How Do Scientists Identify and Classify New Species?

·Swedish botanist / physician that collected plants for their curative properties & needed to organize his collection.·Contributed to the development of our modern system of taxonomy.·Developed binomial nomenclature, a two-word naming system still used today.

Each species is assigned a two-part scientific name

Carolus Linnaeus (1707 - 1778)

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Dashing

King

Philip

Came

Over

For

Great

Soup

What's My Name?

Pecari tejacu Odocoileus virginianus

What's My Name?

Canis lupus

What's My Name?

Homo sapiens

What's My Name?

Javelina

Human Dog

White-tailed Deer

The three domains each contain at least one kingdom. Domains Archaea and Bacteria both contain all the prokaryotes and include organisms from the kingdoms Archaebacteria and Eubacteria. The four remaining kingdoms are all found within the Domain Eukarya.

KINGDOMS

CLICK THE CROW

N:

FIRST CELL

DOMAINBACTERIA

DOMAINARCHAEA

DOMAINEUCARYA

KingdomEubacteria

KingdomProtista

KingdomArchaebacteria

KingdomFungi

KingdomPlantae

KingdomAnimalia

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Identifying Organisms

The names given to organisms often reveal:- The evolutionary history of their species- Ecological relationships with other species- Distinguishing characteristics of that species

Common names are often confusing- Not all are fish: catfish, starfish, silverfish, jellyfish, crayfish

In order to study this diversity:- Species are grouped into larger related classifications- A universal scientific name is given to every species

A dichotomous key is a series of questions used to identify new or unknown species. (eg. flower)

Identifying Organisms

With millions, and perhaps billions, of different species on Earth, identifying organisms can be quite a challenge.

Luckily, a simple set of questions, called a dichotomous key, can systematically lead a scientist from unknown to known.

Try this dichotomous key activity to learn how this works. Then, answer the questions found in the tab on the left.

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1. Give three examples of flower characteristics used in the dichotomous key.The three flower characteristics were the position of the ovary, the overall shape of the flower, and the pattern of symmetry.

2. Which flower did you classify as a crucifer? Describe two flower characteristics you think may be useful in identifying flowers from other crucifer plants.The mustard flower is a crucifer. The flower was not cup-shaped, and the top view of the lower showed radial symmetry with four petals arranged in a shape like a plus sign, +.

3. How do you think white cabbage butterfly larvae might identify crucifer plants?Probably by the number of petals, in the plus sign shape.

Using a dichotomous key

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1. Give three examples of flower characteristics used in the dichotomous key.

2. Which flower did you classify as a crucifer? Describe two flower characteristics you think may be useful in identifying flowers from other crucifer plants.

3. How do you think white cabbage butterfly larvae might identify crucifer plants?

Creating a Dichotomous KeyQuestionHow can you create a dichotomous key to identify organisms?

Figure A3.1 These students are using criteria to sort objects intogroups like scientists use criteria to classify species into groups.

ProcedurePart 1: Everyday Objects1. With a partner or group, empty your kit of items onto a desk or table.

2. Use the dichotomous key to organize the objects into groups. Startby choosing a major characteristic (e.g., metal or plastic, tubular ornontubular) and divide the objects into two groups based on thecharacteristic.

3. On the key, record the defining characteristic of each group and thenames of all the objects that belong in each group.

4. For each group, determine another characteristic that can be used todifferentiate the objects into two groups. Then repeat step 3.

5. Repeat step 4 until you have 20 groups each with a single object.

6. Use the information recorded to create a dichotomous key. For eachstep in your dichotomous key, you need to create a pair of choices thatfocuses on a particular characteristic.Suppose the first characteristic recorded on your key is “presence ofhair.” Then for the first numbered step on your dichotomous key, youwould write:1a hair is present1b hair is absent

7. At each characteristic such as those noted above, lead the reader to thenext step to consider on your dichotomous key. What groups does eachof the characteristics lead to? Write these groups as a step in your keyand direct readers to go to the correct step for each outcome of step 1.Continue this process to construct the rest of your dichotomous key.

8. As you write each step on your dichotomous key, use the followingguidelines:• avoid qualitative terms such as “large” or “many”• use quantifiable characteristics, such as exact measurements (seeTable 1)• ensure each step has an outcome (identification of an object or a nextstep to go to) for both positive and negative responses

Inappropriate

Appropriate

large greater than 60 kg

short less than 150 cm

light coloured

red

many 10 or more

beautiful more than 6 coloursTable 1

Analyzing and InterpretingPart 1: Everyday Objects11. Give three examples of characteristics used in the dichotomous key.12. Based on your dichotomous key, what characteristics do all theobjects share?Part 2: Organisms from the Kingdoms13. Did your partner successfully use your key? Explain why or why not.14. Why is it important to use clear terms in a dichotomous key?15. Why should qualitative terms be avoided in creating dichotomous keys?Skill Practice16. List some characteristics that would be useless for a dichotomous key.Explain your choices.17. Why are there always two choices at each step of a dichotomous key?Forming Conclusions18. Is there a “right” and “wrong” dichotomous key? Justify your answer.19. What improvements might be made to your key?

Attachments

BiologySource2.flv

Biological Classification Kingdoms - YouTube.flv