chapter 10 p1

Question 1

Classification systems:

Answer 1

Classification is the name given to the process by which living organisms are sorted into groups.
The organisms within each group share similar features.
A number of different classification systems exist.
Until recently the most widely used system contained seven groups ordered in a hierarchy - these are referred to as taxonomic groups.

Question 2

The seven groups: p1

Answer 2

• kingdom, phylum (plural phyla), class, order, family, genus (plural genera) and species
• Kingdoms are the biggest and broadest taxonomic group, with species being the smallest and most specific classification.
• Similar or related groups at one hierarchical level are combined into more inclusive groups at the next higher level.
• Hierarchical classification systems are often referred to as Linnaean classification, after the 18 century Swedish botanist, Carl Linnaeus who was the first to propose such a system.
• Based on recent studies of genetic material many scientists now add a further level of classification into the hierarchy - It is known as a domain
• This level of classification is placed at the top of the hierarchy.
• As new scientific discoveries are made (for example, through genome sequencing), the current system of classification may change again.

Question 3

The development of classification systems:

Answer 3

• The system of classification of living organisms provides a good example of how our scientific knowledge and understanding has developed over time, as new information is gathered or discovered.
• Advances in scientific techniques have provided more detailed information on the genetic and biological make up of organisms, which has led to several revisions in the way organisms are classified.
• Our current system of classification may well change in the future, as further discoveries are made.
• Some of the key steps in the development of the current system of classification are shown here:

Question 4

Some of the key steps in the development of the current system of classification are shown here:

Answer 4

Question 5

Why scientists classify organisms:

Answer 5

To identify species - by using a clearly defined system of classification, the species an organism belongs to can be easily identified.

To predict characteristics - if several members in a group have a specific characteristic, it is likely that another species in the group will have the same characteristic.

To find evolutionary links - species in the same group probably share characteristics because they have evolved from a common ancestor.

Question 6

Use of a single classification system:

Answer 6

scientists worldwide can share their research.
Links between different organisms can be seen, even if they live on different continents.
Remember, though, that classification systems have been created to order observed organisms.
This form of hierarchical organisation is not defined by ‘nature’.

Question 7

How are organisms classified p1
Domains of Life:

Answer 7

• The classification system begins by separating organisms into the three domains - Archaea, Bacteria, and Eukarya - These are the broadest groups.
• As you move down the hierarchy there are more groups at each level, but fewer organisms in each group.
• The organisms in each group become more similar and share more of the same characteristics.
• The system ends with organisms being classified as individual species.
• These are the smallest units of classification - each group contains only one type of organism.

Question 8

Species Classification: e.g

Answer 8

• A species is defined as a group of organisms that are able to reproduce to produce fertile offspring.
• For example, donkeys can reproduce with other donkeys, the offspring of which can subsequently breed.
• Likewise, horses can breed with other horses to produce fertile offspring.
• However, when a horse is bred with a donkey, the offspring produced (a mule or a hinny) is infertile.
• Therefore, donkeys and horses are classified as belonging to different species.
• Mules or hinnies are not a species.
• Mules and hinnies are infertile because their cells contain an odd number of chromosomes (63).
• This means that meiosis and gamete production cannot take place correctly as all chromosomes must pair up.
• This chromosome number is created because horses have 64 chromosomes (32 pairs) whereas donkeys have 62 chromosomes (31 pairs).

Question 9

Answer 9

Question 10

Classification of humans:

Answer 10

You belong to a species named Homo sapiens.
This is the scientific name for humans. Humans are classified as shown in Table 2.

Question 11

Study tip:

Answer 11

The abbreviation for species ‘sp is used after genus, when not identifying the species fully.
For example, you may only know the willow tree in your garden to be Salix sp.
The plural ‘spp.’ is used to refer to multiple species within a genus.

