LIVING ORGANISMS

Characteristics of Living Things

MRS  NERG

M – movement 

R – respiration 

S – Sensitivity 

N – Nutrition 

E – Excretion 

R – Reproduction 

G – Growth 

MR NIGER D

CLASSIFICATION OF LIVING THINGS

Kingdom

Phylum (or Division in the case of plants)

Class

Order

Family

Genus

Species

Kingdoms

• Monera
• Protista
• Fungi
• Plantae
• Animalia

Kingdom Monera

The bacteria and blue-green algae belong to this kingdom.

• They are made up of single procaryotic cells enclosed within rigid cell walls
• Simple cell structure 
• No definite cell wall

The bacteria can only be seen through a light microscope as they range in size 0.1 to 10 micrometers. They are found in air, water, soil and inside living organisms. They occur singly, in groups or in chains. bacteria may be motile or non-motile. The motile ones have flagella which enable them to move. A few types of bacteria make their own food by taking in energy from the breakdown of inorganic compounds. But most bacteria take in ready-made food (saprophtyes) such as breaking down the food present in dead organisms. They cause the organisms to decay or decompose – an important process of nature. 

A lot of bacteria also live and feed on living organisms harming them in the process (parasites).

Most bacteria reproduce by dividing into daughter cells. This is known as binary fission, a type of asexual reproduction. This process of cell division is called mitosis.

Blue-green algae are found mainly in freshwater or in damp places on land. They contain chlorophyll and so make their own food

Kingdoms – Protista

Unicellular organisms made up of eucaryotic cells

They have complex cell structure and a well-defined nucleus

Phyllum includes protophyta (plant-like enabling them to make their own food

and protozoa (animal-like because they feed on ready-made food and have no cellulose cell wall)

Some protist reproduce by simply dividing in daughter cells but many reproduce sexually, i.e. they produce make and female sex cells or gametes which fuse together to form a zygote. This zygote undergoes a special type of cell division called meiosis

Kingdom Fungi

They include mushrooms, bread moulds, toadstools, slime mould. Some are free living in soil and water, or in food or clothing, while others form parasitic or symbiotic relationship with plants and animals

• They are eukaryotic organisms, non-motile (except slime mould)
• Saprophytes because they do not have chlorophyll and cannot maKe their own food. They are also heterotrophic
• Some fungi are parasites (living and feeding on living organisms) and cause diseases especially in plants
• Fungi reproduce rapidly by sexual and asexual reproduction

some economic benefits of fungi include

1. they are decomposers because they break down organic matter and hence improve the soil fertility
2. they are employed in the fermentation process in industries for wine-making and beer-brewing
3. Some mushrooms are edible and serve as food
4. Yeast is used in baking as a raising agent and they are used to produce

Kingdom Plantae

This includes organisms that are multicellular and eukaryotic. 

They possess chlorophyll that help to convert sunlight energy into chemical energy through the process of photosynthesis. They are thus amyotrophic and store their excess food as macromolecules of starch.

• They are non-motile
• They are surrounded by more or less rigid cell wall made of the carbohydrates cellulose and connected to adjacent cells.
• Many plants have the capacity for unlimited growth
• They undergo sexual and asexual reproduction

Plants can be classified into 3 –

1. Differentiatedbody such as root, stem and leaves e.g pteridophyta
2. Seed formation e.g gynosperms and angiosperms
3. Non-vascular (no true roots or stems) such as bryophyta and thallophyta

Kingdom Animalia

They are the largest kingdom

• They are multicellular eukaryotic organisms
• They have muscles and are mobile since they do not possess a rigid cell wall
• They reproduce sexually 
• They possess collagen, a protein of great tensile strength, that binds cells to tissues
• They are heterotrophie

Some important phylum includes

Porifera (sponges)

Cnidaria (hydra, jellyfish)

Nematode (round worm)

Annelida (earthworm)

Antropoda (sipers, butterflies, mosquitoes) 

Molluscs (snail, octopus)

Chordata (elephant, man)

Echinodermata (star fish)

Platyhelminthes (tapeworm)

Cells

A cell is the basic structural and functional unit of life.

Robert Hooke discovered cells in 1665 when he observed a bottle cork under a microscope.

All organisms are made up of cells. It could be one cell – unicellular or many cells – multicellular

Functions of the cells

Cell Membrane

The cell membrane supports and protects the cell. It controls the movement of substances in and out of the cells. It separates the cell from the external environment. The cell membrane is present in all the cells.

The cell membrane is the outer covering of a cell within which all other organelles, such as the cytoplasm and nucleus, are enclosed. It is also referred to as the plasma membrane.

By structure, it is a porous membrane (with pores) which permits the movement of selective substances in and out of the cell.  Besides this, the cell membrane also protects the cellular component from damage and leakage.

It forms the wall-like structure between two cells as well as between the cell and its surroundings.

Plants are immobile, so their cell structures are well-adapted to protect them from external factors. The cell wall helps to reinforce this function.

Cell Wall

The cell wall is the most prominent part of the plant’s cell structure. It is made up of cellulose, hemicellulose and pectin.

The cell wall is present exclusively in plant cells. It protects the plasma membrane and other cellular components. The cell wall is also the outermost layer of plant cells.

It is a rigid and stiff structure surrounding the cell membrane.

It provides shape and support to the cells and protects them from mechanical shocks and injuries.

Cytoplasm

The cytoplasm is a thick, clear, jelly-like substance present inside the cell membrane.

Most of the chemical reactions within a cell take place in this cytoplasm.

The cell organelles such as endoplasmic reticulum, vacuoles, mitochondria, ribosomes, are suspended in this cytoplasm.

Nucleus

The nucleus contains the hereditary material of the cell, the DNA.

It sends signals to the cells to grow, mature, divide and die.

The nucleus is surrounded by the nuclear envelope that separates the DNA from the rest of the cell.

The nucleus protects the DNA  and is an integral component of a plant’s cell structure

Mitochondria

They produce energy for the cell through cellular respiration (powerhouse)

Ribosome: They are involved making proteins since they help link amino acids together to form proteins

Chloroplast: it contains a green pigment called chlorophyll and is where photosynthesis takes place

Endoplasmic Reticulum

It is a network of sac like structures and tubes through which protein and other molecules move. The outer surface can be rough or smooth

Golgi body: They help in the transportation of materials in and out of the cell

lysosome: they protect the cell by engulfing foreign bodies entering the cell

NUTRITION

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TRANSPORT SYSTEM

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RESPIRATION

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EXCRETORY SYSTEM

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PROPERTIES & FUNCTION OF CELLS

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SUPPORTING SYSTEM & MOVEMENT

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DIGESTIVE SYSTEM

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REPRODUCTIVE SYSTEM

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NEURAL COORDINATION & SENSORY ORGANS

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ECOLOGY

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VARIATION

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ADAPTATION

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HEREDITY & GENETICS

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