Integrated Science SME

Key Unit competence: Apply the basic knowledge of classification
                                              to group living organisms in three domains
Introductory Activity 3
Observe organisms in the figure below and answer asked questions:

3.1.Taxonomic hierarchy and Three domains of life:
Archaea, Bacteria and Eukarya

3.1.1.The taxonomic hierarchy

Activity 3.1.1

You are provided with cards written on a list of words such as continent,
district, country, cell, province, sector, village and family.
1. Arrange the above words in increasing size
2. What is your opinion about the people of the same family and those
in the whole country?
3. Compare your arrangement in 1. above with possible groupings of
organisms in biological taxonomic hierarchy.

Taxonomy is the study of classification of living organisms in taxonomic
levels called taxa (singular: taxon). In biological classification, these taxa
form a hierarchy. Each kind of organism is assigned to its own species, and similar species are grouped into a genus (plural: genera). Similar genera are grouped into a family, families into an order, orders into a class, classes into a phylum (plural: phyla) and phyla into a kingdom. The hierarchy classification starts from the largest group, the domain.

The eight taxonomic levels of classification are known as taxa (taxon in
singular), these include: Domain, Kingdom, phylum, class, order, family, genus and species. As one moves down the taxonomic hierarchy, it follows that the number of individuals decreases but the number of common features increases.

Application activity 3.1.1
1. What are the three domains of living things?
2. Discuss the ways in which a domain differs from a kingdom?

3.1.2. Three domains: archaea, bacteria and eukarya
Activity 3.1.2
Visit the computer lab and search the characteristics archaea, bacteria
and eukaryadomains and present them on manila paper.

There are three domains used by biologists to divide organisms into three large groups based on their cell structure. The domain is the highest taxon in the hierarchy. The prokaryotes are divided between the domains Eubacteria and Archaebacteria, while all the eukaryotes are placed into the domain Eukarya.

a). Domain Eubacteria
Domain bacteria include prokaryotic organisms as their cells have no true nucleus.
They are all microscopic that vary in size between 0.2 to 10 micrometers.
The characteristic features of bacteria are:
• Cells with no true nucleus
• DNA exists in circular chromosome and does not have histone proteins
associated with it.
• No membrane-bound organelles (mitochondria, endoplasmic reticulum, Golgi body, chloroplasts)
• Contain mesosomes as infolding of membrane and acts as sites for
respiration as they lack mitochondria.
• Ribosomes (70 S) are smaller than in eukaryotic cells
• Cell wall is always present and contains peptidoglycans in place of
cellulose
• Cells divide by binary fission
• Usually exist as single cells or colonies.

b). Domain Archaea (Archaebacteria)
This includes bacteria that live in extreme environments where few other
organisms can survive, like in volcanic hot springs and black organic mud totally devoid of oxygen.

They are classified according to the environments they live in:

• Methanogenic bacteria that live in habitats deprived of oxygen and give
off methane as a product of metabolism, for example those that live in
the guts of ruminant animals.
• Halophilic bacteria live only in salty conditions
• Thermoacidophilic bacteria tolerate extreme acid and temperature that
exceed boiling point of water and a pH below 2.

c). Domain Eukarya
All the organisms classified into this domain have cells with true nuclei and membrane-bound organelles. It includes the four remaining kingdoms: protists, fungi, plantae and Animalia. Their characteristic features are:
• Cells with a nucleus and membrane-bounded organelles
• linear DNA associated with histones arranged within a chromosome in
the nucleus
• Ribosomes (80S) in the cytosol are larger than in prokaryotes, while
chloroplasts and mitochondria have small ribosomes (70S ribosomes),
like those in prokaryotes.

• Chloroplast and mitochondrial DNA is circular as in prokaryotes
suggesting an evolutionary relationship between prokaryotes and
eukaryotes
• A great diversity of forms: unicellular, colonial and multicellular
organisms
• Cell division is by mitosis.
• Many different ways of reproduction including asexually and sexually.

Application activity 3.1.2
1. What are the six kingdoms of living things as they are now identified?
2. List three domains of living organisms.
3. Which kingdoms include only prokaryotes? Which kingdoms include
only heterotrophs?
4. How do domains and kingdoms differ?
5. Suppose that you discover a new single-celled organism which has
a nucleus, mitochondria and a giant chloroplast. In which kingdom
would you place it? What are your reasons?
6. It is confirmed that: “Some bacteria can survive in extreme
temperatures such as hot springs”. Justify this statement.

