Lesson Notes By Weeks and Term - Senior Secondary School 3

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Term: 1st Term

Week: 7

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 2 periods each


Subject:    Agriculture

Topic:-      Crop improvement

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Define crop improvement
  2. State the aims of crop improvement
  3. Discuss the Mendellian laws of inheritance
  4. Highlight the processes of crop improvement
  5. Outline the methods of improving crop productivity

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures








The teacher reviews the previous lesson on farm records and accounts

Students pay attention



She defines crop improvement.

She further states the aims of crop improvement

Students pay attention and participates



She discusses the Mendellian laws of inheritance

She further highlights the processes of crop improvement.

She outlines the methods of improving crop productivity


Students pay attention and participate



The teacher writes a summarized note on the board

The students copy the note in their books




Crop Improvement refers to the ways of developing and breeding of crop varieties which are better than the existing varieties in a number of characters



  1. To increase Yield
  2. To improve the quality of produce
  3. To adapt to climatic condition
  4. To increase resistance to diseases
  5. To obtain uniformity of plant
  6. To breed crops with early maturity
  7. To improve the nutritional value of the produce



To understand the mendelian laws the following terms need to be understood

  1. Character or Traits: these are the inherited attributes which the plant breeders select. E.g. seed colour , seed size , plant height , disease resistance etc.
  2. Chromosomes: these are the rods or thread shaped bodies found in the nucleus of a cell. The chromosomes houses or contains the genes.
  3. Gene: these are hereditary units or units of inheritance.
  4. Gamete: this is a mature sex cell which takes part in sexual reproduction. There are two types of male gamete or spermatozoa (in animals) and pollen grains (in plants) and female gamete or egg or ovum (in animals) and ovules (in plants). Gamete is usually Haploid
  5. Zygote: is a single cell formed as a result of union of a male gamete with a female gamete.
  6. Allelomorphs: these are pairs of genes on the position of a chromosome (i.e. locus) that control contrasting characters.
  7. Phenotype: these are the physical and physiologically expressed traits of an individuals, e.g. height
  8. Genotype: this is a term used to describe those traits or sum total of the genes inherited from both parents.
  9. Dominant Character: this is the character shown in an individual without any significant influence of the contrasting characters present in the same individual on the dominant character.
  10. Recessive character: this is unexpressed character in the presence of a dominant character in an individual.
  11. Homozygous: a plant is said to be homozygous if the two members of a pair of genes controlling a given pair of contrasting characters are identical.
  12. Backcross: is a cross between an offspring and one of the parents
  13. Heterogeneous: a plant is said to be heterogeneous if the two members of a pair of genes controlling a given pair of contrasting characters are different e.g. (Tt) for tallness
  14. Hybrid: this is the offspring got from crossbreeding two pure varieties of any species.
  15. Filia generation: the offspring of parents make up the filia generation.


Mendel’s laws of inheritance are in two forms

  1. Mendel’s 1stlaw of segregation of genes: this states that genes are responsible for the development of the individual and that they are independently transmitted from one generation to another without undergoing any alteration
  2. Mendel’s 2ndlaw of independent assortment of genes: states that each character behaves as a separate unit and is inherited independently of any other character



  1. Introduction

This involves the importation of introduction or some varieties of crop with desirable characteristics into area where they have not existed before.

Advantages of introduction

  1. It helps to introduce new varieties of crops to a new area
  2. It may enhance greater productivity
  3. It may perform better if there is better climatic condition in the new location
  4. It may also perform better if there is better soil condition in the new area
  5. Absence of pests and diseases
  6. It helps to upgrade the quality of the local varieties of crops

Disadvantages of introduction

  1. There is the possibility of introducing new crop diseases
  2. The new crop may not be able to adapt to climatic condition of the new location
  3. It also introduce new pests to the new environment
  4. The introduced crop may not be able to adapt to soil conditions of the condition


  1. Selection

This involves the artificial picking of crops with desirable characteristic which are most favoured by the environment.

Method of selection includes:

  1. Mass selection: crops are selected or rejected on the basis of their own performance or merits
  2. Pure line selection: only one crop plant with good character
  3. Pedigree selection: crops are selected on the basis of the performance of their ancestors.
  4. Progeny selection: crop plants are selected on the basis of the performance of their offspring of progeny.

Advantages of selection

  1. It ensures that only the best naturally available crop is grown
  2. Crops with desired qualities are selected
  3. Seeds from best stands are multiplied for distribution
  4. Crops with undesirable characters are detected and rejected.
  5. It reduces the spread of diseases and pests

Disadvantages of selection

  1. Selection is tedious and time consuming
  2. It is very expensive in terms of time and money.
  3. It requires expertise which may not be available.
  4. It brings about the elimination of some desirable traits f the parent stock.


  1. Breeding or hybridization

Hybridization is a method by which an offspring is produced through the crossing of two different plant varieties of the same species.

Types of breeding

  1. In-breeding: this is pollination and fertilization of closely related crop plants in order to retain certain desirable characteristics. This can lead to pure breed or pure line.
  2. Cross breeding: this is the pollination and fertilization of unrelated crop plants belonging to different breeds. This results in the production of an offspring which is superior to the average performance of the parents. This is called Hybrid vigour “heterosis”.

Advantages of breeding

  1. It can produce a superior offspring resulting in hybrid vigour or heterosis (cross breeding)
  2. Progeny grows more rapidly (cross breeding).
  3. Production of pure-line (in breeding).
  4. Offspring can withstand variations of environment (cross breeding).

Disadvantages of breeding

  1. It could lead to “inbreeding depression”. Which is the depression of loss in vigour and performance of offspring (in breeding ).
  2. There is a drop in production or yield of crops in terms of quantity and quality (in breeding)
  3. It may lead to poor or low resistance to disease attack (in-breeding).



  1. Crop improvement processes
  2. Proper timing of planting
  3. Adoption of better cultivation methods
  4. Use of manures and fertilizer
  5. Control of pests and diseases of crops
  6. Use of resistance varieties

EVALUATION:   1. Define crop improvement

  1. State the aims of crop improvement
  2. Discuss the Mendellian laws of inheritance
  3. Highlight the processes of crop improvement
  4. Outline the methods of improving crop productivity

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively