TOPIC 5: CLASSIFICATION OF LIVING THINGS | BIOLOGY FORM 1

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TOPIC 5: CLASSIFICATION OF LIVINGTHINGS

By the end of this topic, you should be able to; –

– Explain the concept of classification

– Group living things according to their similarities and differences

– Explain the importance of classifying living things

– Outline types of classification system and their differences

– Explain merits and demerits of each type of classification system

– Mention the major groups of living things

– Outline ranks of classification

– carry out practical activities to group organisms into their respective major groups

– Explain general and distinctive features of viruses

– Describe the structure of viruses

– Outline advantages and disadvantage of viruses

– Explain general and distinctive features of the kingdom monera

– Describe structures of the representative organisms of the kingdom Monera

– Outline the advantages and disadvantages of bacteria

– Outline the characteristics of pathogenic and non-pathogenic bacteria

– Explain general and distinctive features of the kingdom protoctista

– Mention phyla of the kingdom protoctista

– Describe the structure and disadvantages of Amoeba, Euglena, Paramecium and plasmodium

 

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)

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
  1. Protoctists that moves by means of temporary projections called pseudopodia.
  2. The only Kingdom of Prokaryotic organisms.
  3. An organism that cause malaria
  4. The structures that a paramecium uses for movement.
  5. A disease-causing particle that consists of nucleic acid and a protein coat.
  6. The structure the euglena sp. Uses for movement.
  7. An organism whose cells do not contain nucleus or membrane bound organelles
  1. Flagellum
  2. Bacterium
  3. Monera
  4. Amoeba
  5. Virus
  6. Cilia
  7. Plasmodium
  8. Eukaryotes

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.

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