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The correct answer is Archegonium.

Key Points

• Archegonium is the female reproductive organ found in ferns and mosses.
• Archegonium is flask-shaped and produces a single egg.
• At maturity, the archegonium consists of two parts - basally swollen part venter and a slender long neck.
• The male reproductive organ is called the Antheridium, which produce biflagellate antherozoids.
• The antherozoids are released into the water where they come in contact with archegonium. An antherozoid fuses with the egg to produce the zygote.
• The zygote do not undergo reduction division immediately.
• The zygote develops into the multicellular embryo within the archegonium.
• This is known as the sporophyte.

Additional Information

Moss: General characteristics 

• Mosses and liverworts are plants that belong to Phylum Bryophytes and include various plants that are found commonly growing in moist shaded areas in the hills.
• They are amphibious plants that can live in soil but are dependent on water for sexual reproduction.
• It is thallus-like and prostrate or erect and attached to the substratum by unicellular or multicellular rhizoids.
• They may possess root-like, leaf-like or stem-like structures
• The main plant body of the bryophyte is a haploid. It produces gametes, hence is called a gametophyte.
• The sex organs in bryophytes are multicellular.
• The sporophyte is not free-living but attached to the photosynthetic gametophyte and derives nourishment from it.
• Reproductive organs
• Antheridium - It is a male sex organ in Moss, fern, fungi, and non-flowering plants.
• Oogonium - It is the female sex organ of certain algae and fungi, typically a rounded cell or sac containing one or more spores.

The correct answer is Phytomastigophora.

Concept:

• Euglena is a single-celled eukaryote placed under Kingdom Protista.
• They are primarily aquatic organisms.
• The cell body of Protistans contains a well-defined nucleus and other membrane-bound organelles.
• Some have flagella or cilia.
• Protists reproduce asexually and sexually by a process involving cell fusion and zygote formation.
• Euglena contains chloroplasts or chromatophores that bear the pigments.
• They contain the green pigment chlorophylls a and b as well as β-carotene pigment.
• The chloroplasts are slender, elongated and band-like structures present in the endoplasm of cell.

Key Points

According to the locomotive organs, Protozoans are classified into 4 classes -  

1. Mastigophora (Flagellates) -

• This class is classified into -

1. Phytomastigophora
2. Zoomastigophora
3. Sarcodina (Amoeboids) -

• They move using pseudopodia or false legs, which are an extension of the cytoplasm.
• The most common example is Amoeba.
• This class is further divided into -

1. Rhizopoda
2. Phyrophasmida
3. Actinopoda
4. Sporozoa (Non-motile) -

• This Class is further divided into - Teleospora, Taxoplasmea, Haplosporea

4. Ciliophora (Cilliates) - 

• This Class is further divided into class - Cilliatae

Important Points

• Phytomastigophora :
• These are pigmented, aquatic and covered by an exoskeleton of calcium.
• These are autotrophic and perform photosynthesis.
• Examples- Chlamydomonas, Euglena, and Volvox.
• Zoomastigophora:
• They are found as symbionts or parasites.
• Some organisms are found in marine habitats.
• Examples- Leishmania, & Trypanosoma.
• Rhizopoda:
• It is a large group of Protista.
• They capture prey using pseudopodia.
• They are heterotrophic.
• Example- Entamoeba histolytica.
• Actinopoda:
• ​They have shells (exoskeleton) made up of silica.
• Pseudopodia are needle-like.
• Examples- Radiolarians, Actinosphaerium.

Therefore, Euglena belongs to Phytomastigophora.

The correct answer is Allium.Concept:

• Embryo-sac is the oval structure present in the ovule of flowering plants, which is also the female gametophyte.
• The female gametophyte of a flowering plant, which develops within the ovule, is protected by the nucellus and the integuments of the ovule.
• It typically consists of an egg cell, a central cell, 2 synergids and 2 antipodal cells.
• An embryo sac is said to form when the haploid megaspore nucleus divides. It possesses 8 haploid nuclei and 7 haploid cells which do not have cell walls.
• At the event of fertilization, one male nucleus and egg nucleus combine for the formation of zygote leading to the development of the embryo.
• Endosperm forms with the triple fusion of the 2 polar nuclei and the second male nucleus.

