Living Organisms have to exhibit 7 characteristics of life:
Nutrition - organisms either make food or obtain food to
sustain their life.
Respiration - organisms oxidize food to obtain energy.
Excretion - removal of metabolic wastes.
Movement(Locomotion) - organisms move their whole or part of
Irritability - organisms detect stimuli and make corresponding
Growth - organisms grow by increasing in size and complexity.
Reproduction - organisms produce offsprings similar to
There are over one million kinds of animals and plants in this
planet. We call this wide range of organisms as diversity of
1.1.2 Methods of Classification
Classification means sorting things into groups. We classify
organisms to make recognition and
description easier. Organisms are divided into groups
according to their characteristics. They are grouped step by step in
the following order:
*scientific names are in italics The number of kinds of
organisms decreases down the spectum until there is only one kind of
organism left for the group 'species'.
1.1.3 Plant and Animal
Organisms can be classified into 2 groups: animals and
Here are some major differences between animals and plants:
Heterotrophic nutrition. They have to obtain
food from other organisms.
nutrition. They can make their own food by
body can move from place to place
parts of the body can move
by cell wall
Classification of animal:
Animals can be classified into animals without
backbones(invertebrates) and animals with
Invertebrates - many classes. No need to remember all.
Vertebrates - 5 classes.
The characteristics of the five classes of vertebrates are as
Water and land
Naked slimy skin
Hard dry scales
Development of embryo
Within mother's body, born
Fins for swimming
Wings and beaks
Classification of plant:
Plants can be classified into flowering and non-flowering
Flowering plants - have flowers for reproduction.
Non-flowering plants - do not have flowers. There are 5
classes of them.
The characteristics of the five kinds of non-flowering plants are
Mainly in damp areas
Roots, stems and leaves
1.1.4 Dichotomous Key
Biological keys are methods used to identify
organisms. Dichotomous key is one in which each feature has two
alternatives at each stage and choosing either one of them will lead
to two different stages. The process is repeated until the organism
is identified. Below is an example to illustrate the method: