Brittany Brown --Evolution

Earth’s Change Over TimeEarth’s Change Over Time
(Evolution)(Evolution)
Brittany BrownBrittany Brown
Biology 1-5Biology 1-5thth
periodperiod
May 1,2007May 1,2007

IntroductionIntroduction
In life there have been different theories asIn life there have been different theories as
to how life came about. Many scientists haveto how life came about. Many scientists have
wonder how Earth continued to change over awonder how Earth continued to change over a
period of time. In Mr. Parr class he has ask hisperiod of time. In Mr. Parr class he has ask his
students to present a power point presentationstudents to present a power point presentation
and the Earth Change Over Time or somethingand the Earth Change Over Time or something
related to that topic. These are the followingrelated to that topic. These are the following
students in his 5students in his 5thth
period class:period class:

Key ConceptsKey Concepts
 Earth has been home to living things forEarth has been home to living things for
about 3.8 billion years.about 3.8 billion years.
 Species change over time.Species change over time.
 Many types of evidence support evolution.Many types of evidence support evolution.

Vocabulary Chapter 1Vocabulary Chapter 1
 AdaptationAdaptation
 AncestorAncestor
 EvolutionEvolution
 FossilFossil
 GeneGene
 Mass ExtinctionMass Extinction

Vocabulary Chapter 1Vocabulary Chapter 1
 Multicellular OrganismMulticellular Organism
 Natural SelectionNatural Selection
 SpeciationSpeciation
 Unicellular OrganismUnicellular Organism
 Vestigial OrganVestigial Organ

Earth has been home to living thingsEarth has been home to living things
for about 3.8 billion years.for about 3.8 billion years.

Earth has been home to livingEarth has been home to living
things for about 3.8 billion years.things for about 3.8 billion years.
 Fossils provide evidence about the history of lifeFossils provide evidence about the history of life
on Earth. Most fossils are hard body parts oron Earth. Most fossils are hard body parts or
bone. Others form when minerals replace thebone. Others form when minerals replace the
remains of organisms. Fossils also include printsremains of organisms. Fossils also include prints
left by organisms, such as footprints. Very rarely,left by organisms, such as footprints. Very rarely,
a fossil is the preserved remains of an organism,a fossil is the preserved remains of an organism,
such as a wooly mammoth in ice or an insectsuch as a wooly mammoth in ice or an insect
preserved in sap.preserved in sap.

Earth has been home to living thingsEarth has been home to living things
for about 3.8 billion years. (cont.)for about 3.8 billion years. (cont.)
Relative ageRelative age is how old a rock oris how old a rock or
fossil is compared to other rocksfossil is compared to other rocks
or fossils. Ancient organismsor fossils. Ancient organisms
settled to the bottom of a body ofsettled to the bottom of a body of
water in layers of mud and sandwater in layers of mud and sand
that later formed rock.that later formed rock.

Absolute ageAbsolute age is the actual age ofis the actual age of
the rock or fossil. To measure thethe rock or fossil. To measure the
absolute age of a fossil, scientistsabsolute age of a fossil, scientists
measure its radioactivity. Overmeasure its radioactivity. Over
time, radioactive materialtime, radioactive material
disappears. The older the fossil,disappears. The older the fossil,
the less radioactive material itthe less radioactive material it
has.has.

TheThe fossil recordfossil record is all of theis all of the
information that can be gatheredinformation that can be gathered
from the fossils in a particularfrom the fossils in a particular
location. Scientists can then uselocation. Scientists can then use
the record to identify whichthe record to identify which
species lived and died duringspecies lived and died during
different periods of time.different periods of time.

Earth has been home to living things forEarth has been home to living things for
about 3.8 billion years. (cont.)about 3.8 billion years. (cont.)
Unicellular organisms, made ofUnicellular organisms, made of
only one cell, were the first livingonly one cell, were the first living
things on Earth. They appearedthings on Earth. They appeared
about 3.8 billion years ago. Theabout 3.8 billion years ago. The
atmosphere then did not have asatmosphere then did not have as
much oxygen as it does now.much oxygen as it does now.
Some of the early organismsSome of the early organisms
added oxygen to the atmosphere.added oxygen to the atmosphere.

