CIE A Level Biology (9700) 2019-2021

Revision Notes

18.2.3 Kingdoms


  • The domain Eukarya can be divided into 4 kingdoms:
    • Protoctista
    • Fungi
    • Plantae
    • Animalia
  • Organisms from each of the four kingdoms have distinct characteristics and features, but share similarities in that they have cells with membrane-bound nuclei separating genetic material from the cytoplasm, and compartmentalisation within their cells as a result of the presence of other organelles

Kingdom Protoctista

  • All Protoctista are eukaryotic, and this broad group of cellular life encompasses all eukaryotic cells that do not belong to the other three eukaryotic kingdoms
  • Members of this kingdom show great diversity in all aspects of life including structure, life cycle, feeding and trophic levels and well as modes of locomotion
  • Protoctists can exist as single-celled organisms or as a group of similar cells
  • A group of Protoctista known as protozoa possess cells similar to animal cells
    • Their cells have no cell wall
  • Another group of Protoctista known as algae possess cells similar to plant cells
    • Their cells have cellulose cell walls and chloroplasts
  • Stentor roseli is a protoctist that has flagella all over its body which help it feed and move

Kingdom Fungi

  • The oldest organism in the world is thought to be a fungus aged somewhere between 1500 – 10,000 years old
  • All fungi are eukaryotic cells
  • The cells of fungi:
    • Possess non-cellulose cell walls (often made of the polysaccharides chitin and glucans
    • Don’t have cilia
  • Fungi are heterotrophs:
    • They use organic compounds made by other organisms as their source of energy and molecules for metabolism
    • They obtain this energy and carbon by digesting dead/decaying matter extracellularly or from being parasites on living organisms
  • Fungi reproduce using spores that disperse onto the ground nearby
  • Fungi have a simple body form:
    • They can be unicellular (like the common baker’s yeast Saccharomyces cerevisiae
    • Some consist of long threads called hyphae that grow from the main fungus body (mycelium)
    • Larger fungi possess fruiting bodies that release large numbers of spores
  • The mould found on bread is actually a fungus: bread mould fungus Rhizopus nigricans

Kingdom Plantae

  • Plants are multicellular eukaryotic organisms
  • Plant cells:
    • All have cell walls composed of cellulose
    • Possess large (and usually permanent) vacuoles that provide structural support
    • Are able to differentiate into specialized cells to form tissues and organs
    • Possess chloroplasts that enable photosynthesis (not all plant cells have chloroplasts)
    • Can sometimes have flagella
  • They are autotrophs
    • This means they can synthesize their organic compounds and molecules for energy use and building biomass from inorganic compounds
  • Plants have complex body forms
    • They have branching systems above and below the ground
  • Bristlecone pines are found in the USA, it is estimated that some of them could be 3000 years old

Kingdom Animalia

  • Animals are also multicellular eukaryotic organisms
  • Animal cells:
    • Are able to differentiate into many different specialised cell types that can form tissues and organs
    • Have small temporary vacuoles (for example, lysosomes)
    • Have no cell walls
    • Sometimes have cilia
  • They are heterotrophs
    • They have a wide range of feeding mechanisms
  • They have a wide range of body forms:
    • Communication within their complex body forms takes place through a nervous system and chemical signalling
  • Blue whales are the largest living animal species

Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

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