1. Chasmogamous flowers are the bisexual, open flowers with exposed anthers and stigma. 
2. Cross-pollination cannot occur in cleistogamous flowers because they remain in bud throughout their life and form seeds via self-pollination.

An embryo sac is called monosporic because it develops from one of the four megaspores formed from the division of megaspore mother cell.

1.Fitness, according to Darwin, refers ultimately and only to reproductive fitness.
2.Those who are better fit in an environment would outbreed others, who are less fit in that environment; they leave more progeny (with more fit individuals) than others.
3.They will survive better and are selected by nature (natural selection) to reproduce and increase their population size.

Hardy-Weinberg principle states that allele frequencies in a population are stable and remain constant generation after generation; it is called genetic equilibrium.
Genetic drift
Genetic drift refers to the random changes in the allele frequencies of a population, in the allele frequencies of a population, that occur only by chance.
When the change in the allele frequency is so different in the original drifted population that it becomes a new species, the original population becomes founders and such an effect, is called founder effect.

1. Apomixis is a form of asexual reproduction that mimics sexual reproduction and seeds are formed without fertilisation.
2. Apomictic embryos are genetically identical to the female parent.
3. If hybrid seeds can be made apomictic, the desirable characters can be maintained in the progeny.
4. It is often associated with polyembrony.

There is an adaptation in angiospermic plants to provide assured nutrition to the developing embryo. Most zygotes divide only after certain amount of endosperm is formed. Therefore, zygote remains dormant for sometime in a fertilised ovule.

1. Male gametophyte - In the Anther (microsporangia) and later on the stigma and style.
2. Female gametophyte - inside the ovule.

Tapetum is the innermost layer of the microsporangium. It produces the exine layer of the pollen grains, which is composed of the sporopollenin, the most resistant organic material. During microsporogenesis, the cells of tapetum produce various enzymes, hormones, amino acids and other nutritious materials required for the development of pollen grains.

Triple fusion:
It is  the process of fusion of three nuclei, two polar nuclei (fuse to form a diploid secondary nucleus) and a male gamete.
It occurs in the central cell of the embryo sac of the ovule of angiosperms.
Then nuclei involved are two polar nuclei and a male gamete.

Alexander I. Oparin (1894-1980), a Russian biochemist and J.B.S. Haldane (1892-1964), a British scientist have put forward the concept of biogenesis. According to Oparin and Haldane primeval earth had reducing condition and atmosphere is free from oxygen. Oxygen remained bound in HO and metallic oxides on the surface of rocks and its particles. The early gas cloud was rich in hydrogen, in form of methane (CH₄) and ammonia (NH₃) and water (H₂O). The organic nolucles formed due to atmospheric reaction accumulated slowly and gradually in sea and constitute what is called "Hot, dilute soup".
Significance of hot dilute soup. Thus conditions of reducing nature are unable to oxidize these organic compounds which form the basis of life.

Yes, had Darwin been aware of Mendel's work, he would have been able to explain the origin of variations. Darwins observation of different forms of an individual in a population could be related to the presence of different forms of alleles of a gene.
The gene express as the most adaptive traits are selected naturally and become more adaptive traits.
Over the time, the accumulation of these traits might change the species to an extent that it develops into a new one and adapted to the specific environment.

Meiosis occurs during sporogenesis.
The structure formed at the end are microspores and megaspores respectively.