CLASSIFICATION OF LIVING THINGS
THE CONCEPT OF CLASSIFICATION
Meaning of
classification
Classification – is the process of grouping
organisms based on their similarities and differences
- Classification is a
branch of biology that deals with the grouping of living organisms according to
their structures, way of life and origin.
- Organisms that are
similar are placed in the same group. These similarities can be in terms of
their evolutionary relationship or the way they carry out life processes such
as feeding and reproduction.
- The study of
classification is called taxonomy
- A person who studies
taxonomy is called a taxonomist.
Importance of classification
Classification of living
things is very important because
(i) It makes the study
of living things easier
(ii) It helps to know
the characteristics of different living organisms
(iii) It makes
communication among biologists in the world easier
(iv) It helps to prevent
confusion among biologists in the world as most organisms are given scientific
names which are known all over the world
(v) It helps us to
understand how organisms are related in terms of evolutionary history
(vi) It enables man to
identify and name every organism
(vii) It enables scientists to make predictions about characteristic of different organisms.
For
example, eagle and chicken are both birds, therefore if we know what the heart
of a chicken looks like we can predict what the heart of an eagle looks like even
if we have not seen it.
(viii) It brings
together living organisms with similar characteristics but separate those with
different features.
TYPES OF
CLASSIFICATION
There are two main types
of classification systems namely;-
(i) Artificial
classification
(ii) Natural
classification
ARTIFICIAL
CLASSIFICAION
Is a system of
classifying organisms based on few observable features of an organism.
Artificial
classification is based on easy, external and simple characteristics of an
organisms for example, the presence of legs or wings. Based on this, bees,
birds and bat would be grouped together. Snakes, earthworms and snails would
also be grouped together because they do not have legs or wings.
- Artificial
classification also involves classifying organisms according to their size, how
they move, where they live or what they eat.
QUESTION
You have been provided
with the following living things: Bird, Bat, Bee, Snake, Snail, Earthworm
(a) Classify them based
on the following features:
(i) Size
(ii) How
they move
(iii) Where they live
(iv) Presence
of legs or absence of legs
(v) Presence
of wing or absence of wings
(b) How many organisms
did you get for each feature?
ADVANTAGES/MERITS
OF ARTIFICIAL CLASSIFICATION
(i) It
is easy to use. This is because it involves only one or few observable features
(ii) Takes
short time to classify organisms
(iii) It is very stable.
This means that, it does not change as a result of any new information
(iv) It
can be done by anybody. This is because it does not need much knowledge
(v) It
is less expensive. This is because it uses few observable features to group the
organisms
(vi) It
does not require high knowledge to classify living organism
DISADVANTAGES/DEMERITS
OF ARTIFICIAL CLASSIFICATION
(i) Closely
related organisms are placed into different groups eg human being and bat
(ii) Unrelated
organisms are placed in the same groups e.g. birds and bat
(iii) It is less
accurate, because it uses only few observable characteristics
(iv) It
creates confusion among biologists from different parts of the world
(v) It
provides us with limited information about the organisms
(vi) It
depends much on the views of an individual or a society and not scientific
evidence.
NATURAL CLASSIFICATION
Is a system of
classifying organisms based on many features
OR
Is the type of
classification, which based on the evolutionary trend or sequence.
- In the natural system
of classification organisms are grouped based on many features in common
particularly those related to evolutionary relationship.
- In this system,
characters that show homology or similarity of origin must be distinguished
from those that exhibit analogy or similarity of use.
HOMOLOGOUS
STRUCTURES
Are structures that
perform different functions but have similar ancestral origin
Example of homologous
structure
- Fore limbs of a man
and the wings of a bird.
- Therefore, animals
that are closely related in many ways are placed in the same natural group.
ANALOGY
Refers to similarity in
functions between organs, which evolved from different ancestry origin.
- The fossil records
show that bat wings and bird wings evolved independently from walking forelimbs
of different ancestors.
- Such anatomical signs
of evolution are called analogous structures.
ANALOGOUS
STRUCTURES
Are structures that
perform similar functions but have different ancestral origin.
Examples of analogous
structures
- Wings of birds and
insects
MERITS/ADVANTAGES
OF NATURAL CLASSIFICATION
(i) Biologically
related organisms are grouped together
(ii) It
is more accurate because it involves scientific research to gather enough
information.
(iii) It is flexible and
allows addition of new features when discovered
(iv) It allows us to
predict about newly found organisms.
(v) It avoids confusion
among biologists, since it is based on international standards.
DEMERITS/DISADVANGES
OF NATURAL CLASSIFICATION
(i) It
is very expensive. This is because it involves scientific research, experiments
and high classification skills
(ii) It
is time consuming. This is because it uses many features in grouping organisms
(iii) It is difficult to
be conducted. This is because it needs much knowledge and skills to be
conducted, therefore, it cannot be done by anybody.
(iv) It is not stable.
This is because it can change any time due to addition of newly discovered
features or information
DIFFERENCES
BETWEEN ARTIFICIAL AND NATURAL CLASSIFICATION
|
ARTIFICIAL
CLASSIFICATION |
NATURAL
CLASSIFICATION |
|
(i) It
does not consume much time |
It
consumes much time |
|
(ii)
It is stable |
It is
not stable |
|
(iii)
It is less expensive |
It is
expensive |
|
(iv)
It requires simple skills and knowledge to be done |
It
requires advanced scientific skills and knowledge |
|
(v) It
is less accurate |
It is
more accurate |
|
(vi)
It is based on individual's interest |
It is
based on international standards |
|
(vii)
It is easy to be conducted |
It is
difficult to be conducted |
QN, Explain the
following observations.
i. Artificial
classification can be done by any body
ii. Artificial
classification is less accurate
iii. Artificial
classification is easy to use
iv. Artificial
classification does not bring confusion
v. Artificial
classification is stable
RANKS OF
CLASSIFICATION OR TAXA OF CLASSIFICATION
These are the levels or
groups of classification to which organisms are assigned according to the
principles of taxonomy
- They are also called
hierarchies of classification, unit of classification or taxa (taxon in
singular form).
