CLASSIFICATION II - KCSE BIOLOGY NOTES

CONTENTS

1. Review of binomial nomenclature
2. General principles of classification
3. General characteristics of kingdoms
   1. Monera
   2. Protoctista
   3. Fungi
   4. Plantae
   5. Animalia
4. Main characteristics of major divisions of plantae
   1. Bryophyta
   2. Pteridophyta
   3. Spermatophyta (cover only up to class level)
5. Main Characteristics of the Phyla Arthropoda and Chordata (cover up to classes as shown)
   1. Arthropoda
      1.  diplopoda chilopoda
      2.  insecta
      3.  crustacean
      4.  arachnida
   2. Chordata
   3.  Pisces
   4.  Amphibian
   5.  Reptilian
   6.  Ayes
   7. mammalia
6. Construction and use of simple dichotomous keys based on observable features of plants and animals 
7. Practical activities
   1. Examine live/preserved specimen or photographs of representatives of major divisions of plantae and phyla arthropoda and chordata
   2. Construct simple dichotomous keys using leaves/parts of common plants/arthropods/ common chordates in the local environment
   3. Use dichotomous keys to identify organisms

SPECIFIC OBJECTIVES

By the end of the topic, the learner should be able to:

1. state briefly the general principles of classification of living organisms
2. state general characteristics of each of the five kingdoms
3. state the main characteristics of arthropoda, chordata and major divisions of plantae
4. name classes of spermatophyta
5. describe the main characteristics of classes of phyla arthropoda and chordata
6. use observable external features to construct simple dichotomous keys of plants and animals
7. use already constructed dichotomous keys to identify organisms.

Classification II
General Principles of Classification 

• Classification is the science that puts organisms into distinct groups to make their study easy and systematic.
• Modern scientific classification is based on structure and functions.
• Organisms with similar anatomical and morphological characteristics are placed in one group while those with different structures are grouped separately.
• Modern studies in genetics and cell biochemistry are used to give additional help in classifying organisms.
• There are seven major taxonomic groups.
• The kingdom is the largest group.
• Others are phylum (division for plants) class, order, family, genus and species, the smallest.

Binomial Nomenclature

• Living organisms are named using Latin or Latinised names.
• Every organism has two names.
• This double naming is called binomial nomenclature.
• This system of naming was devised by Carolus Linnaeus in the 18th Century.
• The first name is the generic name - the name of the genus.
• The second name is the name of the species.
• The generic name starts with a capital letter while that of the species starts with a small letter.
• The names are written in italics or are underlined in manuscripts.

Examples:

• Bean =Phaseolus vulgaris.
• Phaseolus is the generic name,
• vulgaris is specific name.
• Dog =Canis familiaris.
• Canis is the generic name
• ,familiaris the specific name.

General Characteristics of Kingdoms
Organisms are classified into five kingdoms.

• Monera,
• Protoctista,
• Fungi,
• Plantae
• Animalia.

Viruses do not fit neatly into any of the above kingdoms.

• They are simple and not cellular.
• They are metabolically inactive outside the host cell.
• Most of them can be crystallised like chemical molecules.
• Therefore they do not exhibit the characteristics of living organisms. 

​Examples of Organisms in Each Kingdom and Their Economic Importance 

Kingdom Monera
General Characteristics

• Unicellular and microscopic
• Some single cells, others colonial
• Nuclear material not enclosed within nuclear membrane-prokaryotic
• Have cell wall but not of cellulose.
• Have few organelles which are not membrane bound
• Mitochondria absent
• Mostly heterotrophic, feeding saprotrophically or parasitically, some are autotrophic.
• Reproduction mostly asexual through binary fission
• Most of them are anaerobes but others are aerobes
• Most move by flagella

• Examples include Escherichia coli, Vibrio cholerae and Clostridium tetani.
• Spherical known as Cocci.
• Rod shaped - e.g. Clostridium tetani
• Spiral shaped  e.g. sprilla
• Coma shaped- Vibrios -e.g., Vibrio cholerae.

Economic importance of bacteria Benefits to man include:

• They are used in food processing e.g., Lactobacillus used in processing of cheese, yoghurt.
• Involved in synthesis of vitamin Band K, in humans and breakdown of cellulose in herbivores.

Genetic Engineering

• Bacteria are easily cultured and are being used for making antibiotics, amino acids and enzymes e.g. amylase, and invertase e.g. Escherichia coli. 

