Mwl Marco

CLASSIFICATION OF LIVING THINGS

Classification is the grouping of organism based on their similarities and differences.

The system of sorting out and placing organisms into different groups on the basis of their similarities and differences is called classification.

Organism that are similar are placed in the same group.

In the world, there are numerous varieties of living organisms.These organisms do vary in size, structure, shape, habitat, mode of feeding and even mode of reproduction. The organisms can be sorted out and placed into different groups based on their similarities. 

Biologists have designed a system that involves three main features.
1.The system is hierarchical.This means that a large classification group can be subdivided into smaller group or taxa.
2.Important,significant,biological similarities and differences are used to decide which group and organism goes on.Example whether organism is edible or non edible, Has backbone or not,are useful, significant biological differences
3.Every organism is given a name which tells you which group to belong.

The field  of Biology that deals with classifying organism is called Taxonomy

 THE IMPORTANCE OF CLASSIFICATION.

i.Grouping  organisms makes the study of living things easy                                                            

ii.Classification makes communication easy among biologists from different parts of the world          

iii.It provides good organized system in which a newly identified organism can be easily fitted in future.     

iv.It makes it easier to identify organisms    
v.It can be used to make assumption or prediction characteristics that are present in the members of the same group.                  
vi.Provides supportive evidence for evolution.

CLASSIFICATION SYSTEM 

There are are two types of biological classification system. Namely

1.Artificial classification

2.Natural classification                                                                                                                           
ARTIFICIAL CLASSIFICATION  
 An artificial classification is based on one or a few easily observable features.                                       It usually designed for practical purpose with an emphasis on convenience and simplicity. In this type of classification, unrelated organisms are often placed in the same group while closely related organisms are often placed in different groups 

Example. Bats and birds would be placed in the same group because all have the ability to fly since they posses wings. But apart from those two common, features bat and birds show several biologically significant difference.Bat has hair,mammary gland,sweat gland and different types of teeth theses distinguish bat as mammals,birds have beak ,lay shelled eggs hence not placed into mammal

In the third century B.C Aristotle used artificial classification to classify plants. He grouped plants according to  their shapes and size and whether their were useful to man or not.
This types is known as dichotomous key

Advantage of artificial classification

 1.It is easy to classify organisms since it is based on few observable characteristics.

2. It does not take much time to classify organisms based on this system (not time consuming).

3.It does not need expertise (even a layman can do).

4.It is relatively stable i.e. not easily changing from time to time.

Disadvantage  artificial classification

1.It tends to place closely related organisms into different groups instead of being grouped together e.g. a bat can be placed in a group of birds instead of mammals.

2..Different or unrelated organisms may be placed in the same group e.g. bats placed in a group of birds, worms placed with snakes in the same group

3 The system does not provide enough information about its members.

4.It is difficult to incorporate additional information.

2.Natural classification
Natural system of classification 

 This groups organism according to both external and internal features 

or

This type of classification system tries to use natural relationships between organisms. 
It considers many features in common including internal as well as external features.

Similarity of embryology, morphology, anatomy, biochemistry cell, structure and behaviour are all considered relevant. It is based on evolutionary relationship in which organisms belonging to the same group are believed to have a common ancestor.

Organisms are placed in their natural group by using the following criteria

• Relations based on homologous (similarity in term of origin and structure ,but difference in functions E.g Forelimb of animals)characters not Analogous character((similarity in term of function, but no necessarily e.g. Wing of wings and grasshopper)
• Organism with many features in common

Characteristic features which show homology are distinguished from those which show analogy. Example the fore limbs of mammals, whales, birds and bats have the same basic pattern and similar bone arrangement, i.e. homologous. This suggest s that these organisms are coming from the same ancestor and that can be placed in the same group 

Advantages of natural system of classification
i.Closely related organisms are placed in the same group.
ii.It reflects evolutionary relationships.
iii.Unrelated organisms cannot be placed in the same group.
iv.It makes it easy to incorporate additional information.

Disadvantages of natural system of classification.
a.It is difficult since it considers many features.
b.It requires expertise i.e. more knowledge about an organism.
c.It is time consuming.
d.It is relatively unstable i.e. it changes from time to time.
e.It is more expensive since more data are required.

