TOPIC 4: CLASSIFICATION OF LIVING THINGS | BIOLOGY FORM 1
Concept of Classification
Viruses
Viruses
were discovered by a Russian botanist D. I. Ivanovsky and a Dutchman
Beijerink.In 1852 Ivanovsky prepared an infectious extract from tobacco
plants that were suffering from mosaic disease. When the extract was
passed through a filter able to prevent the passage of bacteria, the
filtered fluid was still infectious. 1898 Beijerink gave the name
“virus” (in latin means, “poison”) to describe the infectious nature of
certain filtered plant fluids.
were discovered by a Russian botanist D. I. Ivanovsky and a Dutchman
Beijerink.In 1852 Ivanovsky prepared an infectious extract from tobacco
plants that were suffering from mosaic disease. When the extract was
passed through a filter able to prevent the passage of bacteria, the
filtered fluid was still infectious. 1898 Beijerink gave the name
“virus” (in latin means, “poison”) to describe the infectious nature of
certain filtered plant fluids.
General and Distinctive Features of Viruses
Explain general and distinctive features of viruses
Characteristics of Viruses
- They are the smallest living organisms ranging from 20-30nm. On average, they are about 50times smaller than bacteria.
- Viruses
do not have cellular structures, which mean that they lack certain
important organelles like nucleus, cytoplasm, golgi bodies, etc. - They can only reproduce inside the living cells hence they are parasitic.
- They have a simple structure consisting of either DNA or RNA but not both, surrounded by a protein or lipoprotein coat.
- They can be described as living or non-living.
- They are highly specific to their hosts i.e. each virus recognizes only certain types of cells.
- Viruses are capable of replicating themselves only when they are inside the host cell.
Viruses as living things
- They possess genetic material (RNA or DNA).
- They reproduce when they are in the host cell (replication).
- They are capable of identifying their hosts and attack them.
- They can undergo mutation (they mutate) i.e. they undergo different changes in shape.
- Like other parasites, they are specific to host.
Viruses as non-living things
- They can crystallize outside the host.
- They are metabolically inert in isolation.
- They are non-cellular i.e. they lack cell organelles.
- They do not perform necessary life processes such as respiration, excretion nutrition etc.
The Structure of Viruses
Describe the structure of viruses
Generally viruses have a very simple structure consisting of the following:
- RNA or DNA which may be single stranded or double stranded. They form a structure called core.
- A protective coat of protein surrounding the core called capsid.
- A nucleocapsid which is a combined structure of core and capsid.
- Envelope – an additional layer of lipoprotein layer around the capsid.
- Capsids are made up of identical repeating units known as capsomeres.
Bacteriophage
Bacteriophage is a virus that attacks and kills bacteria. Some of them have head with a tail sheath.
Bacteriophage
Advantages and Disadvantages of Viruses
Outline advantages and disadvantages of viruses
Advantages of viruses
- Viruses
are used in developing vaccines, for example, vaccines for measles,
polio and rubella are made from viruses that have been attenuated
(weakened). - Viruses are used as biological weapons to kill organisms.
- They
are used as vectors in genetic engineering to transfer genes from one
organism to another for improving or treating the defective genes. - Bacteriophages are viruses that attack bacteria and hence they help in controlling infections and diseases.
- Viruses are used as biological weapons in wars and in biological pest control.
Disadvantages of viruses
- Most
viruses cause diseases to both plants and animals. Plant disease such
tomato mosaic, cassava mosaic and tobacco mosaic; and animal diseases
e.g. measles, small pox, poliomyelitis and yellow fever are caused by
viruses.
Kingdom Monera
This
kingdom is made up of organisms known as bacteria (singular:
bacterium). They are the most ancient and smallest organisms with a
cellular structure. They are mainly single celled. Bacteria occupy many
environments such as soil, dust, water and in the bodies of plants and
animals
kingdom is made up of organisms known as bacteria (singular:
bacterium). They are the most ancient and smallest organisms with a
cellular structure. They are mainly single celled. Bacteria occupy many
environments such as soil, dust, water and in the bodies of plants and
animals
Some
bacteria are found in hot springs where temperatures are 78ºC or more.
