Question

fertilization leads to the frmation of embryo.
i)give the technical term for the development of embryo
ii)what are the events that occur during embryo development?
iii)the development of zygote depends on two factors.what are they?
iv)how will you categorise animals based on the development of zygote inside or outside the female body?
v)how does zygote in fungi and algae overcome dessication?

Answer 1

1. The technical term for development of embryo is embryogenesis.
2. The major events that occur during embryo development are:

• Cleavage which is rapid division of cells of the zygote without involving growth in size.
• Morula formation which is a solid ball of cells with a mulberry like shape.
• Blastocyst formation which is a hollow ball of cells with an inner cell mass, a blastocoel and a trophoblast that gets implanted in the uterine wall.
• Now, the placenta and the extra embryonic membranes are formed. Now, the inner cells mass of the balstocyst is called embryo.
• Next, gastrulation occurs which is the process of formation of three germ layers in the embryo, which are ectoderm, mesoderm and endoderm.
• Formation of different body parts continues in the embryo. After about 8 weeks of fertilisation, the embryo is now called foetus.
• After completion of the gestation period a full term foetus is delivered out.

3. The development of zygote depends on: genetic factors which are provided by the fertilising gametes and factors of the mother's body that affect implantation and subsequent development.
4. The animals in which zygote develops outside the body are called oviparous animals where zygote develops inside a fertilised egg. The animals in which zygote develops inside the female's body and a young one is delivered out of the body are called viviparous animals.
5. Algae and fungi protect their zygotes from desiccation by forming a thick wall called cyst around them.