- In classification of
living things, there are seven ranks or taxonomic units which arranged
hierarchically in descending order (from the highest to the lowest rank) or in
ascending order (from lowest to the highest rank):
The following are seven
ranks or taxonomic units of classification arranged in descending order:
(i) Kingdom
(ii) Phylum/division
(iii) Class
(iv) Order
(v) Family
(vi) Genus
(vii) Species
QUESTION
Write down seven ranks
of classification arranged in ascending order
Kingdom
Is the largest (highest)
group or rank of classification.
- It is a group of
closely related phyla or divisions
- Kingdom is subdivided
into phyla or divisions
- Example: kingdom
Animalia, kingdom plantae
Phylum/Division
(Plural: Phyla)
Is a closely related
classes
- In kingdom plantae,
phylum is called division
- Phylum/division is
subdivided into classes
Class
Is a group of closely
related orders
- Class is subdivided
into orders
Order
Is a group of closely
families
- For example, large
animals that adopted to feed on fresh of other animals, e.g. dogs, lions, cats,
leopards are grouped under the order carnivore
- An orders is
subdivided into families
Family
Is a group of closely
related genera
- For example, involves,
foxes, jackals and dogs belong to the family Canidae. - A family is subdivided into
genera
Genus (Plural:
Genera)
Is a group of closely
related species
- For example, Domestic
dogs and wolves belong to different species but have many similar features
hence belong to the same genus called canis
- A genus is subdivided
into species
Species
Is a group of closely
related organisms that can interbreed freely and produce a fertile offspring - It is the smallest (lowest) rank
(taxon) of classification than all groups (taxa), - It is a basic unit of
classification taxa.
- A species cannot be
subdivided into other groups
- For example, All human
being belong to the same species called Homo sapiens
Characteristics
of species
Members of the same
species are characterized by the following features:
(i) They
have many features in common (they share many features and look much alike).
(ii) They
should interbreed freely and produce a fertile offspring
(iii) They should be
distinct and different from other organisms
Note: Usually members of
the same species can interbreed to produce fertile offspring of two different
species cannot interbreed freely. If they interbreed, they do not produce
fertile offspring. This is because of differences in genetic make-up, behaviour,
geographical location and morphological features such as variation in size of
sexual organs.
- For example, a donkey
and a horse can interbreed to produce a mule which is not fertile offspring. A
mule is neither a donkey nor a horse and cannot reproduce.
Therefore:
(i) Species
+species =Genus
(ii) Genus
+Genus =Family
(iii) Family +
family=Order
(iv) Order
+ order =Class
(v) Class
+ class=Phylum/division
(vi) Phylum/division
+ phylum/division=Kingdom
NOMENCLATURE
Is a system of assigning
or giving names to living organisms.
- Nomenclature is also
known as naming of living organism
- Any well-known
organisms on the earth has a name in various language.
- These names are called
Common names or local names.
Common names
Are those names that are
only familiar to the users of a certain language and not known all the world.
- Common names or local
names bring confusion among scientists in the world because they are only
familiar to the users of a certain language and not known all the world.
Therefore, in order to
avoid confusion among scientists, a biologist called Carolus Linnaeus
(1707-1778) introduced a system of giving scientific names to organism, the
system is known as
Binomial Nomenclature.
Linnaeus is referred to as a father of classification
BINOMIAL
NOMEMCLATURE
Is a system of naming
living organisms using two names, which are generic and specific name.
OR
Is a scientific process
of naming living organisms by using two names, which are genus and species
name.
- The first part of the
name represent the genus in which organism belongs and it is called generic
name
- The second part of the
name represents the species in which organism belongs and it is called specific
name
- The two names (generic
and specific name) form a scientific name or the name of a species
Importance
(advantages) of scientific names (Binomial nomenclature)
The following are the
advantages of using scientific names over common names:
(i) Prevents
confusion among scientists. This is because they are known all over the world.
(ii) Makes
the communication among biologists all over the world easier
(iii) Make scientists
all over the world to understand each other
Rules of writing
scientific names (Binomial Nomenclature) The following rules are observed when
writing scientific name:
(i) The
generic name should be written first followed by specific name
(ii) The
generic name should start with capital letter, while specific name should be
written in small letters.
(iii) In published
documents such as books, scientific name should be written in italics e.g.
Panther leo.
(iv) If handwritten,
scientific name should be underlined separately. E.g. Panthera leo
(v) All scientific names
should be written in Latin language otherwise should be Latinised.
