The steps involved in the process of in-vitro fertilisation (IVF) which is also known as test tube programme are:
(i) The ova from the wife/female donor, along with the sperms from the husband/male donor, are collected in the laboratory.
(ii) The ova and sperm are included for the formation of zygote under suitable conditions in the laboratory.
(iii) The zygote up to eight blastomeres can be directly transferred to the fallopian tube. This process is known as zygote intrafallopian transfer – ZIFT.
(iv) If the zygote has more than eight blastomeres, then the zygote is directly transferred to the uterus. This process is known as intrauterine transfer (IUT).
(v) After the process of ZIFT or IUT, the transplanted zygote would form an embryo, and eventually a newborn baby would be born.
(b) The importance of the test tube baby programme is that the couples who cannot bear a child naturally due to certain diseases or infertility disorder in either the male or female or both can have a child by the test tube baby programme.
In both geitonogamy and xenogamy during the process of pollination, the pollen grains from the anther is transferred to the stigma of another flower of the same species.
In geitonogamy, during pollination, the pollen grains of one flower is transferred to another flower of the same plant itself whereas in xenogamy during pollination the pollen grains of one flower is transferred to a flower of another plant which is of the same species.
(b) Three devices developed in flowering plants to discourage self-pollination and encourage cross-pollination are:
(i) Self-incompatibility: It is the phenomenon among flowering plants which inhibits pollen of one flower to germinate on the pistil/stigma of another flower.
(ii) Production of unisexual flowers: Some flowering plants produces unisexual flowers, which prevents them from self-pollination and encourages cross-pollination. Examples are maize and castor.
(iii) Arrangement of anther and stigma: In some flowering plant species the arrangement of the stigma and the anther are positioned differently, which prevents self-pollination.
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