Biology Form One Notes – Classification of Living Things
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TOPIC FOUR
CLASSIFICATION OF LIVING THINGS
The Concept of Classification
Explain the concept of classification
Have you ever visited a library? How are the books arranged and kept? Are they arranged
randomly or systematically? Obviously the books ate arranged systematically in the shelves.
Science books are kept separately in their respective shelves. Science books are kept separately
{rom social or commercial books. Biology books are separated from physics books or chemistry
books. Likewise, inthe shop, laboratory or pharmacy items ate sorted and placed on the basis of |
their similarities,
In the world, there are numerous varieties of living organisms-These organisms do vary in size,
structure, shape, habitat, mode of feeding and even mode of reproduction. The organisms can be
sorted out and placed into different groups based on their similarities. The system of sorting out
and placing organisms into different groups on the basis of their similarities and differences is
called classification.
Living Things According to Their Similarities and Differences
Group living things according to their similarities and differences
Study the extemal features of the following organisms:Lizard, sugar cane plant, maize plant,
shark, Tilapia cactus plant, bat, cockroach, butterfly, hen, goat, toad, frog, spider and orange
plant
1. Sort out the above organisms into plants and animals
2. Classify the animals onthe following basis
3. ‘Those with wings and those without wings
4. Those with tails and those without tails
5. Those with antennae and those without antennae
6, ‘Terrestrial and aquatic organisms
‘The Importance of Classifying Living Things
Explain the importance of classifying living things
The following are importances of classification
1 Classification makes the study of living things easy
2. Classification makes communication easy among biologists from different parts ofthe world
3. It provides good organized system in which a newly identified organism can be easily fitted in
future,
4. Itmakes it easier to identify organisms
5. Iteam be used to predict characteristics that are present inthe members ofthe same group.
Classification Systems
‘Types of Classification Systems and Their Differences
‘There are two types of classification
1. Anificial classification
2. Natural classification
Anifcil classification is based on one or a few easily observable characteristics and usually
designed for practical purpose with an emphasis on convenience and simplicity. In this type of
classification, unrelated organisms are often placed in the same group while closely related
‘organisms are often placed indifferent groups Linnaeus included all,
Linnaeus included all worm-like organisms in a single group, the vermes. This included wide a
range of animals as from nematodes, earthworms to snakes. This was an artificial classification
since it did not consider natural relationships such as the Fact that snakes have backbones and
earthworms do not have. Thus, snakes have more features in common with vertebrates than with
Bats and birds would be placed in the same group because all have the ability to fly since they
posses wings. But bats share many features with mammals. They have features like hair,
‘mammary glands, sweat glands and different types of teeth which are characteristics of
‘mammals. Therefore, bats are more related to mammals than birds Natural
[Natural system of classification This type of classification system tries to use natural relationships
between organisms. It considers many features in common including intemal as well as external
features Similarity of embryology, morphology, anatomy, biochemistry cell, structure and
‘behaviour are all considered relevant. It is based on evolutionary relationship in which organisms
belonging to the same group are believed to have a common ancestor.
Characteristic features which show homology ate distinguished from those which show analogy.
[Example the fore limbs of mammals, whales, birds and bats have the same basic pattern and
similar bone arrangement, ie. homologous. This suggests that these organisms are coming from
the same ancestor and that can be placed in the same group,
‘The wings of birds and grasshoppers are analogous. The wings of birds have internal skeletons
while the wings of grasshoppers do not have bones but they perform similar function, These
‘organisms cannot be placed in the same group since they are diferent in many ways.