Importance
(reasons) of using Latin language in scientific naming (scientific names)
(i) Makes scientists all
over the world to understand each other
(ii) Latin names prevent
confusion among scientists
Example of how
scientific names are written in documents
|
Common
name |
Genus
(Generic name) |
Species
(specific name) |
Scientific
name |
|
(i)
Domestic cat |
Felis |
Catus |
Felis
catus |
|
(ii)
Common frog |
Rana |
Temporaria |
Rana
temporaria |
|
(iii)
Leopard |
Panthera |
Pardus |
Panthera
pardus |
|
(iv)
Lion |
Panthera |
Leo |
Panthera
leo |
|
(v)
Onion |
Allium |
Cepa |
Allium
cepa |
|
(vi)
Garlic |
Allium |
Sativum |
Allium
sativum |
|
(vii)
Coconut palm |
Cocos |
Nucifera |
Cocos
nucifera |
|
(viii)
Mango tree |
Mangifera |
Indica |
Mangifera
indica |
|
(ix)
Pea plant |
Pisum |
Sativum |
Pisum
sativum |
|
(x)
Mimosa plant |
Mimosa |
Pudica |
Mimosa
pudica |
|
(xi)
Rat |
Rattus |
Rattus |
Rattus
rattus |
|
(xii)
Housefly |
Musca |
Domestica |
Musca
domestica |
|
(xiii)
Human being |
Homo |
Sapiens |
Homo
sapiens |
Question 1: The scientific name Lantana
camara refers to a green herbaceous plant. Other related plants include:
Lantana trifoliate and Vitex rifoliate.
(a) From
the list, identify the plants belonging to the same genus.
(b) From
the name Lantana camara, which name represents:
(i) Genus
name
(ii) Species
name
Question 2: (a) Define the term binomial
nomenclature
(b) Name
the main taxonomic units used in classification
(c) State
at least four rules used in binomial nomenclature
Question 3: (a) VITEX is a genus of a tree
found on Mt. Kilimanjaro. The specific name has
been Latinised to KENIESIS. Write the scientific name
of the tree.
(b) Explain why it is
important to use scientific names of organisms in Biology rather than common
names.
Differences
between scientific names and common (local) names
|
Scientific
names |
Common
(local) names |
|
They
are known all over the world |
They
are only familiar to the users of the a certain language |
|
They
are written following the rules |
No
rule of writing them |
|
Do not
bring confusion |
Brings
confusion |
MAJOR GROUPS OF
LIVING THINGS
The major groups of
living things are the kingdoms.
There are five (5) major
groups (kingdoms) into which all living things are grouped, namely;-
(i) Kingdom Monera
(ii) Kingdom protoctista
(iii) Kingdom Fungi
(iv) Kingdom
Plantae
(v) Kingdom
Animalia
Viruses however remain
unclassified because they possess both features of living and non-living
things.
- Kingdom Animalia
includes all animals such as Monkeys, hyenas, buffaloes, insects, birds, worm
etc.
- Kingdom plantae
include all plants such as potato plant, maize plant, mango trees, shrubs, moss
plant, fern plant etc.
- Kingdom Fungi includes
all fungi such as mushroom, bread moulds, pin moulds, yeast etc.
- Kingdom protoctista
includes all protoctista such as amoeba, paramecium, trypanosome, Euglena,
plasmodium.
- Kingdom Monera
includes all bacteria such as salmonella typhi, Treponema pallidum, Neisseria
gonorrhoea etc.
Most of organisms in
kingdom Monera and protoctista together with viruses are very small to be seen
by naked eyes, they are only seen by using a microscope, hence they are
microscopic and they are called microorganisms.
VIRUSES
A virus: is an extremely
small fragment of nuclei acid (DNA or RNA) surrounded by a protein coat.
- It is smaller than a
living cell. Virus is not a cell
- The study of viruses
is called virology
Example of
viruses
- Bacteriophage
- HIV
- Tobacco mosaic virus
- Influenza virus
Note: Viruses do not
belong to any of the five major kingdom of living things because they possess
the features which place them as living and non-organisms. Question: Why virus
is not classified among Kingdoms of living organisms?
Answer: Because, virus
shows features of both living things and non-living things. It shows features
of non-living things when outside the host cell and shows features of living
things when inside the host cell.
Features
(characteristics) that describe viruses as living things
(i) They
reproduce when inside the host cell
(ii) They
possess genetic materials either RNA or DNA
(iii) They grow,
excrete, feed and respire when inside the host cell
(iv) They
are specific to host like other parasites
(v) They
are capable of attacking other organisms and infect them.
Features
(characteristics) that describe viruses as non-living things
(i) They
cannot reproduce when outside the host cell
(ii) They
crystallize in the absence of a living host
(iii) They cannot grow,
excrete, feed or respire when outside the host cell
(iv) They do not have a
nucleus, cytoplasm or cell organelles
GENERAL
STRUCTURE OF VIRUSES
Viruses are composed of
strands of genetic materials (DNA or RNA), which forms a core A core is
enclosed by a protein coat called capsid as in bacteriophage. DNA or RNA are of
different size and shape
(i) RNA or DNA which may
be single stranded or double stranded. They form a structure called core.
(ii) Core is a structure
which is composed of genetic materials and enclosed by capsid
(iii) Capsid (protein
coat) is a protein shell that encloses genetic material in a virus
- It is a protective
coat that surrounding the core.
- Capsid are made up of
identical repeating units known as cashmeres.
(iv) A
nucleocapsid is a combined structure of core and capsid.
(v) Envelope
is an additional layer of lipoprotein layer around the capsid.
Diagrams of
Human Immunodefiency Virus (HIV)
.JPG)
Diagrams of
Corona virus
Diagrams of
Bacteriophage
The table below
showing examples of viruses and the diseases they cause to living
organisms
|
Virus |
Disease
|
|
Polio
virus |
Polio |
|
Human
Immunodeficiency Virus (HIV) |
AIDS
(Acquired Immune Deficiency Syndrome) |
|
Influenza
virus |
Influenza |
|
Tobacco
mosaic virus |
Tobacco
mosaic disease |
|
Measles
virus |
Measles |
|
Chicken
pox virus |
Chicken
pox |
|
Corona
virus |
Corona
Virus disease (COVID- 19) |
|
Herpes
simplex |
Genital
herpes |
|
Hepatitis
B virus |
Hepatitis
B |
General and
distinctive features of viruses
(i) They
are host specific. This means, a certain virus only attacks a specific host.
