Adaptation Over TimeAdaptation Over Time

Chapter 6Chapter 6

EvolutionEvolutionSec 6-1 H.W. pg 161 ques. 1-Sec 6-1 H.W. pg 161 ques. 1-

44 A species is a group of organisms A species is a group of organisms

that share similar characteristics and that share similar characteristics and have the ability to reproduce have the ability to reproduce offspring.offspring.

The special characteristics of a The special characteristics of a species is inherited when they are species is inherited when they are passed on from parent to offspringpassed on from parent to offspring

The changes in these characteristics The changes in these characteristics over time is called evolution.over time is called evolution.

Darwin’s Model of EvolutionDarwin’s Model of Evolution

The modern theory of evolution is based on The modern theory of evolution is based on the concept of the concept of natural selectionnatural selection. This was . This was first proposed in a joint 1858 paper by first proposed in a joint 1858 paper by Charles DarwinCharles Darwin

Natural selection is the idea that individuals Natural selection is the idea that individuals who possess advantageous genetic traits who possess advantageous genetic traits are more likely to survive and reproduce. In are more likely to survive and reproduce. In doing so, they increase the frequency of doing so, they increase the frequency of such traits in subsequent generations. such traits in subsequent generations.

Natural selection “survival of Natural selection “survival of the fittest"the fittest"

This theory says that the organism that has traits This theory says that the organism that has traits to survive the best will survive and those that lack to survive the best will survive and those that lack the best traits have a good chance of dying off.the best traits have a good chance of dying off.

This happens over a long period of time. Over This happens over a long period of time. Over this time the genetic makeup of a species could this time the genetic makeup of a species could change its appearance so that it can survive change its appearance so that it can survive better in an environment.better in an environment.

An example is the Galapagos finch has a bigger, An example is the Galapagos finch has a bigger, stronger beak than normal finches, so it can eat stronger beak than normal finches, so it can eat the types of food in the Galapagos islands. the types of food in the Galapagos islands.

This change occurred inside of the DNA of the This change occurred inside of the DNA of the finch over a long period of time and through many finch over a long period of time and through many generations.generations.

So, one way that a new species can form is if a large So, one way that a new species can form is if a large population of organisms becomes separated into smaller population of organisms becomes separated into smaller populations that no longer breed with others of their populations that no longer breed with others of their own kind.own kind.

One way that a large group of animals can become One way that a large group of animals can become separated is by a mountain range or a river.separated is by a mountain range or a river.

So, lets say that we have a large population of lizards So, lets say that we have a large population of lizards that became separated into two smaller populations by a that became separated into two smaller populations by a river. river.

Now the lizards can only mate with other lizards that are Now the lizards can only mate with other lizards that are in their environment.in their environment.

Because the environment on each side of the river is Because the environment on each side of the river is going to be a little bit different, each small population is going to be a little bit different, each small population is going develop different adaptations to their own going develop different adaptations to their own environment.environment.

These two new groups have now become a different These two new groups have now become a different species. And since all of the lizards in this example arose species. And since all of the lizards in this example arose from one population we can then call them common from one population we can then call them common ancestors. ancestors.

Now each species has its own specific traits but all the Now each species has its own specific traits but all the species do share common traits that they inherited from species do share common traits that they inherited from their ancestors.their ancestors.

Speed of EvolutionSpeed of Evolution Gradualism is the model that describes Gradualism is the model that describes

evolution as a slow, ongoing process by evolution as a slow, ongoing process by which one species changes into a new which one species changes into a new species.species.

It also states that a continuing series of It also states that a continuing series of mutations and variations of DNA will result mutations and variations of DNA will result in a new species.in a new species.

This doesn’t explain the evolution of all This doesn’t explain the evolution of all species though. Some fossils show that species though. Some fossils show that some species changed to a new species some species changed to a new species very quickly. very quickly.

Punctuated equilibrium shows that the Punctuated equilibrium shows that the mutations of a few genes results in the mutations of a few genes results in the appearance of a new species over a short appearance of a new species over a short time span.time span.

Punctuated equilibrium Punctuated equilibrium todaytoday

This still occurs today. Every time we This still occurs today. Every time we expose a bacteria to a drug, the bacteria expose a bacteria to a drug, the bacteria tries to make changes in its DNA so that tries to make changes in its DNA so that the drug won’t kill it anymore. the drug won’t kill it anymore.

The flu virus does this about every 30-50 The flu virus does this about every 30-50 years, and we are responsible to create years, and we are responsible to create new vaccines that are able to kill it.new vaccines that are able to kill it.

FossilsFossilsSec 6-2 H.W. pg 169 ques. 1-4Sec 6-2 H.W. pg 169 ques. 1-4

Most of the evidence for evolution comes Most of the evidence for evolution comes from fossils. A fossil is the remains, from fossils. A fossil is the remains, imprint, or trace of a organism.imprint, or trace of a organism.

Scientists have the ability to study the Scientists have the ability to study the past analyzing fossils, which are evidence past analyzing fossils, which are evidence of ancient life on Earth.of ancient life on Earth.

Fossils help scientists form pictures of the Fossils help scientists form pictures of the past and provide a history for life on Earth. past and provide a history for life on Earth.

The Earths crust is a kind of graveyard The Earths crust is a kind of graveyard that holds fossil remains of species that that holds fossil remains of species that have lived throughout Earths history.have lived throughout Earths history.

FossilsFossils Most fossils are found within Most fossils are found within

sedimentary rock, which is rock made sedimentary rock, which is rock made of compressed sediments of sand, of compressed sediments of sand, clay, mud and other rock.clay, mud and other rock.

Limestone is the sedimentary rock Limestone is the sedimentary rock that we find most fossils.that we find most fossils.