Others can withstand very low temperatures. Some are found in very deep
cracks in the ocean floor, at very high temperatures, about 360ºC
(extreme thermophiles).
bacteria are found in hot springs where temperatures are 78ºC or more.
Others can withstand very low temperatures. Some are found in very deep
cracks in the ocean floor, at very high temperatures, about 360ºC
(extreme thermophiles).
General and Distinctive Features of the Kingdom Monera
Explain general and distinctive features of the kingdom monera
General characteristics of the kingdom monera
- They are mainly unicellular and very small.
- They are all prokaryotic (nucleus not bound by membrane)
- They reproduce by binary fission.
- Some members of the kingdom are autotrophs while others are heterotrophs
- They have cell wall made up of protein material and sometimes lipids.
- Some
bacteria form spores during adverse conditions i.e. extreme conditions
e.g. high or low temperatures, drought etc. The spores allow them to
survive as they have very thick resistant walls. - Some are aerobes while others are anaerobes.
- The
genetic material (DNA) is scattered in the cytoplasm and they lack
internal membrane bound organelles such as mitochondria, chloroplasts,
golgi bodies etc.
Structures of the Representative Organisms of the Kingdom Monera
Describe structures of the representative organisms of the kingdom monera
General structure of the bacteria
- Bacteria
have strong and rigid cell walls due to the presence of murein. The
wall prevents the cell from bursting when it absorbs much water (as a
result of osmosis). - Bacterial cells are bounded by partially permeable membranes.
- Bacteria
possess capsules which are slimy or gummy.They have flagella which aid
motility of the bacteria. Motile bacteria can move in response to a
certain stimulus i.e. tactic movement. Flagella can easily be seen by
electron microscope. - They have small self replicating circle of extra DNA called a plasmid.
General structure of bacterium
Forms of bacteria
Bacterial shape is an important aid to classification. There are four main shapes
Coccus (plural: cocci)
They are spherical in shape and can be of the following types.
- Micrococcus – exist singly. They cause sore throat.
- Diplococci – this type of bacteria exist in pairs. The pneumococci (Diplococcus pneumoniae) are the only members. They cause pneumonia.
- Streptococci
– this type of bacteria stick together and form a chain. Most of them
infect upper respiratory surface and cause diseases e.g. sore throat.
- Staphylococci – These bacteria form a grape like bunch. They cause boils, pneumonia, food poisoning and other diseases.
Bacilli (singular: bacillus)
These are rod shaped bacteria. They can be:
- Single rods, for example, Escherichia coli commonly living in the gut and Salmonella typhi which cause typhoid fever.
- Rods in chain, for example, Azotobacter, a nitrogen-fixing bacteria, and Bacillus anthracis which cause the disease anthrax.
- Bacilli with endospores showing various positions, shapes and sizes of spores. They can be:
- Central, not swollen e.g. Bacillus anthracis causes anthrax
- Spherical spore, terminal swollen e.g. Clostridium tetani causes tetanus
- Sub-terminal, swollen e.g. Clostridium botulism causes botulism.Spores may also be central
Spirilla (singular: spirillum)
These are spiral-shaped bacteria e.g. Treponema pallidum which causes syphilis
Sprrilla
Vibrio
These are comma shaped bacteria, for example Vibrio cholerae.
Vibrio cholerae
The Advantages and Disadvantages of the Kingdom Monera
Outline the advantages and disadvantages of the kingdom monera
Economic Importance of Bacteria
In Agriculture, the bacteria are mostly important for following reasons
- Nitrogen fixation:Plantscannot trap nitrogen from the atmosphere but bacteria can fix nitrogen
and change it into nitrogenous compounds. The phenomenon is called
nitrogen fixation. The bacteria, which fix atmospheric nitrogen, are
called nitrogen-fixing bacteria. Some of the nitrogen fixing bacteria
are found freely in soil are called free-living bacteria, eg.
Clostridium and Azotobacter. Some of them are found in root nodules
making association with leguminous plants called symbiotic bacteria, eg.
Rhizobium.