(ii) They
contain only one type of nucleic acid either DNA or RNA and not both.
(iii) They
cannot reproduce on their own. This because, they exist in a dormant state
while outside the host cell. They must attack a host cell and use the materials
in that cell to reproduce. This is called obligate parasitism.
(iv) They
do not have a nucleus, cytoplasm or cell organelles.
(v) They
are considered to be non-living. This because, they lack biochemical
characteristics of living thing. They never grow, feed, excrete or respire
while outside the host cell.
(vi) Most
of viruses are infectious. This means, they can cause diseases to their hosts.
NB: A virus which attacks and kills
bacteria is called a bacteriophage.
ECONOMIC
IMPORTANCE OF VIRUSES
Advantages of viruses
(i) Used
to make vaccines. For example, measles viruses are inactivated and used to
vaccinate people against measles disease and polio viruses are inactivated and
used to vaccinated people against polio disease.
(ii) Used
in the study of cellular and molecular biology. Viruses are used by scientists
to manipulate and investigate the functions of cells
(iii) Help
to control bacterial infections and diseases. E.g. bacteriophage
(iv) Used
in genetic engineering. In genetic engineering viruses are used as vectors to
transfer genes from one organisms to another for improving or treating the
defective genes.
(v) Used
in medical research.
(vi) Some
bacteria are used in biological control to eradicate pests such as insects
(vii) Used
in military as biological weapons to kill enemies
Disadvantages of
viruses
(i) They
attack and cause diseases to plants. For example, Tobacco mosaic disease,
tomato mosaic disease and cassava mosaic disease.
(ii) Viruses
attack and cause infections and diseases to animals. For example polio, AIDS,
measles, small pox, yellow fever, Hepatitis B, Covid 19, influenza etc.
(iii) Viruses destroy
living cells in humans hence weaken the body immunity
(iv) Viral
diseases are difficult to cure. This is because viruses keep on altering
themselves often. For example, there are many different viruses that cause
common cold and influenza. This makes it difficult to cure for these infections.
(v) Pathogenic
viruses reproduce very fast, leading to large-scale epidemics
REVISION QUESTIONS
1. (a)
Why a virus does not belong to any of the five kingdoms of living things (b)
Explain why viruses are considered as both living and non-living things (c)
What are the two components of a virus?
2. Describe
the structure of a bacteriophage
3. (a)
Mention five examples of the diseases caused by viruses (b) A virus that
attacks and kills bacteria is called? 4. Explain the economic importance of
viruses
5. (a)
What are viruses?
(b) List
any two general and distinctive features of viruses
(c) Mention
two advantages and three disadvantages of viruses
6. (a)
Describe the structures of viruses
(b) Do you consider
viruses to be living or non-living? Explain
KINGDOM MONERA
Kingdom Monera: this
kingdom is made up of bacteria and blue- green algae.
- They are the most
ancient and smallest organisms with a cellular structure. They occupy many
environments such as soil, dust, water and in the bodies of plants and animals - The scientific study of bacteria
is knowns as bacteriology.
Common members
of Kingdom Monera are bacteria such as:
- Vibrio cholerae
- Salmonella typhi
- Neisseria gonorrhea
- Mycobacterium
tuberculosis
- Treponema pallidum
General and
distinctive features of Kingdom Monera (bacteria)
(i) They
are unicellular. This means, they are made up of a single cell
(ii) They
are prokaryotic. This means that, their cell nuclei lack nuclear membranes
(iii) They
reproduce asexually by binary fission or through spores. Binary fission is a
form of asexual reproduction where by an organism splits into two equal halves.
(iv) They
have slimy outer layer. This layer protects them from parasites such as viruses
and predators such as protozoa
(v) Some
are free-living while others are parasites or saprophytes.
(vi) Free
living bacteria have flagella for movement
(vii) Some
bacteria occur singly while others occur in clusters known as colonies.
(viii) They
occur in various shapes. They occur in spiral shape, comma or vibrio shape, rod
shape, spherical shape and corkscrew shape.
THE
STRUCTURE OF BACTERIA
Structurally bacteria
are made up of:
(i) Flagella
(singular flagellum) for locomotion
(ii) Circular
DNA suspended in the cytoplasm without being enclosed by the nuclear membrane.
(iii) Slime capsule
(slimy layer) for protection
(iv) Cell
wall which is made up of protein and lipids but not cellulose to enclose the
cell membrane
(v) Cytoplasm
for storage of food and other chemicals
(vi) Plasma
membrane to enclose the cytoplasm
A GENERALIZED
STRUCTURE OF BACTERIUM
SHAPES OF
BACTERIA
Bacteria are classified
into five groups according to their shapes. These groups are:
(a) Rod
shaped bacteria called bacilli (singular: bacillus)
(b) Spherical
shaped bacteria called cocci (singular: coccus)
(c) Spiral
shaped bacteria called spirilla (singular: spirillum)
(d) Comma
shaped bacteria called vibrio (singular: vibrion)
(e) Corkscrew
shaped bacteria called spirochaetes
(a) Bacilli
These are rod-shaped
bacteria
- They can exist as a
single cell or in chain.
