Self-fertilisation occurs in Taenia, while cross-fertilisation occurs in Pheretima, Periplaneta and Rana tigrina.

From 27th segment upt 23-25 segments in front of the anus in intestine of earthworm, lies a highly glandular and vascular part called typhosole. It greatly increases the effective absorption area for digested food in the intestine.

• Balaenoptera which designates genus is a combination of two Latin words, Balaena (meaning whale) and "pteron" (meaning fin). It thus means a whale having a dorsal fin so as to distinguish from Balaena (meaning whale without dorsal fin). "Musculus" designating species is a Latin word originally meaning a "mouse.
• In mammals, reptiles, birds, and some types of fish the gametes meet inside of the female's body. This is called internal fertilization. 
• As Balaenoptera is a mammal the fertilization in Balaenoptera is internaL.
• so, the correct answer is  'Balaenoptera - internal fertilization'.

Sexual reproduction in animals involves the production and fusion of two types of gametes (haploid cells) sperm and eggs. Typically, two different individuals are required. A male parent contributes sperm, and a female parent contributes an egg, or ovum. The sperm provides genes coding for some of the male parents traits, and the egg contributes genes coding for some of the female parents traits. The egg is typically large and nonmotile, with a store of nutrients that supports the development of the embryo. The sperm is usually small and motile and adapted to propel itself by beating its long, whip like flagellum. When sperm and egg unite, a (diploid) zygote, or fertilized egg, is produced. The zygote develops into a new animal, similar to both parents but not identical to either. Sexual reproduction typically involves remarkably complex structural, functional, and behavioural processes. In vertebrates, hormones secreted by the hypothalamus, pituitary gland and gonads regulate these processes.

Syngamy is a process in sexual reproduction that is defined as the fusion of the male gamete i.e., sperm with the female gamete i.e., egg resulting in the formation of a diploid zygote. Thus the correct answer is option A.

The fusion of similar motile gametes is known as isogamous. Monocystis is an endoparasite in the seminal vesicle and coelom of earthworms. Fusing gametes do not differ morphologically but may be different physiologically. The isogamous gametes fuses to form zygote which develops into sporoblast, sporocyst, trophozoite and finally, to young trophozoite.

Ovarian cell is the cells of ovary.
Oocyte is the female gametocyte or germ cell. It is involved in reproduction.
Zygote is the diplod cell, formed by the fusion of two gametes i.e., by the fusion of male gamete (sperm) or female gamete (ovum).
Graafian follicle is the mature follicle in the ovary of mammals. It contains cavity, which is filled by liquid and it ruptures during ovulation to release ovum.
Thus, the correct answer is option C.

In oogamy, fertilization involves the fusion of a large non-motile female gamete and a small motile male gamete. The large motile female gamete is the ovum which is produced in the ovary. The ovum after maturation is released from the ovary under the influence of LH hormone. The small motile male gametes are known as sperm which is produced in the testis. The two dissimilar gametes fuse to form a diploid zygote by the process of syngamy.

The process of fusion between haploid male nucleus and egg nucleus is known as amphimixis. It is also known as syngamy. The process is known as fertilization which leads to formation of a diploid zygote and restores diploid condition in zygote. The statement is true.

Syngamy is sexual reproduction by fusion of male gamete( sperm) with female gamete ( egg ) to form a zygote which eventually develops in the new organism.

The fusion of similar motile gametes is known as isogamous.

Fertilization is the process of union of a haploid sperm cell with haploid ovum to form a diploid zygote.

Fertilization is the process of formation of the zygote by the fusion of male and female gamete. It was discovered by Strasburger. Lamarck and Darwin worked on the theories of evolution and Robert Brown discovered the nucleus.

Chromosomal sex determination is carried out at fertilisation. This is done based on the presence or absence of the Y chromosome. Either the X or Y chromosome from the sperm fuses with the X chromosome of the egg and so females have XX and males have XY. So, the correct option is 'During fertilization'.

Sexual reproduction is a characteristic of animals, although many animals reproduce sexually as well asexually. Reproduction is essential to the survival of any species. Most animals are involved in some variety of sexual reproduction. The methods vary greatly from the simultaneous release of sperm and eggs into the water for many marine organisms, to fertilization inside the body for most terrestrial organisms and high degrees of parental care in birds and mammals.

Aquatic animals like fishes and amphibia usually show external fertilisation, whereas terrestrial animals like reptiles, birds and mammals show internal fertilisation. Egg of animal showing external fertilization is not covered by a hard, protective shell and after fertilisation the embryo develops into larva in water. 

