Kingdoms (Cambridge International A-Level Biology)

Spec point — 18.1.5 · outline the characteristic features of the kingdoms Protoctista, Fungi, Plantae and Animalia

Kingdoms

• The domain Eukarya can be divided into 4 kingdoms:

  • Protoctista(protoctists)
  • Fungi
  • Plantae (plants)
  • Animalia (animals)

• Organisms from each of the four kingdoms have distinct characteristics and features

• Although they share similarities:

  • They have cells with membrane-bound nuclei separating genetic material from the cytoplasm
  • They have compartmentalisation within their cells as a result of the presence of other organelles

The four kingdoms within the Eukarya domain: protoctista, fungi, plantae and animalia

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 cellulosecell walls and chloroplasts

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 structure of a fungus with its hyphae, mycelium and fruiting bodies

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 specialised 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 synthesise 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

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