Multicellular organismsMulticellular organisms began to livebegan to live
in Earth's oceans about 1.2 billionin Earth's oceans about 1.2 billion
years ago. The fossil record showsyears ago. The fossil record shows
that the earliest multicellularthat the earliest multicellular
organisms were tiny seaweeds. Theorganisms were tiny seaweeds. The
earliest animals were similar toearliest animals were similar to
jellyfish.jellyfish.

 Life appeared on land about 500 million yearsLife appeared on land about 500 million years
ago. Before that, all living things met their needsago. Before that, all living things met their needs
while living in water. Simple plants were the firstwhile living in water. Simple plants were the first
land-dwelling organisms, getting water from theland-dwelling organisms, getting water from the
soil through roots. The plants in turn providedsoil through roots. The plants in turn provided
food and shelter to the first fungi and insects onfood and shelter to the first fungi and insects on
land. After insects, amphibians and reptilesland. After insects, amphibians and reptiles
began to live on land, followed by birds andbegan to live on land, followed by birds and
mammals.mammals.

A species becomes extinct whenA species becomes extinct when
all members of the species haveall members of the species have
died. Many species have onlydied. Many species have only
been seen as fossils becausebeen seen as fossils because
they became extinct long ago. Athey became extinct long ago. A
mass extinction is a period whenmass extinction is a period when
a large number of speciesa large number of species
become extinct in a very shortbecome extinct in a very short
time.time.

 TheThe Permian ExtinctionPermian Extinction occurred aboutoccurred about
250 million years ago. Approximately 90250 million years ago. Approximately 90
percent of the species in the ocean, aspercent of the species in the ocean, as
well as many land-dwelling animals,well as many land-dwelling animals,
became extinct. This mass extinction maybecame extinct. This mass extinction may
have been caused by climate change duehave been caused by climate change due
to all of Earth's landmasses joiningto all of Earth's landmasses joining
together to form a single, enormoustogether to form a single, enormous
continent.continent.

Example of Cretaceous ExtinctionExample of Cretaceous Extinction

TheThe Cretaceous ExtinctionCretaceous Extinction
occurred about 65 million yearsoccurred about 65 million years
ago. More than half of all theago. More than half of all the
species on Earth, includingspecies on Earth, including
dinosaurs, became extinct. Thisdinosaurs, became extinct. This
mass extinction may have beenmass extinction may have been
caused by a meteorite, a giantcaused by a meteorite, a giant
space object, colliding with Earth.space object, colliding with Earth.

Mass extinctionsMass extinctions are oftenare often
followed by the appearance of afollowed by the appearance of a
large number of new species. Forlarge number of new species. For
example, the extinction ofexample, the extinction of
dinosaurs may have allowed newdinosaurs may have allowed new
species of mammals to developspecies of mammals to develop
and thrive.and thrive.

Species change over time.Species change over time.

Species change over time.Species change over time.
Evolution is the process by which species changeEvolution is the process by which species change
over time.over time.
 In the early 1800s, Jean-In the early 1800s, Jean-
Baptiste de LamarckBaptiste de Lamarck
proposed a theory ofproposed a theory of
evolution. He suggestedevolution. He suggested
that organisms developthat organisms develop
traits during their livestraits during their lives
and then pass them on toand then pass them on to
offspring. For example, aoffspring. For example, a
giraffe stretches its neckgiraffe stretches its neck
to get high leaves, andto get high leaves, and
then passes that longerthen passes that longer
neck to the nextneck to the next
generation. But Lamarckgeneration. But Lamarck
could not find evidence tocould not find evidence to
support his theory.support his theory.

Evolution is the process by which species changeEvolution is the process by which species change
over time.over time.
 Charles Darwin was aCharles Darwin was a
naturalist who traveled to thenaturalist who traveled to the
Galapagos Islands in the lateGalapagos Islands in the late
1830s. Darwin's theory of1830s. Darwin's theory of
evolution developed fromevolution developed from
observing different species ofobserving different species of
tortoises and finches on thetortoises and finches on the
Galapagos Islands. ForGalapagos Islands. For
example, he found someexample, he found some
finches with beaks useful forfinches with beaks useful for
cracking seeds and others withcracking seeds and others with
beaks useful for capturingbeaks useful for capturing
insects. Darwin wonderedinsects. Darwin wondered
whether the birds had evolvedwhether the birds had evolved
differently because they weredifferently because they were
in different environments.in different environments.

