3.4 Taxonomy Questions and Answers

3.4 Taxonomy – Questions and answers

Q1.

Bk Ch3 S3.4 Q1

Why do biologists try to classify organisms?

A1.

Bk Ch3 S3.4 A1

The classification of organisms helps scientists to understand the relationships between different kinds of organisms. Once organisms are classified they can be referred to by internationally accepted names that make communication about organisms easy.

Q2.

Bk Ch3 S3.4 Q2

aOutline the characteristic features of organisms in kingdoms Plantae and Animalia.

bList the three other kingdoms. Describe their distinguishing features, providing examples in each case.

A2.

Bk Ch3 S3.4 A2

aDistinguishing features of organisms in kingdom:

•Plantae: contain chlorophyll and are autotrophic, manufacturing their own organic compounds; cells characterised by the presence of a cellulose cell wall.

•Animalia: do not contain chlorophyll and cannot manufacture their own food; cells do not have cell walls.

bKingdom Protista: unicellular organisms that are eucaryotic, for example protozoans, some kinds of algae.

Kingdom Monera: unicellular organisms that are procaryotic, for example bacteria and cyanobacteria.

Kingdom Fungi: eucaryotic organisms that do not contain chlorophyll and so do not make their own food; cells are surrounded by a cellulose cell wall; may be unicellular, for example yeasts, or multicellular, for example mushrooms.

Q3.

Bk Ch3 S3.4 Q3

Choose one classification system and discuss its advantages and disadvantages.

A3.

Bk Ch3 S3.4 A3

Classification schemes break living things into two, three, four, five or six kingdoms. Select one of these schemes and list its advantages and disadvantages.

Q4.

Bk Ch3 S3.4 FQ4

One biologist insists that algae should be classified as plants. Another says only some algae are in the plant kingdom, others are protists. Who is right? How does this illustrate the arbitrary nature of classification systems?

A4.

Bk Ch3 S3.4 FA4

The placement of organisms into particular classification groups depends in part on how the features of organisms are interpreted and the definitions associated with classification groups. Sometimes there is debate about where a particular kind of organism should be placed. This usually occurs for organisms that present with features related to more than one classification group. The arbitrary nature of classification systems is perhaps best illustrated by the changes in defining and naming classification groups because of our increased knowledge, particularly due to advances in technology.

Q5.

Bk Ch3 S3.4 FQ5

Give two reasons why structure is a useful characteristic in classifying organisms. Give reasons why colour, size and habitat are not usually used to classify organisms at the major grouping levels.

A5.

Bk Ch3 S3.4 FA5

Structure is a useful feature in classifying organisms because it is easily observable and because such features tend to be more static during an organism’s lifetime than other kinds of features that can alter with seasons or with an organism’s maturity. Features such as colour, size and habitat are less useful in classification for several important reasons. For example, all of these features can change over an organism’s lifetime and even seasonally, so it becomes more difficult to draw comparisons between similar kinds of organisms that would otherwise belong together within a group. Also, different kinds of organisms may share these characteristics but these features may also be the only ones they have in common and so the organisms really don’t belong in the same classification group.

Q6.

Bk Ch3 S3.4 FQ6

Which level of classification contains organisms that are more similar to each other: order or species? Why is this so?

A6.

Bk Ch3 S3.4 FA6

Species is the most basic classification grouping, containing organisms that are more alike than they are with members of other groupings. Organisms within a particular species belong to the same order; however, not all organisms within a particular order belong to the same species. For example, humans and chimpanzees belong to the order Primate; humans belong to the species Homo sapiens and chimpanzees belong to the species Pan troglodytes.

Q7.

Bk Ch3 S3.4 Q7

Advances in technology have improved our knowledge of living things. Outline two examples of how technological advances have affected classification systems.

A7.

Bk Ch3 S3.4 A7

Advances in technology have adjusted our understanding of the relationships between some groups of organisms previously believed to be closely related or more distantly related. Before such advances scientists relied largely on structural features to draw conclusions about the relationships between different kinds of organisms. For example, embryological studies have determined that the major group to which the vertebrates belong is closely related to the group that includes starfish.

Studying the molecular structure of certain kinds of molecules also sheds light on the closeness of relationships between different kinds of organisms. For example, the greater the degree of similarity between proteins and/or DNA bases between species the more closely related the species are believed to be in evolutionary terms.

Q8.

Bk Ch3 S3.4 Q8

Explain the difficulties that can arise in classifying extinct organisms.

A8.

Bk Ch3 S3.4 A8

Classifying extinct organisms can be difficult for several reasons. Fossil remains of an organism may be incomplete or may no longer have sufficient detail to arrive at a definitive classification. For organisms that have been extinct for a very long time there may not be any living organism that is sufficiently similar to make meaningful comparisons and so accurate classification cannot occur.

Q9.

Bk Ch3 S3.4 Q9

Describe the binomial system of naming organisms. Include a specific example to illustrate your answer.

A9.

Bk Ch3 S3.4 A9

The binomial system of naming organisms is the system in which two names are applied to a particular organism (bi: two; nom: name). The first name is the genus name and the second name is the species name. For example, the scientific name for the greater glider is Petauroides volans.

Q10.

Bk Ch3 S3.4 Q10

Classification systems are designed to do more than just help us identify living things. What else can they do?

A10.

Bk Ch3 S3.4 A10

As well as helping to identify living things classification systems bring a sense of order and therefore understanding to what is an enormous range of different kinds of organisms. They enhance communication between scientists by using internationally accepted names, so that there is no confusion about the organism in question. Because of technological advances in classification tools, classification systems continue to more accurately reflect the evolutionary relationships between organisms. Describing and classifying organisms provides an increasingly clear picture of the diversity of organisms and this assists our understanding of the relationships between organisms and their environments. This information helps scientists to put conservation strategies in place to protect species.

3.4 Taxonomy QApage 1 of 3