Define evolution. How does it occur? Describe how fossils provide us evidences in support of evolution.
iii. Genetic Drift refers to the fact that variations in gene frequencies within populations can occur by chance rather than by natural selection. Random genetic drift may be an important mechanism in evolutionary change in small population.
All this leads to changes in the heritable characters and finally results in evolution of the organism.
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.
21.How do Mendel’s experiments show that the
(a) traits may be dominant or recessive
(b) traits are inherited independently
(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.