bio wa2

• Types of consumers


  • Primary consumers (Herbivores)
  • Secondary consumers
  • Tertiary consumers
• Food chain


  A series of organisms, beginning with the producer, through which energy and nutrients are transferred
• Trophic level


  A position in a food chain
• A food web is a network of interconnected food chains
• Short food chains have fewer trophic levels than long food chains
• Energy flow in an ecosystem is non-cyclic, it flows from light to chemical energy
• Pyramid of numbers


  • The length of each bar represents the number of organisms
  • Can be inverted due to the number of small organisms feeding on one large organism
• Pyramid of biomass


  • The length of each bar represents the total biomass of the organisms
  • Considered a more accurate representation of energy flow than a pyramid of numbers
• Organisms have to be killed to obtain their biomass for a pyramid of biomass
• A pyramid of biomass has to be constructed at a particular point in time
• Carbon sink


  An area that absorbs more carbon from the atmosphere than it releases, storing it for a long period of time
• The largest carbon sinks on Earth are oceans
• Role of oceans as carbon sinks

  • Solubility and photosynthesis drive the role of oceans as carbon sinks
• Forests as carbon sinks


  • Plants absorb carbon dioxide during photosynthesis
  • Trees store lots of carbon compounds
  • When trees die, the remains form coal after being buried for millions of years
• Nucleus

  Carries genetic information
• DNA (Deoxyribonucleic Acid)


  Two strands of polynucleotides that form a double helix and twist and coil
• Nucleotide


  The basic building block of DNA, consisting of a sugar molecule, a phosphate group, and a nitrogenous base
• Polynucleotide

  Nucleotides joined together to form a polymer
• If adenine forms 25% of the bases in a particular DNA molecule, then guanine would form 25% and the remaining 50% would be cytosine and thymine
• Rule of Base Pairing

  • Adenine bonds with Thymine
  • Cytosine bonds with Guanine
• DNA does not move out of the nucleus
• Gene

  Part of the DNA that produces a specific protein
• Chromosome

  DNA molecule wrapped around special proteins
• How a Polypeptide or Protein is Made

  1. Message in gene is copied into mRNA in the nucleus

  2. mRNA travels to the cytoplasm and attaches to a ribosome

  3. Ribosome reads the mRNA and assembles amino acids into a polypeptide

  4. Polypeptide is released when ribosome leaves the mRNA
• Transcription is the process where a gene is copied in the nucleus to produce an mRNA strand
• Menstruation


  Process where blood from the uterus is discharged through the vagina every month
• Menstrual cycle


  A monthly cycle of events that include menstruation and ovulation
• Factors affecting length of menstrual cycle

  • Stress
  • Unbalanced diet
  • Illness
  • Tiredness
  • Malnutrition
• Menstrual cycle


  1. Estrogen causes repair and growth of uterine lining

  2. Progesterone helps thicken uterine lining for implantation

  3. Ovulation

  4. Menstruation
• Fertilisation


  Process by which the nucleus of the male gamete fuses with the nucleus of the female gamete to produce a zygote
• Implantation


  1. Zygote slowly moves to uterus

  2. Zygote divides by mitosis to form an embryo

  3. Embryo gets embedded in uterine lining
• HIV


  Human Immunodeficiency Virus, a virus that attacks lymphocytes (white blood cells) and weakens the immune system
• AIDS


  Acquired Immune Deficiency Syndrome, an advanced stage of HIV infection
• Signs and symptoms of AIDS

  • Pneumonia
  • Fever
  • Tuberculosis
  • Brain infection
  • Kaposi sarcoma
  • Diarrhoea
• How HIV is transmitted

  • Sexual intercourse
  • Sharing intravenous needles
  • Blood transfusion
  • Pregnancy
• How to prevent and control HIV transmission

  • Have only one sexual partner or abstain from sex
  • Use a condom
  • Do not share personal care items
  • Use new or sterile needles
• Oviduct

  • Muscular tube leading from ovary to uterus
  • Site of fertilisation of egg cell by sperm
  • Cilia on inner walls help to sweep the egg cell through oviduct
• Uterus

  • Thick muscular walls
  • Site where the fetus develops
• Ovary

  • Produces egg cells (ovum) and female sex hormones (oestrogen + progesterone)
  • Mature egg is released from ovary during ovulation
• Uterine lining

  Where embryo is implanted