Key Points

• Megasporogenesis is the process by which megaspores are formed from the megaspore mother cell (MMC) by meiosis.
• After meiosis, the megaspores may develop into embryo sac by different methods, which is characteristic of each plant.

Formation of Embryo Sac:

1. Monosporic or Polygonum-type embryo sac (Most common type of embryo sac):

• In this type, meiosis of the diploid megaspore mother cell in the nucellus produces four haploid megaspores as a megaspore tetrad.
• Three of the megaspores, usually those at the micropylar end of the nucellus, subsequently undergo programmed cell death, leaving only one functional megaspore.
• A single functional megaspore differentiates towards micropylar end with two haploid nuclei.

2. Bisporic Embryosac:

• In this type, meiosis produces only two megaspores, each containing two haploid (n) nuclei as a diad.
• This is due to the absence of cytokinesis (division of cytoplasm) and cell plate formation following the second meiotic division.
• It is commonly found in Allium.

3. Tetrasporic Embryo sac:

• In this type of embryo sacs, cell plates fail to form after both meiotic divisions, resulting in a single four-nucleate megaspore.

All three patterns give rise to a single functional megaspore that contains either one (monosporic), two (bisporic), or four (tetrasporic) haploid nuclei.

Concept-

• Steroid hormones, such as testosterone, are hydrophobic molecules that diffuse freely into and act within all cells.
• Therefore, there is no need for a receptor bound to the cell membrane, instead, there is a mobile receptor protein in the cytoplasm.

Key Points

• Testosterone can easily cross cell membranes.
• Cells do not need to invest in a trans-membrane delivery system if they can do the same for their intracellular receptors.
• The signal gain may be lower (shorter signal steps mean fewer gain steps).
• This means that the signalling pathway is less sensitive and/or slower, but is ideal for transmitting hormonal signals where transmission speed and specificity (in terms of precise location) are not very important.
• It is intended to affect systems in the most cost-effective way at the right time.

Additional InformationTSH

• TSH binds to the thyroid hormone (TR) receptor, a member of the nuclear hormone receptor family.
• TR acts as a ligand-activated transcription factor that binds to the cognate thyroid hormone response element (TRE) in the promoter of the target gene.

PTH

• The receptor binds to parathyroid hormone and belongs to the GPCR family of transmembrane proteins.
• The parathyroid hormone 1 receptor (PTH1R) is a classical PTH receptor that is expressed at high levels in bone and kidney and modulates calcium ion homeostasis by activating adenylic acid cyclase and phospholipase C.

FSH

• Follicle Stimulating Hormone (FSH), a glycoprotein hormone. , an essential component of the endocrine system that regulates gonad function and fertility.
• FSH must bind to a receptor (FSHR) on Sertoli cells of the testis and granulosa cells of the ovary to transmit a signal.

Concept-

• A tadpole is a larval stage in the life cycle of an amphibian.
• Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial.

Key Points Structure of a freshly hatched tadpole larva:

• A freshly hatched tadpole larva has a limbless body.
• The body is divided into an ovoid head, a short trunk and a slender tail.
• A small opening situated ventrally at the root of the tail is known as the anus.
• An adhesive sucker is present on the ven­tral side of the head by which the tadpole larva attaches itself to the aquatic weeds.
• The mouth is lacking and as a result, it cannot take anything from outside.
• The yolk material provides the nutrition.
• The respiratory organs comprise three pairs of highly vascular and branched feathery external gills.
• After a few days the mouth is formed near the sucker.
• A pair of horny jaws surround the mouth.
• The tail becomes more elongated and develops a dorsal and a ventral fin.
• V­-shaped myotomes develop on both sides of the tail.

Concept-

• The theory of evolution by natural selection was proposed by Charles Darwin.
• It stated that all life forms arise due to natural selection of small inheritable changes that increase the survivability of a species.
• Darwin also defined evolution as descent with modification, meaning we have evolved from our ancestors through inheritable variations of characteristics.
• The evidences for evolution include:
• Paleontological Evidence - Study of fossils have revealed that different life forms existed in different geological time-periods and similarities exist between existing and pre-existing life forms.
• Anthropogenic Evidence - Overuse of pesticides and herbicides have resulted in natural selection of resistant varieties in much lesser time.
• Comparative Anatomy & Morphology - Homology and analogy are based on comparisons between structure and functions of organs that show evolutionary adaptations in nature.