- Nitrification:Some bacteria convert
ammonium compounds into nitrates in the soil. The process is called
nitrification. The bacteria that take part in this process are called
nitrifying bacteria, eg. Nitrobacter and Nitrosomonas. Nitrosomonas
NitrobacterAmmonia—————>Nitrites————->Nitrates
- Ammonification:Some
bacteria utilize proteins of dead bodies and convert it into amino
acids. These amino acids are converted into ammonia by some bacteria.
The process is called ammonification and the bacteria involve in the
process are called ammonifying bacteria. Then the ammonia reacts with
CO2 and H2O and gives ammonium carbonate which is absorbed by plants.
- Bacteria decompose dead bodies. They convert complex organic compounds into simple inorganic compounds. Therefore they’re called natural scavengers.
- Bacteria make the milk sour and produce flavor. They are responsible for coagulation of milk. E.g. Lacto bacillus.
- Bacteria convert sugary substances into alcohol, acids, acetones; etc the process is called fermentation.
- Bacteria also help to produce different types of enzymes like Amylase secreted from Bacillus, Protease from Bacillus, Streptokinase from Streptomyces.
- Bacteria are useful for vitamin production like Vitamin B (Cabalmin) is secreted from Pseudomonas, Vitamin B (Riboflavin) is secreted from Clostridium.
- They are important for antibiotic production like Terramycin from Streptomyces rimosus, Streptomycin from S. griseus, Neomycin from S. fradiae.
- They are also important to produce hydrogen commercially. During the process they ferment carbohydrate and hydrogen gas is produced.
- Bacteria decompose waste products.
Disadvantage of Bacteria
- Some
of the species cause food poisoning. They secret some toxic chemical
substances on out food stuff which cause food poisoning, eg
Staphylococcus and Clostridium. - Some are responsible for human
diseases: Cholera: Vibrio cholera, Pneumonia: Staphylococcus pneumoniae,
Diarrohea: Escherechia coli, Tuberclosis: Mycobacterium tuberclosis
Leprosy: M. leprae, Meningitis: Nisseria meningitides. - Some
bacteria are responsible for plant diseases. Red stripe in sugarcane,
Leaf streak in rice, black rot in cabbage and yellow rot in wheat are
caused by Xanthomonas and Pseudomonas.
The Characteristics of Pathogenic and Non-pathogenic Bacteria
Outline the characteristics of pathogenic and non-pathogenic bacteria
Pathogenic bacteriaare bacteria that can cause infection. This article deals with human pathogenic bacteria.
Although
most bacteria are harmless or often beneficial, several are pathogenic.
One of the bacterial diseases with the highest disease burden is
tuberculosis, caused by the bacteriumMycobacterium tuberculosis,
which kills about 2 million people a year, mostly in sub-Saharan
Africa. Pathogenic bacteria contribute to other globally important
diseases, such as pneumonia, which can be caused by bacteria such asStreptococcusandPseudomonas, and foodborne illnesses, which can be caused by bacteria such asShigella,Campylobacter, andSalmonella.
Pathogenic bacteria also cause infections such as tetanus, typhoid
fever,diphtheria,syphilis, and leprosy. Pathogenic bacteria are also the
cause of high infant mortality rates in developing countries.
most bacteria are harmless or often beneficial, several are pathogenic.
One of the bacterial diseases with the highest disease burden is
tuberculosis, caused by the bacteriumMycobacterium tuberculosis,
which kills about 2 million people a year, mostly in sub-Saharan
Africa. Pathogenic bacteria contribute to other globally important
diseases, such as pneumonia, which can be caused by bacteria such asStreptococcusandPseudomonas, and foodborne illnesses, which can be caused by bacteria such asShigella,Campylobacter, andSalmonella.
Pathogenic bacteria also cause infections such as tetanus, typhoid
fever,diphtheria,syphilis, and leprosy. Pathogenic bacteria are also the
cause of high infant mortality rates in developing countries.
Nonpathogenic organismsare
those that do not cause disease, harm or death to another organism and
is usually used to describe bacteria.It describes a property of a
bacterium – its ability to cause disease. Most bacteria are
nonpathogenic. It can describe the presence of non-disease causing
bacteria that normally reside on the surface of vertebrates and
invertebrates as commensals. Some nonpathogenic microorganisms are
commensals on and inside the body of animals and are called microbiota.
