that is a well tested concept that explains a wide range of observations.explains a wide range of observations.

◊ After Darwin returned home he continued to think After Darwin returned home he continued to think about his observations and how the animals with about his observations and how the animals with different adaptations arose on the Galapagos.different adaptations arose on the Galapagos.

◊ He reasoned that when the animals arrived on the He reasoned that when the animals arrived on the Islands they found living conditions different then Islands they found living conditions different then those on the mainland. He thought that over time, those on the mainland. He thought that over time, each species changed and became better adapted each species changed and became better adapted to the new conditions.to the new conditions.

◊ The gradual change in a species over time is called The gradual change in a species over time is called evolution.evolution.

◊ His ideas are referred to as the His ideas are referred to as the theory of evolution.theory of evolution.

◊ A A scientific theoryscientific theory is a well tested concept that is a well tested concept that explains a wide range of observations.explains a wide range of observations.

Evolution (cont.)Evolution (cont.)Evolution (cont.)Evolution (cont.)◊ Darwin knew that people used selective Darwin knew that people used selective

breeding to produce organisms with desired breeding to produce organisms with desired traits and that a similar process must traits and that a similar process must happen in nature.happen in nature.

◊ Darwin proposed that these changes occur Darwin proposed that these changes occur as a result of as a result of natural selection.natural selection.

◊ Natural selectionNatural selection is a process by which is a process by which individuals that are better adapted to their individuals that are better adapted to their environment are more likely to survive and environment are more likely to survive and reproduce than other members of the same reproduce than other members of the same species.species.

◊ Darwin identified three factors that affect Darwin identified three factors that affect the process of natural selection:the process of natural selection: overproduction, competition, and variations.overproduction, competition, and variations.

◊ Darwin knew that people used selective Darwin knew that people used selective breeding to produce organisms with desired breeding to produce organisms with desired traits and that a similar process must traits and that a similar process must happen in nature.happen in nature.

◊ Darwin proposed that these changes occur Darwin proposed that these changes occur as a result of as a result of natural selection.natural selection.

◊ Natural selectionNatural selection is a process by which is a process by which individuals that are better adapted to their individuals that are better adapted to their environment are more likely to survive and environment are more likely to survive and reproduce than other members of the same reproduce than other members of the same species.species.

◊ Darwin identified three factors that affect Darwin identified three factors that affect the process of natural selection:the process of natural selection: overproduction, competition, and variations.overproduction, competition, and variations.

Natural SelectionNatural SelectionNatural SelectionNatural Selection◊ OverproductionOverproduction is where a species like is where a species like

insects or turtles produce many more insects or turtles produce many more offspring than can survive on the offspring than can survive on the available resources (like food, living available resources (like food, living space, or water).space, or water).

◊ Since these resources are limited, the Since these resources are limited, the offspring mustoffspring must competecompete against each against each other to survive. This is other to survive. This is competitioncompetition.. Some will be better than others at getting Some will be better than others at getting food to eat or at escaping predators.food to eat or at escaping predators.

◊ As a consequenceAs a consequence, only a few will survive , only a few will survive long enough to reproduce.long enough to reproduce.

◊ OverproductionOverproduction is where a species like is where a species like insects or turtles produce many more insects or turtles produce many more offspring than can survive on the offspring than can survive on the available resources (like food, living available resources (like food, living space, or water).space, or water).

◊ Since these resources are limited, the Since these resources are limited, the offspring mustoffspring must competecompete against each against each other to survive. This is other to survive. This is competitioncompetition.. Some will be better than others at getting Some will be better than others at getting food to eat or at escaping predators.food to eat or at escaping predators.

◊ As a consequenceAs a consequence, only a few will survive , only a few will survive long enough to reproduce.long enough to reproduce.

Natural Selection (cont.)Natural Selection (cont.)Natural Selection (cont.)Natural Selection (cont.)◊ Remember from your study of genetics, Remember from your study of genetics,

members of a species differ from each other members of a species differ from each other in many of their traits.in many of their traits.

◊ The differences between individuals of a The differences between individuals of a species is called species is called variationvariation..

◊ Some Some variationsvariations make an individual better make an individual better adapted to their environment and more adapted to their environment and more likely to survive and reproduce. Their likely to survive and reproduce. Their offspring may inherit the allele for the offspring may inherit the allele for the helpful trait. In effect, the environment has helpful trait. In effect, the environment has selectedselected for the individuals with the helpful for the individuals with the helpful trait to be the parents of the next trait to be the parents of the next generation. generation.

