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An organization may be school, factory, bank, company with group of members that work together to achieve a united goal. In the Same way organization of life means the body of a living that has different parts, but all work and functions together to achieve a united goal.

The Cell

Cell is the structural, functional unit of life, each organisms is made up of one or more. An organism with one cell is known as unicellular organism, also an organism with no cell is known as non-cellular organism while an organism with two or more is known as multi-cellular organisms.

In multicellular cell organism are arranged in a specialized way to form tissues. 

Tissues are group of cells that are similar in function and are specialized to perform a particular function.examples of tissue in animals are; epithelial, skeletal,nervous,connective,muscular. Example of tissue in plant include epidermal, collenchyma, parenchyma, xylem, phloem and cork tissues.

Tissue in Animal

Muscular tissue: this is a soft tissue that composes muscles in animal bodies and give rise to muscles ability to contract. It is made of three types: cardiac, smooth, and skeletal.

Cardiac muscle cell are located in the walls of the heart, appear striated and are under involuntary action.

Connective tissue:these are tissues that connect, supports, bind or seperate other tissues. Connective tissue consist of fibrous, cartilage, bone, and blood. Fibrous tissues are found in dermis, tendons.

Epithelial tissue:Epithelial tissue covers the body surface or lines a body cavity.it line most internal organs and are the major tissues of gland.

Nervous tissue:this is the main tissue than consists of the central nervous system and the pheripheral nervous system.the nervous system consists of brain, spinal cord.the nervous system is the part of an organism that control the voluntary and involuntary action.

Tissue in Plants

Phloem: in vascular plants phloem is the living tissue that carries organic nutrients (known as photosynthate) in particular sucrose, sugar, to all parts of the plants where needed. In trees, the phloem is the inner most layer of band, tissue has column cells called sieve tube cell, the tubes are made from living cell. Their function is to transport glucose that is produced  by  photosynthetic leaves to where it is needed  Phloem can be found in root, stem, fruit of a plant.

Xylem: xylem transport water from the root to shoot and leaves, but it also transport some nutrients and  convey dissolved minerals to where it is needed.

Parenchyma: it is a functional tissues that distinguished the connective and supportive tissue. It is a cellular tissue that is typically soft and succulent, found in softer part of the plants. It is also found in animals lying between the body wall and organs of the vertebrate.

Collenchyma: Collenchyma provides extra-structural support, particularly in regions of new growth they have thin primarily wall with some areas of secondary thickening their cells are elongated, their cell wall are composed of cellulose and pectin.they are found under epidermic or the outer layer of cell in young stem in leaf vein.

Cork tissue: A tissue found in every vascular plants. It is also found in woody seed plant, producing cork on the outside of the ring. It  has lower number of chloroplasts or lack them completely, it absorbs water and mineral nutrients and regulate gas exchange and protect against water lost.  
A group of tissues form an organ.  An organ consists of a number of different tissues which are organized, and work together to perform a special function in an organism. Examples of organs include an eye, or a leaf. The leaf is a plant organ which contains epidermal, parenchyma, phloem and xylem tissue other examples of organ include, heart, lungs, kidney, and liver in animals, and flower, rhizome, roots in plants.

Heart: The heart is a muscular organs in humans and other animals, it helps to pump blood through the blood vessels.

Lung: The lungs helps oxygen from the air we breathe to enter the red cells in the blood. Red blood cells then carry oxygen around the body to be used in the cells found in our body.

Kidney: Kidney are two beans shape they are located under the ribcage. Everyday the two kidney filters 120- 150 quartz of blood to produce about 1-2 quartz of urine composed of waste and extra fluid as the kidney filters blood urine is created. The kidney removes waste, control the body's fluid balance and regulate the balance of electrolyte.

Liver: The liver is a gland which help in decomposition of red blood cells, plasma protein synthesis, hormone product to detoxification.