Merits and Demerits of Each Type of Classification System
Explain merits and demerits of each type of clasification system
Advantages of artificial system of classification,
1. Itis easy to classify organisms since it s based on few observable characteristic,
2. Itdoes not take much time to classify organisms based on tis system (not time consuming)
3. Itdoes not need expertise (even a layman can do),
4, Itis relatively stable ie. not easily changing from time to time
Disadvantages of artifical system of elasification
1 Ittends to place closely elated organisms into different groups instead of being grouped together
eg. bat can be placed ina group of birds instead of mammals,
2. Different or unrelated organisms may be placed in the same group e.g bats placed ina group of
birds, worms placed with snakes inthe same group
3. The system does not provide enough information about its members,
4. Itis difficult to incorporate addtional information.
Advantages of natural system of classification
1 Closely retated organisms are paced inthe same group.
2. Itreflects evolutionary relationships
3. Unrelated organisms cannot be placed in the same group.
4. Itmakes it easy to incorporate additional information
Disadvantages of natural system of elasification
1 lis difficult since it considers many features.
2. Itrequies expertise ie. more knowledge about an organism,
3. Itis time consuming
4. tis relatively unstable ie it changes from time to time
5. Itis more expensive since more data are required
Differences between natural classification and artificial classification
Antfcial classification ‘Natural classification
Considers few features in common ‘Considers many features in common
i Does not reflect on evolutionary relationships Reflects on evolutionary relationships
(ii) is easy to classify tis difficult to classify
(Gv) Not time consuming tis time consuming
(¥) Does not require expertise Requires expertise
(vi) New information cannot be added “New information can be added
Major Groups of Living Things
Mention major groups of living things
‘The major groups of living things are the kingdoms, Previously, living things were categorized
into two main groups; plantae and animalia kingdom. But this classification eaused difficulties
since some organisms seemed to posses some of the characteristics of both groups. For example,
ceuglena is capable of feeding like an animal and locomote like an animal. Therefore, itis placed
in animalia kingdom, But the same euglena has chlorophyll and it is capable of manufacturing its
own food. Therefore, it should also be placed in plantae kingdom. Such an organism does not
seem to fit exactly in animalia or plantae kingdom. Thus, euglenas are assigned in the major
group oftheir own,
Currently, there are five major groups (kingdoms) of living things.
1, Kingdom monera
2. Kingdom protoctsta
3. Kingdom fungi
4. Kingdom plantae
5. Kingdom animalia
Ranks of Classification
Outline ranks of elassification
In the millions of organisms found on earth some are more similar while others are less similar.
For example, all human beings resemble each other more closely than they resemble with the
chimpanzees. Humans have more resemblance with chimpanzee than eats and dogs, and more
like dogs than birds.Therefore when classifying the organisms, groups are established which are
called ranks or taxa,
‘There are seven ranks of classification
1. Kingdom
2. Phylumvdivsion
3. Class
4. Onder
5. Family
6. Genus
7. Species
The highest rank of classification is the kingdom. The lowest rank of classification is
the species. Every known organism has particular place in each group.
1. Kingdom: this i the highest rank (taxon). It comprises of several related taxa. It comprises of|
‘many organisms than any othe axon,
2. Plytum/division— this isthe second largest rank of classification. It consist of several closely
related clases
3. Class – members or this group have more characteristics in common than do members of division
or phylum.
4. Onder it consists of groups that are more alike than those ina class.
5. Family -this is made up of groups that are more alike than those in the order. Wolves and cats
are both inthe order Carnivore but wolves are inthe family Canidae while cts belong to the
family Felidae
6. Genus ~ it consists of very similar species but members of different species eannot breed one
another.
7. Species ~ Species can be defined as a group of closely related organisms which are capable of
interbreeding and produce fertile offspring
It is the basic unit of scientific classification, Organisms that need to be placed in the same
species must have the following characteristics
1 Must have many features in common
b. Must be able to breed one another to produce fertile offipring.