Example of rod-
shaped bacteria or bacilli
(i) Salmonella
typhi which causes typhoid
(ii) Escherichia
coli – cause cramping, diarrhoea and urinary tract infection
(iii) Bacillus anthracis
– causes anthrax
(iv) Mycobacterium
tuberculosis which causes tuberculosis
(v) Clostridium tetani
that causes tetanus
Diagram of
rod-shaped bacteria (Bacilli)
(b) Cocci
(singular coccus)
These bacteria are
spherical in shape
- The spherical bacteria
can be in a single cell (single cocci), a pair of cells (diplococcus), a
cluster of cells (staphilococcus),
a chain of cells (streptococcus).
Example of
spherical shaped bacteria
- Neisseria gonorrhoea
(an example of a diplococcus) – cause gonorrhoea
- Streptococcus pneumoniae
(an example of a diplococcus) – cause pneumonia disease
- Streptococcus pyogenes
(an example of streptococcus) – cause sore throat
- Streptococcus aureus
(an example of staphilococcus) – cause boils
Diagram of cocci
shaped bacteria
(c) Spirilla
(singular: spirillum)
These are spiral shaped
bacteria or resemble a corkscrew
Example of spiral shaped
bacteria
(i) Treponema pallidum –
causes syphilis
(ii) Campylobacter jejuni
– causes diarrhea in children
Diagram of spiral shaped bacteria
(d) Vibrio
(plural vibrion)
These are comma shaped
bacteria
Examples of comma shaped
bacteria
Vibrio cholerae – causes
cholera
Diagram of comma
shaped bacteria (vibrio)
(e) Spirochaetes (singular: spirochaete)
These are corkscrew
shaped bacteria
Example of corkscrew
shaped bacteria
Borrelia sp. – causes
Lyme disease and relapsing fever
Diagram of corkscrew shaped bacteria
TYPES
OF BACTERIA
There are two types of
bacteria, namely
(i) Pathogenic
bacteria
(ii) Non-
pathogenic bacteria
PATHOGENIC BACTERIA
These are bacteria that
cause infections and diseases.
- They live in the
bodies of plants or animals from which they get their nutrients and cause
diseases to the organisms.
Example of diseases
caused by pathogenic bacteria
- Tuberculosis
- Cholera
- Syphilis
- Gonorrhoea
- Typhoid
- Tetanus
CHARACTERISTICS
OF PATHOGENIS BACTERIA
Pathogenic bacteria have
the following features that facilitate the spread of disease and infections
(i) They have
fimbriae or Pilli.
Fimbriae
(Pilli):
are hair- like structures on the surface of some bacteria
Function of
fimbriae
- Used for attachment to
the host.
(ii) They have
flagella
Flagella- are tail like
structures that help pathogenic bacteria to move to the site where they can
survive
Function of
flagella
- Used as locomotary
structures for movement.
(iii)They
produce toxic substances.
- The toxins produced by
pathogenic bacteria harm the host cells and tissues and lead to severe
vomiting, diarrhoea, fever and muscle fatigue.
(iv) They have ability
to reproduce rapidly and destroy the host cells in a short period (v) They have
ability to release biofilm that resist certain types of medicines
NON-PATHOGENIC BACTERIA
These are harmless
bacteria even when they are in body of animal or plant.
- Such bacteria are
beneficial to plants, animals and the environment.
Examples of non-
pathogenic bacteria
- Rhizobium sp: Bacteria
found in the roots nodules of leguminous plants that convert atmospheric
nitrogen to nitrates in the soil.
- Escherichia coli:
Bacteria found in the human gut that manufacture vitamins K and B12
CHARACTERISTICS
OF NON-PATHIGENIC BACTERIA
(i) They
do not produce any toxic materials
(ii) They
are autotrophs
(iii) They are found in
leguminous plants that help to convert atmospheric nitrogen to nitrates
(iv) They
produce lactic acid that is used to give flavor to dairy foods like cheese and
yoghourt
(v) They
are found in the human gut helping to manufacture vitamins K and B12.
(vi) They
are found in the stomach of ruminants helping to secrete cellulose enzymes that
help to digest cellulose
REVISION
QUESTIONS
1. Give
at least four differences between pathogenic and non-pathogenic bacteria.
2. Give
the function of the following structures
(a) Fimbriae
(b) Flagella
3. Name
three species of harm bacteria
4. Why
are bacteria classified as kingdom Monera
ECONOMIC
IMPORTANCE OF KINGDOM MONERA (BACTERIA)
This includes the
advantages and disadvantages of bacteria.
Advantages (merits) of
kingdom Monera (bacteria)
(i) Used in genetic
engineering.
Some bacteria are used
in genetic engineering to produce hormones such as insulin and human growth
hormones.
(ii) Used as source of
oxygen in the atmosphere.
Some bacteria such as
autotrophic bacteria release oxygen in the atmosphere through the process of
photosynthesis. Oxygen released by autotrophic bacteria is important in
respiration process.
(iii) Used in production
of antibiotics
Some bacteria are used
to produce antibiotics, which are used to treat bacterial infections
(iv) Used as decomposers
hence add soil fertility
Some bacteria such as
saprophytic bacteria are used to decompose (break down) the dead bodies of
plants and animals to release important elements such nitrogen, carbon and
phosphorous which are very essential to plants growth and development.
(v) Used as environment
cleaner hence used to clean the environment. Some bacteria such as saprophytic
bacteria clean the environment by decomposing and neutralizing harmful
substances. Saprophytic bacteria feed on substances that are harmful to the
environment and in the process neutralize them, thereby making the environment
clean. For example, they are used to neutralize petroleum wastes from petroleum
industries, dyes and pesticides.
