Classification

Question 1

What is classification?

Answer 1

The sorting of living organisms into groups which share similar characteristics (physical, biochemical, behavioural).

Question 2

List the hierarchical/Linnaean system.

Answer 2

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 3

Horses and donkeys can breed to produce mules, so why are horses and donkeys classified as different species?

Answer 3

• A mule is infertile, mules cannot breed to produce any offspring.
• The reason for this is that horses have 64 chromosomes in a normal body cell, so 32 in a gamete. A donkey has 62 chromosomes in a normal body cell, so 31 in a gamete.
• This means that when a gamete from a horse fertilises a gamete from a donkey, the resulting zygote has 63 chromosomes (the mule).
• So, if mules have an odd number of chromosomes, they are not in pairs, so it cannot do meiosis, so it is infertile.

Question 4

Why do scientists classify organisms?

Answer 4

• 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 5

What are the changes to the classification system?

Answer 5

• Originally, living systems were classified into just 2 kingdoms, animals and plants.
• The animal kingdom included all organisms that moved, ate and grew to a certain size.
• The plant kingdom included all organisms that did not move or eat, and continued to grow throughout life.
• As more new species were discovered, it became increasingly difficult to divide all organisms into just 2 groups. Also, advances in scientific equipment, such as the introduction of the microscope showed that some cells have very different structures to others.
• From the 1960’s the Five Kingdom system was used.

Question 6

Definition of kingdom

Answer 6

The highest taxonomic rank, and the most general taxon used in classifying organisms.

Question 7

Definition of a species.

Answer 7

A group of closely related organisms that are similar to each other physically and biochemically. Organisms belonging to the same species can interbreed to produce fertile offspring.

Question 8

What was wrong with common names for organisms that came from physical characteristics?

Answer 8

Does not provide information about relationships between organisms.

Question 9

What are the 2 parts of the scientific name given to all species?

Answer 9

Genus - first word (generic name plural is genera)
Species - second word (specific name).

Question 10

Example of prokaryote.

Answer 10

Bacteria.

Question 11

Four examples of eukaryotae.

Answer 11

• Protoctista.
• Fungi.
• Plantae.
• Animalia.

Question 12

General features of prokaryotae.

Answer 12

• Unicellular.
• No nucleus or other membrane-bound organelles - a ring of DNA - small ribosomes.
• No visible feeding mechanism - nutrients are absorbed through the cell wall or produced internally by photosynthesis.
• Contain “70S’’ ribosomes.