Topic 12

Question 1

molecular homology

Answer 1

-important concept in modern evolution biology, used to test relationships between modern taxa, examine evolutionary processes driving evolution at molecular level

Question 2

molecular homology

Answer 2

• relatedness refers to how recent species split from common ancestor
• if species are related by evolution-should show similarity in biochemical and genetic composition
• greater degree of similarity should be evident in species that are closely related by descent- share a common ancestor more recently than other more distantly related species

Question 3

comparative proteins

Answer 3

• proteins from different organisms can be compared in terms of their amino acid sequence
• more closely related species- fewer differences in amino acid sequence of their comparative proteins
• longer period since species diverged- more time available for change to occur in protein present in both species
• more differences observed- further back in time since divergence

Question 4

comparing base sequence

Answer 4

• gene conservation refers to particular gene present in related species- passed down by common ancestor
• DNA sequences of conserved genes will be very similar in related species
• degree of similarities of DNA sequences is determined by number of mutations occurred
• more distant species- had more time for differences to accumulate
• greater the similarity in base sequence of DNA in genes- more closely related two species- share more recent common ancestor

Question 5

comparative genomics

Answer 5

-more recent common ancestor between two species, greater degree of conservation of DNA and position of genes within genome

Question 6

comparing chromosomes

Answer 6

• chromosomes banding pattern and chromosome painting- can be matched to patterns on regions of chromosomes of other closely related species
• more similar banding patterns on chromosome- more recent a common ancestor

Question 7

phylogenetic trees

Answer 7

• phylogeny- evolutionary history of organisms
• branching diagrams that show inferred evolutionary relationships or lines of evolutionary descent among biological groups/taxa
• can be based on structure, DNA sequences or molecular similarity
• more similar basic body plan or biochemistry- more closely related two species are- more recent shared common ancestor

Question 8

parts of phylogenetic tree

Answer 8

tips/terminals-descendant groups- can be single species, large taxonomic groups or even individual genes

• node- denotes common ancestor
• branch- speciation event- shows relationship between ancestor and descendant
• root- common ancestor of all taxa
• sister taxa- two groups with common ancestor, not shared with any other taxa
• branch length- denotes period of time

Question 9

cladograms

Answer 9

• approach to biological classification- organisms are categorised based on shared derived characteristics- not present in more distant ancestors
• derived character is novel feature assumed to evolve from original character present in ancestral organism
• cladistics- only look at presence of shared derived features
• groups always appear at endpoint- living extinct
• length of branch lines in cladogram- don’t convey information about evolutionary time

Question 10

differences between cladograms and phylogenetic trees

Answer 10

cladograms- branching diagrams showing relationships among group of clades
-shape of cladogram shows relatedness among group of organism
-doesn’t represent evolutionary time/distance
-based on morphological characteristics
-represents hypothesis about actual evolutionary history
phylogenetic tree
-branching diagrams showing inferred evolutionary relationship between various biological species
-distance of branch depends on amount of inferred evolutionary change
-branches represent evolutionary time and genetic distance between groups of organisms
-based on morphological characteristic and genetic relationships of organism
-represents true evolutionary history to extent