Chapter

18

Classification

18 – 1 Finding Order in Diversity

Evolution has lead to a staggering variety or organisms Biologists have identified and named about __________________________ species

so far They estimate anywhere between 2 and 100 million additional species have yet to be

discovered

Why Classify?

To study the diversity of life, biologists use a classification system to name organsisms and group them in a logical manner

Taxonomy - _____________________________________________________________

Assigning Scientific Names

By the 18th century, European scientists recognized that referring to organisms by common names was confusing

Common names vary among regions within a country

Ex.)

Scientists use Latin and Greek for scientific names

Early Efforts at Naming Organisms

First attempts at standard scientific names often described physical characteristics As a result, these names could be 20 words long!Ex.) The English translation of the scientific name of a particular tree might be “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges.”

Binomial Nomenclature

Carolus Linnaeus (18th Century) Swedish Botanist Developed a system for naming organisms

Binomial Nomenclature - ___________________________________________________

Rules for Binomial Nomenclature

1.

2.

3.

Ex.) Genus species or Genus species or G. species

The name often tells you something about the speciesEx.) Tyranosaurus Rex

Linnaeus’s System of Classification

Taxon (taxonomic category) - _______________________________________________________________________________________________________________________

Linnaeus’s system of classification uses seven taxonomic categories

Mnemonic Device

K______________________

P______________________

C______________________

O______________________

F______________________

G______________________

K _______________________

P________________________

C________________________

O________________________

F________________________

G________________________

s ________________________

s_______________________

Name _________________________________ Date _____________________ Per ____

18 -1 Section Review

1. How are living things organized for study?

2. Describe the system for naming species that Linnaeus developed.

3. What are the seven taxonomic categories of Linnaeus’s classification system?

4. Why do scientists avoid using common names when discussing organisms?

5. Which category has more biological meaning—all brown birds or all hawklike birds? Why?

18 -2 Modern Evolutionary Classification

Back in Linneaus’s time when classifying organisms he compared structures and details of anatomy

Problems with Traditional Classification

Sometimes, due to convergent Evolution organisms that are quite different from each other evolve similar body structures

Ex.)

Evolutionary Classification

Darwin’s theory of evolution changed the entire way that biologists thought about classification

Biologists now group organisms into categories that represent ______________________________________________________, not just physical similarities

Classification Using Cladograms

Many biologists now prefer a method called _________________________________ This method of classification identifies and considers only those characteristics that

arise as lineages evolve over time

Derived characteristics - _________________________________________________________________________________________________________________________________________________________________________________________________

Cladogram - _____________________________________________________________________________________________________________________________________________________________________________________________________________

Similarities in DNA and RNA

Suppose you were trying to compare diverse organisms such as yeast and humans It wouldn’t make sense to try to classify anatomical similarities The genes of many organisms show important similarities at the molecular level These similarities can be used as criteria to help determine classificationEx.) Myosin in humans & yeast

Molecular Clocks

Comparison of DNA can also be used to mark the passage of evolutionary time

Molecular clock - _________________________________________________________________________________________________________________________________________________________________________________________________________

Mutations happen all the time at about the same rate A comparison of DNA sequences in two species can reveal how dissimilar the genes

are The degree of dissimilarity is an indication of how long ago the two species shared a

common ancestor

Name _________________________________ Date _____________________ Per ____

18 -2 Section Review

1. How is information about evolutionary relationships useful in classification?

2. How are genes used to help scientists classify organisms?

3. What is the principle behind cladistic analysis?

4. Describe the relationship between evolutionary time and the similarity of genes in two species.

5. have new discoveries in molecular biology affected the way in which we classify organisms compared with the system used by Linnaeus?

18 -3 Kingdoms and Domains

In taxonomy, as in all areas of science, ideas and models change as new information arises, some explanations have been discarded altogether, whereas others such as Darwin’s theory of evolution by natural selection, have been upheld

So it should not be surprising that since the 1800’s, the tree of life has been revised and edited since the discovery of all this new information

The Tree of Life Evolves

Before Linnaeus’s time, the only two Kingdoms that existed were _________________________________________________

As scientists discovered new organisms that didn’t fit into the plant or animal category, they made a new category

The Old 5 Kingdom System for Classification

1.

2.

3.

4.

5.

In recent years, as evidence about microorganisms continued to accumulate, biologists come to recognize that the Monera were composed of two distinct groups

The New 6 Kingdom System for Classification

1.

2.

3.

4.

5.

6.

The Three Domain System

Molecular analysis has given rise to a new taxonomic category that is now recognized by many scientists

Domain - _______________________________________________________________

3 Domains

1. o

2.o

3.o

Domain Bacteria

Important Characteristics

Prokaryotic - __________________________________________________________ Some photosynthesize

Some need oxygeno Aerobic - ______________________________________________________

Some don’t need oxygeno Anerobic - _____________________________________________________

Domain Archaea

Important Characteristics

Live in extreme environmentsEx.)

Domain Eukarya

Consists of all organisms that have a ___________________________

Protista

Important Characteristics

eukaryotic - __________________________________________________________ cannot be classified as animals, plants or fungi, but share many characteristics with

plants, animals and fungi

Plant Like Protists

Photosynthetic - _______________________________________________________

Animal Like Protists

heterotrophic - ________________________________________________________

Fungus Like Protists

Fungi

Important Characteristics

Ex.) Mushrooms, Yeast

o heterotrophs feed on ________________________________________________ secrete digestive enzymes into food source then absorb the food into their bodies some are parasites spread and reproduce by _________________________ Many are used in medicine

ooo

Plantae

Important Characteristics

Photosynthetic autotrophs - ______________________________________________________________________________________________________________________

Animalia

Important Characteristics

heterotrophic incredible diversity

Name _________________________________ Date _____________________ Per ____

18 -3 Section Review

1. What are the six kingdoms of life as they are now identified?

2. What are the three domains of life?

3. Why was the kingdom Monera divided into two separate kingdoms?

4. Why might kingdom Protista be thought of as the “odds and ends” kingdom?

5. Which kingdoms include only prokaryotes? Which kingdoms include only heterotrophs?