Unit 1 AOS 2 Biology

• Major systems of the body

  • Respiratory system
  • Digestive system
  • Musculoskeletal system
  • Circulatory system
  • Lymphatic system
  • Immune system
  • Excretory system
  • Endocrine system
  • Nervous system
  • Integumentary system
  • Reproductive system
• Vascular cylinder/Stele


  • Structure in the root containing xylem and phloem
• Vascular bundles


  • Arrangement of xylem and phloem in the stem, situated in a circle around the cambium layer
• Cambium


  • Layer of dividing cells between phloem and xylem responsible for lateral growth
• Mesophyll


  • Photosynthetic cells in a leaf, including palisade and spongy mesophyll
• The transpiration stream


  Water moves from roots to leaves through xylem vessels, driven by osmosis, adhesion, transpiration, and cohesion
• Adhesion


  Attraction of water molecules to surfaces, causing capillarity and surface tension
• Cohesion


  Attraction of water molecules to other water molecules, due to the polar nature of water
• Stomata


  Minute pores in the leaf epidermis that allow gas exchange and water loss
• Cohesion


  The attraction of water molecules for other water molecules
• Stoma


  A minute pore in the epidermis of a leaf that allows the exchange of gases between intercellular spaces in the leaf, and the air outside the leaf
• Guard cell


  One of a pair of cells surrounding a stoma
• Apoplastic phloem

  Active transport of sugars into companion cells by carrier proteins
• Symplastic phloem

  The passive diffusion of sugars from the source to companion cells through plasmodesmata
• Chyme


  Partially digested food leaving the stomach
• Emulsify


  Break into a fine dispersion of minute droplets of one liquid in another
• The large intestine

  1. Absorption of water

  2. Storage of the remainder of the waste material, which is stored in the rectum for defecation

  3. Contains about 700 species of bacteria and archaea (known as 'gut flora'), which perform diverse important functions, such as metabolising bile acids and other chemicals, and producing vitamins B and K
• Crop


  A pouch in the oesophagus used for storage of food
• Gizzard


  A stomach that can grind food, found in toothless animals
• Ruminant


  An animal that can ferment fibrous plant material in a specialised stomach, before regurgitating it, rechewing it and swallowing it again to be digested in another stomach
• Some fibrous-plant eating animals (called ruminants) have a four-chambered stomach. The two front chambers are responsible for fermentation of plant material before the food (or 'cud') is regurgitated, chewed again and passed to the second two chambers for chemical digestion.
• The purpose of the digestive system is to digest food and absorb it.
• The digestive system has numerous organs that all contribute to this purpose.
• Other animals have structures that vary from ours, based on their diet.
• Specialisation and organisation of animal cells

  Into tissues, organs and systems with specific functions: digestive, endocrine and excretory
• Purpose of the digestive system

  To obtain nutrients from food that is ingested
• Digestive system aims

  1. Food must be digested (broken down so that it can be absorbed)

  2. Enough absorptive surface area must be provided, for sufficient absorption
• Mechanical digestion


  Breaks food into smaller chunks of food, increasing surface area to volume ratio for more efficient chemical digestion
• Mechanical digestion does not alter the chemical nature of the food
• Chemical digestion


  Changes what the food is made of, through catabolic chemical reactions catalysed by enzymes
• Enzyme


  A protein that speeds up a chemical reaction without being used up in the reaction
• pH


  A scale (from 1-14) indicating how acidic or basic a solution is. Acids have a pH less than 7, bases have a pH greater than 7
• Chemical digestion of lipids

  Lipids (fats and oils) are broken into fatty acids and glycerol by enzymes called lipases
• Chemical digestion of complex carbohydrates


  Complex carbohydrates (or polysaccharides) are broken into simple sugars (monosaccharides) by enzymes called amylases
• Chemical digestion of proteins


  Proteins are broken into amino acids by enzymes called proteases
• Anatomy


  The structure of body parts
• Physiology


  The function of body parts
• Organs of the digestive system

  • Mouth (including teeth and tongue)
  • Salivary glands
  • Oesophagus
  • Stomach
  • Small intestine
  • Large intestine (including rectum and anus)
  • Liver
  • Gall bladder
  • Pancreas
• The mouth


  Involved in mechanical digestion through mastication (chewing) by teeth and churning of food by the tongue. Also mixes food with saliva from salivary glands, which contains salivary amylase for chemical digestion of starch
• Bolus


  Food that is ready to be swallowed