A group of organ which work together to perform a function is called a system. Example of system in animals are circulatory, excretory, respiratory, digestive and nervous system.. in plants example or system are, transport, root and shoot system. All the organ systems in one organism make up the organism.

The system in animals

Circulatory: they are also known as cardiovascular. This system circulates blood and lymph through the body consisting of heart, blood vessel, blood, lymph. It permits blood to circulate and transport nutrients ( amino acid, electrolyte ,oxygen and carbondioxide

Cell- tissue- organ- organ system-organism

Makes up the organization of life.               
Excretory: it helps to maintain internal chemical homeostasis and prevent damages .it remove unnecessary material from the body fluid of an organism. It also remove excess nitrogen and other toxins that can cause harmful effect to the body .

Nervous: This is the part of an organisms that control the involuntary action. The nervous system consist of the brain, spinal cord. The pheripheral nervous system consists of the nerve and ganglia on the outside of the brain and spinal cord. The main function of the pheripheral nervous system is to connect the central nervous system to the limbs and organ essentially serving as a communication relay.
Respiratory: this is a sense of organ responsible for the in take of oxygen and expelling carbondioxide. Example include: lungs, bronchi, bronchioles.

Bronchioles are tiny air ways that Carry oxygen to the alveoli or air sacs in the lungs and help to stablize breathing

Alveoli: they are tiny air sacs within our lungs that allows carbondioxide to move between the lungs and bloodstream.

Bronchi : this is an airway sacs that conduct air into the lungs. 
The blood vessel- there are three main blood vessel
The arteries
The capillaries
The vein
The arteries carries away blood from the heart . The capillaries enables actual exchange of water and chemical between blood and the tissue while the vein carries the blood from the capillaries back to the heart. The arteries are strong, flexible.

Blood :this is a body  fluid  in animala that delivers necessary substances such as nutrients and Oxygen to the cell. 
Levels of organisation

The biological levels of organization of living things are arranged from the simplest to the most complex.

*Organ system

Cell level of organisation: this is where the activities of life is being perform in the specific parts of the cell called the organelles to perform specific function. Organism that are made up of one cell are called unicellular organism and are said to be at the cell level of organization. Example Paramecium, Amoeba, Euglena, protozoa, chylamadomonas. 

 Paramecium: these organism are found in freshwater, Marine environment, brackish. They can reproduce and digest food  also function independently and do not depend on other organisms for food therefore ther are autotrophic in nature (producers). Paramecium have cilia for locomotion and food gathering also posses micronuclei and macronuclei.

Amoeba: Amoeba are parasitic living organism livin in damp environment.it has the ability to alter it shapes primarily, they exhibit amoeboid movement. Their temporary pseudopods are use for locomotion and capturing food and also posses a nucleus.
Infectious disease of Amoeba:

Gastrointestinal amebiasis is an infectious disease of the large intestine cause by microscopic one celled parasite commonly known as amoebas ( Entamoeba histolytical) these parasite lives in the large intestine of an organism, they travel in the feaces of an infected  person and contaminate water supplies in places where sanitation is poor. 

Also, these parasite can contaminate fruits and grown in areas Where human feaces are used as fertilizers and can be transferred from dirty hands of an infected person. Once Amoeba enters the mouth it travel through the digestive systems and settle in the large Intestine. It can live there without causing damage or any symptoms but can cause severe disease. 

This Amoeba may invade the wall of the intestine leasing to amoebic dysentery and illnesses that cause intestinal ulcers, bleeding, increase mucus production and diarrhoea. These Amoeba also may pass into the bloodstream and travel to the liver or infrequently to the brain.

Protozoa: protozoa are phototrophic organism that has no cell wall. Many protozoa causes diseases in animals and human . Example plasmodium which causes malaria, Trichomonas ,which causes sexually transmitted diseases.

Tissue level of organization

We have four basic types of tissues they are: 
Muscle  and neural
Epithelial tissue covers the surfaces exposed to the environment, airways, digestive tracts, glands.

