Chapter 15: Biological Classification

The Importance of Scientific Names

Each kind of organism on Earth is assigned a unique ______

______

o______

All biologists, regardless of their native language, use scientific names when speaking or writing about organisms

Most organisms also have ______

Using scientific names enables scientists to exchange information about an organism and to be certain that they are referring to the same living thing

What’s in a Scientific Name?

First word describes the organism in a ______

The second word identifies the ______of living thing

The first word of a scientific name is the name of the ______to which the organism belongs

oGroup of animals that share major characteristics

The second word in a scientific name identifies one particular kind of organism within the genus

Scientists call each different kind of organism a ______

The correct name for an organism must include ______parts of its scientific name

Scientific Names Must Conform to a Set of Rules

All scientific names must consist of ______words

Two different organisms cannot be assigned the same name

Organisms in different genera cannot have the same ______

______

When choosing a name for a species, biologists often pick a name that describes the ______of an organism

Why are Scientific Names in Latin?

In the Middle Ages, when scientists began to name organisms, Latin was used in academic circles

Scientists and other scholars found it easier to communicate with each other in Latin

Latin was the language of the scholar and was used for all spoken and written communication

Easier to still use Latin than to rename all ______known organisms

Latin is a ______

Linnaeus Devised the Two-Name System

The modern system of naming organisms was developed by Swedish botanist ______

In Linnaeus’s day, organisms were given very long Latin names (sometimes more than 15 words), which were often changed according to the whims of particular scientists

Linnaeus assigned a standard, two-word Latin name to each organism known in his time

Writing a Scientific Name is Simple

When you write a scientific name, always ______the genus name

Begin the second word with a ______

Both part of a scientific name are underlined or written in italics

oHomo sapiens

After the first use of the full scientific name, the genus name can be abbreviated as a single letter if the meaning is clear

oH. sapiens

Classification of Living Things

The Greek philosopher ______grouped animals by their physical similarities

Today biologists classify organisms based on their physical, genetic, biochemical, and behavioral similarities

The classification of organisms is based on decisions made by many scientists using available information

The science of classifying living things is called ______

Taxonomists are scientists who examine, classify, and argue about where organisms fit in a group

In a hierarchical system of classification, species are assigned to genera, genera are assigned to families, and families are assigned to groups of ______

Organisms are Classified by Similarity

In biological classification, organisms are assigned to a group because they ______with other members of that group

The biological hierarchy of classification has seven different levels

oKingdom, phylum, class, order, family, genus, and species

The smallest group in biological classification is the ______

Similar species are collected into a ______

Similar genera are united into a ______

Families that are alike are combined into an ______

Similar orders are collected into a ______

Classes are united into a ______

Finally, similar phyla are collected into a ______

The more classification categories two species share, ______

______

Biological Classification

Kristy

Poured

Coffee

On

Fred’s

Green

Shirt

______

Classification and Evolution

The biological hierarchy of classification is based on the fact that different degrees of similarity exist among organisms

For Darwin, classification provided strong evidence supporting ______

Organisms are similar because they descended from a common ancestor

The more similarities two organisms share, the ______they shared a common ancestor

Thus, the more classification categories two organisms share, the more closely related they are

Similarity Does not Guarantee Close Relationship

Compare the two ocean-dwelling animals seen here

Both have ______, ______

______, and ______

Would you say these organisms are closely related?

______does not guarantee ______

______

Because the number of differences between sharks and dolphins far exceeds the number of similarities, it is easy to reject the hypothesis that these animals are close relatives

Methods of Taxonomy

The example of the shark and dolphin illustrates the difficulty in determining which similarities will be useful when classifying an organism

There are two alternative methods of choosing which similarities are important

The first method is ______

Taxonomy and Technology

Biologists have traditionally compared the appearances of organisms in order to discover the relationships among them

Biologists also consider the ______, ______, ______

______, and ______from fertilization to adulthood

Technological advances have enabled biologists to study the genes that produce the traits used to classify organisms

Taxonomists use techniques of molecular biology to compare the DNA nucleotide sequences of different organisms

Comparisons of ______are especially important for the taxonomist because mutations are random events

As time passes, more mutations tend to occur in the DNA of a particular species

Thus, DNA acts as a ______

What Is a Species?

A species is just a level in the classification system to which scientists assign very similar organisms

Over time, species change and give rise to new species in a process known as ______

Biologists have traditionally defined a species as organisms that are able to ______with each other to produce fertile offspring and that usually do not reproduce with members of other groups

This definition works well for most animals

For example, the horse and the zebra belong to different species

Although they can mate, the resulting offspring, the “zebroid”, is ______

______between species are not always perfect

______are offspring that result from interbreeding by individuals of different species

o______

A Species is a Unique Kind of Organism

A species is basically a unique kind of organism

Members of a species share at least ______

______not found in other similar organisms

In sexually reproducing species, this distinctive characteristic is maintained from generation to generation because members of different species do not interbreed

Six – Kingdom System

Biologists used to classify every living thing into either kingdom ______or kingdom ______

However, numerous living things do not quite fit either description

For example, where would a mushroom fit?

Since Linnaeus’s time, biologists have learned a great deal about the ______of living things

This information has enabled them to make increasingly precise distinctions among the major groups of organisms

Most biologists now use a ______system of classification

o______

Bacteria

All prokaryotes, also called ______, are in the kingdoms Archaebacteria or Eubacteria

The bacteria represent the ______groups on earth

They have adapted to almost every environment

All bacteria ______

Kingdom Archaebacteria

The archaebacteria evolved before ______filled our atmosphere and now are found in extreme environments

Fewer than ______have been recognized so far

Archaebacteria are believed to be the ancestors of the ______

Kingdom Eubacteria

Contains most of the ______that share our world

They are an extremely diverse group, containing both autotrophic and heterotrophic forms

Approximately ______have been characterized so far, but many more exist

Eubacteria are believed to be the ancestors of ______

______, organelles within eukaryotic cells

Kingdom Protista

All the multicellular eukaryotes not classified as plants, animals, or fungi are assigned to this kingdom

Protists include ______, such as Amoeba and Paramecium, and algae, such as seaweeds and kelps

Slime molds and water molds also belong to this kingdom

Kingdom Fungi

______are members of this kingdom

Instead of roots, stems, and leaves, fungi are made of ______

______that penetrate the soil or decaying organisms, absorbing nutrients from them

Fungi do not contain ______and cannot make their own food by photosynthesis

Kingdom Plantae

This kingdom includes only terrestrial multicellular organisms that use photosynthesis to obtain their nutrients

Nearly all plants occur on ______, but a few grow submerged in fresh water, and a very few grow at the edges of the sea

Plants cells have ______

Because some green algae are so similar to plants they have been identified as the ancestral groups for this kingdom

Kingdom Animalia

The first members of this kingdom evolved in the ______

The largest number of animal phyla are still found only in the ______

Organisms in kingdom Animalia are ______

Animals do not photosynthesize

Their cells do not have cell walls

Nearly all animals have some sort of ______