These fossils are removed from the These fossils are removed from the ground by scientists and are added to ground by scientists and are added to the fossil record.the fossil record.

The fossil record id the collection of all The fossil record id the collection of all the fossils that scientists have the fossils that scientists have recovered.recovered.

Determining a Fossils ageDetermining a Fossils age Scientists use relative dating to estimate a Scientists use relative dating to estimate a

fossils age. Relative dating looks at the fossils age. Relative dating looks at the age of the rock the fossil is removed from.age of the rock the fossil is removed from.

Since rock is usually stacked up in layers Since rock is usually stacked up in layers we can estimate that if a fossil is in a rock we can estimate that if a fossil is in a rock layer, estimated to be 30 million years old, layer, estimated to be 30 million years old, than the fossil is 30 million years old.than the fossil is 30 million years old.

We also use radioactive elements to see We also use radioactive elements to see how old a fossil is. Radioactive elements how old a fossil is. Radioactive elements give off a certain amount of radiation and give off a certain amount of radiation and over time that amount lessens.over time that amount lessens.

So if we test the amount of radiation So if we test the amount of radiation emitted from a fossil we can tell the age.emitted from a fossil we can tell the age.

FossilsFossils

The fossils record of Earth is a very vast The fossils record of Earth is a very vast one. one.

We have fossils from almost every major We have fossils from almost every major plant and animal group in our fossil record.plant and animal group in our fossil record.

As vast as it is, the fossil record does not As vast as it is, the fossil record does not show a complete history.show a complete history.

Not every species is represented in the Not every species is represented in the fossil record. And this is because it is fossil record. And this is because it is much more common for an organism to much more common for an organism to decay before ever becoming a fossil.decay before ever becoming a fossil.

EmbryologyEmbryology Since not every organism is fossilized Since not every organism is fossilized

we also look at other things that we also look at other things that suggest evolution.suggest evolution.

One is embryology, or the study of One is embryology, or the study of how an organism develops from an how an organism develops from an embryo to an adult.embryo to an adult.

The embryos of a fish, a chicken, and The embryos of a fish, a chicken, and a rabbit all look very similar and a rabbit all look very similar and suggest an evolutionary relationship suggest an evolutionary relationship between vertebrate species. (pic on between vertebrate species. (pic on pg 167)pg 167)

Similar structuresSimilar structures Similar structures of species also suggest a Similar structures of species also suggest a

evolutionary relationship.evolutionary relationship. The arm bones in a frog, a human, a The arm bones in a frog, a human, a

porpoise, and a bat are all very similar.porpoise, and a bat are all very similar. Also, vestigial structures, or structures that Also, vestigial structures, or structures that

seem to have no function give us evidence of seem to have no function give us evidence of evolution.evolution.

An example is our appendix, we don’t use it An example is our appendix, we don’t use it but other large mammals use it to digest but other large mammals use it to digest grass.grass.

This suggests that our diet, long ago, greatly This suggests that our diet, long ago, greatly consisted of grass and plant material.consisted of grass and plant material.

DNA and evolutionDNA and evolution

If we look a the DNA of a species we If we look a the DNA of a species we can see how closely related species can see how closely related species really are.really are.

Chimps, apes, orangutans all have 24 Chimps, apes, orangutans all have 24 pairs of chromosomes and humans pairs of chromosomes and humans have 23 pairs. have 23 pairs.

We only differ from apes by about We only differ from apes by about 3,000 genes. This suggests that our 3,000 genes. This suggests that our common ancestor were apes.common ancestor were apes.

PrimatesPrimatesSec 6-3 H.W. pg 179 ques. 1-Sec 6-3 H.W. pg 179 ques. 1-

1515 Humans, monkeys, and apes belong to Humans, monkeys, and apes belong to

a group of mammals called primates.a group of mammals called primates. All primates have opposable thumbs, All primates have opposable thumbs,

binocular vision, and flexible shoulders binocular vision, and flexible shoulders that allow rotation of the arm.that allow rotation of the arm.

The opposable thumb is very important The opposable thumb is very important because it allows a primate to grasp because it allows a primate to grasp and hold things.and hold things.

Binocular vision allows depth Binocular vision allows depth perception or to be able to judge perception or to be able to judge distances.distances.

HominidsHominids 4-6 million years ago humanlike primates 4-6 million years ago humanlike primates

appeared and they are called Hominids.appeared and they are called Hominids. They ate both meat and plants, and walked They ate both meat and plants, and walked

upright on two legs, and had larger brains upright on two legs, and had larger brains than apes.than apes.

In 1974 Lucy was found. This was the first In 1974 Lucy was found. This was the first Hominid fossil ever discovered in Africa.Hominid fossil ever discovered in Africa.

In the 1960’s a hominid named Homo In the 1960’s a hominid named Homo habilis, or the handy man was found.habilis, or the handy man was found.

It is thought that this hominid gave rise to It is thought that this hominid gave rise to homo erectus, another human ancestor, homo erectus, another human ancestor, because of the similar features they shared. because of the similar features they shared.

HumansHumans About 400,000 years ago Homo sapiens About 400,000 years ago Homo sapiens

evolved.evolved. Neanderthals were short, heavy bodied, thick Neanderthals were short, heavy bodied, thick

boned humans that lived in families in caves boned humans that lived in families in caves and made stone tools to hunt animals.and made stone tools to hunt animals.

Next, Cro-Magnon fossils were found in Asia, Next, Cro-Magnon fossils were found in Asia, and are almost the same physically to modern and are almost the same physically to modern humans.humans.

There is evidence that they lived in caves, There is evidence that they lived in caves, which they painted the walls of, and buried which they painted the walls of, and buried their dead.their dead.

They might be direct ancestors to modern They might be direct ancestors to modern humans.humans.

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