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Stoma in a tomato leaf shown via colorized scanning electron microscope image A stoma in horizontal cross section The underside of a leaf. In this species (Tradescantia zebrina) the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigments.
Most IGCSE subjects offer a choice of tiered examinations: Core or Extended papers (in Cambridge International), and Foundation or Higher papers (in Edexcel). This is designed to make IGCSE suitable for students with varying levels of ability. In some subjects, IGCSE can be taken with or without coursework.
Triple Award Science, commonly referred to as Triple Science, results in three separate GCSEs in Biology, Chemistry and Physics and provide the broadest coverage of the main three science subjects. The qualifications are offered by the five main awarding bodies in England; AQA, Edexcel, OCR, CIE and Eduqas.
Stomatal conductance, usually measured in mmol m −2 s −1 by a porometer, estimates the rate of gas exchange (i.e., carbon dioxide uptake) and transpiration (i.e., water loss as water vapor) through the leaf stomata as determined by the degree of stomatal aperture (and therefore the physical resistances to the movement of gases between the air and the interior of the leaf).
Photosynthesis depends on the diffusion of carbon dioxide (CO 2) from the air through the stomata into the mesophyll tissues. Oxygen (O 2), produced as a byproduct of photosynthesis, exits the plant via the stomata. When the stomata are open, water is lost by evaporation and must be replaced via the transpiration stream, with water taken up by ...
Parastomal hernia is the most common late complication of stomata through the abdominal wall, occurring in 10 to 25% of the patients. [1] Stomata are created in particular in surgical procedures involving the gastrointestinal tract (GIT) or gastrointestinal system (GIS). The GIT begins at the mouth or oral cavity and continues until its ...
In 1997, [2] the AEB entered into an alliance with two other exam boards, NEAB and City & Guilds, known as the Assessment and Qualifications Alliance (AQA). [2] The 1998 examination certificates featured just the AQA name. By 1999, examination papers were dual-branded with both the AQA and AEB or SEG names.
However the exam papers of the GCSE sometimes had a choice of questions, designed for the more able and the less able candidates. When introduced the GCSEs were graded from A to G, with a C being set as roughly equivalent to an O-Level Grade C or a CSE Grade 1 and thus achievable by roughly the top 25% of each cohort.