2.1- All organisms are related through their evolutionary history

Question 1

(a)

Classification

Answer 1

Classification groups organisms based on evolutionary relationships. It’s hierarchical (large groups split into smaller ones) and phylogenetic (organisms in the same group are closely related). Each group is a taxon, and organisms can only belong to one group at each taxonomic level, making it discrete.

Question 2

(b)

The need for classification and its tentative nature

Question 3

(c)

Domain classification system

Answer 3

Eubacteria, Archea, Eukaryota

Question 4

(c)

Kingdom
classification system

Answer 4

Prokaryotae, Animalia, Plantae, Fungi, Protoctista

Question 5

(d)

Characteristics of prokaryotae

Answer 5

Lack a nucleus and membrane-bound organelles, have 70S ribosomes, circular DNA and a cell wall of
peptidoglycan.

Question 6

(d)

Characteristics of Protoctista

Answer 6

Mostly unicellular eukaryotes, algae have no tissue differentiation

Question 7

(d)

Characteristics of Plantae

Answer 7

Multicellular eukaryotes, photosynthetic containing chloroplasts, have a cell wall of cellulose

Question 8

(d)

Characteristics of Fungi

Answer 8

Heterotrophic eukaryotes with a cell wall made of chitin; most are composed of thin threads called hyphae, reproduce by spores

Question 9

(d)

Characteristics of Animalia

Answer 9

Multicellular eukaryotes, no cell wall, heterotrophic and have nervous co-ordination

Question 10

(e)

Homologous structures

Answer 10

Structures in different species with a similar anatomical position and development origin, derived from a common ancestor.

Question 11

(e)

Pentadactyl

Answer 11

Having five digits.

Question 12

(e)

Divergent evolution

Answer 12

The development of different structures over long period of time, from the equivalent structures in related organisms.

Question 13

(e)

Convergent evolution

Answer 13

The development of similar features in unrelated organisms over long periods of time, related to natural selection of similar features in a common environment.

Question 14

(e)

Analogous structures

Answer 14

Have a corresponding function and similar shape, but have a different developmental origin.

Question 15

(e)

Assessing relatedness with genetic evidence - DNA sequence

Answer 15

DNA sequences change over time, accumulating differences between species. Closely related species have more similar DNA than distantly related ones. DNA analysis confirms evolutionary relationships and corrects errors in classification based on physical traits.

Question 16

(e)

Assessing relatedness with genetic evidence - DNA hybridisation

Answer 16

DNA hybridisation compares DNA base sequences between species by mixing single-stranded DNA fragments. Complementary sequences hybridise, showing genetic similarity. For example, humans and chimpanzees share at least 95% of their DNA, while humans and rhesus monkeys share about 93%. This method reveals evolutionary relationships, such as the close link between hippos and whales.

Question 17

(e)

Assessing relatedness with genetic evidence - Amino acid sequences

Answer 17

Amino acid sequences in proteins reflect the DNA base sequence. Similarity in these sequences shows how closely related species are. For example, differences in fibrinogen amino acid sequences have been used to propose an evolutionary tree for mammals.

Question 18

(e)

Assessing relatedness with genetic evidence- Immunology

Answer 18

Immunological techniques compare proteins between species. When antigens (e.g., albumin) of one species mix with antibodies of another, coagulation occurs. Greater coagulation indicates a closer evolutionary relationship.

Question 19

(f)

Species

Answer 19

A group of organisms with similar characteristics that can interbreed to produce fertile offspring.

Question 20

(g)

The use of the binomial system in naming organisms

Answer 20

All species have a binomial name consisting of two parts: the generic name (genus), which is capitalised, and the species name, which is in lowercase. Organisms in the same genus are more closely related than those in different genus. Binomial names are written in italics to follow convention and are universally recognised, preventing confusion from local names and language differences.

Question 21

(h)

Biodiversity

Answer 21

Biodiversity refers to the number of different species (species richness) and the number of individuals of each
species (species evenness) in a given environment.

Question 22

(i)

Biodiversity varying spatially and temporally

Answer 22

Biodiversity varies spatially – the closer to the equator, the
more biodiversity there is.

Biodiversity varies temporally – through time biodiversity
has varied, e.g. mass extinctions reduce biodiversity.

Question 23

(i)

Factors affecting biodiversity

Answer 23

Sucession
Natural selection
Human influence