4.2.2 Classification

Question 1

Define classification

Answer 1

Placing living organisms into groups based on similarities or differences

Question 2

Define taxonomy

Answer 2

The system of classifying organisms according to their observable features or genetic characteristics

Question 3

Why do we classify things?

Answer 3

• for convenience
• to make the study of living things more manageable
• to make it easier to identify organisms
• to predict characteristics of other species in a group
• to help see evolutionary relationships (phylogeny) between species

Question 4

Explain how organisms were classified originally

Answer 4

Morphology/anatomy/observable features

Question 5

What modern evidence is used to classify organisms?

Answer 5

• DNA base sequences of genes
• amino acid sequences of proteins (e.g. cytochrome c)
• embryonic similarities
• behaviour + physiology
• shared evolutionary past

Question 6

Who first classified organisms?

Answer 6

Carl Linnaeus (1701-1778)
- 250 years ago
- classified by visible features
- put organisms into series of ranked categories

Question 7

List the taxanomic groups in order from broadest to most specific

Answer 7

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 8

How do you know organisms are the same species?

Answer 8

• they can interbreed to produce fertile offspring
• have similar shape, physiology, biochemistry + behaviour

Question 9

How do you organisms aren’t the same species?

Answer 9

• genetically incompatible - DNA sufficiently different
• may have a different number of chromosomes
• physical or behavioral reason for reproductive incompatibility

Question 10

Explain the binomial system of naming

Answer 10

• one internationally accepted scientific name in Latin that has two parts
• just the Genus and species name
• always in italics
• Genus capital FIRST letter
• species lower case FIRST letter

Question 11

Why is the binomial system used?

Answer 11

• some organisms have different common names which can be confusing
• universal and recognised worldwide
• the binomial name tells us the Genus and the species of an organism
• allow to see related species

Question 12

Define autotrophic

Answer 12

Organisms that use light energy or chemical energy along with inorganic molecules to synthesise complex organic molecules

Question 13

Define heterotrophic

Answer 13

Organisms that ingest and digest complex organic molecules, releasing the chemical potential energy stored in them

Question 14

Define Saprotrophic/saprophytic

Answer 14

Organisms that gain nutrients by absorption, mainly of decaying material

Question 15

What are the five kingdoms?

Answer 15

Prokaryotae
Protoctista
Fungi
Plantae
Animalia

Question 16

Give information about Prokaryotes

Answer 16

• mostly unicellular
• no nucleus, nucleolus, nuclear membrane
• no histone proteins or chromosomes
• no other membrane bound organelles
• 70s ribosomes
• respiration carried out on special membrane systems(mesosomes)
• smaller cells than eukaryotes
• cell wall always presemt (peptidoglycan)
• free living or parasitic
• heterotrophic and autotrophic
• some have flagella
• no nervous co-ordination

Question 17

Give information about Protoctista

Answer 17

• eukaryotic - nucleus + nuclear envelope
• mostly single-celled
• wide variety of forms
• shows various plant or animal like features
• mostly free-living
• heterotrophic or autotrophic nutrition
• some have cell walls
• some have flagella or cilia
• no nervous co-ordination

Question 18

Give information about fungi

Answer 18

• eukaryotes
• unicellular (yeast) or multicellular (bread mould)
• multicellular have a body made of mycelium - network of numerous strands called hyphae + form spores
• polysaccharide chitin cell wall
• multinucleate cytoplasm
• large permanent vacuoles
• mostly free living
• heterotrophic + saprophytic
• no nervous co-ordination

Question 19

Give information about plantae

Answer 19

• eukaryotic
• multicellular
• cellulose cell walls
• large permanent vacuole
• produces multicellular embryos from fertilised eggs
• photoautotrophic
• gametes of some plants have flagella
• no nervous co-ordination

Question 20

Give information about Animalia

Answer 20

• eukaryotes
• multicellular
• heterotrophs
• have fertilised eggs that develop into balls of cells
• able to move around (presence of muscle tissue
• no cell walls
• small temporary vacuoles
• most have nervous co-ordination

Question 21

What molecular evidence used to classify organisms?

Answer 21

• differences will reflect evolutionary relationships

Question 22

What biochemicals are used in classification?

Answer 22

• cytochrome c
• haemoglobin
• DNA + RNA

Question 23

How is DNA + proteins used to classify organisms?

Answer 23

• amino acid sequences compared in proteins
• DNA base sequence of specific genes compared in DNA
• If amino acid sequences/nucleotide base sequences in DNA are the same = two species are not related

Question 24

What is the 3 domain system?

Answer 24

• proposed by Carl Woese in 1977
• prokaryotae divided into bacteria + archaea
• based upon study of ribosomal RNA

Question 25

What is the evidence for the 3 domain system?

Answer 25

• based on the fact bacteria is very different from archeae + eukaryote
• bacteria have different cell membrane structure, different flagella structure, different RNA polymerase + peptidoglycan cell wall
• archea + eukaryotae share similar membrane structure, similar RNA polymerase, similar mechanisms for building DNA + RNA, similar proteins at bind to DNA

Question 26

Compare Archaebacteria and Eubacteria

Answer 26

Archae
- known as ‘ancient bacteria’
- live in extreme environment

Bacteria
- known as ‘true bacteria’
- most bacteria in this group

Question 27

Summarise the 3 domain system

Answer 27

• more accurately reflects origin of prokaryotes + eukaryotes
• divides prokaryotes
• reflects differences of bacteria + archaea
  groups eukaryotes together
• reflects that fact there are similarities between eukaryotic kingdoms

Question 28

What is the six kingdom system?

Answer 28

Combines the three-domain + five-kingdom classification system together.
- seperates Prokaryotes into Eubacteria and Archaebacteria
- keeps eukaryotic kingdoms seperate
- having domain as a further level of classification at the top of the hierarchy

Question 29

What are the five kingdoms?

Answer 29

Eubacteria
Archaebacteria
Protoctista
Fungi
Plantae
Animalia

Question 30

Define phylogeny

Answer 30

The study of the evolutionary relationships between organisms and the closeness of these relationships

Question 31

Give key facts about phylogeny

Answer 31

• explains who is related to who + how closely related
• all organisms have evolved from shared common ancestors (relatives) - not alive today
• evolutionary relationships and closeness of these relationships show in a phylogenetic tree
• basis of modern classification

Question 32

Give key aspects of phylogenetic trees

Answer 32

• represent the evolutionary relationships between organisms
• shows how different species have evolved from a common ancestor

Question 33

Summarise phylogeny + phylogenetic trees

Answer 33

• phylogeny produces a continuous tree
• can be done without reference to Linnaean classification
  -phylogeny confirms classification groups are correct