​Nutrient cycling: 

1. ​What is meant by the term binomial nomenclature?
2. State briefly the general principles of classification of living organisms
3. ​Describe the economic importance of:
   1. fungi
   2. bacteria
4. State the importance of plants
5. Give the general characteristics of phylum arthropoda
6. State the economic importance of insects
7. State the general characteristics of chordate
8. What is a dichotomous key?
9. State the necessity of using a dichotomous key.
10. List the rules followed in constructing a dichotomous key.
11. Describe the procedure of using a dichotomous key. Make a list of major features of the characteristics to be identified.

answers

QUESTION 1

scientific system of naming organisms using the generic(genus) and specific (species) names

QUESTION 2

1. scientific names must be in Latin or should be latinised
2. family names are formed by adding the suffix “idea” to the stem of the genus e.g. the genus Rana become Ranaidea
3. generic names should be a single unique name

QUESTION 3

Fungi

• some cause decay to our food
• some cause diseases to humans and animals e.g. ringworms
• may be used as food e.g. mushrooms, yeast
• some are used in production of antibiotics e.g. penicillin, chloromycin, streptomycin
• yeast is used in brewing industry, baking and source of vitamin B
• many cause diseases to our crops e.g. late blight 
• important in recycling nutrients in soil since they cause decay of organic matter
• mycorrhizal association in forest development may help in water intake/absorption
• help in nitrogen fixation

Bacteria

• are useful in the manufacture of antibiotics
• silage formation,
• fermentation of cheese, butter, milk yoghurt
• curing of tea, tobacco and retting flax
• formation of vitamin B12 and K
• enzymes such as amylase and invertase
• hormones such as insulin
• vinegar, acetic acid, lactic acid, citric acid
• in septic tanks and modern sewage works make use of bacteria
• biogas production
• saprophytic bacteria are used in compost decomposition or cause decay
• symbiotic bacteria are used in compost decomposition or cause decay
• symbiotic bacteria in herbivores/ruminants help in digestion
• some diseases in animals/humans and plants are caused by bacteria
• many bacteria cause food spoilage/decay
• nitrifying and nitrogen fixing bacteria increase soil fertility/make nitrates available
• denitrifying bacteria reduce soil fertility/convert nitrates into nitrogen/reduce nitrates

QUESTION 4

• balancing carbon IV oxide and oxygen in the atmosphere during photosynthesis and respiration
• influence water cycle
• reduce soil erosion by bind soil particles together
• useful products e.g. food, medicine, timber, paper and clothing
• habitat ( e.g. forests and grassland) for animals which may also be tourist attraction
• earn money from sales of products
• aesthetic value/beauty e.g. flowers, shade/shelter, live fences, windbreaks
• Some are harmful e.g. poisons, weeds, injurious (stinging nettles, thorns), water hyacinth.

QUESTION 5

• jointed appendages
• presence of exoskeleton
• triploblastic and coelomate
• segmented body
• bilateral symmetry (similar halves)

QUESTION 6

Beneficial effects

• food supply
• important in food chains
• pollinators
• biological control of pests and other organisms
• aesthetic value
• contribute to decomposition e.g. litter feeders like beetles

Harmful effects

• pests
• vectors
• dirt and disease carriers
• injurious e.g. stings and bites

QUESTION 7

• notochord
• dorsal slits (pharyngeal cleft during development)
• bilateral symmetry
• triploblastic (three layer body-ectoderm, mesoderm and endoderm)
• clear cut head formation
• multilayered epidermis
• post anal tail
• closed circulatory system
• segmented muscle blocks(myotomes)
• single pair of gonads

QUESTION 8

​A biological device (tool) which enables one to identify an organism by progressively opting between two alternative observable characteristics

QUESTION 9

• used to identify organisms quickly and accurately
• by following the statements in the key we are able to identify each organism on the basis of a characteristic which is not to be found in other specimens

QUESTION 10

• use observable characteristics only
• start with major characteristics, placing organisms into two groups at each stage
• use a single characteristics at a time
• use contrasting characteristics at each stage e.g 1(a) short, 1(b) tall
• avoid repeating the same characteristics

QUESTION 11

• look at the features of similarities
• look at the features of differences between the organisms
• we can then be able to identify the organisms by distinguishing one from another
• the key uses a method of elimination by following statements that are correct only for the organism

K.C.S.E Topical Questions And Answers

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