Answer
the following questions
1- What is the
Tillite?
2- Why the
Devonian often called "age of fishes"?
3- What is the
main invertebrate group in the late Paleozoic?
4- How can the age of the Precambrian rocks
determined?
5- When
brachiopods and trilobites appeared in the
geologic time?
6- Why
trilobites and graptolites are significant, and for what reason?
7- What is the
age and type of oldest rocks?
8- Why the
mollusks become more important in the late Paleozoic?
9- When did the
life in land expand?
10- When did most
of the marine group decline
11- What happened
after temporary contraction of epeiric seas at the end of Paleozoic?
12- What are the
major protestant groups of the Mesozoic?
13- Why the
cephalopods were the most important group of mollusks in the Mesozoic?
14- Describe the
Cenozoic Era?
The Answers:
(1)- Another rock
type of the Precambrain is tillite, is a poorly sorted mixture of clastics of
all sizes from boulder to clay. It causes of glaciations.
(2)- The Devonian
often called "Age of fishes" because every fish class was present and
common during the period. These are Ostracoderms, Placoderms, the cartilage
skeletons, and the ancestors of bony fish.
(3)- The chief
invertebrate group is the Arthropods e.g. scorpions, spiders, and insects.
Flight less insets evolved in the Devonian.
(4)- It is determined by radio activety
(5)- They appeared
at the base of Cambrian
(6)- Because they
are major Fossils in the time correlation of Ordovician and Silurian.
(7)- The oldest
rocks are assigned to an Archean Era.
a- High- grade
metamorphic belts of gneiss and green stones.
(8)- Because of
appearance and radiation of the ammoniods.
(9)- In the late
Paleozoic.
(10)- At the end of
Paleozoic.
(11)- Life in the
seas flourished in the Mesozoic.
(12)- The major
marine prositan group of the Mesozoic were the green algae (dasycladaceous),
cocolithophores, diatoms, dinoflagellates, foraminifera, radilaria, and
tintinnids
(13)-
a- They are
chiefly nektonic mode of life.
b- They are wide
geographic distribution so vital for long distance time correlations.
c- They are the
most abundant Mesozoic cephalopods.
(14)-
-
South America and Africa further separated as Atlantic
ocean basin widened.
-
Africa started to be sundered by the development of
great rift valleys.
-
Arabia has already spilt off and incipient ocean basin
of the red sea has formed.
-
On the land the mammals dominated large animal group
and give common name for this era the age of mammals
|