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Living things are also known as living organisms.

Organisms (forms of life) have distinguishing characteristics and therefore are grouped.

The Magnifying lens

-Is used for enlarging small objects.


Procedure of its use

  • Place the object on the bench.
  • Move the hand lens from the object to the eye.
  • An enlarged image is seen.

Drawing magnification = Length of the drawing/ drawing Length

                                                Length of the object/Actual Length

External features of plants and animals

External features of plants

  1. Rhizoids as in moss plant.
  2. Fronds in ferns.
  3. Roots, stems, leave, flowers, seeds, fruits, and cones in higher plants.

External  features of animals

  1. Tentacles in hydra
  2. Feathers in birds
  3. Shells in snails
  4. Wings in birds
  5. Fur and hair in mammals
  6. Scales and fins in fish
  7. Proglotids in tapeworms
  8. Mammary glands in mammals
  9. Locomotory Structures e.g. limbs in insects
  10. Body pigmentation

Practical activity 1

To collect and observe animal specimens

To collect and observe plant specimens

What is classification?

-Is an area of biology that deals with the grouping of living organisms according to their structure. Organisms with similar structures are put under one group referred to as a taxon—taxa (plural).

The groupings also consider evolutionary relationships (phylogeny)—since all living organisms had a common origin at one time.

Taxonomy—Science of classification.

Taxonomist—Biologist who studies taxonomy.

Need for classification.


  1. To identify living organisms into their correct groups for reference and study
  2. To bring together living organisms with similar characteristics but separate those with different features.
  3. To arrange information of living organisms in an orderly manner. This avoids chaos and confusion.
  4. To understand the evolutionary relationship between different organisms

Taxonomic Units

Are groups (taxa) into which organisms are placed as a matter of convenience.

Groups are based on observable characteristics common in the group.

In a classification scheme (taxonomic units or groups, a hierarchy of groups are recognized starting with the first largest and highest group; the Kingdom to the smallest and lowest unit; the species.

There are 7 major taxonomic units.



The Kingdom

There are five Kingdoms of living organisms, namely:

  1. Kingdom Monera: bacteria
  2. Kingdom protoctista: algae, protozoa, amoeba, paramecium
  3. Kingdom Fungi: Moulds, Yeast, Mushrooms
  4. Kingdom Plantae: Moss plants, ferns, maize, garden pea, pine, meru oak, bean etc.
  5. Kingdom Animalia: hydra, tapeworms, bees, human beings etc.

A kingdom is divided into Phyla in animals or divisions in plants and sorts out organisms based on body plan and form.

Plan is the adaptation to a special way of life.

The Class is further divided into small groups; Orders using structural features.

Orders are divided into families using structural features, then Families into Genera (singular genus) –based on recent common ancestral features that are less adaptive.

Genus is divided into species i.e. kind of plant, or animal.

Down the hierarchy, the number of organisms in each group decreases but their similarities increases.

The Species group members naturally interbreed to produce fertile off springs.

Minor differences are exhibited in the species groups e.g. on colour of the skin in human beings and varieties of plants.

The groups of the species are termed to as varieties, races or strains.

Classification of A human being and a maize plant

Taxonomic unitHuman beingmaizebean
Phylum or divisionChordataAngiospermaphytaAngiospermae
species sapiensmaysVulgaris  

Scientific name                  Homo sapiens                        Zea mays                               phaseolus vulgaris

Scientific Naming Of Living Organisms

Present naming was developed by carolus Linnaeus 18th c, where organisms were given 2 names in Latin language.

Living organisms have their scientific names and common names i.e. local or vernacular names.

Scientific naming uses the double naming system—Binomial system.

In binomial system, an organism is given both the genus and species name.

Binomial nomenclature (Double –naming system)-Is the assigning of scientific names to living organisms governed by a definite set of rules recognized internationally.

Principles of binomial nomenclature

  1. The first, genus name, should begin with a capital letter and the second name, species, should begin or written in small letters e.g.

