Levels of organization

Learning outcomes:
2.1
describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems.
Organisms are made from organizations of smaller structures. You need to know the following hierarchy of structures.

Organelles - intracellular structures that carry out specific functions within a cell
Cells - the basic structural and functional unit from which all biological organisms are made
Tissues - a group of specialized cells, which are adapted to carry out a specific function
Organs - a collection of two or more tissues, which carries out a specific function or functions
Organ Systems - a group of two or more organs

Cell structureLearning outcomes:
2.2
describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole
2.3
describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole
2.4
compare the structures of plant and animal cells.
You need to know the differences between plant and animal cells, the functions of the organelles and be able to recognize them in a microscope picture or drawing.

animal cell.GIF

plant cell.GIF

Organelle
Animal Cell
Plant Cell
Chloroplast
no
yes
Cell Wall
no
yes
Sap Vacuole
no
yes
Chlorophyll
no
Found in chloroplast
Size
Roughly 50чm long
Roughly 150чm long
Shape
No fixed shape
Rectangular
N.B. The cells are measured in чm (micrometers). One micrometer is 1/1000th of a millimetre.

Functions of the Organelles:

Cytoplasm - site of chemical reactions in the cell

Cell Membrane - controls what enters / leaves the cell (selectively permeable)

Nucleus - contains nucleic acids, which code for the synthesis of specific proteins. These proteins control all activity in the cell

Mitochondrion - site of respiration

Chloroplast - site of photosynthesis

Cell Wall - made from cellulose. Strengthens the cell and allows it to be turgid

Sap Vacuole - contains the cell sap. Acts as a store of water, or of sugars or, in some cases, of waste products the cell needs to excrete.

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