في هذا الدرس سوف نتعلم أسماء أسماء مفردات الحشرات Creepy-Crawlies | Learn English | insects باللغة الانجليزية, فيديو سهل لتعليم النطق بأسماء وعبارات اللغة الانجليزية, تعليم الانجليزية ومفردات المختلفة, تعلم بالصوت والصورة أسماء بالانجليزية, كورس فيديو تعليم الانجليزية, كتب تعليم أسماء بالمجان, أهم أسماء بالانجليزية, كل ما تحتاج تعلم في اللغة الانجليزية من جمل ومحادثات, مصطلحات ومفردات بالانجليزية. دروس للمبتدئين وللأطفال المتعلمين للغة الانجليزية, كورس تعليم الانجليزية للمتقدمين.
What makes an insect an insect? Many people think that any tiny creature is an insect, but they would be better off using the non-scientific term, creepy-crawly.
Which of these three creepy-crawlies is an insect?
The one on the left is not an insect. It is a spider.
The one on the right is not an insect, either. It's a millipede.
It's the one in the middle that is classed as an insect. It is an insect because it has a hard outer skeleton called an exoskeleton.
You and I have a hard skeleton, but it's inside our bodies. We have an endoskeleton and are therefore not insects.
Insects' bodies are also divided into three main parts. It is divided into a head, a thorax and an abdomen.
Indeed, the word insect comes from the Greek and means cut into sections.
The insect's wings and its legs are attached to the thorax.
To be classed as an insect, you need to have three pairs of jointed legs, compound eyes and two antennae.
If you have all these features, you are probably an insect.
Insects don't have lungs to breathe with. Most of them breathe through holes in the sides of their bodies called spiracles. Some of them breath through their skin. Either way, the diffusion of gasses is quite effective on the small scale, and this is why insects are small.
The biggest insect in terms of mass is the aptly named Goliath beetle. This beetle can grow over 11 cm long and weigh up to 100 gram.
Not having lungs is no hindrance to the Goliath beetle. It can carry up to 850 times its own weight, which makes it one of the strongest creatures alive, relatively speaking.
Insects have been around since the Silurian period in Earth's history. That's around 440 million years ago.
In the Carboniferous age, around 299 million years ago, there was a lot more oxygen in the atmosphere.
The more oxygen there is in the atmosphere, the more oxygen can diffuse into an insect's body. More oxygen means bigger insects and in the Carboniferous there were insects that made the Goliath beetle look puny in comparison.
Dragonflies had a wingspan as wide as 50 cm.
Having been around for such a long time, the insects have evolved into many different types. There are estimated to be anything up to ten million different species of insect alive today.
They make up over 90% of today's animal species.
Some insects, such as fireflies, even produce their own light and have been doing so since long before Thomas Edison invented the light bulb.
Some insects are social. They live in huge, well-organised colonies. Ants and many bees and wasps are social insects.
While some insects, such as the mosquito, spread disease, most would be sorely missed if they were to disappear. Pollinator decline is the reduction of insects which have evolved as the only pollinators of flowering plants.
The misuse of pesticides, the destruction of habitat for intensive agriculture, the pollution of the air, and the many other ways human beings are messing up the world's delicate balance, means far fewer insects.
Fewer insects means fewer pollinators of important food crops. This means a reduction in food yield and possible global hunger.
Perhaps it will be possible in an insect-free future to find work as a professional pollinator, going from tree to tree and plant to plant to spread pollen.
Mind you, if you don't have a head, a thorax, an abdomen, three pairs of jointed legs, compound eyes and two antennae, you're probably not going to be awfully good at it.
Best, I think, to leave it to the professionals.
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