Differences between natural classification and artificial classification

Artificial classification	Natural classification
(i) Based on external features only	Consider both external and internal features
(ii) Does not reflect on evolutionary relationships	Reflects on evolutionary relationships
(iii) Requires simple skills	Requires advanced scientific skills
(iv) It is usually fast and inexpensive	Take more time and it is costly
(v) Less accurate	More accurate
(vi) New information cannot be added	New information can be added.

MAJOR GROUP OF LIVING THINGS

The major groups of living things are the kingdoms. Previously, living things were categorized into two main groups; plantae and animalia kingdom. But this classification caused difficulties since some   organisms seemed to posses some of the characteristics of both groups. 

For example, euglena is capable of feeding like an animal and locomote like an animal. Therefore, it is placed in animalia kingdom. But the same euglena has chlorophyll and it is capable of manufacturing its own food. Therefore, it should also be placed in plantae kingdom. Such an organism does not seem to fit exactly in animalia or plantae kingdom. Thus, euglenas are assigned in the major group of their own.

Ranks of classification or Taxa

The ranks of classification are

Kingdom

Phylum/division

Class

Order

Family

Genus

Species

Currently, in Biology  organism are classified   into five major groups (kingdoms) of living things

i..Kingdom monera. Foe example Bacteria

ii..Kingdom protoctista. For example amoeba

iii Kingdom fungi. For example mushroom

iv..Kingdom plantae For example maize

v..Kingdom animalia. For example Human being

Kingdom are  subdivided into smaller units.

Kingdom  Animalia is subdivided in Phyla (phylum singular) Kingdom plantae  subdivided into division.

1.Kingdom- this is the highest rank (taxon). It comprises of several related taxa. It comprises of many organisms than any other taxon.

2.Phylum/division– this is the second largest rank of classification. It consists of several closely related classes.

3. Class - members or this group have more characteristics in common than do members of division or phylum.

4.Order- it consists of groups that are more alike than those in a class.

5.Family –this is made up of groups that are more alike than those in the order. Wolves and cats are both in the order Carnivore but wolves are in the family Canidae while cats belong to the family Felidae.

6.Genus – it consists of very similar species but members of different species cannot breed one another.

7 Species – is a group of closely related organisms which are capable of interbreeding and produce fertile (viable)offspring.

• Must have many features in common.
• Must be able to breed one another to produce fertile offspring.
• Must be distinct and different from other organisms.

	Human being	Dog	Maize plant
Kingdom	Animalia	Animalia	Plantae
Phylum/Division	Chordata	Chordata	Spermatophyta
Class	Mammalia	Mamalia	Angiospermae
Order	Primate	Canivore	Graminales
Family	Hominidae	Canidae	Graminaceae
Genus	Homo	Canis	Zea
Species	spiens	familaris	May
Scientific name	Homo sapiens	Canis familaris	Zea mays

NB.Organism from difference species can interbreed and produce offspring..Normally the offspring is infertile.Examples
i.Mule-Mate between male donkey and female horse
ii.Geep - Matebetween a male goat and female sheep
iii.Zeedonk- Mate between femaleZebra and male donkey
iv.Ligers- Mate between male lion and female tigior
Binomial nomenclature

Binomial nomenclature is a scientific system of naming organisms where by name is made up of two latin words

The scientific process of naming organisms is called nomen- clature. Biological nomenclature is based on the binomial system (double naming system) pioneered by the work of a Swedish naturalist Carl Linnaeus (1707-1778).

Biologists assign scientific names to organisms so as to avoid confusion among themselves since scientists from different countries use different languages. The scientific names are uniform in all languages.

Rules of binomial nomenclature
Scientific names of organisms must be in Latin language and if the names are derived from other languages, they must be latinized.

1. A scientific name of an organism has two parts, genus name and species name.
2. A genus name always starts with a capital letter and a species name follows with a small letter.
3. In typed scripts, a scientific name must be written in italics or underlined if hand written.
4. A specific name is sometimes accompanied with the name of the author who first described and named the organism.
5. When an organism is known by several names, the valid name is the one which was established after the work of Linnaeus.

