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BUDDING IN HYDRA
BUDDING IN HYDRA
So far, we have learnt about reproduction in some familiar animals. But what about very small animals like hydra and microscopic organisms like amoeba? Do you know how they reproduce? Let us find out.
Activity 9.3:
* Get permanent slides of hydra.
* Observe them using hand lens or a microscope.
* Look out for any bulges from the parent body.
* Count the number of bulges that you see in different slides.
* Also, note the size of the bulges.
* Draw the diagram of hydra, as you see it.
* Compare it with the Fig. 9.11.
Figure 9.11: : Budding in Hydra
In each hydra, there may be one or more bulges. These bulges are developing new individuals and they are called buds. Recall the presence of buds in yeast. In hydra too the new individuals develop as outgrowths from a single parent. This type of reproduction in which only a single parent is involved is called asexual reproduction. Since new individuals develop from the buds in hydra, this type of asexual reproduction is called budding.
Source: This topic is taken from NCERT TEXTBOOK
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BINARY FISSION IN AMOEBA
BINARY FISSION IN AMOEBA
Another method of asexual reproduction is observed in the microscopic organism, amoeba. Let us see how this happens.
You have already learnt about the structure of amoeba. You will recall that amoeba is a single-celled organism [Fig. 9.12(a)]. It begins the process of reproduction by the division of its nucleus into two nuclei [Fig. 9.12(b)]. This is followed by the division of its body into two, each part receiving a nucleus [Fig. 9.12(c)]. Finally, two amoebae are produced from one parent amoeba [Fig. 9.12(d)]. This type of asexual reproduction in which an animal reproduces by dividing into two individuals is called binary fission. Apart from budding and binary fission, there are other methods by which a single parent reproduces young ones. You will study about these in your higher classes.
Figure 9.12: Binary fission in Amoeba
Story of Dolly, the Clone
Cloning is the production of an exact copy of a cell, any other living part, or a complete organism. Cloning of an animal was successfully performed for the first time by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland. They successfully cloned a sheep named Dolly [Fig. 9.13 (c)]. Dolly was born on 5th July 1996 and was the first mammal to be cloned.
Figure 9.13(a): Finn Dorsett sheep
Figure 9.13(b): Scottish blackface ewe
Figure 9.13(c): Dolly
During the process of cloning Dolly, a cell was collected from the mammary gland of a female Finn Dorsett sheep [Fig. 9.13 (a)]. Simultaneously, an egg was obtained from a Scottish blackface ewe [Fig. 9.13 (b)]. The nucleus was removed from the egg. Then, the nucleus of the mammary gland cell from the Finn Dorsett sheep was inserted into the egg of the Scottish blackface ewe whose nucleus had been removed. The egg thus produced was implanted into the Scottish blackface ewe. Development of this egg followed normally and finally, Dolly was born. Though Dolly was given birth by the Scottish blackface ewe, it was found to be absolutely identical to the Finn Dorsett sheep from which the nucleus was taken. Since the nucleus from the egg of the Scottish blackface ewe was removed, Dolly did not show any character of the Scottish blackface ewe. Dolly was a healthy clone of the Finn Dorsett sheep and produced several offspring of her own through normal sexual means. Unfortunately, Dolly died on 14th February 2003 due to a certain lung disease.
Since Dolly, several attempts have been made to produce cloned mammals. However, many die before birth or die soon after birth. The cloned animals are many-a-times found to be born with severe abnormalities.
Source: This topic is taken from NCERT TEXTBOOK