Crinoids comprise three basic sections; the stem, the calyx, and the arms. The stem is composed of highly porous ossicles which are filled with muscular tissue. The Calyx contains the crinoid's digestive and reproductive organs, and the mouth is located at the top of the dorsal cup, while the anus is located peripheral to it. The arms facilitate feeding by moving the organic media down the arm and into the mouth.
Crinoids feed by filtering small particles of food from the sea water with their feather like arms.
Crinoids reproduce sexually by the males releasing their sperm and the females releasing their eggs into the current where they will develop into non-feeding larval stage and then eventually grow a stalk (in the stalked crinoids), and within 10 to 16 months will be able to reproduce.
The earliest known crinoids come from the Ordovician The long and varied geological history of the crinoids demonstrates how well the echinoderms have adapted to filter-feeding. The fossils of other stalked filter-feeding echinoderms, such as blastoids, are also found in the rocks of the Paleozoic era.
In 2006, geologists isolated complex organic molecules from 350-million-year-old fossils of crinoids -- the oldest such molecules yet found.
TIPS FOR LEARNING 2
- Expose yourself to English as much as possible.
The more you expose yourself to English, the more you get used to it and the more familiar it becomes to you. You will start to recognize what sounds right and what sounds wrong. You will also start to understand why certain words or phrases are used instead of others, and you will start to use them in your own conversations and writing. English will start to become a habit, and little by little you will find it easier to use English.
Specific ways to increase exposure to English:
-Watch TV and movies.
-Listen to the radio.
-Read as much as possible.
- Enlarge your vocabulary.
Having a large vocabulary is basic to learning any language, and it is especially true in English. Reading is a very good way to learn new words. So is doing puzzles or playing different kinds of word games.
- Have fun.
Having fun increases your ability to remember, so the more you enjoy yourself as you learn English, the easier it will be to remember. Play games and puzzles. Even simple ones, like ones written for children, provide good experience and practice for English. Comic books and newspaper comic strips are also a good way to have fun, and the pictures make it easier to understand than stories.
- Cultivate friendships with native speakers
If you make friends with some Americans, you will find that they can be a very valuable help in your learning English. Having American friends means that you will find yourself in situations where you have no choice but to speak English. Yet since they are your friends, you will be doing things you enjoy together with them. So these situations will probably have little or no stress. Friendships with Americans also means that you'll have someone whom you can ask questions regarding language, culture, the suburbs, and so on.
- Make regular study a habit.
Regular study is a key to success in learning a language. It is easier to study a little each day instead of trying to study several hours only one day a week. Also, studying a little each day makes it easier to review what you've learned and remember new things.
- Acknowledge the progress you've made.
Finally, it is important to recognize that you will improve as you study English. Sometimes when you set your goals, they seem very difficult. Progress comes little by little, so it's hard to see if you have grown in your language skills. Think about where you are at today, and where you were last week or last month. Maybe it doesn't seem like you have come very far. But if you stop and think about where you were six months ago, or even a year ago, then you see that you have made progress. You have improved your English, and that is a reason to celebrate your accomplishment. It gives you hope that as you continue to study and work hard at improving your English, you will reach your goal sooner or later!
Thank you Alberto for this song. Your classmates should be encouraged with your example.