CCEA A Level Biology
CCEA A Level Biology 1.7 Tissues and Organs Exam Questions
Free CCEA A Level Biology revision for 1.7 Tissues and Organs: what you need to know, common mistakes and exam-style questions with answers. Covers tissue and organ definitions, the structure and function of the ileum wall and villi, and the mesophytic leaf.
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About CCEA A Level Biology 1.7 Tissues and Organs
Section 1.7 completes Unit AS 1 by applying cell biology to whole organs. CCEA uses two named examples: the mammalian ileum and the mesophytic leaf. For the ileum you need the layers of the wall (mucosa, muscularis mucosa, submucosa, muscularis externa and serosa), villi, columnar epithelium with microvilli and goblet cells, crypts of Lieberkuhn with Paneth cells, and how products of digestion are absorbed. For the leaf you need each tissue and how it is adapted for photosynthesis and gas exchange. Expect to identify tissues on slides and micrographs and produce accurate drawings and block diagrams.
What you need to know
- Definitions A tissue is a group of similar cells performing the same function. An organ is several tissues grouped together to carry out a particular function.
- Ileum wall From inside out: mucosa, muscularis mucosa, submucosa, muscularis externa (circular and longitudinal muscle) and serosa. Villi increase surface area; crypts of Lieberkuhn contain Paneth cells.
- Ileum epithelium Columnar epithelial cells with microvilli forming a brush border and many mitochondria for active transport. Goblet cells secrete mucus.
- Absorption Monosaccharides and amino acids are absorbed by diffusion and active transport into blood capillaries; fats enter the lacteals. Some material is taken up by pinocytosis. Pendular movements, segmentation and peristalsis mix and move contents.
- Mesophytic leaf Waxy cuticle and upper epidermis; palisade mesophyll packed with chloroplasts; spongy mesophyll with air spaces; xylem and phloem in vascular bundles; lower epidermis with stomata and guard cells.
- Practical Identify ileum and leaf tissues on prepared slides and photomicrographs, and make clear low power plans (block diagrams) showing tissue layers without individual cells.
Common mistakes in 1.7 Tissues and Organs
- Drawing individual cells in a low power plan. A plan shows tissue boundaries only, in correct proportions, with clear continuous lines.
- Confusing villi and microvilli. Villi are folds of the whole mucosa; microvilli are projections of the cell membrane of epithelial cells.
- Saying fats are absorbed into blood capillaries in the villi. Fatty acids and glycerol reform triglycerides and enter the lacteals.
- Saying the palisade layer is at the bottom of the leaf. It lies under the upper epidermis where light intensity is highest.
- Calling an epithelium an organ. It is a tissue; the ileum is the organ.
Try three 1.7 Tissues and Organs exam-style questions
1. Explain how the epithelial cells of the ileum are adapted for absorption. (3 marks)
Show the mark scheme answer
Microvilli increase surface area; many mitochondria provide ATP for active transport; carrier proteins in membrane; thin cells so short diffusion distance.
2. Name the layers of the ileum wall from the lumen outwards. (2 marks)
Show the mark scheme answer
Mucosa; muscularis mucosa; submucosa; muscularis externa; serosa (all correct for 2, three or four in order for 1).
3. Explain how the structure of the spongy mesophyll is related to its function. (2 marks)
Show the mark scheme answer
Large air spaces allow diffusion of carbon dioxide and oxygen; large surface area of moist cell walls for gas exchange.
1.7 Tissues and Organs FAQs
What does CCEA A Level Biology 1.7 Tissues and Organs cover?
It covers definitions of tissues and organs and the detailed structure and function of the ileum and the mesophytic leaf.
Which unit is 1.7 Tissues and Organs examined in?
It is examined in Unit AS 1: Molecules and Cells, a 1 hour 30 minute written paper of structured questions and an essay.
How do I prepare for slide and micrograph questions on 1.7?
Learn to recognise each ileum layer and each leaf tissue on photomicrographs and practise drawing tidy low power plans with labels.
