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.
Speciation is the the formation of new and distinct species in the course of evolution.
Reasons for speciations are:
i. Reproductive isolation
ii. Genetic drift.
iii. Geographical isolation
iv. Natural selection
In the case of plant species with self pollinating flowers the factor reproductive isolation will not have much effect because the plant is not dependent on any other species for reproduction but has male and female parts in the same flower or the same plant. Thus there is no effect of reproductive isolation.
(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.
21.How do Mendel’s experiments show that the
(a) traits may be dominant or recessive
(b) traits are inherited independently
Define evolution. How does it occur? Describe how fossils provide us evidences in support of evolution.
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.