3.2. Characteristic features of the kingdoms

Activity 3.2
Observe carefully the photo of organisms below and answer asked
questions.

1. Identify the characteristics of organism found on photo.

2. Among other organisms you know, apart from that you are seeing on photo, search their characteristics and present them in your exercises book

Living organisms are classified in five kingdoms namely Protoctista, Fungi, Plantae, Monera and Animalia.

3.2.1. Characteristic features of the kingdom Protoctista

This kingdom is made up of a very diverse range of eukaryotic organisms, which includes those that are often called protozoans and algae. Living things such as paramecium, amoeba, euglena, algae and plasmodia belong to the kingdom Protoctista.

The characteristic features of protoctists are listed according to the different phyla due to their diverse range:
• Rhizopus that have pseudopodia for locomotion. Example, amoeba.
• Flagellates which are protoctista which move by using flagella. Example, Trypanosoma.
• Sporozoans which are mainly parasitic organisms that reproduces by
multiple fission. Example plasmodium.
• Ciliates are protoctista which move with cilia. Example paramecium.
• Euglenoid flagellates which are organisms with flagella but with a
biochemistry quite distinct from that of flagellates. Example Euglena.
• Green algae are photosynthetic protoctista with chlorophyll pigments.
Example chlorella.

• Red algae are photosynthetic protoctista with red pigment as well as
chlorophyll. Example, chondrus
• Brown algae which are photosynthetic protoctista with brown pigments
as well as chlorophyll. Example Fucus and sea weed.

3.2.2. Characteristic features of the kingdom fungi

Fungi are all heterotrophic, obtaining energy and carbon from dead and
decaying matter or by feeding as parasites on living organisms. There is a
vast range in size from the microscopic yeasts to macroscopic fungi.

Other characteristic features of fungi are:
• Heterotrophic nutrition.
• They use organic compounds made by other organisms as their source
of energy and source of molecules for metabolism.
• Reproduce asexually by means of spores and sexually by conjugation.
• Simple body form, which may be unicellular or made up of long threads
called hyphae (with or without cross walls).
• Large fungi such as mushrooms produce large compacted masses of
hyphae known as fruiting bodies to release spores.
• Cells have cell walls made of chitin or other substances.

3.2.3. Kingdom Plantae

Plants are all multicellular photosynthetic organisms. They have complex
bodies that are often highly branched both above and below the ground.
Characteristic features of plants are:
• Multicellular eukaryotes with cells that are differentiated to form tissues
and organs.
• Few specialized cells.
• Cells have large and often permanent vacuoles for support with cell
walls made of cellulose.
• Most plants store carbohydrates as starch or sucrose.

3.2.4. Kingdom Animalia

Animals are multicellular organisms that are all heterotrophic with different methods of obtaining their food.

Organisms in this kingdom have other additional features:
• Different types of specialized cells.
• Cells do not have chloroplasts and cannot photosynthesize (although
some, such as coral polyps have photosynthetic protoctists living within
their tissues).
• Cell vacuoles are small and temporary (for example lysosomes and
food vacuoles).
• Cells do not have cell walls.
• Communication is by the nervous system

3.2.5. Kingdom Monera
Organisms in this kingdom are unicellular, that do not have a nucleus. They are prokaryotic. They are the smallest and simplest organisms. Some of them stick together to form chains or clusters while others are single cells. The figure below shows a typical structure of a bacterial cell which contains all the main features of prokaryotes.
Although some of them are harmful in causing human diseases, others are beneficial species that are essential to good health, as they are involved in food industry, medicine and in pharmacy.

3.2.6.Common bacterial diseases in plants and animals

Activity 3.2.6
Suppose there is cholera outbreak in your village and the executive
secretary invited you to sensitize people about preventive measures
against cholera. Prepare a brief presentation for this purpose and include causes, mode of transmission and then preventive measures

The bacteria that causes diseases are harmful to humans and other animals and are referred to as pathogenic bacteria. The body is a home to many millions of bacteria. Some are useful while others are harmful to humans. A bacterial disease is caused by entry of bacteria into a host which can grow and flourish in the host, causing harm to the host. Bacteria cause diseases like cholera, tuberculosis (TB), typhoid fever, pneumonia, tetanus, and diphtheria, and bacterial meningitis, tooth decay in humans and anthrax in cattle.

