1. EVIDENCE FOR EVOLUTION
A1 A A2 C A3 B A4
comparative anatomy of groups of animals or plants shows certain structural features are basically similar;
homologous structures are those that are similar in shape in different types of organisms;
structural similarities imply a common ancestry;
(homologous structures) used in different ways;
example is pentadactyl limb in vertebrates / other suitable example;
adapted to different mode of locomotion in particular environment / example of two differences such as bat’s wing and human hand;
illustrates adaptive radiation since basic plan adapted to different niches;
the more exclusive the shared homologies the closer two organisms are related;
certain homologous structures in some species with no apparent function such as human appendix (homologous with functional appendix in herbivores); max
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2. EVIDENCE FOR EVOLUTIONA5
initially isolated populations may have been genetically different/different allele frequencies;
different mutations in two gene pools;
different parts of population subject to different selective pressures / OWTTE;
over time leads to changes in allele/gene frequencies;
may lead to reproductive isolation;
2 max
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3. NATURAL SELECTION A1 & A2 D A3
members of a population of the same species show variation; some organisms are more likely to survive due to selective advantage / survival of the fittest; some organisms have a reproductive advantage; these variations may be genetically controlled/heritable; these genes are most likely to be passed on to offspring; this can change the characteristic of the population; bacteria can normally be killed with antibiotics; antibiotics impose a selection pressure; if a few bacteria have natural resistance to the antibiotic they will survive; if the resistance is heritable they will pass it on to their offspring; they will reproduce/evolve to form bacterial colonies resistant to the antibiotic; example of organism selected by use of antibiotic; (eg. MRSA bacteria) max
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4. CLASSIFICATION OF BIODIVERSITY
A1 A
A2 D
A3 D
A4 D A5
Organisms with shared characteristics that are capable of producing viable offspring.
Archaea, Bacteria, Eukaryote
Genus and Species
11 – IB BIOLOGY 4

5. CLASSIFICATION OF BIODIVERSITY
Cnidaria have radial symmetry; Mollusca have bilateral symmetry Cnidaria have tentacles/nematocysts/stinging cells; Mollusca don’t Mollusca (may) have a (hard) shell; Cnidaria don’t Mollusca have a mouth and anus; Cnidaria have only one opening Mollusca have a muscular/large foot; Cnidaria don’t other valid external difference.
Annelida are segmented, Mollusca aren’t (visibly segmented); Annelida may have bristles/chetae/chaetae, Mollusca don’t; Mollusca (may) have a (hard) shell, Annelida don’t; Mollusca have a muscular/large foot while Annelida don’t; other valid external difference.
11 – IB BIOLOGY 5

6. CLADISTICS A1
all living organisms use DNA as genetic material; genetic code is (almost) universal; idea that mutations accumulate gradually in DNA; 2max
A is most similar to B; A is equally similar to C and D; A is least similar to both C and D; 2 max
methods used to prepare cladograms use a different approach from traditional classification; show ancestral relationships; reflect how recently two groups shared a common ancestry; cladograms are (objective/accurate because they are usually) based on molecular differences; they should be considered as a good complement to traditional classification; max
11 – IB BIOLOGY 6

7. CLADISTICS A2
Either of: – Mammoth ancestors left Africa; Over a long period of time genetic differences accumulated; Characteristics of the species changed through natural selection due to different environment. – Within the original species, genetic differences accumulate; Through natural selection individuals with suitable characteristics survived and reproduced; Due to a survival advantage, this group developed and over time evolved.
M. primigenius had limited genetic variation and due to, for example, increased hunting by humans, was unable to evolve. E. maximus lived in an environment with more stable selection pressures.
11 – IB BIOLOGY 7