4.2.2 Classification and evolution

Question 1

What is biological classification?

Answer 1

The organisation of living organisms into hierarchical groups based on similarities and differences.

Question 2

What is the taxonomic hierarchy in classification?

Answer 2

Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species

Question 3

What is the binomial naming system?

Answer 3

A two-part scientific name: Genus (capitalised) + species (lowercase), e.g. Homo sapiens.

Question 4

What are the advantages of the binomial system?

Answer 4

Universal naming, avoids confusion across languages, shows relationships.

Question 5

What evidence was used in early classification systems?

Answer 5

Similarities in observable features (morphology and anatomy).

Question 6

What modern evidence is used in classification?

Answer 6

Genetic and molecular evidence, such as DNA sequencing, protein structure, and biochemical pathways.

Question 7

What are the three domains?

Answer 7

Bacteria, Archaea, Eukarya

Question 8

How does the domain system differ from the five kingdom system?

Answer 8

The domain system groups organisms based on rRNA sequences and cell type, while the kingdom system is based on observable traits.

Question 9

Name the five kingdoms and their key features.

Answer 9

Prokaryotae – unicellular, no nucleus; Protoctista – mostly unicellular, nucleus; Fungi – chitin cell walls, saprophytic; Plantae – cellulose walls, autotrophic; Animalia – no cell wall, heterotrophic

Question 10

Why did the three-domain system develop?

Answer 10

Genetic evidence revealed that Archaea are more closely related to Eukarya than Bacteria.

Question 11

What is phylogeny?

Answer 11

The study of evolutionary relationships between species, often represented as a phylogenetic tree.

Question 12

Who proposed the theory of evolution by natural selection?

Answer 12

Charles Darwin and Alfred Russel Wallace

Question 13

What are the key stages of natural selection?

Answer 13

1. Genetic variation; 2. Selection pressure; 3. Differential survival and reproduction; 4. Inheritance of advantageous alleles; 5. Over time, adaptation and speciation

Question 14

What types of evidence support evolution?

Answer 14

Fossils – show gradual change; DNA evidence – similar genes; Molecular evidence – e.g. cytochrome c, haemoglobin similarities

Question 15

What is intraspecific variation?

Answer 15

Differences within a species (e.g., height in humans).

Question 16

What is interspecific variation?

Answer 16

Differences between species (e.g., dogs vs. cats).

Question 17

What is continuous variation?

Answer 17

Variation with a range of values (e.g., height, mass).

Question 18

What is discontinuous variation?

Answer 18

Variation with distinct categories (e.g., blood groups).

Question 19

What causes genetic variation?

Answer 19

Mutations, meiosis, and random fertilisation.

Question 20

What causes environmental variation?

Answer 20

Factors like climate, diet, habitat, lifestyle.

Question 21

What are the three types of adaptation?

Answer 21

Anatomical – physical traits; Physiological – internal processes; Behavioural – habits/actions

Question 22

What is convergent evolution?

Answer 22

Unrelated species evolve similar adaptations due to similar environments (e.g., sharks and dolphins).

Question 23

How does natural selection affect a population over time?

Answer 23

Favourable traits become more common; leads to adaptation or speciation.

Question 24

Example of evolution affecting humans?

Answer 24

Antibiotic resistance in bacteria; Pesticide resistance in insects; Could lead to treatment failure in medicine.

Question 25

Why is evolution considered a dynamic process?

Answer 25

It’s ongoing, influenced by mutation, environmental changes, and human activity.

Question 26

Why is observable features used in early classification?

Answer 26

Easy to identify and compare; useful before molecular tools existed. However, it can be misleading due to convergent evolution or environmental adaptations.

Question 27

Why is DNA sequencing used in modern classification?

Answer 27

DNA reveals genetic similarity and common ancestry more accurately than appearance. The more similar the sequences, the closer the evolutionary relationship.

Question 28

Why is rRNA sequencing used in domain classification?

Answer 28

rRNA evolves slowly, making it ideal for comparing ancient lineages like Bacteria, Archaea, and Eukarya — leading to the three-domain system.

Question 29

Why is protein structure (e.g. cytochrome c) used in classification?

Answer 29

Highly conserved proteins indicate relatedness. Similar amino acid sequences suggest a shared evolutionary origin.

Question 30

Why is fossil evidence used to support evolution?

Answer 30

Shows gradual changes in form over time, revealing transitional forms and extinction events — supports the idea of descent with modification.

Question 31

Why is genomic DNA important in studying evolution?

Answer 31

Reveals inherited mutations, conserved genes, and shared sequences — offering insight into common ancestry and divergence.

Question 32

Why is molecular evidence better than observable traits for classification?

Answer 32

It’s objective, quantifiable, and less affected by environmental changes. It reflects true evolutionary relationships, even in very different-looking organisms.

Question 33

Why is drug resistance in bacteria considered evidence for evolution?

Answer 33

It shows natural selection in real time: genetic variation → survival of resistant strains → population change over time.

Question 34

Why is variation important in natural selection?

Answer 34

Without variation, there’s no differential survival. Variation provides the raw material for evolution to act upon.

Question 35

Why do scientists now use multiple forms of evidence in classification?

Answer 35

Combining morphological, molecular, and genetic data provides a more complete and accurate picture of evolutionary relationships.