(a) Draw a sectional view of human female reproductive system and label the part where
(i) eggs develop.
(ii) fertilisation takes place.
(iii) fertilised egg gets implanted.
(b) Describe, in brief, the changes the uterus undergoes
(i) to receive the zygote.
(ii) if zygote is not formed.
i. Eggs develop in - Ovary
ii. Fertilisation takes place in - Fallopian tube
iii. Fertilised egg gets implanted in the - Uterus
(b)
(i) On recieving the zygote the uterine walls becomes thicker and if the zygote gets implanted in the into the uterus then the female becomes pregnant. The
embryonic development of the zygote starts immediately. The embryo moves
down into the uterus forming a thick and soft lining of blood vessels around
itself. After implantation, placenta which is a special tissue, develops between the uterine wall and the embryo.
(ii) If the egg released by the ovary is not fertilized and the zygote is not
formed, then the thick lining of the uterus breaks down and comes out
through the vagina in the form of blood and mucous. This is called
menstruation.
21.How do Mendel’s experiments show that the
(a) traits may be dominant or recessive
(b) traits are inherited independently
How many pairs of chromosomes are present in human beings? Out of these how many are sex chromosomes? How many types of sex chromosomes are found in human beings?
The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it. Draw a flow chart showing the determination of sex of a newborn to justify this statement.
What is meant by speciation? List four factors that could lead to speciation. Which of them cannot be a major factor in the speciation of a self pollinating plant species. Give reason to justify your answer.
Define evolution. How does it occur? Describe how fossils provide us evidences in support of evolution.