(vi) Bacteria in the gut
of ruminants are used in cellulose digestion
Bacteria living in the
gut of ruminants such as cow, goat, rabbit, and zebra are used to produce
cellulase enzyme which is used to digest cellulose which forms a large part of
the diet of ruminants.
(vii) Some bacteria are
used in production of vitamins K and B12 in the humans Bacteria living in the
human gut are used to synthesize vitamins K and B12 which are very important
for the health of human beings.
(viii) Bacteria are used
in fermentation process.
Some bacteria are used
in fermentation process to produce yoghurt, alcohol, cheese and vinegar in the
industries.
(ix) Nitrogen fixing
bacteria are used to convert atmospheric nitrogen to nitrates Bacteria living
in the root nodules of leguminous plants called rhizobium bacteria are used to
convert atmospheric nitrogen to nitrates which used to promote healthy growth
and development of plants.
DISADVANTAGES
(DEMERITS) OF KINGDOM MONERA (BACTERIA).
(i) Some
bacteria cause infections and diseases to animals.
Most of common
infections and diseases such as typhoid, cholera, tuberculosis, tetanus and
gonorrhea are caused by bacteria.
(ii) Some
bacteria cause infections and diseases to plants
Most of common plant
diseases such as leaf spot in cotton is caused by pathogenic bacteria called
Xanthomonas campestris, fire blight on pea and apple caused by Erwinia
amylovora.
Bacterial diseases in
crops cause reduction of in yield hence loss to farmers
(iii) Some bacteria
cause food spoilage.
Some bacteria cause food
decay by decomposing stored food and making it unsuitable for health.
(iv) Denitrifying
bacteria reduces nutrients in the soil.
Some bacteria living in
the soil called denitrifying bacteria convert nitrates from the soil to
nitrogen hence reduce plant nutrients from the soil
REVISION
QUESTIONS
1. Mention
three examples of beneficial bacteria
2. With
the aid of diagram, describe a generalized structure of a bacterium
3. What
are the economic importance of bacteria
4. (a)
List the different shapes of bacteria
(b) Draw
the shapes you have named in 4 (a) above.
(c) State
the locomotary structure of bacteria
5. Give
the scientific names of the bacteria that cause the following diseases
(a) Tuberculosis
(b) Typhoid
(c) Tetanus
(d) cholera
6. explain
ways in which organisms in Kingdom Monera are:
(a) useful
to man
(b) harmful
to man
7. explain
the economic importance of bacteria in the following fields:
(a) Agriculture
(b) Medicine
(c) Industries
(d) Lab
8. (a)
Give three difference between virus and bacteria
(b) Write
down four differences between pathogenic bacteria and non-pathogenic bacteria
(c) With
the aid of a well labelled diagram, describe the structure of bacteria and give
three advantages and disadvantages of bacteria in daily life.
KINGDOM PROTOCTISTA
Kingdom Protoctista:
this kingdom comprises all protoctists or protozoans such as amoeba, euglena,
plasmodium, paramecium and Trypanosoma.
Example of common
representative members (protozoans) of kingdom protoctista
- Plasmodium
- Paramecium
- Amoeba
- Euglena
- Trypanosoma
GENERAL
AND DISINCTIVE FEATURES OF KINGDOM PROTOCTISTA
Members of Kingdom
Protoctista have the following characteristics:
(i) They are eukaryotic.
This means that, their cells have true nuclei
(ii) Most of them are
unicellular while few are multicellular.
(iii) Most live in or
near water or in moist places
(iv) Some are
autotrophic while others are heterotrophic. Autotrophic protoctists are able to
manufacture their own food while heterotrophic protoctists obtain their
nutrients from other organisms
(v) Some are mobile
while others are sessile
(vi) Some reproduce
asexually while others reproduce sexually. But some reproduce both sexually and
asexually
(vii) Most of them they
have locomotary structures for movement.
Example of protoctists
and their appropriate locomotary structures: Organism (Protoctists)
Locomotary structure used
(i) Amoeba
Pseudopodia
(ii) Euglena
Flagellum
(iii)Paramecium
Cilia
(iv) Plasmodium
No locomotary structure
(v) Trypanosoma
Flagellum
PHYLA OF KINDOM
PROTOCTISTA
Kingdom protoctista is
subdivided into several phyla, namely
(i) Phylum
Rhizopoda e.g. Amoeba
(ii) Phylum
Euglenophyta e.g. Euglena
(iii) Phylum Ciliophora
e.g. Paramecium
(iv) Phylum
Apicomplexa e.g. Plasmodium
(v) Phylum
Zoomastigina e.g. Trypanosoma
1.
PHYLUM RHIZOPODA
This phylum comprises
free living and parasitic unicellular organisms called amoeba
Example of
representative members of phylum Rhizopoda
- Parasitic Entamoeba
histolytica
- Free living amoeba living
in sea water, fresh water and in the soil such as green algae, red algae and
brown algae.
CHARACTERISTICS
OF AMOEBA
(i) Most
are free living while others are parasitic.
(ii) Free
living amoeba feed on plants and animals matter
(iii) They
have pseudopodia which are used for both locomotion and feeding
Pseudopodia (means false
limbs): These are projections which help amoeba to move and capture food.
(iv) They
have contractile vacuoles which regulates the amount of water in the fresh
water amoeba.
(v) They
form temporary vacuole (food vacuoles) to hold and digest food particles
(vi) They
excrete waste products such as urea and ammonia by simple diffusion
(vii) They
constantly change shape (have no permanent shape)
(viii) They
are unicellular organisms (single celled organisms)
(ix) They
reproduce asexually by binary fission
(x) They
exchange oxygen and carbondioxide gas by diffusion
(xi) They
have two layers of cytoplasm: a viscous layer called ectoplasm and a more fluid
internal layer called endoplasm.