Examples of scientific names

Human being:Homo sapiens

Homo is the generic name and sapiens is the specific name.

Other examples of organisms with their scientific names

Common name	Scientific name
Earthworm	Lumbricus  terrestris
Cockroach	Periplaneta americana
Amoeba	Amoeba  proteus
Coffee	Coffea arabica
Maize	Zea mays
Bean	Phaseous vulgaris
Domestic Cat	Feris catus
Sisal	Agave sisalana
Mango tree	Mangifera indica
Coconut palm	Cocos nucifera
Lion	Panthera leo
Housefly	Musca domestica

VIRUSES, KINGDOM MONERA and  KINGDOM PROTOCTISTA

1.Viruses

A virus is particle or fragment with only one type of nucleic acid (either DNA or RNA) surrounded by a protein coat (Capsid).It is an extremely small microorganism.

-A virus is not a cel.lt smaller than a living cel

-A study of virus is called Virology

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.

Characteristics of Viruses.

a.A virus has a very simple structure, consisting of genetic materials within a protein shell(capsid).    b.Viruses do not have cellular structures, that they lack certain important organelles like nucleus, cytoplasm, Golgi bodies,                                                                                         

c.They can only reproduce inside the living cells hence they are parasitic.                                              d.They have a simple structure consisting of either DNA or RNA but not both, surrounded by a protein or lipoprotein coat.                                                                                                               

e.They can be described as living or non-living.                                                                           

f.They are highly specific to their hosts i.e. each virus recognizes only certain types of cells.         g.Viruses are capable of replicating themselves only when they are inside the host cell.               
 Distinctive features of virus                                                                                                              

 A virus has both living and non -living characteristics

Viruses as living things

1. They possess genetic material (RNA or DNA).
2. They reproduce when they are in the host cell (replication).
3. They are capable of identifying their hosts and attack them.
4. They can undergo mutation (they mutate) . thus they undergo different changes in shape.
5. Like other parasites, they are specific to host.

Viruses as non-living things

1. They can crystallize outside the host.
2. They reproduce only when inside the host
3. They are non-cellular i.e. they lack cell organelles.
4. They do not perform necessary life processes such as respiration, excretion nutrition e

Generally viruses have a very simple structure consisting of the following:

1. RNA or DNA which may be single stranded or double stranded. They form a structure called core.
2. A protective coat of protein surrounding the core called capsid.
3. A nucleocapsid which is a combined structure of core and capsid.
4. Envelope – an additional layer of lipoprotein layer around the capsid.
5. 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

HOW VIRUSES REPRODUCE

a.The virus attaches itself onto the host cell and inject its genetic materials into the cell

b.The virus's genetic materials reproduces in the cell

c. The host cell dies and bursts, releasing new viruses

N.B virus do not grow . feed. excrete or respire

Advantages of viruses

1.Viruses are used in developing vaccines, for example, vaccines for measles, polio and rubella are made from viruses that have been attenuated (weakened).                                                           

2.Viruses are used as biological weapons to kill organisms.                                                             

3.They are used as vectors in genetic engineering to transfer genes from one organism to another for improving or treating the defective genes.                                                                                   

4. Bacteriophages are viruses that attack bacteria and hence they help in controlling infections and diseases.                                                                                                                                               

5.Viruses are used as biological weapons in wars and in biological pest control.

Disadvantages of viruses

1. Most viruses cause diseases to both plants and animals. 
2. 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.
3. They can reproduce very fast, leading to large scales epidemics
4. Viruses can alter themselves often, and thus become difficult to destroy

KINGDOM MONERA
The monera are also referred to as prokaryotes(no nucleus)

This kingdom is made up of organisms known as bacteria (singular: bacterium). and Cynobacteria .Cynobacteria  are able to photosynthesize.Example blue-green bacteria

The scientific study of bacteria is called Bacteriology

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).
Many species are responsible for desease in plants and animals. Many however, have little effect on their host and some areactuallr beneficial. Example Rhizobium species are symbiotic improving the nitrogen metabolism of legume plants
Ruminants are dependent on the bacterial flora of their gut to digest cellulose that provides the bulk of their diet

