3. THE FORAMINIFERA

3. THE FORAMINIFERA

  1. oraminiferans are commonly called for:ans.
  2. They are primarily a marine group of amoebae.
  3. Foraminiferans possess reticulopodia
  4. They secrete a test of calcium carbonate.
  5. The foramini ferans grow secrete new larger chambers. These chambers remain attached to the older chambers. Therclbre. the test enlargement follows a symmetrical pattern. It may from two types of chambers:

             (a) Straight chain of chambers

             (b) Spiral arrangement that resembles a snail shell.

Many of these tests become relatively large. For example. Mermaid’s pennies. It is several centimeters in diameter. It is fflund in Australia.

Importance of Foraminiferans

  1. Their tests are abundant in the fossil record of Cambrian period.
  2. They’ lbrm a large component of marine sediments.
  3. Their tests accumulate on the floor of oceans. They form limestone and chalk deposits. The white cliffs of Dover in England are one example of a foraminiteran chalk deposit.
  4. Oil geologists use fossilized forams to identify geologic strata during oil exploration.

Heliozoans

The are aquatic amoebae. They may be plankton or attached by a stalk to some substrate. Some heliozoans are naked. Some are enclosed within a test. The test contains openings for axopodia.


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Radiolarians

They are marine and freshwater amoebae. They are planktons. They are rclativek large. Some colonial forms min reach several centimeters in diameter.  They possess a test. This test is siliceous. It is composed of long, movable spines and needles. Sometimes. it forms highly sculptured and ornamented lattice. The tests of dead radiolarians die settle in ocean floor. Some of the oldest known fossils of eukaryotic organisms are radiolarians.

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