(xii) They
reproduce by binary fission
STRUCTURE OF
AMOEBA
Amoeba is a single
celled organism (unicellular organism) which contains the following structures:
(i) Cell
membrane to protect the inner parts of the amoeba
(ii) Contractile
vacuole to control amount of water in the organism.
(iii) Temporary food
vacuole to hold and digest food particles
(iv) Pseudopodium for
both locomotion and feeding.
(v) Nucleus
takes active part in reproduction and conducts the functions of the cell body.
(vi) Cytoplasm
divided into two layers namely ectoplasm and endoplasm.
Function of
Ectoplasm
- Helps amoeba to
maintain its body shape
- Helps amoeba in
producing pseudopodia
Function of
endoplasm
- Serves as the site of
the cellular processes.
- Helps amoeba in
producing pseudopodia
- Site where organelles
such nucleus, contractile vacuole and food vacuoles are located
A WELL LABELLED
DIAGRAM OF AMOEBA
Advantages of
Amoeba
(i) Used
in laboratories to study cell structure and function.
(ii) Amoeba
kill and feed on harmful bacteria that would cause diseases.
(iii) Used as food by
other organisms in water
Disadvantages of
Amoeba
- Amoeba because
diseases e.g. Entamoeba histolytica causes amoebic dysentery in human being
Entamoeba gingivalis causes teeth and gum diseases (dental diseases).
2.
PHYLUM EUGLENOPHYTA
This phylum consists
unicellular autotrophic organisms.
- Most of members in
this phylum are aquatic. They live in fresh water and marine water
- Euglena sp. cause
green scum that often appears on stagnant water
Examples of organisms
found in phylum Euglenophyta
- Euglena gracilis
CHARACTERISTICS
OF EUGLENA
(i) They
are unicellular.
(ii) They
are eukaryotic cells.
(iii) They
have eyespots for detection of light intensity.
(iv) They
have chloroplasts contain chlorophyll for photosynthesis.
(v) They
live in fresh and marine water.
(vi) They
have flagella for movement.
(vii) They
reproduce asexually.
(viii) They
possess both plant and animal characteristics. The plant characteristic is
possession of chloroplasts contain chlorophyll for photosynthesis. The animal
characteristic includes ability to move using a flagellum, an eye spot for
light intensity detection and gullet for ingesting food
(ix) They
have pellicle which offers protection and allows euglena to change shape.
Pellicle is an outer cover which surrounds the cytoplasm of euglena since they
lack cell wall.
STRUCTURE OF
EUGLENA
Euglena is a single
celled organism (unicellular organism) made up of the following structures:
(i) Pellicle
to offer protection and allow euglena to change shape
(ii) Eyespot
to detect light intensity
(iii) Contractile
vacuole to control amount of water in the organism.
(iv) Gullet to ingest
food
(v) Flagellum for
locomotion.
(vi) Chloroplasts
which contain chlorophyll for photosynthesis
(vii) Nucleus
to control body activities and processes such as asexual reproduction.
A WELL LABELLED
DIAGRAM OF EUGLENA
ADVANTAGES OF EUGLENA
(i) Euglena are used to
treat sewage. This is because of their unique capacity to change from being
autotrophic to heterotrophic.
(ii) Euglena are used as
source of food to fish and other aquatic animals e.g. Phytoplankton euglena
(iii) Euglena are used
to produce oxygen gas. Oxygen produced by euglena through photosynthesis is
used by aquatic animals for respiration and for sewage treatment.
DISADVANTAGES OF
EUGLENA
- Euglena blooms and
produce toxins which kill fish and other aquatic organisms.
3.
PHYLUM CILIOPHORA
This phylum consists of
unicellular heterotrophic organisms which contain short projections called
cilia.
- Most of members in
this phylum are found in aquatic habitats (live in water)
- Members of this phylum
are also called ciliates because they have cilia for movement.
Examples of organisms
found in phylum Ciliophora
Paramecium.
CHARACTERISTICS
OF PARAMECIUM (PHYLUM CILIOPHORA)
(i) They
are unicellular and slipper-shaped.
(ii) They
are heterotrophs.
(iii) They
have cilia for movement and for collecting food.
(iv) They
possess two nuclei, the micronucleus and macronucleus. The micronucleus is
smaller and used in asexual reproduction while macronucleus (mega nucleus) is
larger and controls body activities and processes.
(v) The
body of paramecium is covered (enclosed) by pellicle (a stiff but elastic
membrane)
(vi) They have oral
groove to ingest food.
(vii) They
have two contractile vacuoles to regulate amount of water in the cytoplasm
(viii) They
reproduce either asexually or sexually depending on the environmental
conditions. Asexual reproduction takes place when enough nutrients are
available while sexual reproduction takes place under conditions of starvation.
(ix) They
have anal pore to egest undigested food
(x) They
have food vacuole which hold and digest food particles.
(xi) They
feed on bacteria and other microorganisms
STRUCTURE OF
PARAMECIUM
Paramecium is a single
celled organism (unicellular organism) made up of the following structures:
(i) Pellicle
to enclose and offer paramecium protection
(ii) Contractile
vacuole to control amount of water in the cytoplasm by removing excess water.
(iii) Oral
groove to ingest food particles such as bacteria
(iv) Cilia for movement
and to create a feeding current.
(v) Macronucleus to
control body activities and processes
(vi) Micronucleus used
in asexual reproduction.
