T3 - Classification and Biodiversity

Question 1

What is classification?

Answer 1

The process of sorting living things into groups.

Question 2

List the taxonomic groups in the classification system in order of hierarchy

Answer 2

Domain, kingdom, phylum, class, order, family, genus and species

Question 3

Explain how organisms can be classified into taxonomic groups

Answer 3

Organisms with similar characteristic are sorted into groups based on molecular phylogeny, e.g. similarities in DNA/protein sequences, or similarities in morphology or behaviour.

Question 4

Who developed the binomial naming system?

Answer 4

Carl Linnaeus

Question 5

What taxonomic groups are included in a species’ binomial name?

Answer 5

Genus species e.g. Homo sapiens

Question 6

i Historically, what was classification based on?

Answer 6

Morphological differences (i.e. structural characteristics). Closely related species were expected to show similar structural features, indicating common ancestry.

Question 7

Describe two key limitations to using morphological differences as a basis for classification

Answer 7

Closely related organisms can exhibit very different structural features due to e.g. pentadactyl limb.
Distantly related organisms can display very similar structural features due to (adapting to the same
environment) e.g. sharks and dolphins.

Question 8

What is convergent evolution?

Answer 8

Convergent evolution occurs when different species occupy the same habitat and are thus subjected to the same selection pressure.
The shared conditions cause common adaptations to be selected in different species, resulting in structural similarity (analagous structures) e.g. dorsal fins of sharks and dolphins.

Question 9

What is divergent evolution?

Answer 9

The accumulation of differences between closely related populations within a species, sometimes leading to speciation.

Question 10

How does divergent evolution occur?

Answer 10

When two populations of the same species separate and are exposed to different selection pressures.

Question 11

What are analagous structures?

Answer 11

Analagous structures are sperficially similar structures in different species that have arisen due to convergent evolution; they have the
same function but differ in fundamental structure and have different ancestry e.g. wings in bats, birds, insects.

Question 12

What are homologous structures?

Answer 12

Homologous structures are similar in fundamental structure due to common ancestry but have different functions e.g. the pendactyl limb in vertebrates.

Question 13

What is classification based on?

Answer 13

Phylogeny - evolutionary reletionships - how closely related species are. The more closely related they are, the more recent they have
evolved from a common ancestor.

Question 14

Define species

Answer 14

A group of organisms with similar anatomical, behavioural, genetic, physiological, biochemical and morphological features that are capable of interbreeding to produce fertile offspring.

Question 15

What is the Morphological Species Concept?

Answer 15

A group of organisms with morphological similarities (i.e. similar appearance)

Question 16

What are the limitations of the morphological species concept?

Answer 16

There is huge morphological variation within some species (e..g breeds of dog).
In a species that shows sexual dimorphism, males and females could be thought be a different species. (e.g. peacocks).
Some organisms look the same due to convergent evolution (adapting to same environment) but are reproductively isolated.

Question 17

What is the Biological Species Concept?

Answer 17

A group of organisms with similar characteristics that are capable of interbreeding to produce fertile offspring. Genes are combined or ‘flow’ from parent to offspring.

Question 18

State 3 ways organisms can be reproductively isolated.

Answer 18

temporal i.e. different breeding times,
mechanical i.e. physical incompatibility e.g. genitalia,
behavioural i.e. don’t recognise courtship behaviour / songs.

Question 19

What are the limitations of the biological species concept?

Answer 19

It doesn’t apply to species that produce fertile hybrids
It doesn’t apply to species that reproduce asexually
It doesn’t apply to species.
Two populations may not interbreed due to geographical isolation.
It is difficult to apply to ring species

Question 20

What are cryptic species?

Answer 20

Two or more distinct species disguised under one species name.
Morphologically indistinguishable but don’t interbreed.
(e.g. African bush and African forest elephants)

Question 21

What is a ring species?

Answer 21

Ring species form one continuous interbreeding population in a circuit, immediate neighbours interbreed, but where the extreme ends of the ring overlap they do not interbreed.

Question 22

Explain how a DNA profile is produced from a small sample of DNA.

Answer 22

Make multiple copies of DNA using polymerase chain reaction (PCR)
Cut fragments out of DNA using restriction enzymes
Use gel electrophoresis to separate mixture of DNA fragments based on their size the
Stain DNA molecules so bands appear under UV light.

Question 23

Explain why DNA fragments can be separated using gel electrophoresis

Answer 23

They are negatively charged due to phosphate groups, so move towards the positive terminal when a current is applied.
The smaller DNA fragments travel the furthest

Question 24

How are DNA profiles compared?