General characteristics of the kingdom Monera

i.They are mainly unicellular and very small.Some bacteria stick together to form chains or clusters called colonies.
ii.They are all prokaryotic (nucleus not bound by membrane)   
iii.They reproduce by binary fission. 
iv.Some members of the kingdom are autotrophs while others are heterotrophs 
v.They have cell wall made up of protein material and sometimes lipids   
vi.Some bacteria form spores during adverse conditions i.e. extreme conditions.Example high or low temperatures, drought etc. The spores allow them to survive as they have very thick resistant walls 
vii.Some are aerobes while others are anaerobes. 
viii.The genetic material (DNA) is scattered in the cytoplasm and they lack internal membrane
x.Bacteria has a slimy outer layer.This layer help to protect the bacteria from predators such as virus and protozoa bound organelles such as mitochondria, chloroplasts, Golgi bodies 

ix.some are free living while other are parasites

General structure of the bacteria

1.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).                                                    

2.Bacterial cells are bounded by partially permeable membranes.                                                                      

3.Bacteria possess capsules which are slimy or gummy.
4.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.           5.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

1.Coccus (plural: cocci)

They are spherical in shape and can be of the following types.

• Micrococcus – exist singly. They cause sore throat.

• Diplococci (in pairs) - This type of bacteria exist in pairs. The pneumococci (Diplococcus pneumoniae) are the only members. They cause pneumonia.

• Streptococci( form cluster)  – 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(form chain) – These bacteria form a grape like bunch. They cause boils, pneumonia, food poisoning and other diseases.

2.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:

1. Central, not swollen e.g. Bacillus anthracis causes anthrax
2. Spherical spore, terminal swollen e.g. Clostridium tetani causes tetanus
3. Sub-terminal, swollen e.g. Clostridium botulism causes botulism.Spores may also be central

3..Spirilla (singular: spirillum)

These are spiral-shaped bacteria e.g. Treponema pallidum which causes syphilis

4.Comma

These are comma shaped bacteria, for example Vibrio cholerae.which cause Cholera

Vibrio cholerae

 TYPE OF BACTERIA.

1.Pathogenic bacteria

 are bacteria that can cause infection. and disease

 Some of the disease caused by bacteria are Leaf spot, Potato blight, and tobacco mosaic. in plants

in animals are tuberculosis, typhoid, tetanus, anthrax, cholera, syphilis and gonorrhoea

Features help pathogenic bacteria to spread disease ad infections.

i. Fimbriae or pili.

These are hair-like structures on the surface of some bacteria.The hairs attach themselves to the host so that they can not be removed.Example Escherichia coli produce fimbriae that attach them selves to the lining of the urinal tract or intestines

 ii. Flagella

.These are long tail- like structures that help some pathogenic bacteria to move to a site where they can survive

iii. Toxins

Some bacteria produce toxic compound that harm their hosts. Example .clostridium.

iv.invasion and colonization.

Some bacteria attach cells and tissues and reproduce rapidly. Example Salmonella bacteria destroy intestinal cells to feed on their contents.

v.Transformation

Bacteria an transform themselves and become resistant to modes of treatment.Example the bacterium that cause tuberculosis has become resistance to the antibiotics.

vi. Resistance

 Some types of bacteria release a substance known as Biofilm that protects them from harmful substance such as drugs.

2.Non-pathogenic bacteria 

are those that do not cause disease, harm or death to another organism and even when there in in the plants's  and animal's body 

Characteristics of Non-pathogenic

1.Some non-pathogenic bacteria feed on substances that are harmful to the environment and in the process neutralize them.Example they neutralize petroleum waste from petroleum industries. dyes and pesticides. thereby making the environment clean.

2.Bacteria sch as Rhizodium that found in the root nodules of leguminous plants, Clostridium and Azotobacter help to covert atmospheric nitrogen to nitrates.Plants need nitrates for health growth

3.Bacteria in the stomach of ruminant animals such as goats and cows secrete cellulose which forms a large part of the diet of ruminants.

