What makes something alive?

In order for something to be alive, it must meet the criteria for the characteristics of living things. These characteristics are;

M - movement (relocate from one place to another)

R - respiration (break down glucose to produce energy)

S - sensitivity (respond to changes in the environment)

 

H - homeostasis (maintain a constant internal environment)

 

G - growth (achieve a permanent change is size)

R - reproduction (produce offspring)

E - excretion (get rid of waste products produced by chemical reactions in cell)

N - nutrition (obtain nutrients by feeding or making food)

 

Are viruses alive?

Firstly, what is a virus. Viruse s are microscopic parasites, generally much smaller than bacteria. They lack the capacity to thrive and reproduce outside of a host body. Many people debate about whether they are alive because they most reproduce without the help of a host body

 

Cells

Cells are the building blocks of life, they are smallest units of life. Many organisms are made up of one cells these are called unicellular organisms such as plankton or bacteria. Larger organisms like humans are multicellular meaning they are made up of lots of cells. Cells are made up of organelles that carry out specific functions to power the cell.

There are over 250 different types of cells in your body, each of which have specific functions. There are discrete structures found in cells called organelles. Each organelle carries out a specific function which helps a cell in carrying out its role.

Organelles

Organelle	Function	Found in (plants, animals or both)
Mitochondria	Site of cellular respiration	Both
Nucleus	Contains DNA and controls the cell	Both
Cytoplasm	Site of metabolism (all chemical reactions in cells)	Both
Cell membrane	Controls what enters and exits a cell	Both
Ribosomes	Protein builders	Both
Cell wall	Provides rigid shape	Plants
Chloroplast	Site of photosynthesis	Plants
Vacuole	Stores nutrients (water, sugar salt)	Plants

 

Types of cell:

 

Prokaryotic - A cell that does not contain a nucleus (examples: plants, animals, fungi)

Eukaryotic - A cell that contains a nucleus (examples: bacteria)

 

Plant Cell Diagram:

 

Organism classification:

Organisms are classified into 5 different kingdoms, then into separate phylum, class, order, family, genus, species. There is also a hierarchy of life.

 

5 Kingdoms:

Kingdom	Characteristics
Protista	Unicellular Nuclear No cell wall Unique Examples: some algae, amoeba, diatom
Fungi	Multicellular Has organelles Chitin cell wall No movement Eats by absorption Reproduces using spores Examples: yeast, mushrooms, moulds
Plantae	Multicellular Cellulose cell wall Produce food via photosynthesis Nuclear No movement Examples: mosses, ferns, trees
Animalia	Multicellular Nuclear Movement No cell wall Gains nutrients by eating other organisms Examples: worms, fish, frogs, lions, deer, insects, humans
Monera	Unicellular Cell wall Non-nuclear Doesn’t have all common organelles Feeds by absorption or photosynthesis Examples: bacteria, E. coli, blue-green algae

 

The order of classification can be remembered using this simple acronym:

King - kingdom

Philip - phylum

Came - class

Over - order

For - family

Great - genus

Sex - species

 

Hierarchy of life:

 

Order of hierarchy	Description	Example
Atom	Smallest unit of matter	Helium
Molecule	Two or more atoms with a chemical bond	Water (H2O)
Organelle	Discrete structures inside cells which carry out specific functions	Cell membrane
Cell	Basic unit of life and are the  building blocks of life	Plant cell
Tissue	A group of similar cells working together to perform a specific function	Muscle
Organ	A group of similar tissues working together to perform a specific function	Lungs
Organ system	A group of organs working together to perform a specific function	Respiratory system
Organism	A biotic being made of one or more cells (must have all characteristics of life)	Dog

 

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