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Date May 2019 Marks available 2 Reference code 19M.2.HL.TZ2.4
Level Higher level Paper Paper 2 Time zone Time zone 2
Command term Outline Question number 4 Adapted from N/A

Question

The images show parts of plants belonging to two different phyla.

State the phylum of plant X and of plant Y.

X:

Y:

[2]
a.

Some plant families, such as the figwort family, have been reclassified on the basis of evidence from cladistics. Explain the methods that have been used recently to reclassify groups of plants.

[3]
b.

Successful sexual reproduction in flowering plants depends on several essential processes. Outline the role of pollination and seed dispersal.

Pollination:

 

Seed dispersal:

 

 

[2]
c.

Markscheme

X: Filicinophyta ✔

Y: Coniferophyta/Conifera/Gymnosperms ✔

a.

a. «previous» classification used to be based on the appearance/structures of the plant/leaves/flowers/seeds/analogy/phenotype ✔

b. «modern cladistics uses» RNA/DNA nucleotide/base sequencing/amino acid sequencing/homology ✔

c. DNA mutation occurs at a relatively constant rate allowing estimation of when species diverged ✔

d. a shared/common derived characteristic places organisms in the same clade ✔

e. the number of changes in sequences indicates distance from common ancestor
OR
the fewer the differences «in sequences» means the closer the relationship ✔

b.

pollination:
transfer/dispersal/movement of pollen from anther/stamen to stigma
OR
transfer/dispersal/movement of pollen between plants/flowers prior to/allowing fertilization ✔ 

seed dispersal:
«strategy of» distribution of seeds so that new plants have space/nutrients to develop/avoid competition/colonize new habitats ✔

Accept any other valid role.

Accept OWTTE. Answers must be about the role.

c.

Examiners report

This question requiring students to identify plant phyla from images was successfully answered by most. It was more common for students to correctly identify Plant Y as a member of the Coniferophyta phylum with a greater number being unable to identify Plant X as a member of the Filicinophyta phylum.

a.

Many students were able to identify molecular sequencing as a method used to re-classify plants. Fewer were clear on the notion of original classification being mistakenly based on analogous features.

b.

Most students were able to outline the role of seed dispersal in minimizing competition between parent and offspring. Slightly fewer were successful in correctly outlining the role of pollination in sexual reproduction with a number being unable to correctly draw upon the necessary vocabulary.

c.

Syllabus sections

Additional higher level » Topic 9: Plant biology » 9.4 Reproduction in plants
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Additional higher level » Topic 9: Plant biology
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