WJEC Biology for AS: Study and Rev Guide

Adaptations for transport in plants ◾ ◾ Distribution of vascular tissue in plants is different in roots, stems and leaves. Xylem transports water and dissolved mineral ions whilst phloem sieve tubes transport solutes (sucrose and amino acids) from SOURCE to SINK via mass flow theory ◾ ◾ Water moves through the root via apoplast, symplast and vacuolar pathways ◾ ◾ Transpiration is the loss of water vapour from the leaf via stomata. Forces involved include: adhesive and cohesive forces, root pressure and transpiration pull ◾ ◾ Plants have become adapted to living in dry (xerophytes) and wet (hydrophytes) environments Adaptations for nutrition ◾ ◾ Modes of nutrition – plants are autotrophic and can manufacture food by photosynthesis. Animals are heterotrophic and consume complex organic material ◾ ◾ Food is processed by ingestion, digestion, absorption and egestion. Different regions of the gut are specialised for these roles. The end products are glucose, amino acids, fatty acids and glycerol ◾ ◾ Adaptations to different diets – herbivores and carnivores have evolved different dentition. Ruminants have a specialised stomach in which cellulose digesting bacteria live ◾ ◾ Parasitism – parasites live in or on a host causing it harm. They have evolved adaptations to survive in hostile conditions, e.g. inside the human gut 117 Unit 2 Summary