Organisation of Life

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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