The Five Kingdoms (Cambridge (CIE) O Level Biology): Revision Note

The Five Kingdoms

• The first division of living things in the classification system is to put them into one of five kingdoms. They are:

  • Animals

  • Plants

  • Fungi

  • Protoctists

  • Prokaryotes

• Main features of all animals:

  • they are multicellular

  • their cells contain a nucleus but no cell walls or chloroplasts

  • they feed on organic substances made by other living things

A typical animal cell

• Main features of all plants:

  • they are multicellular

  • their cells contain a nucleus, chloroplasts and cellulose cell walls

  • they all feed by photosynthesis

A typical plant cell

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

  • usually multicellular

  • cells have nuclei and cell walls not made from cellulose

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

A typical fungal cell

• 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

Two examples of protoctist cells

• Main features of all prokaryotes (bacteria, blue-green algae)

  • often unicellular

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

A typical bacterial cell

The Animal Kingdom

• Several main features are used to place organisms into groups within the animal kingdom

Vertebrates

• All vertebrates have a backbone

  • There are 5 classes of vertebrates

Vertebrate classification

Invertebrates

• Invertebrates do not possess a backbone

• One of the morphological characteristics used to classify invertebrates is whether they have legs or not

• All invertebrates with jointed legs are part of the arthropod phylum

• They are classified further into the following groups:

Invertebrate Table 

Arthropod classification

The Plant Kingdom

• 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

Ferns reproduce by spores found in the underside of their 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

Wheat plants are monocotyledons

Sunflowers are dicotyledons

How do you distinguish between monocotyledons and dicotyledons?

1) Flowers

• Flowers from monocotyledons contain petals in multiples of 3

• Flowers from dicotyledons contain petals in multiples of 4 or 5

2) Leaves

• Leaves from monocotyledons have parallel leaf veins

• Leaves from dicotyledons have reticulated leaf veins (meaning that they are all interconnected and form a web-like network throughout the leaf)

Comparing monocots and dicots