Species change over timeSpecies change over time..
 A group of organisms may evolve due toA group of organisms may evolve due to
artificial selectionartificial selection
 artificial selectionartificial selection is the process thatis the process that
breeders use to produce animals withbreeders use to produce animals with
desirable traits. A breeder will selectdesirable traits. A breeder will select
individuals with desired traits from aindividuals with desired traits from a
group, then allow only those individuals togroup, then allow only those individuals to
mate. In the next generation, the breedermate. In the next generation, the breeder
will again select the individuals withwill again select the individuals with
desired traits and mate them to producedesired traits and mate them to produce
the next generation.the next generation.

Species change over timeSpecies change over time..
Natural SelectionNatural Selection
 Natural selectionNatural selection is the hypothesis Darwinis the hypothesis Darwin
developed based on his observations fromdeveloped based on his observations from
his voyage and from his hobby of breedinghis voyage and from his hobby of breeding
pigeons. Darwin proposed that memberspigeons. Darwin proposed that members
of a species that are best suited to theirof a species that are best suited to their
environment survive and reproduce at aenvironment survive and reproduce at a
higher rate than other members of thehigher rate than other members of the
species. This process is called naturalspecies. This process is called natural
selection.selection.

The process of natural selection depends on a fewThe process of natural selection depends on a few
key principles.key principles.
 OverproductionOverproduction is theis the
idea that mostidea that most
organisms produceorganisms produce
more offspring thanmore offspring than
can possibly survive.can possibly survive.
For example, aFor example, a
female salmon laysfemale salmon lays
thousands of eggs,thousands of eggs,
but only severalbut only several
dozen will survive todozen will survive to
adulthood, and evenadulthood, and even
fewer will reproduce.fewer will reproduce.

 VariationVariation is the naturalis the natural
differences in traitsdifferences in traits
among the members of aamong the members of a
species. Some mightspecies. Some might
have slightly larger fins,have slightly larger fins,
others different patternsothers different patterns
of spots. Mutations areof spots. Mutations are
changes in geneticchanges in genetic
material that cause amaterial that cause a
variation. Variations, duevariation. Variations, due
either to mutation or theeither to mutation or the
random combination ofrandom combination of
genes from parents, aregenes from parents, are
passed from onepassed from one
generation to the next.generation to the next.

 AnAn adaptationadaptation is anyis any
inherited trait that givesinherited trait that gives
an organism anan organism an
advantage in its particularadvantage in its particular
environment. Anenvironment. An
adaptation is a variationadaptation is a variation
that makes an individualthat makes an individual
better able to survive thanbetter able to survive than
others. For example, aothers. For example, a
slight change in theslight change in the
shape of a fin might makeshape of a fin might make
a fish swim faster anda fish swim faster and
avoid predators.avoid predators.

 SelectionSelection is the processis the process
that passes the mostthat passes the most
successful variations, orsuccessful variations, or
adaptations, into the nextadaptations, into the next
generation. Of thegeneration. Of the
organisms that thenorganisms that then
survive to reproduce,survive to reproduce,
more and more of themmore and more of them
will have the adaptation.will have the adaptation.
The favorable traits areThe favorable traits are
"selected" for the next"selected" for the next
generations. In this way,generations. In this way,
the species as a wholethe species as a whole
becomes more suited tobecomes more suited to
its environment.its environment.

 SpeciationSpeciation is the evolution of a new species fromis the evolution of a new species from
an existing species. Speciation can occur whenan existing species. Speciation can occur when
the environment changes. When geneticthe environment changes. When genetic
changes within two groups of the same specieschanges within two groups of the same species
build up, the two groups may not be able tobuild up, the two groups may not be able to
interbreed anymore. When this happens, twointerbreed anymore. When this happens, two
different species have formed and speciationdifferent species have formed and speciation
has occurred. The diagrams show how threehas occurred. The diagrams show how three
species of cichlid fish evolved from one originalspecies of cichlid fish evolved from one original
species in Lake Tanganyika.species in Lake Tanganyika.

 IsolationIsolation is essential to speciation. For a speciesis essential to speciation. For a species
to separate, two groups must be prevented fromto separate, two groups must be prevented from
reproducing with one another. A geographicreproducing with one another. A geographic
boundary, such as a mountain range or ocean,boundary, such as a mountain range or ocean,
can result in isolation. The cichlids in Lakecan result in isolation. The cichlids in Lake
Tanganyika and the finches Darwin observed inTanganyika and the finches Darwin observed in
the Galapagos Islands are examples of isolationthe Galapagos Islands are examples of isolation
leading to new species.leading to new species.