. Must be distint and different from other organisms,
N.B: The term division is used by botanists instead of phylum when classifying plants or
‘organisms related to plants
Classification of some members of animals
Human Leopard Domestic eat
Kingdom Animalia Animalia Avimalia
Phylum Chordata Chordata Chordata
Class Mammalia Mammalia Mammalia
Order Primates Camivore Carnivore
Family Hominidae Felidae Felidae
Genus Homo Panthera Felis
Species sapiens padus caus
Scientific naming of living organisms
‘The scientific process of naming organisms is called nomen- clature. Biological nomenclature is
based on the binomial system (double naming system) pioneered by the work of a Swedish
naturalist Carl Linnaeus (1707-1778)
Biologists assign scientific names to organisms so as to avoid confusion among themselves since
scientists from different countries use different languages. The seientifie names are uniform in all
languages
Latin language is used in assigning the scientific name because its an official language and that
this language is no longer subject to changes; itis considered to bea dead language hence names
‘once given remain unchanged
Rules of binomial nomenclature
1 Scientific names of organisms must be in Latin language and ifthe names ate derived from other
languages, they must be latinized.
2. A scientific name of an organism has two parts, genus name and species name,
3. A genus name always starts with a capital letter and a species name follows with a small letter.
4. Intyped scripts, a scientific ame must be writen in tales or underlined ifhand writen
5. A specific name is sometimes accompanied with the name of the author who first described and
‘named the organism,
6. When an organism is known by several names, the valid name is the one which was established
after the work of Linnaeus.
Examples of scientific names
‘Human being: Homo sapiens
Homo isthe genetic name and sapiens is the specific name.
Other examples of organisms with their scientific names
Common name Scientific name
Earthworm Lumbricus terrestris
Cockroach Periplaneta ‘americana
Amoeba Amoeba proteus
Coffee Coffea arabica
Maize Zea mays
Bean Phaseolus vulgaris
Domestic cat Felis caus
Sisal Agave sisalana
Ashok tree Polyanthia longifolia
Housefly Musca domestica
Neem tree Azadirachta indica
Flamboyant (Christmas tree) Delonix regia
‘Tropical almond (mkungu) Terminalia catapa
Viruses
Viruses were discovered by a Russian botanist D. 1 Ivanovsky and a Dutchman Beijerink. In
1852 Ivanovsky prepared an infectious extract from tobacco plants that were suffering from
mosaic disease. When the extract was passed through a filter able to prevent the passage of
bacteria, the filtered fuid was still infectious. 1898 Beijerik gave the name “virus” (in latin
‘means, ‘poison”) to describe the infectious nature of certain filtered plant uid.
General and Distinctive Features of Viruses
(Characteristics of Viruses
1. They are the smallest living organisms ranging from 20-30nm. On average, they are about
‘SOtimes smaller than bacteria,
2. Viruses do not have cellular structures, which mean that they lack certain important organelles
like nucleus, eytoplasm, golgi bodies, ete
3. ‘They can only reproduce inside the living cells hence they are parasitic.
4. They have a simple structure consisting of either DNA or RNA but not both, surrounded by a
protein or lipoprotein coat
5. ‘They can be described as living or non-living
6. ‘They are highly specific to their hosts i. each virus recognizes only certain types of cells.
7. Viruses are capable of replicating themselves only when they are inside the host cell
Viruses as living things
1. They possess genetic material (RNA or DNA).
2. ‘They reproduce when they are inthe host cell (replication).
3. ‘They are capable of identifying ther hosts and attack them,
4. They can undergo mutation (they mutate) ic. they undergo different changes in shape.
5. Like other parasites, they are specific to host
Viruses as non-living things
1 They can crystallize outside the host.
2. ‘They are metabolically inert in isolation,
3. They are non-cllular ie, they lack cell organelles.
44. They do not perform necessary life processes such as respiration, exeretion nutrition ete
“The Structure of Viruses
Describe the structure of viruses
Generally viruses have a very simple structure consisting of the following:
1. RNA or DNA which may be single stranded or double stranded. They form a structure called
2. A protective coat of protein surrounding the core called capsid
3. A nucleocapsid which is a combined structure of core and capsid,
4. Envelope ~an additional layer of lipoprotein layer around the capsid
5. Capsids are made up of identical repeating units known as capsomeres
Bacteriophage
Bacteriophage is a virus that attacks and kills bacteria. Some of them have head with a tail
sheath
Head
Tall sheath
(protein)
Elongated process
for attachment to
bacterium
End plate
(Canal for expulsion
ofDNA
Bacteriophage
Advantages and Disadvantages of Viruses
Outline advantages and disadvantages of viruses
Advantages of viruses
1 Viruses are used in developing vaccines, for example, vaccines for measles, polio and rubella are
‘made from viruses that have been attenuated (weakened),
2._ Viruses are used as biological weapons to kill organisms.
