Revision

• What are the organelles that can be identified in an electron micrograph of a cell?


  Cell wall, cell membrane, cytoplasm, nucleus, cell vacuoles, chloroplasts, mitochondria, ribosomes
• What are the functions of organelles in a cell?


  They perform specific tasks necessary for cell survival and function
• How can you differentiate between an animal and a plant cell?

  By identifying chloroplasts, cell wall, and large central vacuole
• What are the adaptations of structure to function in specialized cells?


  (A) Red blood cell:

  • Biconcave shape
  • Elastic
  • No nucleus
  • Contains hemoglobin

  
  

  (B) Root hair cell:

  • Mitochondria for active transport
  • Long and narrow for increased surface area to volume ratio
  • Large vacuole for cell sap storage

  
  

  (C) Muscle cell:

  • Mitochondria for energy release during aerobic respiration
• What is the shape of a red blood cell?


  Biconcave
• Why do root hair cells have mitochondria?


  For active transport of mineral ions
• How does the structure of a muscle cell relate to its function?

  It has mitochondria to release energy for contractions
• What is the definition of diffusion?


  Net movement of particles from a region of higher to lower concentration
• What is osmosis?


  Net movement of water molecules from a region of higher to lower water potential through a partially permeable membrane
• What are the techniques for answering questions on osmosis and diffusion?


  1. Determine if it’s osmosis or diffusion and provide definition
  2. Compare concentration or water potential
  3. Indicate direction of movement of particles
  4. Describe changes in cells (plasmolysed, flaccid, turgid) or color changes (iodine test)
• What is the main function of carbohydrates?


  Immediate source of energy
• What is the basic unit of carbohydrates?

  Monosaccharides
• What are the phases of the menstrual cycle in relation to oestrogen and progesterone?


  Day 0-5, 6-13, 14, 15-22, 23-28
• What is HIV?


  A virus that attacks the immune system
• How can HIV be transmitted?


  Through bodily fluids, sexual contact, and sharing needles
• What is the difference between a gene and an allele?


  A gene is a segment of DNA that codes for a polypeptide, while an allele is an alternative form of that gene
• What does a dominant allele do?


  It expresses itself in both homozygous dominant and heterozygous conditions
• When does a recessive allele express itself?


  Only in homozygous recessive conditions
• What should be included in a genetic diagram?


  • Labels
  • Gametes (circled)
  • F1 generation
  • Ratio/possibility
• What is a Punnett square used for?


  To predict the genetic outcomes of a cross between two organisms
• Why might the observed ratio differ from the expected ratio in genetic crosses?


  Due to small sample size and random fertilization
• What does XX represent in terms of sex chromosomes?


  Female
• What does XY represent in terms of sex chromosomes?


  Male
• What is a gene mutation?


  A change in the nucleotide sequence resulting in a change in the polypeptide produced
• What is a chromosome mutation?


  A change in the chromosome number
• What can cause mutations?

  Ionizing radiation such as X-rays and chemical mutagens
• Why is a shorter food chain more efficient?

  • More energy is passed on to the last trophic level
  • Less energy is lost at each trophic level
• What are the challenges of sustaining a long food chain?

  • Too little energy is passed on to the last trophic level
  • Increased energy loss at each trophic level
• What are the pyramids of biomass and numbers?


  • Pyramids of biomass show the mass of living material at each trophic level
  • Pyramids of numbers show the number of organisms at each trophic level
• What are the six processes involved in the carbon cycle?


  1. Decomposition
  2. Combustion of fossil fuels
  3. Respiration
  4. Photosynthesis
  5. Fossilization
  6. Feeding
• What roles do forests and oceans play in the carbon cycle?


  They act as carbon sinks through fossilization and photosynthesis
• What are the effects of deforestation and burning fossil fuels on climate change?


  They increase carbon dioxide levels, contributing to global warming
• How can we reduce the effects of deforestation and fossil fuel combustion?


  • Education for awareness
  • Laws for logging and fishing
  • Selective logging and fishing
  • Designate lands as forest reserves
  • Reforestation
• What is the relationship between DNA, genes, and chromosomes?


  1. DNA is a macromolecule made of two anti-parallel polynucleotide strands forming a double helix
  2. A gene is a segment of DNA that codes for a single polypeptide
  3. A chromosome is a tightly coiled DNA molecule around histone proteins during cell division