(vii) Food
vacuole formed to hold (store) and digest food particles.
(viii) Anal
pore to eliminate undigested food materials
A WELL LABELLED
DIAGRAM OF PARAMECIUM
ADVANTAGES OF
PARAMECIUM
(i) They
are used as food by small water animals.
(ii) They
help to clean up small particles of debris in water as well as feeding on small
animals.
DISADVANTAGES OF
PARAMECIUM
(i) Paramecium
called Balantidium coli cause disease. They invade and destroys the lining of
the intestine , causing a disease called balantidiasis
(ii) They
delay decomposition of sewage by feeding bacteria which decompose sewage.
REVISION
QUESTIONS
1. (a) In which ways are
Euglena similar to and yet different from paramecium?
(b) List
two features showing that paramecium belong to Kingdom Protoctista?
(c) Explain
any three characteristics of paramecium
4.
PHYLUM APICOMPLEXA
This phylum consists of
unicellular and parasitic organisms.
Example of organisms
found in phylum Apicomplexa
Plasmodium
CHARACTERISTICS OF
PLASMODIUM
(i) They
are unicellular.
(ii) They
are parasite with a complex life cycles involving the host and the vector.
(iii) They have no
structures for movement
(iv) They
reproduce sexually in the host and sexually by multiple fission in the vector.
(v) When
plasmodium enters the human body, it attacks the red blood cells and liver
cells.
(vi) They
are eukaryotes.
Effects of
plasmodium
- Plasmodium parasite
causes malaria. Malaria can lead to inflammation and rapture of the spleen and
miscarriages. It can also cause anaemia due the destruction of red blood cells
and severe malaria cause death.
DIAGRAM OF
PLASMODIUM
Advantages of
plasmodium
- Used by scientists in
the laboratories for research.
Disadvantages of
plasmodium
- They cause malaria to
human beings
5.
PHYLUM ZOOMASTIGINA
This phylum consists
unicellular flagellate protozoans.
- Generally members of
this phylum are found in the intestine, but can also found in the blood or in
the heart, for example Trypanosoma
DIAGRAM OF
TRYPANOSOMA
CHARACTERISTICS
OF TRYPANOSOMA
(i) They
are unicellular, slender, elongated and dorsal ventrally flattened in shape.
(ii) They
are heterotrophic
(iii) They
are parasites in wild animals, domesticated animals and human beings.
(iv) Have
a mass of mitochondrion in a structure called kinetoplast
(v) The
body is covered with a thin, elastic and firm pellicle
(vi) Most
of them reproduce asexually by binary fission while inside the host
(vii) Some
have an undulating membrane for locomotion
DISADVANTAGES OF
TRYPANOSOMA
- Trypanosoma brucei is
the causative agent of the disease called trypanosomiasis or sleeping sickness.
- This disease affects
mostly African countries. It can be transmitted through bites of a vector
called tsetse fly or through blood contact from an infected individual.
ECONOMIC
IMPORTANCE OF KINGDOM PROTOCTISTA
This includes both
advantages and disadvantages of Kingdom Protoctista
ADVANTAGES
(MERITS) OF KINGDOM PROTOCTISTA
(i) They release oxygen
gas to the atmosphere.
Photosynthetic
protoctists such as euglena and algae release oxygen gas during photosynthesis.
Oxygen gas produced is
used by aquatic organisms in breathing process
(ii) They are used in
medical research.
Most of protoctists are
used by scientists in medical research, this is because they can be grown in
large numbers under controlled condition without occupying large area.
(iii) They are used as
fertilizer
Some protoctists such as
Brown algae (sea weeds) have been used as fertilizer because they contain high
amount of potassium and other nutrients. These nutrients are useful for plant
growth.
(iv) They produce
alignic acid used to manufacture ice cream.
Some protoctists such as
algae produce alignic acid which is used in production of ice creams,
cosmetics, car polishes and paints.
(v) They are source of
food for many aquatic organisms.
Some protoctists such as
euglena are eaten by aquatic organisms such as fish as food.
(vi) They are used in
sewage treatment.
Some protoctists such as
Euglena are used in sewage treatment this is because of their unique capacity
to change from being autotrophic to heterotrophic.
(vii) They are used in
laboratories to study cell structure and function
Some protoctists such as
amoeba are used by scientists in the laboratories in studying cell structure
and function.
DISADVANTAGES
(DEMERITS) OF KINGDOM PROTOCTISTA
- They cause diseases to
human being and other animals.
Parasitic protoctists
attack and cause disease to animals for example plasmodium cause malaria to
human and Entamoeba histolytica cause amoebic dysentery, sleeping sickness,
tooth decay
REVISION
QUESTIONS
1. Match
the item in List A with the correct item in List B by writing the letter of the
correct response from List B below the number of the corresponding item in List
A in the table provided.
|
LIST A |
LIST B |
|
|
2. (a)Describe
the characteristics of Trypanosoma
(b) Distinguish between
Apicomplexa and other protoctists
3. Draw
a well labelled diagram of a paramecium
4. How are euglena
beneficial to the environment?
5. How
does amoeba (a) Move?
(b) Feed?
(c) Reproduce?
6. Explain
the effects of the following organisms to humans
(a) Amoeba
(b) Plasmodium
(c) Trypanosoma
7. Study
the diagrams below and answer the following questions.
(a) Give
the common names for organisms X and Y
(b) State
the phyla in which organism X and Y belong
(c) Give
two advantages of organism X
(d) Name
the parts labelled A – F in organism X and parts labelled H – L in organism Y.