◊ Remember from your study of genetics, Remember from your study of genetics, members of a species differ from each other members of a species differ from each other in many of their traits.in many of their traits.

◊ The differences between individuals of a The differences between individuals of a species is called species is called variationvariation..

◊ Some Some variationsvariations make an individual better make an individual better adapted to their environment and more adapted to their environment and more likely to survive and reproduce. Their likely to survive and reproduce. Their offspring may inherit the allele for the offspring may inherit the allele for the helpful trait. In effect, the environment has helpful trait. In effect, the environment has selectedselected for the individuals with the helpful for the individuals with the helpful trait to be the parents of the next trait to be the parents of the next generation. generation.

Natural Selection (cont.)Natural Selection (cont.)Natural Selection (cont.)Natural Selection (cont.)◊ Over a long period of time, Over a long period of time, natural natural

selectionselection can lead to can lead to evolutionevolution. Helpful . Helpful variations gradually accumulate in a variations gradually accumulate in a population, while unfavorable ones population, while unfavorable ones disappear.disappear.

◊ For example, suppose a fast moving For example, suppose a fast moving predator moves into a turtle’s habitat. predator moves into a turtle’s habitat. The turtles that can swim faster are more The turtles that can swim faster are more likely to avoid being eaten and reproduce. likely to avoid being eaten and reproduce. Over time, more and more turtles of that Over time, more and more turtles of that species would have the species would have the fastfast swimming swimming trait.trait.

◊ Over a long period of time, Over a long period of time, natural natural selectionselection can lead to can lead to evolutionevolution. Helpful . Helpful variations gradually accumulate in a variations gradually accumulate in a population, while unfavorable ones population, while unfavorable ones disappear.disappear.

◊ For example, suppose a fast moving For example, suppose a fast moving predator moves into a turtle’s habitat. predator moves into a turtle’s habitat. The turtles that can swim faster are more The turtles that can swim faster are more likely to avoid being eaten and reproduce. likely to avoid being eaten and reproduce. Over time, more and more turtles of that Over time, more and more turtles of that species would have the species would have the fastfast swimming swimming trait.trait.

The Role of Genes in EvolutionThe Role of Genes in EvolutionThe Role of Genes in EvolutionThe Role of Genes in Evolution

◊ Without Without variationsvariations, all the members of a , all the members of a species would have the same traits and species would have the same traits and evolution would not occur because all members evolution would not occur because all members would have an equal chance of surviving and would have an equal chance of surviving and reproducing.reproducing.

◊ VariationsVariations are the result of mutations in genes are the result of mutations in genes or the shuffling of alleles during meiosis.or the shuffling of alleles during meiosis.

◊ As a result, As a result, onlyonly traits that are inherited or traits that are inherited or controlled by genes, can be acted on by natural controlled by genes, can be acted on by natural selection.selection.

◊ Without Without variationsvariations, all the members of a , all the members of a species would have the same traits and species would have the same traits and evolution would not occur because all members evolution would not occur because all members would have an equal chance of surviving and would have an equal chance of surviving and reproducing.reproducing.

◊ VariationsVariations are the result of mutations in genes are the result of mutations in genes or the shuffling of alleles during meiosis.or the shuffling of alleles during meiosis.

◊ As a result, As a result, onlyonly traits that are inherited or traits that are inherited or controlled by genes, can be acted on by natural controlled by genes, can be acted on by natural selection.selection.

Evolution in ActionEvolution in ActionEvolution in ActionEvolution in Action◊ For example, prior to the industrial For example, prior to the industrial

revolution, light colored peppered moths revolution, light colored peppered moths made up most of the species. Their made up most of the species. Their coloration enabled them to blend into the coloration enabled them to blend into the light colored backgrounds of trees and avoid light colored backgrounds of trees and avoid being eaten by birds.being eaten by birds.

◊ After the industrial revolution and years of After the industrial revolution and years of soot blackening the trees, black peppered soot blackening the trees, black peppered moths made up most of the population. This moths made up most of the population. This is because now light-colored moths showed is because now light-colored moths showed up against the dark background and were up against the dark background and were eaten by birds and black ones could blend in.eaten by birds and black ones could blend in.

