Page 34 - 01. Classification of living things - Biology Notes IGCSE

#13 Summary of Classification of Living things

• All living things have 7 characteristics: Nutrition, Respiration,
Growth, Excretion, Movement, Reproduction and Sensitivity.

• Living organisms are classified into groups according to how closely
related they are. Each species of organism is given a unique two-word
Latin name called a binomial. The first word of the binomial is
the genus and the second word is the species.

• Vertebrates are classified into 5 classes: fish, amphibians,
reptiles, birds and mammals. They each have their own distinctive
set of features. E.g. amphibians have a smooth skin, fish and reptiles
have scales, birds have feathers and scales, and mammals have hair.

• Arthropods are invertebrates with joined legs and segmented bodies.
They can be further classified
into insects, arachnids, crustaceans and myriapods.

• Annelids are worm with segmented bodies but no legs.

• Nematodes are worms with unsegmented bodies.

• Molluscs have unsegmented bodies, and often have a shell.

• Bacteria are single-celled organisms whose cells do not have nuclei.

• Fungi include moulds, mushrooms and toadstools. They have cells
with cell walls but do not photosynthesise.

• Viruses are not generally considered to be alive at all. They are not
made of cells and cannot carry out any of the characteristics of living
things on their own.

• Flowering plants can be classified in to monocotyledonous plants
and dicotyledonous plants. Monocots have seeds with one
cotyledon, and their leaves often have parallel veins. Dicots have
seeds with two cotyledons, and their leaves generally have branching
veins.

• A dichotomous key is a set of paired contrasting
descriptions which lead you through to the identification of an
unknown organism.