3. ‘They are used as vectors in genetic engineering to transfer genes from one organism to another
{or improving or treating the defective genes.
‘4. Bacteriophages are viruses that attack bacteria and hence they help in controlling infections and
diseases.
5. Viruses are used as biological weapons in wats and in biological pest contol
Disadvantages of viruses
1. Most viruses cause diseases to both plants and animals. Plant disease such tomato mosaic,
cassava mosaic and tobacco mosaic; and animal diseases e.g. measles, small pox, poliomyelitis
and yellow fever are caused by viruses
‘Kingdom Monera
This kingdom is made up of organisms known as bacteria (singular: bacterium). They are the
‘most ancient and smallest organisms with a cellular structure. They are mainly single celled.
Bacteria occupy many environments such as soil, dust, water and in the bodies of plants and
animals
Some bacteria are found in hot springs where temperatures are 78°C or more. Others can
withstand very low temperatures, Some are found in very deep cracks inthe ocean floor, at very
high temperatures, about 360°C (extreme thermophiles)
General and Distinctive Features ofthe Kingdom Monera
Explain general and distinctive features ofthe kingdom monera
General characteristics of the kingdom monera
1. They are mainly unicellular and very small.
2. ‘They ae all prokaryotic (nucleus not bound by membrane)
3. They reproduce by binary fission.
4. Some members ofthe kingdom are autotrophs while others are heterotrophs
5. ‘They have cell wall made up of protein material and sometimes lipids.
6. Some bacteria form spores during adverse conditions ie. extreme conditions eg high or low
temperatures, drought ete. The spores allow them to survive as they have very thick resistant
walls
7. Some are aerobes while others are anaerobes.
8. The genetic material (DNA) is scattered inthe cytoplasm and they lack internal membrane bound
‘organelles such as mitochondria, chloroplasts, golgi bodies et.
Structures of the Representative Organisms ofthe Kingdom Monera
Describe structures ofthe representative organisms of the kingdom monera
General structure ofthe bacteria
1. Bacteria have strong and rigid cell walls due to the presence of murein. The wall prevents the
cell from bursting when it absorbs much water (as a result of osmosis),
2. Bacterial cells are bounded by partially permeable membranes,
3. Bacteria possess capsules which ate slimy or gummy:They have flagella which aid motility of
the bacteria, Motile bacteria can move in response to a certain stimulus ie. tactic movement.
Flagella can easily be seen by electron microscope.
4, They have small self replicating circle of extra DNA called a plasmid.
‘Chromosomal
DNA Plasmid DNA.
(
Flagellum (not
always present) Cell wall
Cell membrane
Forms of bacteria
‘acteral shape is an important aid to classification, There are four main shapes
Coceus (plural: cocci)
“They are spherical in shape and can be of the following types.
+ Micrococcus ~ exist singly. They cause sore throat.
DOG
oo ON
Dy SEERRD
Qo?
+ Saphylococel — These bacteria form a rape Tike busch. They couse boils, poesia, fod
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AITO
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Bac (singslr: baci)
These ae rod shaped bacteria They canbe:
+ Rods in chain, for example, Azotobacter, a nitrogen-fixing bacteria, and Bacillus anthracis which
cause the discase anthrax.
