الأحد، 21 مايو، 2017

تعبير انجليزي عن حيوان بحري

تعبير انجليزي عن حيوان بحري
قنديل البحر في الإنجليزية
موضوع بالانجليزي عن حيوان بحري
أريد موضوع تعبير عن حيوان باللغة الإنجليزية مهم
حيوان بحري لافقاري رخوي يعيش داخلها
قنديل البحر (بالإنجليزية: jellyfish)
اكتب تقرير عن حيوان بحريWrite a report a bout marine animal Paragraph : Write
الانجليزية •حيوان مهدد بالانقراض باللغة الانجليزية • تعبير عن الدب القطبي بالانجليزي
تعبير انجليزي عن حيوان بحري
موضوع عن سمك القرش بالانجليزي
موضوع انجليزي عن الكائنات البحرية
بحث عن قنديل البحر باللغة الانجليزية
بحث عن الحيوانات البحرية باللغة الانجليزية
بحث عن حيوان بحري باللغة الانجليزية

تعبير عن حيوان بالانجليزي
The term jellyfish is a vernacular name designating the free forms of many decidial groups and thus opposing polyps, sessile forms. Jellyfish are usually predatory, they paralyze their prey with their cnidocytes and may possess very elaborate sensory structures such as ocelli, gathered within derhopalies. Some jellyfish belonging to the Cubozoape class can be deadly to humans. In the life cycle of certain groups of cnidarians, the jellyfish form can alternate with the polyp phase, but others live only in the jellyfish state. Although mostly found in salt water, it is possible to observe certain types of jellyfish in fresh water.
There are about 1,500 species of jellyfish recorded in the early nineteenth century, mostly dehydromedos. In view of the recent results of molecular phylogeny, jellyfish are considered as a characteristic of one of the two decidial groups, called Medusozoa (composed of the classes Cubozoa, Scyphozoa and Hydrozoa). The other group being the Anthozoa2. However, the exact evolutionary origin of the medusa form is still poorly understood.

The majority of species feed on microplankton trapped by their marginal or peri-shadow tentacles, shrink filaments attached to the edge of the parasol. Some species, such as in the order Rhizostomeae, have welded mouth extensions without a distinct buccal orifice, feeding at numerous and tiny oral orifices on the coalescent buccal arms, and supplement themselves with sugars thanks to symbiotic algae Who live in these arms. Others feed by capturing larger prey (copepods, larvae and fish eggs, fish a few cm in length). Some jellyfish fall over, with the umbrella facing upwards, waiting for the plankton falling to the bottom to fall into their oral cavity21.
In their optimal search strategy for food, jellyfish practice both passive hunting and hunting. These strategies differ depending on the size and shape of the umbrella, the number, size and arrangement of the tentacles22.

Reproduction
Some jellyfish may bud, other jellyfish on the edge of the umbrella but the majority of asexual reproduction is done from the polyp. At the moment of sexual reproduction, jellyfish become genuine "floating gonads", all their food being committed to producing these glands. Sex cells are differentiated in the gonads that develop around the manubrium in anthomedos, along the radial canals in leptomedos and trachymeduses, in genital pockets connected to the stomach in the scyphomeduses. They release into the water column the gametes (spermatozoa for male jellyfish, ova for females) which disperse in the ocean and fertilize the eggs: fertilization is external, with the exception of Stygiomedusa gigantea (en) or Of Aurelia aurita which are viviparous. Once reproduction is assured, jellyfish die. This life cycle is a semi-parity which is favored by the short duration of the free form, which can correspond to a specific energy strategy23. By dispersing the eggs, they contribute to the colonization of new geographical areas. The embryonic development is marked by different stages and leads to the formation of a ciliate larva, the planula. The polyps then line the bottom of the ocean. These polyps develop differently depending on the species. Some can develop only after half a century. More generally, a significant change must take place (eg change in temperature, oxygen, thunder) to allow them to release the jellyfish thus formed24.

Human consumption
A dozen species of jellyfish are eaten in Asia, particularly in Japan (kurage), especially cut into strips in the form of salads, the main species consumed during gala meals in Asia being Rhopilema esculentum. Each year, the Japanese consume about 13 tons47. In China, which breeds them in Korea, Thailand and Malaysia, jellyfish are also eaten dried, especially in the form of kebabs. Their nutritional value is relatively limited since they are composed of more than 98% water, but the remaining 2% contains protein and carbohydrates48.

Overfishing or disappearance of predatory species of jellyfish (tunas, herring, anchovies, turtles) 49, the disappearance of competitors such as sardines, which increase the amount of food available, "the destruction of seabed by trawlers Breeding, water warming, and eutrophication of coastal environments "stimulate their proliferation, so much so that researchers Philippe Cury and Daniel Pauly make the provocative conjecture that" we will have to content ourselves with eating jellyfish! "

ليست هناك تعليقات:

إرسال تعليق