Some of these same nonpathogenic microorganisms have the potential of
causing disease, or being pathogenic if they enter the body, multiply
and cause symptoms of infection.
those that do not cause disease, harm or death to another organism and
is usually used to describe bacteria.It describes a property of a
bacterium – its ability to cause disease. Most bacteria are
nonpathogenic. It can describe the presence of non-disease causing
bacteria that normally reside on the surface of vertebrates and
invertebrates as commensals. Some nonpathogenic microorganisms are
commensals on and inside the body of animals and are called microbiota.
Some of these same nonpathogenic microorganisms have the potential of
causing disease, or being pathogenic if they enter the body, multiply
and cause symptoms of infection.
Immunocomprised
individuals are especially vulnerable to bacteria that are typically
nonpathogenic but because of a compromised immune system, disease occurs
when these bacteria gain access to the body’s interior. Genes have been
identified that predispose disease and infection with nonpathogenic
bacteria by a small number of persons.Nonpathogenic colistrains normally
found in the gastrointestinal tract have the ability to stimulate the
immune response in humans, though further studies are needed to
determine clinical applications.
Kingdom Protoctista
General and Distinctive Features of the Kingdom Protoctista
Explain general and distinctive features of the kingdom protoctista
This
Kingdom comprises of unicellular and simple multicellular organisms
whose cells have organized nucleus and membrane bound organelles. It
includes the algae and protozoa.
Kingdom comprises of unicellular and simple multicellular organisms
whose cells have organized nucleus and membrane bound organelles. It
includes the algae and protozoa.
Algae
have chlorophyll hence make their own food through the process of
photosynthesis.Protozoa are heterotrophic taking in ready-made food.
have chlorophyll hence make their own food through the process of
photosynthesis.Protozoa are heterotrophic taking in ready-made food.
Other
organisms, which are included in this Kingdom are red algae, Brown
algae, Amoeba, Euglena, plasmodium, trypanosome and paramecium.
General features of Kingdom Protoctista
- Some are autotrophs, for example Euglena while others are multicellular.
- They are all eukaryotes with most of them having locomotery structure.
- Most of them live in moist places or in water.
Distinctive features
- Most are unicellular eukaryotes
- They reproduce by binary fission
Phyla of the Kingdom Protoctista
Mention phyla of the kingdom protoctista
The phyla of kingdom protoctists include the following:
- Euglenophyta e.g. Euglena
- Rhizopodia e.g. Amoeba
- Zoomastigma e.g. Trypanosoma
- Apicomplexa e.g. Plasmodium
- Oomycota e.g. White root
- Chlorophyta e.g. Spyrogyra
- Cilliaphora e.g. Paramecium
- Rhodophyta e.g. Red algae
Structure of Amoeba and Paramecium
Describe structure of amoeba and paramecium
Amoeba belong to phylum Rhizopoda, organisms with the following extra features:
- They are eukaryotes
- Unicellular
- Parasitic
- They move using pseudopodia
Pseudopodia are projection of the cytoplasm that extend and pull the amoeba forward or engulf food particles.
The Advantages and Disadvantages of Amoeba, Euglena Paramecium and Plasmodiu
Explain the advantages and disadvantages of amoeba, euglena paramecium and plasmodium
Advantages of Paramecium:Are eaten by small water animals
Disadvantages of Paramecium:Causes diseases of bulanterdium eoli destroying the lining of intestines
Osmoregulation:Paramecium
has two contractile vacuoles and each is associated with permanent
system of collecting channels, which empty, into the main vacuole.
has two contractile vacuoles and each is associated with permanent
system of collecting channels, which empty, into the main vacuole.
Feeding:Paramecium feed on bacteria. These are obtained from the surrounding water by the beating of the cilia-lining o the oral grove.
Reproduction:Paramecium
reproduces both asexually and sexually. The asexual method is more
common and it is binary fission. Sexual method is called conjugation.
reproduces both asexually and sexually. The asexual method is more
common and it is binary fission. Sexual method is called conjugation.
Movementin paramecium is caused by cilia beating. This movement is called cilliary movement.
