EVOLUTIONARY CLASSIFICATION

Sz2- Students will explain the evolutionary history of animals over the geologic history of Earth.

Geologic History Geologic time- time that began when earth was

formed until present day

http://geopolicraticus.files.wordpress.com/2009/12/geologic-time-scale.gif

200 Million Years Ago

150 Million Years Ago

100 Million Years Ago

50 Million Years Ago

Present

Evolution of the Earth with Time: Continental Drift

Important Terms Evolution- gradual change in a species over

time- sci. theory Theory-well-tested explanation that

explains a wide range of observations. Adaptation- any trait that helps an

organism survive and reproduce

Natural Selection- the process by which

individuals that are better adapted to their environment are more likely to survive and reproduce.

Charles Darwin

Natural Selection cont. Over a long time, natural

selection can modify a population enough to produce a new species

Helpful variations accumulate in a species while unfavorable ones disappear.

SpeciationWhen a group of individuals remain

separated from the rest of the species long enough to evolve different traits

HOW this happens- Pangaea /Continental DriftLandform isolation- river, mountain, water.

(ex. Squirrels of N. Grand Canyon) Australia

A Problem with Traditional Classification

Traditional classification systems relied on body structure comparisons only

Due to convergent evolution, organisms that are quite different from each other evolve similar body structures.

Convergent Evolution: Process by which unrelated organisms independently evolve similarities when adapting to similar environments.

A Problem with Traditional ClassificationExample: The Crab, The barnacle, & The limpet

• The barnacle and the limpet have similarly shaped shells & look alike

• The crab has a very different body form

• Based on anatomy, the barnacle & limpet could be classified together and the crab in a different group.

Related

This incorrect because crabs and barnacles are actually related

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TRADITIONAL CLASSIFICATION

CLADOGRAM

Appendages Conical Shells

Crab Barnacle Limpet Crab Barnacle Limpet

Crustaceans Gastropod

Molted exoskeleton

Segmentation

Tiny free-swimming larva

Section 18-2Traditional Classification Versus Cladogram

Go to Section:

Crustaceans

Even though they do not look a like, crabs & barnacles are actually

related

Gastropods

Molted Exoskeleton

Segmentation

Free swimming Larva

Evolutionary Classification Biologists now group organisms into categories

that represent lines of evolutionary descent, not just physical similarities

Evolution Classification: Is the strategy of grouping organisms together based on their evolutionary history.

If these three species belong to the same genus, they are descended from a common ancestor.

Genus species

Felis

domestica

leo

margarita Sand cat`

Lion

Domestic Cat

Felis domestica

Felis leo

Felis margarita

Classification Using CladogramsCladogram: A diagram that shows the

evolutionary relationships among a group of organisms.

Crustaceans

Using Cladograms, you can see that crabs and barnacles share similar characteristics

because they both molt & are segmented

Gastropods

Molted Exoskeleton

Segmentation

Free swimming Larva

Crustaceans

You can also see that ALL have a free

swimming larval stage

Gastropods

Molted Exoskeleton

Segmentation

Free swimming Larva

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Modern Evolutionary Classification  Similarities in DNA and RNA

The genes of many organisms show important similarities at the molecular level that can be used as criteria to help determine classification.

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Modern Evolutionary Classification

Molecular Clocks

A model known as a molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently.

Comparison reveals more DNA in common, the more recent the common ancestor

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Terminology Classification

Assigning organisms to different catagories based on their relationship

Taxonomy The science of naming

organisms Systematics

Determining evolutionary relationships of organisms

Phylogeny Evolutionary history

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Phylogenetic Tree Shows evolutionary

relationships More historical than

cladogram

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Myxozoa

Arthropoda AnnelidaMollusca

Lophophorates

Hemichordata

Chordata

Other pseudocoelomates

Nematoda

Porifera

CtenophoraCnidaria

Placozoa

PlatyhelminthesNemertea

CiliophoraSarcomastigophora

MicrosporaApicomplexa

Mesozoa

Echinodermata

CrustaceaChelicerata

Uniramia

Protochordates

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Birds MammalsReptile

AmphibianFish

Four LimbsAmniotic Egg

EndothermicFur

Feathers

Vertebrae

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Monophyletic A group of all the

descendants of a common ancestor

The common ancestor is in the group

Example: Birds and ReptilesAncestor was a bird

like reptile

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Polyphyletic group that has some

similarities Contains organisms that

have not descended from a common ancestor

Based on physical characteristics instead of evolutionary evidence

Example: Flying vertebrates- pterosaurs, birds, mammals

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Cladogram Evolutionary

relationship of a group of organisms

Each clad (group) share something in common

Ancestral traits are the oldest

Derived traits evolved later

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Cladogram for Transportation

Wheels are the most ancestral

Wings are the most derived

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Construct a Cladogram

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Gorilla Four limbs Fur Lost tail

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Tiger Four limbs Fur Tail

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Lizard Four limbs Tail

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Fish Tail

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Chimpanzee Four limbs Fur Lost tail

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Clad With 4 Limbs

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Clad With Fur

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Clad With No Tail

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Characteristics for Constructing Cladogram Tail is the most ancestral Four limbs is the oldest derived trait Fur is a later derived trait Loss of tail is the most derived trait

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Gorilla ChimpanzeeTiger

LizardFish

Four LimbsFur

Tail Lost

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Gorilla Tail? How do we know the

gorilla lost its tail?

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Gorilla’s Vestigial Tail

Gorilla Human

The End.