Answer 24

Position of bands.
Total number of bands.
Thickness of bands.

Question 25

State what the thickness of the bands on a DNA profile indicates.

Answer 25

Amount of fragments.

Question 26

Explain how are DNA profiles compared to determine evolutionary relationships?

Answer 26

Closely related organisms have similar gene sequences, so fragments will be similar sizes, which will result in similar banding patterns on the gel.

Question 27

Explain how a protein profile is produced.

Answer 27

Extract proteins from samples.
Add loading buffer to give proteins a negative charge so they move towards the postiive terminal.
Denature proteins using buffer or hot water so they move through gel more easily.
Cut into smaller polypeptides using protease enzymes
Use gel elctrophoresis to separate mixture of polypeptides based on their size.

Question 28

Explain why protein profiles can determine evolutionary relationships

Answer 28

Closely related organisms have similar gene sequences.
Proteins are synthesized according to the genetic code, so closely related organisms will have similar proteins, which will result in similar banding patterns on a gel.

Question 29

What is molecular phylogeny?

Answer 29

The analysis of base sequences in DNA and amino acid sequences in proteins e.g. haemoglobin and cytochrome c, in different species to infer their evolutionary relationships.
The more similar their DNA/amino acid sequence, the more recently organisms evolved from a common ancestor, so the more closely
related they are.

Question 30

What is gene sequencing?

Answer 30

The process by which the base order of a gene is revealed.

Question 31

How is a gene sequenced using the Sanger method?

Answer 31

The DNA is to separate the two strands.
PCR is used to get multiple copies of the gene.
Copies are added to four reaction vessels with
DNA polymerase
Nucleotides modified with terminator bases (ddNTPs) labelled with a radioactive tag are added - one type in each vessel.
The terminator bases stop DNA replication at random T, C, G, A sites, creating fragments of different sizes.
Fragments are separated using gel electrophoresis and analysed by autoradiography

Question 32

Why are four reaction vessels required?

Answer 32

A reaction vessel is needed for each modified base / ddNTP, otherwise you wouldn’t be able to distinguish between the bases once separated on the electrophoresis gel

Question 33

Explain why DNA sequencing can be used to distinguish between species / determine evolutionary relationships

Answer 33

All organisms use DNA and RNA as genetic material and the genetic code by which proteins are synthesised is (almost) universal.
This means that base and amino acid sequences can be compared to determine how related organisms / species are.
Mutations accumulate gradually so there is a positive correlation between the number of base differences between two species and the time since they diverged from a common ancestor.
Hence, the more similar the base sequences of two species are, the more closely related they are.

Question 34

What is bioinformatics?

Answer 34

Bioinformatics is the use of computers to sort, store, and analyse sequence data in biological research.
The data is stored in databases, which use algorithms to collate relevant data for interpretation and analysis.

Question 35

What is a clade?

Answer 35

A group of species derived from a common ancestor.

Question 36

What is a cladogram?

Answer 36

A phylogenetic/evotionary tree.

Question 37

What are cladograms/evolutionary trees based on?

Answer 37

Molecular phylogeny - DNA base sequences or amino acid sequence

Question 38

How do scientists get new theories/claims/evidence accepted?

Answer 38

Publish a paper in a peer reviewed journal present results at a conference so other scientists could repeat the experiments to validate their findings.

Question 39

Who developed the three domain system of classification?

Answer 39

Carl Woese

Question 40

Name the three domains

Answer 40

Archaea, bacteria, eukaryota

Question 41

Compare and contrast bacteria and archaea

Answer 41

Both have no nucleus (prokaryotic).
Both have small (70S) ribosomes.
Both have no membrane-bound organelles.
Archaea have unused sections in their DNA, whereas bacteria have no unused sections.

Question 42

State key features of eukaryotes.

Answer 42

True nucleus
Large (80S) ribsomes.
Membrane-bund organelles.
Unused sections in DNA.

Question 43

What domain includes photosynthetic cyanobacteria?

Answer 43

Bacteria

Question 44

Which domain includes primitive bacteria which usually live in extreme environment (extremophiles)?

Answer 44

Archea

Question 45

Explain the evidence for the three-domain system.

Answer 45

All prokaryotes discovered before Archaea use all of a gene to code for proteins. Other kingdoms do not use all of a gene to code for a protein, meaning that their genes contain unused sections. Genetic analysis showed that Archaea organisms had unused sections in their genes. As a result, Carl Woese proposed the three domain system of classification.

Question 46

How did Woese get his three-domain system accepted?

Answer 46

Published a paper in a peer reviewed journal present results at a conference so other scientists could repeat the experiments to validate their findings.