Evolution of leaves

The lycopod Isoetes bears microphylls with a single
vascular trace.Leaves today are, in almost all
instances, an adaptation to increase the amount of
sunlight that can be captured for photosynthesis. Leaves
certainly evolved more than once, and probably
originated as spiny outgrowths to protect early plants
from herbivory.

The rhyniophytes of the Rhynie chert comprised nothing
more than slender, unornamented axes. The early to
middle Devonian trimerophytes, therefore, are the first
evidence we have of anything that could be considered
leafy. This group of vascular plants are recognisable by
their masses of terminal sporangia, which adorn the ends
of axes which may bifurcate or trifurcate. Some
organisms, such as Psilophyton, bore enations. These are
small, spiny outgrowths of the stem, lacking their own
vascular supply.

Around the same time, the zosterophyllophytes were
becoming important. This group is recognisable by their
kidney-shaped sporangia, which grew on short lateral
branches close to the main axes. They sometimes branched
in a distinctive H-shape. The majority of this group
bore pronounced spines on their axes. However, none of
these had a vascular trace, and the first evidence of
vascularised enations occurs in the Rhynie genus
Asteroxylon. The spines of Asteroxylon had a primitive
vasuclar supply - at the very least, leaf traces could
be seen departing from the central protostele towards
each individual "leaf".

Publishing on the school website

Schools are contributing to this rich vein of online information by publishing information on the web about their activities. These websites are available to Internet users across the world.

The value

A school website encourages communication with a wider audience including schools in other countries, parents, past pupils, business and the community, and provides up to date information about the school's activities.

The development of such a site by pupils and staff is truly cross-curricular.

The potential risks

Personal Safety

* Feeling uncomfortable

If a website includes a pupil's picture, then this could be downloaded from the web, and edited in an unpleasant or embarrassing way. This new image could be circulated via newsgroups or on another webpage.

Parents have concerns that information about their children may be made available worldwide by schools, and that their children can be identified and traced.

Schools could find themselves the centre of unwarranted media attention if the content of a school's website is not carefully overseen. For example, search engines deal with words individually rather than in context, and deliver sites to the browser based upon those individual words. A website that included the phrase "Ourtown school is a single sex education establishment", could be proffered to a web user who was looking for occurrences of "sex".

* Child protection

A pupil could be traced if their name and picture appear on the school's website. It would be possible for them to be contacted by someone wishing them harm.

The recommendations

* Education Authorities should be approached for guidelines concerning parental permission for publishing pupils' pictures on the web.

* Schools may wish to consider whether pupils are put at risk when pictures of them appear on the school website.

* References to specific pupils should only be made if they do not conflict with the school's Personal Safety Programmed and Child Protection Guidelines.

* School website developers should take special care that pupils' safety and justifies are not compromised.

* The methods that search engines use to index the contents of websites should be borne in mind when producing text for a school website.

Preparing for Safe Internet Use

Although a new experience for many, the Internet is no more than another medium with associated risks, and general risk avoidance strategies are applicable. It remains true that good advice online has its roots in good advice offline.

Every aspect of life brings its own risk and schools cope by: -

* identifying the risks

* understanding the context

* assessing the level of risk

* introducing strategies to maximize the gain, whilst limiting the risk

* integrating new concepts into the curriculum

* sharing best practice

WHAT COULD HAPPEN IF YOU HAD A BIKE CRASH AND WEREN'T WEARING A HELMET?

* "You could be paralyzed, killed, or you could suffer damage."

* "You could bust your head open on the sidewalk or a rock."

* "You could go into a coma."

* "You could break your neck or crack your head.

* "You could have serious brain damage and you might have to learn all you know over again."