classification

Question 1

What is classification?

Answer 1

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

Question 2

What is the order of the 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 classed 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.
• 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

why is DNA analysis so useful in classification?

Answer 5

• when organisms evolve, we see their characteristics change. This is due to changed in their DNA ( mutations cause new alleles to appear)
• Mutations take time, so the more difference between organisms, the longer ago they diverged from each other in evolutionary terms.
• By comparing the DNA of different organisms, we can understand evolutionary relationships between species.