4. Vitamins produced by bacteria are important for health of animals including man.

5.Decay of dead organisms releases nutrients for use by plants

6. Fermentation is used in the production of cheese, yogurt , vinegar and alcohol

7.Some bacteria are used to produce to antibiotics which are used to treat bacterial disease

8.In genetic engineering. bacteria are used to produce insulin  and human growth hormone

9. During photosynthesis autotrophic bacteria release oxygen in atmosphere. Oxygen is vital for respiration in all living things

10.Saprophytic bacteria feed on feed on dead organism causing decay.

Advantage of kingdom of Monera
1.Many  bacteria are decomposers.They break down the dead bodies of plants and animals and release important elements such as Nitrogen , carbon and phosphorous which can be recycled

2.Some bacteria have a symbiotic relationship with other organism. For example
i. Certain bacteria live in alimentary canal of human supplying vitamin K and Vitamin B complex
ii. -Nitrogen- fixing bacteria live root nodules of leguminous plants.They convet free nitrogen in the air to nitrates which can be used by plants
, Example. 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 .
3. In production of foods such as cheese and vinegar
4. In manufacturing industries in the production of soap powder, the tanning of leather and the retting of flax to make linen
5.Making antibiotics, enzymes and single-celled protein(SCP)
6.In research, particularly genetic engineering bacteria have been genetically modified to produce insulin and human growth hormone

Disadvantage of Bacteria

1 .Some of the bacteria species cause food poisoning. They secret some toxic chemical substances on out food stuff which cause food poisoning, eg Salmonella species which attack pigs and  poultry, Staphylococcus and Clostridium.

2.Some are responsible for human diseases: Cholera: Vibrio cholera, Pneumonia: Staphylococcus pneumoniae, Diarrohea: Escherechia coli, Tuberclosis: Mycobacterium tuberclosis Leprosy: M. leprae, Meningitis: Nisseria meningitides.

3.Some bacteria are cause 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.grown gall of fruits frees caused by Agrobacterium tumefaciens and fire blight disease of apple and caused by Erwinia amylovium
4.Some bacteria causes food spoilage by decaying stored food and making it inedible.
5. Sulphur bacteria produce suplhuric acid which damages buried matals pipes

Viruses	Bacteria
It does not possess slime capsule but	It has external covering called slime capsule
protein coat(capsid)
It has not cell wall	It has cell walll
It has only either DNA or RNA at any time	It has both Dna and RNA
They do not have a nucleus	They have nucleus
Lack flagella	Some have flagella foer movement
They smaller in size than bacteria	They large in size
They can not replicate outside of host cell	They cannot crystallize
They can not replicate outside of host cell	They are able to reproduce outside of the cell
Most of the diseaess they causeshave no cure	Most of the diseases they cause have cure

KINGDOM PROTOCTISTA

Protoctista are all eukoryotes with chromosomes.( have a nucleus).Many are unicellular,
some exist as filaments(Chains) or colonies of cells and other are simple , multicellular organism
This 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.
All of the protoctista ive in aquatic environment

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 locomotive 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

The phyla of kingdom protoctists include the following:

1. Euglenophyta e.g. Euglena
2. Rhizopodia e.g. Amoeba
3. Zoomastigma e.g. Trypanosoma
4. Apicomplexa e.g. Plasmodium
5. Oomycota e.g. White root
6. Chlorophyta e.g. Spyrogyra
7. Cilliaphora e.g. Paramecium
8. Rhodophyta e.g. Red algae

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 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.

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.

Movementin paramecium is caused by cilia beating. This movement is called cilliary movement.

ADVANTAGES OF PROTOCTISTA
1.They used in production of oxygen. About of half of the oxygen released into the atmosphere by photosynthetic organisms is produced by algae.The oxygen is used by other living organisms for respiration
2. At least half of the carbon dioxide fixation(absorption) on the Earth is carried out by algae on the surface of oceans to form carbohydrates which can be used as source of energy for non-photosynthetic organisms
3.Large seaweeds such as red and brown algae have been used as fertilizer by coast farmers.They rich in potassium and other nutrients used by plants
4.Some algae are used directly for human consumption .example porphyra
DISADVANTAGES
Many of protozoa are harmful to the living organisms , causing disease in in plants and animals. Examples plasmodium causing malaria, ,Entamoeba histolistca causing dysentry