Page 13 - Reproduction in Animals

2. Observe live hydra yourself and learn how they reproduce by doing
the following activity:
During the summer months collect water weeds from ponds or ditches
along with the pond water and put them in a glass jar. After a day or
so you may see several hydra clinging to the sides of the jar.
Hydra is transparent, jelly-like and with tentacles. It clings to the
jar with the base of its body. If the jar is shaken, the hydra will
contract instantly into a small blob, at the same time drawing its
tentacles in.
Now take out few hydras from the jar and put them on a watch
glass. Using a hand lens or a binocular or dissection microscope,
observe the changes that are taking place in their body. Note down
your observations.
3. The eggs we get from the market are generally the unfertilised ones.
In case you wish to observe a developing chick embryo, get a fertilised
egg from the poultry or hatchery which has been incubated for 36
hours or more. You may then be able to see a white disc-like structure
on the yolk. This is the developing embryo. Sometimes if the heart
and blood vessels have developed you may even see a red spot.
4. Talk to a doctor. Find out how twinning occurs. Look for any twins
in your neighbourhood, or among your friends. Find out if the twins
are identical or non-identical. Also find out why identical twins are
always of the same sex? If you know of any story about twins, write
it in your own words.
For more information on animal reproduction, you can visit :
l www.saburchill.com
l www.teenshealth.org/teen/sexual-health

Did You Know?

An interesting organisation is observed in a honey bee hive, a colony of several
thousand bees. Only one bee in the colony lays eggs. This bee is called the
queen bee. All other female bees are worker bees. Their main job is to build the
hive, look after the young and feed the queen bee adequately to keep her
healthy so that she can lay eggs. A queen bee lays thousands of eggs. The
fertilised eggs hatch into females, while the unfertilised eggs give rise to males,
called drones. It is the job of the worker bees to maintain the temperature of
the hive at around 35°C to incubate the eggs.

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