In a lifespan, the organism has to grow and develop (the juvenile phase). After that the organism mature sexually and enter into the reproductive phase, before it undergoes senescence followed by death.

Since, the entire life cycle of an annual plant is shorter and has to be completed in one growing season, its juvenile phase is shorter than that of a perennial plant.

The correct sequence of events of sexual reproduction in a flowering plant are as follows gametogenesis, pollination, fertilisation, embryogenesis.

The probability of fruit set in a self-pollinated bisexual flower of a plant is far greater than a dioecious plant.

In self-pollinated bisexual plants transfer of pollen to stigma of flowers is easier than the dioecious plants. It is so because the anther and stigma lie close to each other and pollination is not effected even in the absence of pollinator. But in dioecious plants pollinator is necessary to bring about effective pollination as the anther and stigma lie away from each other.

No, presence of large number of chromosomes in an organism is not a hindrance to sexual reproduction. Ophioglossum (a fern) has chromosome number 1260, still it can reproduce sexually.

In higher organisms, the chromosomes are present in a compartment called nucleus, within the cell. Whether the number is small or large, the chromosomes are duplicated and then segregated inside this compartment, during cell division. The basis of sexual reproduction is generation of haploid gametes.

There is no relationship between the size and life span of an organism. e.g.,

(i) The mango tree has a shorter life span as compared to a peepal tree though both are of the same size.

(ii) The size of crow and parrot is almost same but the life span is 15 years and 150 years respectively.