Home / IB DP Biology Topic 5: Evolution and biodiversity : 5.4 Cladistics Question Bank HL Paper 2

IB DP Biology Topic 5: Evolution and biodiversity : 5.4 Cladistics Question Bank HL Paper 2

Question

(a) Describe what is shown in a cladogram [2]

(b) Outline how variation in organisms of the same species could lead to natural selection [3]

▶️Answer/Explanation

Ans :

a

a similarities/differences between organisms/species/clades 

b «probable» evolutionary relationships/closeness/common ancestry/phylogeny 

c divergence/splits/speciation/branches/nodes 

d relative similarity/differences between base sequence/amino acid sequence

mpa and mpd concern actual characteristics, not evolutionary relationships. mpb concerns such relationships mpc concerns the structure branching of the cladogram

b

a survival of the better adapted/fittest 

b more reproduction of better adapted/fittest/individuals with favorable variations 

c genes for favorable variations/adaptations passed on to offspring Accept answers in the converse.

d competition for resources/more offspring produced than the environment can support/a struggle for existence

Question

The image shows part of a cladogram.

Using the cladogram, identify one diagnostic feature that characterizes the given groups of vertebrates at A, B and C.

A:  ……………………………………………………………
B:  ……………………………………………………………
C:  …………………………………………………………… 

[3]
a.

Starting from the concept of gene pool, explain briefly how populations of early vertebrates could have evolved into different groups.

[3]
b.

Mitochondria are thought to have evolved from prokaryotic cells. Describe two adaptations of the mitochondria, each related to its function.

[2]
c.
▶️Answer/Explanation

Markscheme

A: gills or fins or scales or no limbs or external fertilization
B: homeothermic or warm-blooded or endothermic or lungs or tetrapod or four limbs or pentadactyl limbs or internal fertilization
C: hair or fur or mammary glands or milk

a.

Gene pool is all genes/all alleles.  Reject all alleles/genes in a species.

Geographic isolation  Reject isolation if no type of isolation given.
OR
migration to different areas
OR
temporal isolation
OR
behavioural isolation

Speciation/gene pool split if populations are reproductively isolated/do not interbreed 

In different environments there are different selection pressures/opportunities/natural selection/adaptations/niches «to exploit»

Allele frequencies change/diverge  Reject gene frequencies.

b.

Double membrane/small intermembrane space/small gap between inner and outer membrane for a gradient «of protons» to develop
Accept only the first two adaptations in the answer.

Cristae/folds in inner membrane/large surface area of inner membrane for ATP synthesis/chemiosmosis/proton pumping/electron transport chains

ATP synthase/stalked particles generates ATP from ADP + phosphate/Pi. Reject ATPase. Allow ATP synthetase.

Electron transport chains for generating a proton gradient/for releasing energy from reduced NAD

Matrix contains enzymes for Krebs cycle/link reaction/oxidation of fats/oxidation of substrates/aerobic respiration

Ribosomes/DNA for protein synthesis/replication

c.
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