 Many types of evidenceMany types of evidence
support evolution.support evolution.

Many types of evidence supportMany types of evidence support
evolution.evolution.
AA theorytheory is a widely acceptedis a widely accepted
statement, based on scientificstatement, based on scientific
evidence, that helps explain aevidence, that helps explain a
group of facts. Darwin's theory ofgroup of facts. Darwin's theory of
evolution is widely acceptedevolution is widely accepted
because it is supported by fossilbecause it is supported by fossil
evidence, biological evidence,evidence, biological evidence,
and genetic evidence.and genetic evidence.

Many types of evidenceMany types of evidence
 Evidence from fossils supports evolution.Evidence from fossils supports evolution.
An ancestor is an early form of anAn ancestor is an early form of an
organism from which later forms descend.organism from which later forms descend.
According to the theory of evolution,According to the theory of evolution,
different species should have commondifferent species should have common
ancestors. Fossil evidence supports thisancestors. Fossil evidence supports this
idea. For example, modern plants andidea. For example, modern plants and
modern algae share characteristics withmodern algae share characteristics with
fossil algae that point to a commonfossil algae that point to a common

Biological evidence supportsBiological evidence supports
evolution. Biological evidenceevolution. Biological evidence
includes the structure of livingincludes the structure of living
things and how living thingsthings and how living things
develop into adults.develop into adults.

 Vestigial organsVestigial organs areare
physical structures thatphysical structures that
were fully developed andwere fully developed and
functional in an earlierfunctional in an earlier
group of organisms butgroup of organisms but
are reduced and unusedare reduced and unused
in later species. Thesein later species. These
vestigial organs indicatevestigial organs indicate
that the organism had anthat the organism had an
ancestor that needed theancestor that needed the
trait, and can show howtrait, and can show how
the modern organism andthe modern organism and
the ancestor are related.the ancestor are related.

 Similar structuresSimilar structures with different functions indicate thatwith different functions indicate that
organisms shared a common ancestor. For example, theorganisms shared a common ancestor. For example, the
illustrations show that geckos, bats, and manatees haveillustrations show that geckos, bats, and manatees have
similar bones in their forelimb. A shorter bone leads fromsimilar bones in their forelimb. A shorter bone leads from
the shoulder to a joint. From the joint, the longer bonethe shoulder to a joint. From the joint, the longer bone
leads to a wrist. Because the three organisms live in veryleads to a wrist. Because the three organisms live in very
different environments, the similar structures havedifferent environments, the similar structures have
evolved in very different ways.evolved in very different ways.

 Similarities in development of different species that areSimilarities in development of different species that are
unlike as adults indicate a common ancestor. Forunlike as adults indicate a common ancestor. For
example, a chicken, a rabbit, and a salamander areexample, a chicken, a rabbit, and a salamander are
three very different animals. However, their embryosthree very different animals. However, their embryos
look very similar. As the embryos develop, they becomelook very similar. As the embryos develop, they become
more different. This evidence indicates that manymore different. This evidence indicates that many
animals must share a common ancestor whose embryoanimals must share a common ancestor whose embryo
started developing in a similar way.started developing in a similar way.

support evolutionsupport evolution
Genetic evidenceGenetic evidence
supports the theory ofsupports the theory of
evolution.evolution.

support evolutionsupport evolution
DNA contains the genetic materialDNA contains the genetic material
found in all cells. It contains a codefound in all cells. It contains a code
that a cell uses to function properly.that a cell uses to function properly.
The code is a pattern of four chemicalThe code is a pattern of four chemical
units called bases, represented by theunits called bases, represented by the
letters A, T, C, and G.letters A, T, C, and G.

 GenesGenes are segments of DNA that relate to aare segments of DNA that relate to a
specific trait or function of an organism. Forspecific trait or function of an organism. For
example, the clock gene is found in manyexample, the clock gene is found in many
mammals and relates to how the mammalmammals and relates to how the mammal
sleeps and wakes. The clock gene can be usedsleeps and wakes. The clock gene can be used
to compare different organisms. The moreto compare different organisms. The more
similar the code is for the clock gene betweensimilar the code is for the clock gene between
two organisms, the more closely related the twotwo organisms, the more closely related the two
organisms are.organisms are.

Brittany Brown --Evolution

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