Differentiate between (a) oestrus and menstrual cycles; (b) ovipary and vivipary. Give an example for each type.
(a) The differences between oestrus and menstrual cycle are as follows
| $$ \text { Oestrus cycle } $$ |
$$ \text { Menstrual cycle } $$ |
|---|---|
| The cyclic changes in the activities of ovaries and accessory ducts as well as hormones during the reproductive phase of non-primate mammals is called oestrus cycle. | The cyclic changes in the activities of ovaries and accessory ducts as well as hormones during the reproductive phase of primate mammals is called menstrual cycle. |
| Females show strong irresistible sexual urge. | Females do not show irresistible sexual urge. |
| There is estrus/heat production at the time of ovulation and copulation occurs only at that period. | There is no heat period and copulation occurs during any time of the cycle. |
| The shedding of endometrium and bleeding do not occur. e.g., cows, sheep, rats, deers, dogs and tigers etc. | The shedding of endometrium and bleeding occurs. e.g., monkeys, apes and humans. |
$$ \text { (b) The differences between ovipary and vivipary are as follows } $$
| $$ \text { Ovipary } $$ |
$$ \text { Vivipary } $$ |
|---|---|
| In ovipary, animals lay eggs. | In vivipary, animals give birth to young ones. |
| The eggs are covered by hard calcareous shell. | Ovum are not covered by calcareous shell. |
| The development of zygote takes place outside the female's body. | The development of zygote takes place inside the female's body. |
| Females lay eggs in a safe place in the environment, but the chances of survival are less e.g., all birds, most of reptiles are egg laying mammals. | Females deliver young ones and the chances of survival are more. e.g., mammals except monotremes egg laying mammals. |
Rose plants produce large, attractive bisexual flowers, but they seldom produce fruits. On the other hand a tomato plant produces plenty of fruits though they have small flowers. Analyse the reasons for failure of fruit formation in rose.
Rose plants produce large, attractive bisexual flowers, but they seldom produce fruits. The reasons for failure of fruit formation in rose are as follows
(i) Rose plants may not produce viable pollens, hence, no fertilisation can take place.
(ii) Rose plants may not have functional eggs.
(iii) Rose plants may have defective and non-functional ovule ,which is the female gametophyte generator.
(iv) There may be self-incompatibility.
(v) There may be internal barriers for pollen tube growth or fertilisation.
(vi) As rose plants are hybrids and reproduce vegetatively, there are chances for them to be sterile.