3.2.7. Economic importance of bacteria
Activity 3.2.7
When an animal dies in a forest, it decays after a certain period of time.
Once a farmer grows beans in the soil with such dead animal decay,
beans grow well.
1. What cause the dead animal to decay?
2. Why the beans have grown well?
Bacteria are economically important as these microorganisms are used by humans for many purposes and are harmful in causing disease and spoiling food. Bacteria are useful in many ways:

a. Biotechnology
Bacteria are used in biotechnology for example in the manufacturing
industries. They are used to manufacture products such as ethanol, acetone, organic acid, enzymes, and perfumes. In the chemical industry, bacteria are most important in the production of pharmaceuticals. For example, Escherichia coli is used for commercial preparation of riboflavin and vitamin K.

b. Genetic engineering
Bactria are used in genetic engineering through the manipulation of genes, also called recombinant DNA technology. In this case, bacterial cells are transformed and used in production of commercially important products for example, production of human insulin used against diabetes.

c. Decomposition of dead organisms
In addition, bacteria are important in decomposition of dead organisms and animal wastes such as feces to form organic matter. This process improves soil fertility and plays an important role in mineral recycling in an ecosystem.

d. Fibre retting
Some bacteria including Clostridium butylicum are used to separate fibres in a process called retting. In this process, fibres are formed to make ropes and sacks.

e. Nitrogen fixation
Some other bacteria are used to fix nitrogen in form of nitrates into the soil. For example, Rhizobium bacteria which lives in root nodules of leguminous plants. Such bacteria help in improvement of soil fertility especially during nitrogen cycle.

f. Digestion
Some bacteria living in the gut of ruminant animals such as cattle, horses and other herbivores secrete cellulase, an enzyme that helps in the digestion of the cellulose of plant cell walls. Cellulose is the major source of energy for these animals. Another example is Escherichia coli that live in the human large intestine which synthesizes vitamin B and releases it for human use.

g. Biological control
Some bacteria are used as biological agents in biological pest control such as Bacillus thuringiensis (also called BT) instead of pesticides. Because of their specificity, these bacteria are regarded as environmentally friendly, with little effect on humans, wildlife, pollinators, or other beneficial insects.

Application activity 3.2
1. Discuss 4 characteristics for each among the five kingdoms
2. What are the three methods that protists use to obtain food?
3. Identify three characteristics of protists
4. The following is a list of organisms belonging to various kingdoms:
housefly (Musca domestica), maize (Zea mays), Frog (Rana spp),
Bat and Eagle.
a) Classify these organisms into their kingdoms.
b) Name any two organisms that are not closely related and give a
reason.
5. How are fungi different from members of kingdom plantae?
6. Mr. Green lives in one of the slums in a certain city. He prepares and
sells chapattis on street. He is usually very clean, but one morning,
he is late for work so he does not bother to wash his hands after
visiting the toilet. That day he prepares 400 chapattis all of which are
sold. Few hours later, his customer Sandra suffered from a disease
with the following signs and symptoms: severe diarrhea, excessive
loss of water leading to dehydration, and vomiting, after five days.
Later, all his customers were rushed and admitted in hospital due to
the same problem.
a) Suggest the disease that Mr. Green’s customers were suffering
from and what caused the disease?
b) Name three other ways this disease might be spread around city.
c) After reading this scenario, what message do you have for people
who are like Mr. Green?
d) Suppose you were the health officer for the area in town with such
a problem. What steps would you take to prevent the disease
from spreading further?
e) House flies are described as vectors. Describe, how houseflies
transmit diseases tohumans.
7. Discuss 6 economic importances of bacteria.
8. Explain how bacteria are used as biological control.

3.3. Classification of viruses and their economic importance
Activity 3.3
Visit the internet and conduct a research to explain the following:
a). The classification of viruses
b). The economic importance of viruses.

