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How
organisms are formed
Monacia
Williams, Contributor
Welcome
to another lesson in the series. Last
week we looked at specialisation in
cells. This week we are going to see
how these cells are organised to form
organisms.
The
first level of organisation in plants
and animals is the tissue. A tissue
is defined as a group of similar cells
which act together to perform a particular
function.
Below
is a table with examples of different
types of tissues found in animals
and the functions that these tissues
perform.
Table
1: Example of animal tissues, their
nature and their function.
|
Tissue
|
Nature
|
Function
|
| Epithelial |
Sheet
of cells; one cell thick |
Lines
tubes, spaces and forms skins |
| Connective |
Tough,
flexible fibres |
Bind
other tissues together |
| Skeletal |
Bones,
cartilage |
Support
and movement |
| Blood |
Fluid,
free floating cells |
Transport
of hormones, heat, oxygen and
carbon dioxide |
| Nerve |
Network
of cells with long tails |
Coordination
and control |
| Muscle |
Bundles
of elongated cells |
Movement |
Next
I will do the same for the plant tissues.
Table
2: Example of plant tissues, their
nature and their function.
|
Tissue
|
Nature
|
Function
|
| Epidermis |
Sheet
of cells; one cell thick |
Lines
the surface of plant organs |
| Photosynthetic |
Cells
with chloroplast e.g. palisade
and spongy mesophylls |
Make
food in photosynthesis |
| Packing |
Round,
balloon-like cells |
Fills
spaced between specialized cells |
| Vascular |
Long
tubes of xylem and phloem vessels.
(often called veins) |
Transport
water and food |
| Strengthening |
Tough
fibres, lignified |
Support
the plant |
Please
note that the lining tissue is known
as the epithelial in animals and the
epidermis in plants.
When
several tissues together form a distinct
structure, this is called an organ.
An
organ is defined as a structure, which
is made up of two or more tissues
acting together to perform a particular
function.
Examples
include the heart, lung, stomach,
liver, kidney and bladder in humans
and leaves, flowers, fruits, stems
in plants. Organs do not work in isolation.
They need to be connected to each
other so that they can work properly.
They become the building blocks of
what are called systems. An organ
system is defined as two or more organs
acting together to perform a particular
function.
Examples
of systems in animals
- Excretory;
consisting of the kidneys, bladder
and the skin.
- Digestive;
consisting of the alimentary canal,
liver and the pancreas.
Examples
of systems in plants
- Root
systems; consisting of the main
and lateral roots.
- Shoot
system; consisting of the stem,
the leaves and the flowers.
We
will be looking at most of these tissues,
organs and organ systems in more detail
over the next two years as we complete
the requirements for the course.
Here
is my challenge for you this week.
What do you think would happen to
organisms if there were no specialisation
of cells? Have fun! See you next week!
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Students
at the Yallahs High School study
together, during a lab session,
recently.
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Monacia
Williams teaches at Glenmuir
High School.
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