+ Bacill wth endospores showing various postions, shapes and sizes of spores. They can be:
Central, not swollen eg. Bacillus anthracis causes anthrax
»b. Spherical spore, terminal swollen e.g. Clostridium retani causes tetanus
€. Sub-terminal, swollen e.g, Clostridium botulism causes botulism Spores may also be central
Spirita (singular: spirillum)
‘These are spiral-shaped bacteria e g. Treponema pallidum which causes syphilis
Sprrlla
Vibrio
‘These are comma shaped bacteria, for example Vibrio cholerae
Vibrio cholerae
‘The Advantages and Disadvantages ofthe Kingdom Monera
Outline the advantages and disadvantages ofthe kingdom monera
Economic Importance of Bacteria
In Agriculture, the bacteria are mostly important fr following reasons
1. Nitrogen fixation:Plants cannot trap nitrogen from the atmosphere but bacteria can fix nitrogen
and change it into nitrogenous compounds. The phenomenon is called nitrogen fixation. The
bacteria, which fix atmospheric nitrogen, are called nitrogen-fixing bacteria. Some of the
nitrogen fixing bacteria are found freely in soil are called fre-living bacteria, eg. Clostridium
and Azotobacter. Some of them are found in root nodules making association with leguminous
plants called symbiotic bacteria, eg. Rhizobium.
2. Nitrfiention:Some bacteria convert ammonium compounds into nitrates inthe soil. The process
is called nitrification. The bacteria that take part inthis process are called nitrifying bacteria, eg
Nitrobacter and Nitrosomonas. Nitrosomonas Nitrobacter Ammonia–—-——~->Nitrites-=-—-
Nitrates
3. Ammonification:Some bacteria utilize proteins of dead bodies and conver it into amino acids
‘These amino acids are converted into ammonia by some bacteria, The process is called
ammonification and the bacteria involve in the process are called ammonifying bacteria. Then
the ammonia reacts with CO: and H;O and gives ammonium carbonate which is absorbed by
plants.
4. Bacteria decompose dead bodies. They convert complex organic compounds into simple
inorganic compounds. Therefore they’re called natural scavengers.
5. Bacteria make the milk sour and produce flavor. They are responsible for coagulation of
silk. Eg. Lactobacillus.
6. Bacteria convert sugary substances into alcohol, acids, acetones; efe the process is ealled
fermentation.
7. Bacteria also help to produce different types of enzymes like Amylase secreted from Bacillus,
Protease from Bacillus, Streptokinase from Streptomyces
8. Bacteria are useful for vitamin production ike Vitamin B (Cabalmin) is secreted from
Pseudomonas, Vitamin B (Riboflavin is seereted from Clostridium,
9. They are important for antibiotic production ike Terramycin ffom Streptomyces rimosus,
Streptomycin from S. griseus, Neomycin ftom S. fradiae
10. They are also important to produce hydrogen commercially. During the process they ferment
carbohydrate and hydrogen gas is produced.
11, Bacteria decompose waste products,
Disadvantage of Bacteria
1 Some of the species cause food poisoning. They secret some toxic chemical substances on out
{ood stuff which cause food poisoning, eg Staphylococcus and Clostridium.
2. ‘Some are responsible for human diseases: Cholera: Vibrio cholera, Pneumonia: Staphylococcus
pneumoniae, Diarrohea: Fscherechia coli, Tuberclosis: Mycobacterium tuberclosis Leprosy: M.
leprae, Meningitis: Nisseria meningitis.
3. Some bacteria are responsible for plant diseases. Red stripe in sugarcane, Leaf streak in rice,
black rot in cabbage and yellow rot in wheat are caused by Xanthomonas and Pseudomonas.
‘The Characteristics of Pathogenic and Non-pathogenie Bacteria
(Outline the characteristics of pathogenic and non-pathogenic bacteria
Pathogenic bacteria are bacteria that can cause infection. This article deals with human
pathogenic bacteria,
Although most bacteria are harmless or often beneficial, several are pathogenic. One of the
bacterial diseases with the highest disease burden is tuberculosis, caused by the
bacterium Mycobacterium tuberculosis, which kills about 2 million people a year, mostly in sub-
Saharan Aftica, Pathogenic bacteria contribute to other globally important diseases, such as
pneumonia, which ean be caused by bacteria such as Streptococcus and Pseudomonas, and food
bore illnesses, which can be caused by bacteria such as Shigella, Campylobacter,
andSalmoneila, Pathogenic bacteria also cause infections such as tetanus, typhoid fever,
<iphtheria, syphilis, and leprosy. Pathogenic bacteria are also the cause of high infant mortality
rates in developing countries.