3.3.1. Classification of viruses
Viruses can be classified according to:
• Type of nucleic acid molecules they have. Most animal viruses contain
RNA while plant viruses contain DNA.
• Type of host cell: plant or animal viruses as they are specific to their hosts.
• Presence or absence of the envelope: Plant viruses’ bacteriophage
are no enveloped while animal viruses like HIV and influenza virus are
enveloped.

3.3.2.Characteristics of viruses
Viruses are microorganisms whose structure is only visible with electron
microscopes. A typical virus consists of DNA or RNA within a protective
protein coat called capsid which provides protection. Viruses become active in metabolism only once insidethe host cell.When they infect cells, they use biochemical machinery and proteins of the host cellto copy their nucleic acids and to make proteins coats often leading to destructionof the host cells. The energy for these processes is provided by the ATP from the hostcell.

Because viruses do not consist of cells, they also lack cell membranes,
cytoplasm, ribosomes, and other cell organelles. Without these structures, they are unable to make proteins or even reproduce on their own. Instead, they must depend on a host cell to synthesize their proteins and to make copies of themselves. Viruses infect and live inside the cells of living organisms. They are also regarded as parasites since they depend entirely on living cells for their survival. Although viruses are not classified as living things, they share two important traits with living things: They have genetic material, and they can evolve.

Application activity 3.3

1. What is meant by the term virus?

2. State the main components of a virus.

3. Describe the two ways how viruses cause an infection

4. Differentiate between a bacteriophage and a retrovirus?

5. Do you think viruses should be considered as a form of life? Give reasons for your answer.

3.4. Dichotomous keys for identification of organism

Activity 3.4

The figure below represents different types of plant leaves. Make a classification of these plants based on the external structure of the leaves.

The dichotomous key is also called biological identification key. It is made up of a series of contrasting statements called leads indicated by the numbers 1, 2, 3…where each lead deals with a particular observable characteristic. The characteristics used in keys should be readily observable morphological features which may be either qualitative, such as shape of abdomen, nature of legs and color, or quantitative, such as number of antennae, number of pairs of legs and length of the antennae in case of arthropods. It is essential to note that size and color are often less considered to both can be influenced by the environment, the season, the age or state of the organism at the time of identification.

3.4.1. Guidelines used in construction of a dichotomous key
The following guidelines must be considered while constructing a dichotomous key.
• Use morphological characteristics which are observable as much as
possible such as leaf venation, nature of margin, apex, lamina and
nature or length of the petiole (leaf stalk).
• Start with a major characteristic that divide the organism or the specimen into two large groups such as the type of a leaf.
• Select a single characteristic at a time and identify it using a number
for example: simple leaf………go to 2, compound leaf………go to 5.
This means that in 2 you will deal with only simple leaves and 5 only
compound leaves.
• Use similar forms of words for two contrasting statements for example
at 2: leaf with parallel venation …………go to G and leaf with network
venation ………go to 3.
• The first statement should always be positive.
• Avoid generalizations or overlapping variations, be specific and precise
to the point.

Example
• Collect leaves from the following plants: cassava, avocado, jacaranda,
cassia, hibiscus bean, maize or paspalum grass,
• Label different leaves collected as, A, B, C, D, E, F and G
• Observe and familiarize with the specimens before starting the
experiment to minimize errors during the identification process
• Make a table summarising the specimens and steps followed to identify
each of them.
• Construct a dichotomous key basing on the observable features
(characteristics) and table of steps followed.
Solution: The dichotomous key of specimens A, B, C, D, E, F and G.
1a) Simple leaves ----------------------------------------------------------------go to 2
b) Compound leaves ------------------------------------------------------------go to 5
2 a) Parallel venation ------------------------------------------------------------G
 b) Network venation -----------------------------------------------------------go to 3

3 a) Simple digitate ---------------------------------------------------------------------A
 b) Non simple digitate ---------------------------------------------------------go to 4
4 a) Leaf with serrated margin ------------------------------------------------------E
 b) Leaf with smooth margin ---------------------------------------------------------B
5 a) Leaf with three leaflets (compound trifoliate)------------------------------F
 b) Leaves with more than three leaflets -----------------------------------go to 6
6 a) Pinnate leaf ------------------------------------------------------------------------D
b) Bipinnate leaf ---------------------------------------------------------------------- C