In human males the urethra, a tube that exits through the penis, carries urine to the exterior and, alternatively, serves as a conduit for seminal fluid. Sperm is carried in a fluid formed along the male reproductive tract by the seminal vesicles, prostate gland, and cowper's glands, accessory glands of the male reproductive tract. Thus, if cowper's glands are removed process of fertilization will be affected.

Tubectomy is a surgical procedure for sterilization in which a woman's fallopian tubes are clamped and blocked, or severed and sealed, which prevents eggs from reaching the uterus for implantation, thereby no fertilization can takes place. It is considered the permanent method of birth control. 

1)fertilization starts with fusion of male gamete (sperm) and female gamete (zygote). 
2) this fusion results in the formation of zygote. 
3) Zygote divided repeatedly to give rise ball of cells that forms embryo.
4) after the formation of embryo is gets embedded in the wall of uterus where it further forms the foetus so the correct order is in above steps.

Chlorophyceae is a class of algae that is also known as green algae commonly. Different members of this class reproduce differently.

The phenomenon of fertilization was first perceived by the German biologist Oscar Hertwig in sea urchin eggs in 1876. Hertwig observed that the sperm nuclei and egg fused during fertilization resulting in the generation of new organism. Thus the correct answer is option D.

Chlamydomonas reproduces both asexually and sexually. 

Fertilization is the process of fusion of male and female gametes. Gametes are haploid (n) in nature and the fusion of the two results in the diploid (2n) product called as zygote. Zygote is the universal diploid cell. 

Oogamous reproduction involves fusion of one motile male gamete and another non-motile large sized female gametes. 

Oogamy is a form of sexual reproduction. It is a form of anisogamy (heterogamy) in which the female gamete is significantly larger than the male gamete and is non-motile.The male gametes are  smaller in size and motile 
So, the correct option is 'Large non-motile female gamete and small motile male gamete'.

Syngamy and triple fusion are two events of sexual reproduction in plants. Syngamy is the fusion of one of the male gamete with the egg cell to produce a zygote while In triple fusion, second male gamete fuses with two polar nuclei to produce primary endosperm nucleus.

Fasciola is a genus of trematodes. It is commonly known as liver fluke. It shows the phenomena of endogamy where the two fusing gametes are derived from the same parent which means the gametes are uniparental. These are hermaphrodite and has both male and female reproductive organs. The male and female reproductive organs open up into the same chamber within the body, which is called the genital atrium where the two gametes fuses.

The process of fusion between the haploid male nucleus and egg nucleus is known as amphimixis. It is also known as syngamy. It leads to the formation of a diploid zygote. The form of sexual reproduction in which the gametes are of the same size and structure as the somatic cells. Trichonympha lives in the intestine termite species and helps them to break the cellulose which they take from the wood. They produce similar haploid gametes known as zooflagellates so it is classified as hologamy.

Fertilization is the fusion of male and female gametes. In animals, it was first discovered by Aristotle. In plants, it was discovered by Nawaschin.

As the sperm reaches ovum to fertilize it, the ovum gets activated and completes its second meiotic division. After fertilization, a diploid zygote is formed. Fertilization also helps in determining the sex of the offspring. On the one hand, it leads to inherent qualities of a parent and on the other hand, it is the means for variations among the populations.

• An isogamete is a gamete that is indistinguishable in size and form from the other gametes. The sex i.e, the male and female have also exhibited no difference.  It is found in algae and fungi. 

Internal fertilization occurs inside the body whereas external fertilization happens outside the body.
External fertilization requires the presence of water for the sperm to be able to unite with the egg. Large number of offspring are produced but the chances of survival is very less.
With internal fertilization, the presence of water is not needed. Fewer young ones are produced because the mother's body will protect any fertilized eggs from being devoured by predators, so chances of survival is high.
Thus, the correct answer is option (D), 'Both A and C.'

Isogamy is the fusion of gametes that are similar in similar sizes. Anisogamy involves fusion of gametes that are dissimilar in sizes where both gametes are either motile or immobile.

• Oogamy is a system of sexual reproduction in which one gamete (called the egg) is large and nonmotile, while the other (called the sperm) is small and motile. Oogamy is a type of Anisogamy.
  
• During Spermatogenesis, the protoplast of spermatogonium is equally divided into 4 spermatids while during oogenesis, ovum retains the bulk of protoplast and is minimally shared by Polar bodies.