Kingdoms (CIE A Level Biology)

• The domain Eukarya can be divided into 4 kingdoms:
  • Protoctista
  • 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 of Eukaryotes Diagram

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 cellulose cell walls and chloroplasts

• Stentor roeseli is a protoctist that has flagella all over its body which help it feed and move

Stentor roeseli

Public domain, via Wikimedia Commons

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 range of species of fungus
  • Examples include Rhizopus stolonifer, and Penicillium species

Bread mould, showing various species growing

Veronidae, CC BY-SA 3.0 via Wikimedia Commons

Fungal Structure Diagram

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

• Bristlecone pines (one species is Pinus longaeva) are found in the USA, it is estimated that some of them could be 3000 years old

The Gnarly Bristlecone Pine (Pinus longaeva)

Rick Goldwaser from Flagstaff, AZ, USA, CC BY 2.0, via Wikimedia Commons

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 (Balaenoptera musculus) are the largest living animal species
  • The largest recorded specimen was just under 30 metres in length and 200 tonnes (200 000 kg) in mass

A blue whale (Balaenoptera musculus)

NMFS Northeast Fisheries Science Center (NOAA), Public domain, via Wikimedia Commons