Key Points

• Homologous structures refer to the similar structures that differ in functions.
• Example - Forelimbs of whale, bat, cheetah and human.
• They are all made of humerus, radius, ulna, carpels, metacarpels and phalanges.
• Flippers of whales are used for swimming, wings of bats for flying and forelimbs of man for grasping and forelimbs of cheetah for running.
• Homology indicates divergent evolution -
• The same structure evolved in different directions.
• This shows evolutionary adaptations due to varying needs.
• Divergent evolution leads to speciation and works on the premise that there is a variety inside the quality pool of a population.
• It also indicates common ancestry - 
• The functions diverged from a common ancestor.
• Example - Thorns of Bougainvillea and tendrils of Cucurbita are both modified branches.

Additional Information Convergent evolution

• Convergent evolution happens when species have comparable environmental conditions to which they adjust to in comparable ways.
• It is evident for analogous structures.
• Analogous structures refer to different structures with similar functions.
• Example- Sweet potato and potato are root and stem modifications respectively but both function as storage organ.

Macroevolution and microevolution

• Microevolution is the process by which organisms changes in small evolutionary ways over a long time.
• Macroevolution refers to larger evolutionary changes that result in new species.

The correct answer is Palaearctic.

Key Points

• Zoogeography refers to the geographic distribution of animal life or fauna.
• The concept was originated by naturalists like A. R. Wallace in the 19^th century.
• The faunal regions are mostly described on the basis of vertebrate fauna, including invertebrates only at times.
• It was also shown as evidence of continental drift and how migration of species took place from their centers of origin.
• Each region more or less coincides with a major continental land mass separated by oceans, deserts or mountain ranges.
• Earth is broadly divided into 3 realms - Megagea, Neogea and Notogea.
• These realms are again divided into several regions.
• The classification of land masses into regions, based on studies of Wallace (1876) and Darlington(1957), is given below:

• Thus, Palaearctic is a region in Megagea realm.
• Hence, the Palaearctic is not the zoogeographic realm.

Concept:

• Thallus is a plant body that is not divided into stems and leaves and has no roots or vascular system.
• Thalli are found in algae, fungi, lichens and some liverworts.
• It may be unicellular or complex tree-like structures.
• These thalli may develop into reproductive structures called fruiting bodies in fungi.

Key Points

Holocarpic-

• This is a rather spherical unicellular structure in some subspecies of fungi such as Chytrids.
• On maturation, the entire thallus becomes a reproductive structure.
• Thalli with this structure are called a holocarpic thallus.
• The entire thallus functions as a sporangium.
• Example - Synchitrium.

Additional Information

• Eucarpic: It is a thallus in which only a part of it differentiates to form reproductive or structures. Most of the fungi are eucarpic.
• Holozoic: It is a type of nutrition in which liquid or solid organic matter is ingested, digested, absorbed, and assimilated. It requires the conversion of complex substances into simple substances. Example - Humans take food inside its body by ingestion and then it is digested.
• Homothallic: Homothallic means that the male and female reproductive organs are located on the same plant body. It is found in some fungi where opposite sexual functions are performed by different cells of the same mycelium.

The correct answer is Its body cavity is well developed.

Concept:

• Hirudinaria (Indian leech) belongs to the phylum Annelida of Kingdom Animalia.
• Indian leech is the common name of Hirudinaria.
• It inhabits freshwater ponds and still waters near streams and rivers.

