Features of Organisms - 2 | Biology for GCSE/IGCSE - Year 11 PDF Download

The Five Kingdoms: Extended

• 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 fungi (e.g. moulds, mushrooms, yeast)

• Usually multicellular
• Cells have nuclei and cell walls not made of cellulose
• Do not photosynthesize 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
• This means some protoctists photosynthesize while others feed on organic substances made by other living things

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

• Often unicellular
• Cells have cell walls (not made of cellulose) and cytoplasm but lack a nucleus or mitochondria

The Plant Kingdom: Extended

• Plants typically have green parts due to chlorophyll, a pigment that absorbs sunlight for photosynthesis.
• The plant kingdom encompasses various organisms like ferns and flowering plants.

Ferns

• Ferns are characterized by fronds, which are leaf-like structures.
• Unlike flowering plants, ferns reproduce through spores located on the underside of their fronds.

Flowering plants

• Reproduce sexually through flowers and seeds
• Seeds are formed inside the ovary located at the base of the flower
• Can be classified into two groups: monocotyledons and dicotyledons

How do you distinguish between monocotyledons and dicotyledons?

Flowers

• Monocotyledons: Flowers from monocots have petals in multiples of 3.
• Dicotyledons: Flowers from dicots have petals in multiples of 4 or 5.

Leaves

• Monocotyledons: Leaves of monocots possess parallel leaf veins.
• Dicotyledons: Dicots exhibit reticulated leaf veins, forming an interconnected web-like network across the leaf.

Viruses: Extended

• Viruses are not categorized within any classification system since they are not regarded as living organisms.
• They do not perform the essential life processes independently; instead, they hijack a host cell's metabolic pathways to replicate themselves.
• The structure of a virus essentially comprises genetic material (RNA or DNA) enclosed within a protein coat.