STD 12 - 13. biodiversity and conservation — Biology STD 12 Science — Question

$A.$ Barrier methods of contraception

$B.$ Cover the cervix during coitus

$C.$ Protect the user from contracting $STDs$

$D.$ They are reusable
 

$(i)$ Queen Elizabeth shows a number of haemophilic descendents.

$(ii)$ Variation in blood group prevalences due to incomplete dominance.

$(iii)$ Drosophila has three pairs of autosomal chromosomes.

$(iv)$ In birds, female is heterozygous.

$(I)$ Nucleus of the functional megaspore divides meiotically to form two nuclei.

$(II)$ After $8$ nucleate stage, cell walls are laid down leading to organization of typical female gametophyte

$(III)$ The egg apparatus, consists of two synergids and one egg cell.

$(IV)$ Three cells are at the chalaza end are called antipodal cells.