Features of Organisms Continued (Cambridge (CIE) IGCSE Biology): Revision Note

The five kingdoms: Extended

Extended Tier Only

• The first division of living things in the classification system is to put them into one of five kingdoms (opens in a new tab)

• They are:

  • Animals

  • Plants

  • Fungi

  • Protoctists

  • Prokaryotes

• The main features of animals and plants have already been covered on the previous revision note page

• Main features of all fungi (e.g. moulds, mushrooms, yeast)

  • Usually multicellular

  • Cells have nuclei and cell walls not made from cellulose

  • Do not photosynthesise but feed by saprophytic (on dead or decaying material) or parasitic (on live material) nutrition

• Main features of all Protoctists (e.g. Amoeba, Paramecium, Plasmodium)

  • Most are unicellular, but some are multicellular

  • All have a nucleus, some may have cell walls and chloroplasts

  • Meaning some protoctists photosynthesise and some feed on organic substances made by other living things

• Main features of all Prokaryotes (e.g. bacteria, cyanobacteria)

  • Often unicellular

  • Cells have cell walls (not made of cellulose) and cytoplasm but no nucleus or mitochondria

The plant kingdom: Extended

Extended Tier Only

• At least some parts of any plant are green, caused by the presence of the pigment chlorophyll which absorbs energy from sunlight for the process of photosynthesis

• The plant kingdom includes organisms such as ferns and flowering plants

 Ferns

• Have leaves called fronds

• Do not produce flowers but instead reproduce by spores produced on the underside of fronds

Flowering plants

• Reproduce sexually by means of flowers and seeds

• Seeds are produced inside the ovary found at the base of the flower

• Can be divided into two groups – monocotyledons and dicotyledons

How do you distinguish between monocotyledons and dicotyledons?

• Flowers

  • Flowers from monocotyledons contain petals in multiples of three while flowers from dicotyledons contain petals in multiples of four or five

• Leaves

  • Leaves from monocotyledons have parallel leaf veins while leaves from dicotyledons have reticulated leaf veins

    • Reticulated means the veins form a web-like network throughout the leaf

  • Leaves from monocotyledons are narrow and grass-like while leaves from dicotyledons tend to have broader leaves that come in a wide range of shapes 

Viruses: Extended

Extended Tier Only

• Viruses are not part of any classification system as they are not considered living organisms

  • They do not carry out the seven life processes for themselves, instead they take over a host cell’s metabolic pathways in order to make multiple copies of themselves

• Virus structure is simply genetic material (either RNA or DNA) inside a protein coat