biology

• Gametes


  Sex cells like sperm cells and egg cells that only contain half the genetic material of a normal cell (haploid)
• Diploid cells

  Cells that have two sets of genetic information, one from each parent
• Meiosis

  1. Replication of DNA

  2. Chromosomes line up in pairs

  3. Chromosomes pulled apart and cell splits in two

  4. Cell splits in two again resulting in four genetically unique cells
• Chromosomes contain genetic information
• Humans have 23 different types of chromosomes, with two copies of each (46 total)
• One copy of each chromosome is from the mother (maternal), the other is from the father (paternal)
• The left-to-right order of the chromosome pairs during meiosis is random
• The four cells produced by meiosis are all genetically unique
• The gametes (sperm or egg) produced by meiosis can fuse during fertilization to form a diploid cell that can develop into a new organism
• Plants make their own sugars through photosynthesis, but all of this photosynthesis happens in the leaves
• Translocation


  Sugars made in the leaves are transported to the rest of the plant so they can be used for energy
• Phloem cells


  • Arranged end to end to form long columns called phloem tubes
  • Have small pores/gaps between adjacent cells to enable movement of cell sap (water and sugar mixture)
  • Can transport substances in either direction (up or down the plant)
• Xylem tubes


  • Made up of columns of dead xylem cells with no ends, forming one long hollow tube
  • Strengthened with lignin
  • Transport water and mineral ions from roots to leaves
• Transpiration


  Evaporation of water from the leaves, which drives the movement of water up the plant through the xylem
• Transpiration stream


  The chain of water molecules being pulled up the plant as water evaporates from the leaves
• Factors influencing rate of transpiration

  • Light intensity
  • Temperature
  • Air flow
  • Humidity
• Bright light intensity


  More photosynthesis, more stomata open, higher rate of transpiration
• Nighttime (no photosynthesis)


  Stomata closed, very little transpiration
• Warmer temperature


  Water particles have more energy, higher rate of transpiration
• High airflow


  Water molecules blown away quickly, concentration gradient kept high, increased transpiration
• High humidity


  Decreased concentration gradient, less water diffusion, lower rate of transpiration