Under this we have:
* simple and stratified
* squamous, cuboidal columnar
* psuedodtratified, transitional.
Connective tissue: fill internal spaces, supports others tissues, transport material and stores energy.under the connective tissues we have the blood, lymph, adispose, bone, cartilage.

Muscle tissue is specialized for contraction .they include ; skeletal, cardiac, smooth muscles.

Muscle tissue is specialized for contraction, all body movement is produced by muscle tissue.

Muscle cells can be striated ( muscle cells with a banded appearance) or non striated. Muscle cell can be controlled by voluntary or involuntary action.

SKELETAL MUSCLE TISSUE : this tissue forms a large body muscles responsible for major body movement such as walking. Skeletal muscle cell are long and thin and are usually called muscle fibers.

CARDIAC MUSCLE TISSUE: These tissues are found within the walls of hollow organs that controls the blood vessels, urinary bladder, respiratory, digestive and reproductive tracts.

SMOOTH MUSCLE TISSUE:they are small they have a single nucleus  can regenerate and are non- striated.

Neural tissue Carries electrical signals from one parts of the body to another.they are specialize for conducting electrical impulses that rapidly sense the internal or external environment, process information and control responses.

Most neural tissue is contracted in the brain and spinal cord which makes up the cell.

There are two kinds of neural.

1. Neurons : the nerve cells that do the electrical communicating and 
2. The Neuroglia : that supports cells and supply nutrients to neurone. 
Neurone are made up of three parts
The cell body,dendrites and axon.
The cell body contains the nucleus and nucleolus.
Dendrites are short branches extending from the cell body to receive incoming signals.
Axons( nerve fibers) is a long, thin, extension of the cell body that carries outgoing electrical signals into their destinations

Epithelial Tissue

Epithelial tissue includes; Epithelial layers of the cells, glands structure that produce fluid secretions, epithelial line digestive, respiratory, urinary and reproductive tracts. Also fluid or gas filled internal cavities and passage ways such as the chest cavity inner surfaces of blood vessels and chambers of heart

Characteristics of Epithelial cell 

1. Cellularity : cell are tightly bound together by cell junction.
2. Polariry; the structural and functional differences between the exposed ( apical) and atttached (basal) surface of the tissue.
3.Attachment; The base of the membrane is bounded to a lamina or basement membrane.
4. Avascularity; Epithelial cells are avascular ( they lack blood vessel).
5. Regeneration ; A high rate of cell replacement by stem cells in the epithelium.

Classification of Epithelial

Epithelial are sorted into categories by their shapes.
(Squamous-flat, cuboidal- square, columnar- tall)

Classification of Epithelial  cell

Epithelial are sorted into categories by their cell shape. They include;
(Squamous-flat, cuboidal- square, columnar-tall )
One cell layer is simple epithelium,more than one layer is stratified epithelium.

1. Squamous Epithelial

i simple squamous epithelium:this cells are  thin, flat they look like fish scale the lining of the hollow organs of the body , lining of the respiratory and digestive tracts.
- mesothelium: simple squamous epithelium lining ventral body cavities ( pleura, pericardium)

Endothelium :simple squamous Epithelium lining heart and blood vessel.
ii. Stratified squamous epithelium: forms many layers which protects against chemical and physical attacks.it is found lining the mouth, esophagus, anus, and on exposed body surfaces.

2. Coboidal Epithelium

i. Simple coboidal epithelium occurs where secretion or absorption takes place( eg lining of the kidney tubules.
Stratified cuboidal epithelium: they are relatively rare. They are found in the sweat gland ducts and male urethra.

Columnar Epithelial

i.Simple columnar epithelium: they are found where absorption of secretion occur .e.g stomach, small intestine, large intestine.
ii. Pseudostratified columnar epithelium: they appears stratified but is actually simple. Cilia bearings cells are found in portions of the respiratory tract. E.g nasal cavity, trachea and bronchi.

Transitional Epithelium: they are multilayered, their surface cells varies in shape from round  to flat.

Submitted by Annix

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