Concept of Classification
Explain the concept of classification
Have you ever visited a library? How are the books arrangedand kept? Are they arranged randomly or systematically? Obviously the books are arranged systematically in the shelves. Science books are kept separately in their respective shelves. Science books are keptseparately from social or commercial books. Biology books are separated from physics books or chemistry books. Likewise, in the shop, laboratory or pharmacy items are sorted and placed on the basis of their similarities.
In the world, there are numerous varieties of living organisms.These organisms do vary in size, structure, shape, habitat, modeof feeding and even mode of reproduction. The organisms can be sorted out and placed into different groups based on their similarities. The system of sorting out and placing organisms into different groups on the basis of their similarities and differences is called classification.
Living Things According to Their Similarities and Differences
Group living things according to their similarities and differences
Activity 1
Study the external features of the following organisms:Lizard, sugar cane plant, maize plant, shark, Tilapia, cactusplant, bat, cockroach, butterfly, hen, goat, toad, frog, spider andorange plant
Activity 2
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.
General and Distinctive Features of Viruses
Explain general and distinctive features 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.
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.
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.
Describe the structure of viruses
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.
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.
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.
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
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
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.
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.
- 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.
- 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
Economic Importance of Bacteria
Nitrogen fixation:Plants
cannot trap nitrogen from the atmosphere but bacteria can fix nitrogen
and change it into nitrogenous compounds. The phenomenon is called
nitrogen fixation. The bacteria, which fix atmospheric nitrogen, are
called nitrogen-fixing bacteria. Some of the nitrogen fixing bacteria
are found freely in soil are called 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
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.
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 comprises of unicellular and simple multicellular organisms
whose cells have organized nucleus and membrane bound organelles. It
includes the algae and protozoa.
have chlorophyll hence make their own food through the process of
photosynthesis.Protozoa are heterotrophic taking in ready-made food.
organisms, which are included in this Kingdom are red algae, Brown
algae, Amoeba, Euglena, plasmodium, trypanosome and paramecium.
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.
Most are unicellular eukaryotes
They reproduce by binary fission
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
Describe structure of amoeba and paramecium
- They are eukaryotes
- Unicellular
- Parasitic
- They move using pseudopodia
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
has two contractile vacuoles and each is associated with permanent
system of collecting channels, which empty, into the main vacuole.
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.