Important Points

• Its medical use in India dates back to around 1000 BC: TRUE
• Leeches were used since the time of ancient Egypt to treat infections, skin problems, etc.
• In India, H. granulosa has been used in traditionally for therapeutic purposes.
• It sucks blood from fish, frog, cattles and humans: TRUE
• ​​​It is sanguivorous, i.e., feeds on blood.
• It sucks blood from fish, frog, cattles and humans.
• And single meal can last for over a year.
• Digestion of the blood takes 10 to 14 months: TRUE
• In Hirudinaria, digestion tract is straight and complete, starting from the mouth and ending at anus.
• They usually feed once in every 6 months.
• Presence of some bacteria keep the blood from decaying during the long digestion process.
• Thus, digestion of the blood takes 10 to 14 months.
• Its body cavity is well developed: NOT TRUE
• Hirudinaria (Indian leech) lacks head and parapodia.
• Coelom is greatly reduced by the formation of peculiar connective tissue called botryoidal tissue.
• So, the body cavity is not well developed.

Thus, the statement "Its body cavity is well developed" is not true about the Indian leech, Hirudinaria.

The correct answer is Pisum sativum.

Key Points

• Johann Gregor Mendel is considered as the Father of Genetics.
• He conducted hybridization experiments on garden peas for seven years (1856-1863) and proposed the laws of inheritance in living organisms.
• The factors, now known as genes, are responsible for transfer of characteristics from one generation to another.
• Genetics is the science which deals with the inheritance, as well as the variation of characters from parents to offspring.
• Inheritance is the process by which characters are passed on from parent to progeny; it is the basis of heredity.
• This simply means that due to inheritance, the members of the same family possess similar characteristics.
• Variation is the degree by which progeny differ from their parents or to put in simple words, it refers to the differences among individuals of the same species.

Mendel's experiment in short

• Mendel conducted artificial pollination/cross-pollination experiments using several true-breeding pea lines.
• He selected 14 true-breeding pea plant varieties, as pairs which were similar except for one character with contrasting traits like - smooth or wrinkled seeds, yellow or green seeds, inflated (full) or constricted green or yellow pods and tall or dwarf plants.
• The genetic makeup of the plant is known as the genotype. On the contrary, the physical appearance of the plant is known as phenotype.
• The genes are transferred from one generation (parent) to the another (offspring) in pairs known as allele (variant form of genes).

Explanation:

• Pisum sativum was selected by Mendel because:
• It is an annual plant, therefore, many generations can be studied within a short period of time.
• The pea plant can be easily grown and maintained.
• It is a naturally self-pollinating but can also be cross-pollinated.
• It has several contrasting characters.

Additional Information

1. Gallus gallus domesticus (Andulusian Fowl) 

• It is one of the breeds of domestic chicken, also known as the Blue Andalusian.
• They are either black, blue, or white-feathered.
• The Andalusian fowl reveals the heritage of mixing.
• The cross is made between the black and white feathers of the fowls in this breed of the Andalusian fowl. The blue feathered fowl is the product obtained from the cross.

2. Oenothera lamarkiana (Evening primerose)

• This plant is originally native to Brazil, but has become naturalized in many countries and planted as an ornamental plant in gardens.
• De Vries conducted experiment on Oenothera lamarckiana or Evening Primrose plant.
• It is a self-pollinated plant and its seeds were allowed to grow, the majority of F1 plants were similar to the parents, but a few were different plants.
• The same results were found in the F2 generation.
• Later on, it was revealed that most of the variants isolated from Oenothera lamarckiana were due to its anomalous chromosome behaviour.
• The chromosomes form multiple rings at meiosis and chromosomal end segments only involves in recombination (low-level crossing over) and plant shows complex heterozygosity i.e., during meiosis maternal and paternal chromosomes are arranged in alternate order.

3. Drosophila melanogaster (Fruit fly) 

• The phenomenon of linkage was studied by the scientist T.H. Morgan using the common fruit fly or Drosophila melanogaster.
• Linkage and recombination are phenomena that describe the inheritance of genes.
• A linkage is a phenomenon where two or more linked genes are always inherited together in the same combination for more than two generations.
• Morgan performed a cross between a heterozygous red-eyed female with a white-eyed male. This gave a ratio of 1:1:1:1 in the progeny (1 white eyed female, 1 red eyed female, 1 white eyed male and 1 red eyed male).
• He performed many such crosses and came to the determination that the gene responsible for the eye color was situated on the X chromosome (one of the two sex chromosomes).