أهم 100 سؤال فى مراجعة مادة أحياء لغات الجزء السادس الصف الثالث ثانوي

من طرف **حنين الصمت** الأربعاء 01 مايو 2013, 4:22 pm

الدرس في شكل نص مقروء

أهم 100 سؤال فى مادة أحياء لغات - الجزء السادس

C) Give reasons for each of the following:

1. The root is positively hydrotropic.

Because the increase in amount of water on one side more than the
other leads to the accumulation of auxin in the side facing the water
more than the other side So, the

accumulation of auxin will inhibit elongation of the root cells
that facing water, but the law conic. of auxin elongate the cells in
side that away from water .

2. The nerves have white bright colour.

Because the nerves arc surrounded by a fatty coat called epineurium.

3. Some of the nerve axons are surrounded by Myelin layer.

Because in the presence of these layer, the rate of nervous
impulse conduction reaches 140 meters/sec. while in Rainvier's nodes
the rate never impulse reach 12 meters/sec.

4. stimulation of the nerve obeys the all or none law.

Because the generation of nerve impulse will not only initiate
without the sufficient stimulus to produces the response and then any
increase in the strength of the stimulus will not increase the response:
So weak stimuli are insufficient to produce an action potential (the
nerve impulse).

5. Transmission of a nerve impulse across the synapse.

due to the presence of the vesicles that contain the chemical
transmitters, when the impulse reaches the synaptic knob, the vesicles
secrete the chemical transmitters to the synaptic cleft then this
chemical diffuses to dendrite of the adjacent nerve cell where it
initiates a new impulse.

What would happen in each of the following cases?

1. Exposure of plant seedling to the light from one side after removing of its growing point.

The seedling will not respond to the light due to the absence of the tip which secrets axin

2. Sensory centers in occipital lobe are damaged.

losing of vision sense takes place

3. Decrease secretion of prolactin hormone.

the secretion of milk from mammary glands decrease and the secretion of progesterone H. decrease

4. The secretion of follicle stimulating hormone ( FSH) is
sufficiently decreased in a mature human male.

sperms will not produced by the testes ,and the 2 testes and prostate gland may be atrophied.

Compare between DNA in prokaryotes and eukaryotes.

DNA in prokaryotes

1- No neuclear membrane

2- In the form of Circle DNA

3- Not complexed with proteins.

4- Attached to plasma membrane

5- duplicated at the attaché point of the plasma membrane

6- Have plasmids.

7- Most of the genome is codon

8- It is Replicated at the at the point that attach the plasma membra

Transcription

9- A single RNA polymerase transcribes the three types of RNA

10- The transcription & translation takes place in cytoplasm at the same time .

11- e.g. E.coli bacteria

DNA in eukaryotes

1- Surrounded by neuclear membrane

2- Its ends are not joined together

3- Complexed with proteins

4- Not attached to plasma membrane.

5- duplicated at the any point

6- No plasmids.

7- About 70% codon &30%non codon

8- It is Replicated at any point.

Transcription

9- Three different kinds of RNA polymerase transcribes the RNAs.

10- The transcription of m RNA is completed in the nucleus, after that translation starts at the cytoplasm

11- e.g. animal cells