◊ For example, prior to the industrial For example, prior to the industrial revolution, light colored peppered moths revolution, light colored peppered moths made up most of the species. Their made up most of the species. Their coloration enabled them to blend into the coloration enabled them to blend into the light colored backgrounds of trees and avoid light colored backgrounds of trees and avoid being eaten by birds.being eaten by birds.

◊ After the industrial revolution and years of After the industrial revolution and years of soot blackening the trees, black peppered soot blackening the trees, black peppered moths made up most of the population. This moths made up most of the population. This is because now light-colored moths showed is because now light-colored moths showed up against the dark background and were up against the dark background and were eaten by birds and black ones could blend in.eaten by birds and black ones could blend in.

Peppered Moths:Peppered Moths: Light Light phase and Dark phasesphase and Dark phases

How Do New Species FormHow Do New Species FormHow Do New Species FormHow Do New Species Form◊ Darwin’s theory of evolution by natural Darwin’s theory of evolution by natural

selection explains how variations lead to selection explains how variations lead to changes in a species.changes in a species.

◊ But what about the formation of an entirely But what about the formation of an entirely new species? Scientists have found that new species? Scientists have found that geographic isolationgeographic isolation is one of the main ways is one of the main ways this can happen. this can happen. If a group of organisms gets If a group of organisms gets separated from the main group long enough separated from the main group long enough to evolve different traits a new species may to evolve different traits a new species may formform. For example, a river or mountain range . For example, a river or mountain range may isolate a group of organisms so that in may isolate a group of organisms so that in time they may evolve traits that make them time they may evolve traits that make them distinctivedistinctive (different) from their main group.(different) from their main group.

◊ Darwin’s theory of evolution by natural Darwin’s theory of evolution by natural selection explains how variations lead to selection explains how variations lead to changes in a species.changes in a species.

◊ But what about the formation of an entirely But what about the formation of an entirely new species? Scientists have found that new species? Scientists have found that geographic isolationgeographic isolation is one of the main ways is one of the main ways this can happen. this can happen. If a group of organisms gets If a group of organisms gets separated from the main group long enough separated from the main group long enough to evolve different traits a new species may to evolve different traits a new species may formform. For example, a river or mountain range . For example, a river or mountain range may isolate a group of organisms so that in may isolate a group of organisms so that in time they may evolve traits that make them time they may evolve traits that make them distinctivedistinctive (different) from their main group.(different) from their main group.

Continental DriftContinental DriftContinental DriftContinental Drift◊ Geographic isolation may also occur Geographic isolation may also occur

on much larger scales.on much larger scales.◊ For example, continental drift causes For example, continental drift causes

the movement of crustal plates. This the movement of crustal plates. This may push once connected landmasses may push once connected landmasses apart so that their species get apart so that their species get separated and evolve separately. separated and evolve separately.

◊ Geographic isolation may also occur Geographic isolation may also occur on much larger scales.on much larger scales.

◊ For example, continental drift causes For example, continental drift causes the movement of crustal plates. This the movement of crustal plates. This may push once connected landmasses may push once connected landmasses apart so that their species get apart so that their species get separated and evolve separately. separated and evolve separately.

Continental Drift (cont.)Continental Drift (cont.)Continental Drift (cont.)Continental Drift (cont.)◊ Australia is a good example, where most Australia is a good example, where most

of its mammals are marsupials (bear their of its mammals are marsupials (bear their young in pouches) where marsupials have young in pouches) where marsupials have been mostly replaced by placental been mostly replaced by placental mammals almost everywhere else.mammals almost everywhere else.

◊ Madagascar is another good example, Madagascar is another good example, where the island split off from Africa so where the island split off from Africa so long ago most of the animals there like long ago most of the animals there like lemurs have become either extinct or new lemurs have become either extinct or new species have evolves so that many of the species have evolves so that many of the life forms there are found nowhere else.life forms there are found nowhere else.

◊ Australia is a good example, where most Australia is a good example, where most of its mammals are marsupials (bear their of its mammals are marsupials (bear their young in pouches) where marsupials have young in pouches) where marsupials have been mostly replaced by placental been mostly replaced by placental mammals almost everywhere else.mammals almost everywhere else.

◊ Madagascar is another good example, Madagascar is another good example, where the island split off from Africa so where the island split off from Africa so long ago most of the animals there like long ago most of the animals there like lemurs have become either extinct or new lemurs have become either extinct or new species have evolves so that many of the species have evolves so that many of the life forms there are found nowhere else.life forms there are found nowhere else.