Common Features: Eukaryotic Organisms (Edexcel IGCSE Biology)
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Common Features of Eukaryotic Organisms: Basics
All living organisms can be grouped or 'classified' using a classification system that consists of five kingdoms
These five kingdoms are:
Animals
Plants
Fungi
Protoctists
Prokaryotes
The first four kingdoms in this list (the animals, plants, fungi and protoctists) can actually be grouped together, as they are all eukaryotic organisms (also known as eukaryotes)
Animals, plants, fungi and protoctists are all eukaryotes.
Eukaryotic organisms can be multicellular or single-celled and are made up of cells that contain a nucleus with a distinct membrane
An animal cell (left) and plant cell (right) as seen under a light microscope. They are both eukaryotic cells as they both have a distinct membrane-bound nucleus.
Prokaryotic organisms (also known as prokaryotes) are in a separate kingdom and are different from eukaryotes as they are always single-celled and do not contain a nucleus (instead, the nuclear material of prokaryotic cells is found in the cytoplasm)
Bacteria are prokaryotic organisms
Prokaryotic cells are substantially smaller than eukaryotic cells
Animals
The main features of animals:
They are multicellular
Their cells contain a nucleus with a distinct membrane
Their cells do not have cellulose cell walls
Their cells do not contain chloroplasts (so they are unable to carry out photosynthesis)
They feed on organic substances made by other living things
They often store carbohydrates as glycogen
They usually have nervous coordination
They are able to move from place to place
A typical animal cell
Cell structures found in both animal and plant cells table
Structure | Function |
---|---|
Nucleus |
|
Cytoplasm |
|
Cell membrane |
|
Ribosomes |
|
Mitochondria |
|
Plants
The main features of plants:
They are multicellular
Their cells contain a nucleus with a distinct membrane
Their cells have cell walls made out of cellulose
Their cells contain chloroplasts
They feed by photosynthesis
They store carbohydrates as starch or sucrose
They do not have nervous coordination
A typical plant cell
Cell structures found only in plant cells table
Structure | Function |
---|---|
Cell wall |
|
Chloroplasts |
|
A permanent vacuole |
|
Examiner Tips and Tricks
You need to be able to recognise, draw and interpret images of cells, so practice drawing and labelling animal and plant cells as part of your revision.
Fungi
Main features of fungi:
They are usually multicellular but some are single-celled (e.g. yeast)
Multicellular fungi are mainly made up of thread-like structures known as hyphae that contain many nuclei and are organised into a network known as a mycelium
Their cells contain a nucleus with a distinct membrane
Their cells have cell walls made of chitin (chitinous cell walls)
Their cells do not contain chloroplasts (so they cannot carry out photosynthesis)
They feed by secreting extracellular digestive enzymes (outside the mycelium) onto the food (usually decaying organic matter) and then absorbing the digested molecules. This method of feeding is known as saprotrophic nutrition
Some fungi are parasitic and feed on living material
Some fungi store carbohydrates as glycogen
They do not have nervous coordination
Examples of fungi include: moulds, mushrooms, yeasts
A typical fungal cell
The typical structure of a multicellular fungus e.g. Mucor (bread mould)
Protoctists
Main features of protoctists:
The protoctists are a very diverse kingdom of organisms that don't really belong in any of the other eukaryotic kingdoms (animals, plants and fungi)
They are mainly microscopic and single-celled but some aggregate (group together) into larger forms, such as colonies or chains of cells that form filaments
Their cells contain a nucleus with a distinct membrane
Some have features making them more like animal cells e.g. Plasmodium (the protoctist that causes malaria)
Some have features, such as cell walls and chloroplasts, making them more like plant cells e.g. green algae, such as Chlorella
This means some protoctists photosynthesise and some feed on organic substances made by other living things
They do not have nervous coordination
Examples of protoctists include: amoeba, Paramecium, Plasmodium, Chlorella
Two examples of protoctist cells
Examiner Tips and Tricks
You need to be able to recognise, draw and interpret images of cells, so practice drawing and labelling fungal cells and protoctist cells as part of your revision.
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