Biology - Rhinelander School District 2010... · END OF SECTION. Title: Biology Created Date:...

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Biology

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18-2 Modern Evolutionary

Classification

18-2 Modern Evolutionary Classification

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Evolutionary

Classification

Which Similarities Are Most Important?

(Linnaeus grouped species into larger taxa

mainly according to visible similarities and

differences. –Old Way!! In place until late

1990’s/early 2000

The Problem--- Organisms that appear very

similar may not share a recent common

ancestor)


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Evolutionary

Classification

(Now----Biologists currently group

organisms into categories that represent

lines of evolutionary descent, or

phylogeny, not just physical similarities. )


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Evolutionary

Classification

1. evolutionary classification:strategy of grouping organisms based on

evolutionary history

2. Phylogeny:

* study of evolutionary relationships among

organisms.


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Evolutionary

Classification

Different Methods of Classification

Appendages Conical Shells Crustaceans Mollusk

Crab Barnacle Limpet Crab Barnacle Limpet

Molted external

skeleton

CLASSIFICATION BASED ON

VISIBLE SIMILARITY CLADOGRAM

Segmentation

Tiny free-

swimming larva

Resources/ActiveArt/cladograms.html

Resources/ActiveArt/cladograms.html


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Evolutionary

Classification

Superficial similarities once led barnacles and limpets

to be grouped together.

Appendages Conical Shells

Crab Barnacle Limpet


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Evolutionary

Classification

(However, barnacles and crabs share an evolutionary

ancestor that is more recent than the ancestor that

barnacles and limpets share.

Barnacles and crabs are classified as crustaceans,

and limpets are mollusks.)


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Classification Using

Cladograms

3. Classification Using Cladograms

(a. Cladistic analysis:

identifies and considers only new

characteristics that arise as lineages evolve.

b. Derived characters:

Characteristics that appear in recent parts of a

lineage but not in its older members )


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Cladograms

C. cladogram:

*a diagram that shows the evolutionary

relationships among a group of organisms.

(Cladograms help scientists understand how one

lineage branched from another in the course of

evolution.)


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D. Building a Cladogram:

1. Bottom or ―root‖

*represents common ancestor

shared by all organisms in group

(clade)

2. ―Fork‖ or ―node‖

*place where ancestral lineage

splits

* last point at which new lineages

share common ancestor



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Cladograms

A cladogram shows the evolutionary relationships

between crabs, barnacles, and limpets.

Crustaceans Mollusk

Crab Barnacle Limpet

Tiny free-swimming larva

Molted external skeleton

Segmentation

Active Art—Build a

Cladogram


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Similarities in DNA

and RNA

4. Similarities in DNA and RNA

How can DNA and RNA help scientists

determine evolutionary relationships?


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Similarities in DNA

and RNA

A. DNA evidence shows evolutionary relationships

of species.

B. More similar the DNA of two species;

* the more recently they shared a common

ancestor;

* the more closely they are related in

evolutionary terms.

(The more two species have diverged from each

other, the less similar their DNA will be.)

Active Art—Build DNA Cladogram


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Molecular Clocks

5. Molecular Clocks:

uses DNA comparisons to estimate the length of

time that two species have been evolving

independently.


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Molecular Clocks

A. relies on mutations to mark time.

B. Simple mutations in DNA occur often.

C. Neutral mutations accumulate in different

species at about the same rate.

D.Comparing sequences in two species shows:

1. how dissimilar the genes are

2. shows when they shared a common

ancestor.


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Molecular Clocks

Molecular Clock

new mutation

new mutation

2 mutations

A B C

A gene in an

ancestral species

Species Species Species

new mutation

2 mutations

Active Art—

Building

Molecular Clock

- or -

Continue to: Click to Launch:

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18-2

Resources/ch18_sectn02_quiz.qtb



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18-2

Grouping organisms together based on their

evolutionary history is called

a. evolutionary classification.

b. traditional classification.

c. cladogram classification.

d. taxonomic classification.

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18-2

Traditional classification groups organisms

together based on

a. derived characters.

b. similarities in appearance.

c. DNA and RNA similarities.

d. molecular clocks.

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18-2

In an evolutionary classification system, the

higher the taxon level,

a. the more similar the members of the taxon

become.

b. the more common ancestors would be found

in recent time.

c. the fewer the number of species in the taxon.

d. the farther back in time the common

ancestors would be.

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18-2

Classifying organisms using a cladogram depends on identifying

a. external and internal structural similarities.

b. new characteristics that have appeared most recently as lineages evolve.

c. characteristics that have been present in the group for the longest time.

d. individual variations within the group.

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18-2

To compare traits of very different organisms,

you would use

a. anatomical similarities.

b. anatomical differences.

c. DNA and RNA.

d. proteins and carbohydrates.

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Biology - Rhinelander School District 2010... · END OF SECTION. Title: Biology Created Date:...

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Transcript of Biology - Rhinelander School District 2010... · END OF SECTION. Title: Biology Created Date:...