AS GCE EDEXCEL Biology Specification Revision topic 4

Compare the ultrastructure of plant cells (cell wall, chloroplasts, amyloplasts, vacuole, tonoplast, plasmodesmata, pits and middle lamella) with that of animal cells.

Compare the structure and function of the polysaccharides starch and cellulose including the role of hydrogen bonds between β-glucose molecules in the formation of cellulose microfibrils.

Explain how the arrangement of cellulose microfibrils in plant cell walls and secondary thickening contribute to the physical properties of plant fibres, which can be exploited by humans.

Compare the structures, position in the stem and function of sclerenchyma fibres (support) and xylem vessels (support and transport of water and mineral ions).

Describe how the uses of plant fibres and starch may contribute to sustainability, eg plant-based products to replace oil-based plastics.

Describe how the uses of plant fibres and starch may contribute to sustainability, eg plant-based products to replace oil-based plastics.

Explain the importance of water and inorganic ions (nitrate, calcium ions and magnesium ions) to plants. 

Compare historic drug testing with contemporary drug testing protocols, eg William Withering’s digitalis soup; double blind trials; placebo; three-phased testing.

Explain the terms biodiversity and endemism and describe how biodiversity can be measured within a habitat using species richness and within a species using genetic diversity, eg variety of alleles in a gene pool.

Describe the concept of niche and discuss examples of adaptation of organisms to their environment (behavioural, physiological and anatomical).

Describe how natural selection can lead to adaptation and evolution.

Discuss the process and importance of critical evaluation of new data by the scientific community, which leads to new taxonomic groupings (ie three domains based on molecular phylogeny).

Discuss and evaluate the methods used by zoos and seedbanks in the conservation of endangered species and their genetic diversity (eg scientific research, captive breeding programmes, reintroduction programmes and education)