ВУЗ:
Составители:
Рубрика:
split распадаться, расщепляться
fission расщепление, деление
roughly приблизительно
withdraw оттягивать, отдергивать; удаляться
prevent препятствовать
adult взрослый
sluggish медленный, вялый
set free высвобождаться
drought засуха
duck утка
moor-hen белая шотландская куропатка
hatch выводиться
III. Make up 5 questions on the text and ask your friend to answer them.
IV. Sum up what the text has to say on the following points:
1. The process of simple fission.
2. The formation of spores.
3. The properties of spores.
V. Make up a model of the information and sum it up.
Text 7
I. Read the text and say what information it carries.
HYDRA
Hydra, the freshwater polyp, is a small cylindrical animal quite common in
ponds and lakes. The body wall is made up of two layers of cells, an outer
ectoderm, and an inner endoderm. The mouth Is the only opening from the body
cavity and round it are arranged 6-9 hollow tentacles which are used in catching
water-fleas and other small pond animals.
If you have kept hydrae and fed them on water-fleas you will see how they
reproduce by budding. When they are well fed, they usually produce from the
cylindrical body hollow outgrowths known as buds. These develop tentacles at
their free end and finally a mouth, after which they separate from the parent.
Two or three buds may be present at the same time on one hydra, and a bud
may itself start budding before it is free from the parent.
At times a different method of reproduction occurs. You may see hydra
with several pale swellings in the ectoderm Just below the mouth. These are
reproductive organs known as testes and in them develop very large numbers of
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