Question 12

Naming organisms: p1
Common Names vs. Scientific Name:

Answer 12

• Before classification systems were widely used, many organisms were given names according to certain physical characteristics, behaviour or habitat.
• Examples are ‘blackbirds’ for their colour, ‘song thrushes’ for their song and ‘fieldfares’ for their habitat. These are called their ‘common names’
• This was not a very useful system for scientists working internationally, as organisms may have more than one common name, and different names in different languages.

Question 13

Naming organisms p2
Problems with Common Names:

Answer 13

• Another problem is that common names do not provide information about relationships between organisms.
• For example, the blackbird, song thrush, and fieldfare all belong to the genus Turdus, meaning that they have all evolved from a common ancestor, but you wouldn’t know this from their common names, nor necessarily from their observable characteristics.

Question 14

naming organisms p3
Binomial Nomenclature:

Answer 14

To ensure scientists the world over are discussing the same organism we now use a system developed in the 18th century, also by Carl Linnaeus, a Swedish botanist.
This system is known as binomial nomenclature.
All species are given a scientific name consisting of two parts:

Question 15

All species are given a scientific name consisting of two parts:

Answer 15

• The first word indicates the organism’s genus. It is called the generic name; you can think of this as being equivalent to your surname or family name, as it is shared by close relatives.
• The second word indicates the organism’s species - It is called the specific name.
• Unlike people, no two species have the same generic and specific name.
• Two different species could have the same specific name, however their genus would be different.
• An example of this is Anolis cuvieri (a lizard) and Oplurus cuvieri (a bird).
• The only link between them is that they are both named after the famous French naturalist and zoologist Georges Cuvier (1769-1832).
• Many of these scientific names derive from Latin.

Question 16

When naming an organism using its scientific name:

Answer 16

the word should be presented in italics.
As it is difficult to handwrite in italics, the standard procedure in handwritten documents is to underline the name.
The name should be written in lowercase, with the exception of the first letter of the genus name, which should be uppercase.

Some examples of scientific names are included in Table 3.
Split the name into two parts and you can easily work out which genus and species the organism belongs to.

Question 17

The five kingdoms p1

Answer 17

• Originally living organisms were classified into just two kingdoms - animals and plants.
• Aristotle (384-322вс) classified animal species in his text History of Animals, while his pupil Theophrastus (371-287вс) wrote a parallel work, History of Plants.
• The animal kingdom included every living thing that moved, ate and grew to a certain size then stopped growing.
• The plant kingdom included every living thing that did not move or eat and that continued to grow throughout life.

Question 18

The five kingdoms p2

Answer 18

• As more was discovered about organisms and more species were discovered, it became increasingly difficult to divide living organisms into just two kingdoms.
• For example, the introduction of the microscope in the 16” to 17th century enabled scientists to study the cells of an organism and showed that bacteria have a very different cell structure to that of other organisms.
• From the 1960s, scientists classified organisms into five kingdoms.
• This classification system was introduced by Robert Whittaker, an American plant ecologist, based on the principles developed by Carl Linnaeus.

Question 19

Answer 19

Question 20

Answer 20

Question 21

Protoctista
General features:

Answer 21

Examples include species belonging to the genera Paramecium and Amoeba.

• (mainly) unicellular
• a nucleus and other membrane-bound organelles
• some have chloroplasts
• some are sessile, but others move by cilia, flagella, or by amoeboid mechanisms
• nutrients are acquired by photosynthesis (autotrophic feeders), ingestion of other organisms (heterotrophic feeders), or both - some are parasitic.

Question 22

Answer 22

Question 23

Answer 23

Question 24

Animalia

Answer 24

The animal kingdom is the largest kingdom with over 1 million known species.

Examples include mammals such as cats, reptiles such as lizards, birds, insects, molluscs, worms, sponges, and anemones.

General features:
- multicellular
- a nucleus and other membrane-bound organelles (no cell walls)
no chloroplasts
move with the aid of cilia, flagella, or contractile proteins, sometimes in the form of muscular organs

• nutrients are acquired by ingestion - they are heterotrophic feeders
• food stored as glycogen.