Nonpathogenic organisms are those that do not cause disease, harm or death to another
organism and is usually used to describe bacteria. It describes a property of a bacterium – its
ability to cause disease, Most bacteria are nonpathogenic. It ean describe the presence of non-
disease causing bacteria that normally reside on the surface of vertebrates and invertebrates as
commensals. Some nonpathogenic microorganisms are commensals on and inside the body of
animals and are called microbiota, Some of these same nonpathogenic microorganisms have the
potential of causing disease, or being pathogenic if they enter the body, multiply and cause
symptoms of infection,
Immune comprised individuals are especially vulnerable to bacteria that are typically
nonpathogenic but because of a compromised immune system, disease occurs when these
bacteria gain access to the bodys interior. Genes have been identified that predispose disease and
infection with nonpathogenic bacteria by a small number of persons. Nonpathogenic colistrains
‘normally found in the gastrointestinal tract have the ability to stimulate the immune response in
humans, though further studies are needed to determine clinical applications.
Kingdom Protoctsta,
General and Distinctive Features ofthe Kingdom Protoctista
Explain general and distinctive features ofthe kingdom protoctisia
‘This Kingdom comprises of unicellular and simple multicellular organisms whose cells have
‘organized nucleus and membrane bound organelle. It includes the algae and protozoa
Algae have chlorophyll hence make their own food through the process of photosynthesis.
Protozoa are heterotrophic taking in ready-made food.
Other organisms, which are included in this Kingdom are red algae, Brown algac, Amoeba,
Euglena plasmodium, trypanosome and paramecium.
General features of Kingdom Protoctista
+ Some are autotrophs, for example Euglena while others are multicellular,
+ They ae all eukaryotes with most of them having locomotery structure,
+ Most of them live in moist places or in water.
Distinctive features
+ Most are unicellular eukaryotes
+ They reproduce by binary fission
Phyla ofthe Kingdom Protoctsta,
Mention phyla ofthe kingdom protoctista
‘The phyla of kingdom protoctsts include the following:
1. Buglenophyta eg. Euglena
2. Rhizopodia eg. Amocba
3. Zoomastigma eg. Trypanosoma
4. Apicomplexa eg. Plasmodium
5. Oomycota eg. White root
6. Chlorophyta eg, Spyrogyra
7. Cilliaphora e.g. Paramecium
8. Rhodophyta e.g. Red algae
Stra of Amocba and Paramecium
“Amoeba belong to phylum Rhizopda, organisms with he following extra features
+ Theyareeakanoses
+ Unietiar
«They move sing pseuopodia
Psewopodia are projection ofthe eytplsm tat extend and pl the amoxba forward or engulf
food prices
Nucleus
Food Vacuole Cell Membrane
Cytoplasm
Pseudoplasm 5
<—citia
oral
Micronucteus Groove
Contractue
Macronuctous Nacwole
‘Colt Membrane
‘The Advantages and Disadvantages of Amoeba, Euglena Paramecium and Plasmodiu
Explain the advantages and disadvantages of amoeba, euglena paramecium and plasmodium
Advantages of Paramecium: Are eaten by small water animals
Disadvantages of Paramecium: Causes diseases of bulanterdium coli destroying the lining of
intestines
Osmoregulation:Paramecium has two contractile vacuoles and each is associated with
permanent system of collecting channels, which empty, into the main vacuole.
Feeding: Paramecium feed on bacteria. These are obtained from the surrounding water by the
beating ofthe cilia-lining o the oral grove.
Reproduction:Paramecium reproduces both asexually and sexually. The asexual method is more
‘common and it is binary fission, Sexual method is called conjugation,
Movement in paramecium is caused by cilia beating. This movement is called cilliary
movement,