Mod 2 - Condensed

• Unicellular, multicellular and colonial organisms

  • Unicellular
  • Colonial
  • Multicellular
• Unicellular


  A single cell that performs all functions necessary for survival
• Unicellular organisms


  • Escherichia coli (a bacterium)
  • Amoeba (a protozoan)
• Colonial


  A collection of single-celled organisms that live together in a colony, exhibiting characteristics of both unicellular and multicellular organisms
• Multicellular


  Multiple cells that are specialised to perform specific functions within the organism, contributing to a division of labour
• Multicellular organisms


  • Plants
  • Animals
  • Fungi
• Differences between prokaryotes and eukaryotes

  • Size
  • Complexity
  • Location of DNA

  
• Prokaryotes


  Simple organisms, DNA is a bacterial chromosome and plasmids, no membrane bound organelles
• Eukaryotes


  Complex organisms, DNA is in the nucleus, have membrane bound organelles

  
• Prokaryotes


  • Bacteria (cyanobacteria)
  • Archaea (extremophiles like methanogens)
• Eukaryotes


  • Fungi
  • Plantae
  • Animalia
• Similarities between prokaryotes and eukaryotes: DNA, ribosomes, cytoplasm, cell membrane, can be unicellular

  
• Cell organisation


  1. Cells make up tissues

  2. Tissues make up organs

  3. Organs make up organ systems

  4. Organ systems make up organisms
• Cell organisation


  • Specialised cells make up tissues
  • Different types of tissues form organs that carry out particular functions
  • Each type of tissue contains many different functional cell types
• Parts of a leaf

  • Waxy cuticle
  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Vascular bundle
  • Lower epidermis
  • Stomata
  • Guard cells
• Waxy cuticle


  Thin, waxy layer that covers outer surface, helps reduce water loss and protects against pathogens and damage
• Epidermis


  Single layer of closely packed cells that form a protective barrier
• Palisade mesophyll


  Elongated, columnar cells tightly packed with many chloroplasts for photosynthesis
• Spongy mesophyll


  Loosely arranged, irregularly shaped cells with large air spaces to facilitate gas exchange
• Vascular bundle


  Xylem and phloem tissues for structural support and transport of water and nutrients
• Stomata


  Small pores primarily on the lower epidermis that allow gas exchange and transpiration
• Guard cells


  Specialised, crescent-shaped cells that surround each stoma and regulate its opening and closing
• Stomatal function


  1. Guard cells swell, opening the stoma

  2. O2 diffuses out, CO2 diffuses in

  3. Water transpires out
• Factors affecting stomatal opening and closing: light, wind, humidity
• Transpiration


  The passive process of water movement through a plant and its evaporation from leaves, stems and flowers, cooling plants and enabling mass flow of mineral nutrients
• Transpiration-Cohesion-Tension theory


  1. Cohesion: water molecules are attracted to each other, pulling others upwards

  2. Adhesion: water molecules are attracted to xylem walls, forced to travel upwards

  3. Transpiration/tension: pressure from transpiration pull brings water up

  
• Transport systems in animals vs plants

  • Animal circulatory/cardiovascular system: heart, blood vessels, blood
  • Plant vascular system: xylem, phloem, vascular bundles
• Xylem


  Responsible for transport of water and dissolved minerals from soil to leaves, found in centre of vascular bundle, unidirectional upwards, with thick lignin-reinforced walls
• Phloem


  Responsible for transport of organic nutrients and other plant products, found on outside of vascular bundle, multidirectional, with sieve plates
• Vascular bundles reach from roots to leaves in plants
• Microscopic structural features of plant tissues

  • Stem: monocot vs dicot arrangement, ground tissue, dermal tissue
  • Root: circular shape, central vascular bundle, root hairs, dermal tissue
  • Leaf: waxy cuticle, upper/lower epidermis, palisade/spongy mesophyll, vascular bundle, stomata

  
• Translocation of photosynthetic materials in plants

  1. Source cells produce sugar during photosynthesis

  2. Sucrose actively transported into phloem sieve tubes

  3. Water influx creates pressure to push sucrose solution to sink cells

  4. Sucrose unloaded at sink, water returns to xylem
• Van Helmont's experiment showed the importance of water for plant growth but did not account for other factors, so was invalid and unreliable
• Priestley's experiments contributed to understanding the role of oxygen in photosynthesis, even though he incorrectly thought the candle and mouse 'injured' the air
• Microscope magnification


  Magnification = diameter of field of view / actual diameter of object
• Stages of digestion


  • Physical digestion: chewing, churning, peristalsis
  • Chemical digestion: use of enzymes to break down complex molecules
  • Absorption of nutrients in small intestine
• Physical digestion


  Mechanical breakdown of food into smaller pieces, increasing surface area for enzymes
• Chemical digestion


  Use of chemicals and enzymes to break down complex molecules into monomers that can be absorbed
• Mouth


  Where digestion begins, physical chewing and chemical salivary enzyme action

  
• Small intestine


  Main site of absorption, chemical digestion continues with pancreatic enzymes and bile