Lion—- Panthera leo

Leopard—– Panthera pardus

Domestic dog—– Canis farmiliaris

Human being— Homo sapiens

Maize plant—Zea mays

Lion and Leopard are closely related —Same genus but distantly related—different species.

  • The scientific names must be printed in italics in textbooks and where hand written to be underlined e.g. Panthera leo.
  • The specific name (species) is frequently written with the name of the scientist who first adequately described and named the organism e.g.Phaseolus vulgaris i.e. Vulgaris is the scientist who described and named the bean plant.
  • Biologists should give a Latinized name for a newly described animal or plant species where Latin name is missing e.g.

Meladogyne kikuyuensis – Is a scientific name of a nematode from kikuyu.

Aloe kilifiensis — A member of Aloeceae family from Kilifi discovery.

Garinsoga parviflora waweruensis — a member of Macdonald eye family discovered by Waweru.

Study Question 1

Complete the table below

TaxonLionDomestic dogGarden peaNapier grass

Scientific name         ———————     ————————    ———————–   ————————


  • Review of the magnification lens
  • Calculating Magnification
  • External characteristics of plants and animals

Diversity of Living Organisms

  • Organisms with similar characteristics are placed under one group called taxon (taxa).
  • The science of classification is known as taxonomy.
  • Biologists who study taxonomy are called taxonomists.

Need For Classification

  1. Help in identifying living organisms into their correct groups for reference.
  2. It brings together organisms with similar characteristics and separates those with different features.
  3. Help to organize information about living organisms in an orderly manner avoiding any confusion.
  4. Help to understand the evolutionary relationship between different living organisms.

Historical Background of Classification

  • Long time ago classification was artificial where living things were classified as either plants or animals.
  • Plants were classified as herbs, shrubs and trees.
  • Animals were further divided into carnivores, herbivores and omnivores.
  • Today modern classification uses evolutionary relationships between living organisms.

Taxonomic Units of Classification

  • This refers to the groups into which living organisms are placed in classification.
  • These units start from the first largest and highest group (kingdom) to the smallest and lowest unit (species).
  • There are seven taxonomic units as shown below.
  1. Kingdom

Carolus Linnaeus (1707-1778) initially introduced the two kingdom system of classification. However many new life forms have been discovered which are neither animals nor plants. This has led to a more accepted classification system that adopts five kingdoms. These are;

  1. Monera .eg bacteria
  2. Protoctista e.g algae and protozoa
  3. Fungi e.g. mushrooms, moulds and yeast.
  4. Plantae e.g. maize, ferns and all types of trees.
  5. Animalia e.g. man, cow tapeworm, flies etc.

Kingdom is further divided into several phyla in animals or divisions in plants.

  • Phylum (phyla) or Division in plants.

It is the second largest and further divided into classes.

  • Class

Each class is divided into several orders.

  • Order

Orders are divided into smaller groups called families.

  • Family

Family is divided into several Genera.

  • Genus

Here members are closely related. It is further divided into the species.

  • Species

This is the smallest unit of classification.

Species is defined as a group of organisms whose members naturally interbreed to produce fertile offspring’s.

Members of a given species have small differences such as skin colour, height etc.

Classification of Man and Maize plant. ( Table 2.1 Page 15 KLB Bk 1)

Scientific Naming of Living Organisms.

  • Today organisms are given two names in Latin language. This was developed by Carolus Linnaeus.
  • Latin language was used because it was widely spoken during his time.
  • In scientific naming, an organism is given the genus and the species name.
  • This double naming system is known as Binomial system (two name System)

Binomial Nomenclature.

This is the double naming system of organisms where organisms are assigned two names i.e. the generic name and the specific name.

In binomial nomenclature the following rules are observed.

  1. Generic name is written first followed by the specific name. First letter in the generic name is in capital and the rest are in small letters. Specific name is written in small letters.
  2. The two names are underlined separately when handwritten or italicised when printed.
  3. Newly discovered species must be given Latinized names.

Specific name is frequently written with the name of the scientist who first adequately described and named the organism.

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