3.4.2. Common features used for identification of animals
Animals are classified basing on the following features:
• Locomotory structures such as legs, wings and fins
• Antennae (presence, nature and number)
• Presence or absence of eye and eye type
• Number of body parts for example insects have three body parts
• Body segments (nature and number)
• Body surface structures such as fur, hair, feathers and scales
• Feeding structures such as mouth parts in arthropods for example in
insects
• Type of skeleton present such as endoskeleton, exoskeleton and
hydrostatic

3.4.3. Common features used for identification of plants
Plants can be classified basing on the following features:
• The leaf structure such as: nature of apex, margin, venation, lamina
and petiole
• The flower structure including inflorescence type, flower shape and
number of floral parts
• The type of stem (woody, fleshy and herbaceous), shape (rectangular,
cylindrical) and texture of the stem (smooth, spiny and thorny) …
• The type of root system, tap root, storage root, fibrous roots…

Precaution
• Care must be taken while collecting and handling some organisms
because some are poisonous, have thorns and others are able to sting
• Collection of specimen should be done a day or few days before the
experiment depending on nature of the experiment
• Avoid and try to minimize where possible, uprooting, cutting down or
plucking and pruning of plants as this may threaten the biodiversity as
well as result into environmental degradation

Application activity 3.4
Read and interpret the dichotomous tree below and use it to answer the
following questions.

1. Specify the phylum of kingdom animalia represented by the above
dichotomous tree? Give one observable reason to support your
answer.
2. According to this dichotomous tree, which characteristic feature was
used to classify different insects?
3. Which observable characteristic feature distinguishes between a
spider and a mosquito?
4. How does a millipede differ from a centipede?
5. To which classes do a millipede and a centipede belong?
6. Which class of arthropods is not represented on figure 2.12?

Skills lab 3
• Move around the school compound and select a small plant which you
know the scientific name and the the taxonomic hieracrchy.
• Place the plant between two sheets of newspaper and in between
some heavy books. ...
• When your plant is pressed, remove it from the newsprint and carefully
glue it to the 11x16 paper. ...
• Take your printer paper, cut a 3” x 4” piece of paper and glue this onto
the bottom right corner of your herbarium sheet.
• Label your work (Taxonomic hierarch, Sientific name, Local name,
date and your name)

End unit assessment 3
1. Which one of the following living organisms belongs to Domain Bacteria?
a). Euglena
b). Vibrio cholerae
c). Paramecium
d). Moulds
2. The group of classification where organisms resemble one another and are
capable of interbreeding together to produce viable offspring is known as:
a). Species
b). Kingdom
c). Genus
d). Phylum
3. Which one of the following is not a kingdom of living organisms?
a). Monera
b). Animalia
c). Annelida
d). Protoctista
4. Which one of the following is a characteristic feature common to fish, reptiles
and birds but absent in mammals?
a). Possession of scales
b). Has no limbs
c). Possession of feathers
d). Undergo internal fertilization
5. Which one of the following statements about fish is not correct?
a). Fish live both in water and on land and undergo external
fertilization.
b). Most fish have bones while others are cartilaginous
c). Most fish have streamlined body, lateral line and swim bladder.
d). Gills are organs for gaseous exchange in fish
6. Which one of the following is not a characteristic of all insects?
a). They have three body parts namely head, thorax and abdomen.
b). They have three pairs of jointed legs attached on segment of the
thorax.
c). They have four pairs of jointed legs
d). They have a pair of antennae attached on the head.
7. The following are characteristics of all mammals except;
a). They have mammary glands to secrete milk feed their young
ones.
b). Their skin is covered with hair.
c). Undergo internal fertilization and internal development of the
embryo.
d). They have a pair of wings made up feathers.
8. The point where the leaf joins the stem is called;
a). Apex
b). Margin
c). Leaf base
d). Lamina
e). Length of petiole.
9. Which of the following is less considered while identifying feature to
construct
a). dichotomous key of leaves?
b). Nature of margin
c). Nature of apex
d). Size and color of leaf
10. The following are characteristics of arachnids except;
a). Four pairs of jointed legs
b). Two body parts
c). Three body parts
d). Do not have wings
11. Match the structures with the organisms which possess them.

a). Which kingdoms are represented by the letters x and y?
b). State one characteristic that organisms of x may share with:
i. Prokaryotes
ii. Fungi
iii. Plantae
13. What is the significance of classification of living organisms?