Diversity of Life Forms MCQ Quiz in தமிழ் - Objective Question with Answer for Diversity of Life Forms - இலவச PDF ஐப் பதிவிறக்கவும்

Concept:

• Dinoflagellates are a group of unicellular protists that can be identified using the light microscope, and are (usually) recognized by their golden-brown plastids, assimilative cell with indented waist, distinctive swimming pattern, and relatively large nucleus that contains visible chromosomes.
• The name dinoflagellate comes from dinos (Greek) “whirling,” which describes their distinctive swimming pattern, and flagellum (Latin) “a whip.”
• Freshwater dinoflagellates, including one of the most identified unicells in all the plankton, Ceratium hirundinella 

Explanation:

• Currently, there are about 250-300 species of freshwater dinoflagellates known worldwide, and about 150 have been reported from North America.
• Freshwater dinoflagellates are diverse in shape and growth habit, occurring mainly as single cells either in the plankton or attached to substrates such as algal filaments and as nonmotile resting stages in the sediments.
• Historically, individual dinoflagellate taxa have been described as unarmored (naked/athecate) or as thecate (armored with cellulose plates), although it is increasingly realized that some if not many species originally thought to be unarmored actually possess very thin thecal plates that are difficult to observe.
• Dinoflagellates are perhaps best known to the public as the source of red tides leading to fish and other marine animal kills, as well as various types of human illness caused by their toxins: paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning, diarrhetic shellfish poisoning, and ciguatera. 
• Dinoflagellates are neither plants nor animals, but many have plant-like characteristics such as photosynthesis, cellulose-containing walls, and synthesis of starch as an energy storage product.
• Animal-like features of many dinoflagellates include phagotrophy (feeding on prey or hosts), rapid swimming, eyespots, and trichocys.
• Their cells contain chlorophylls a and c and reproduction in dinoflagellates is primarily asexual through binary fission. 

Concept:

• The guidelines and suggestions pertaining to the scientific naming of the official names given to the plants are referred to as the International Code of Botanical Nomenclature.
• Each taxonomic group of plants should only have one valid name that is widely accepted, according to the ICBN.
• As a result, it will be simpler and more effective to research and identify those plants.

​Explanation:

• When the holotype of a species has not been assigned by the name's original author at the time of publication, a specimen is referred to as a lectotype.
• To put it another way, a lectotype is a specimen designated as the type specimen when the original name-giver did not specify a holotype for that specific material and description.
• The best place to choose a lectotype is from the original material or syntypes.
• Therefore, syntypes should always be considered and chosen before lectotypes whenever lectotypes are chosen.
• A specimen chosen to replace a species' nomenclatural type is known as a neotype.
• Typically, a neotype is designated when the holotype is lost or destroyed.
• Although an original description has been published, there is no nomenclatural type specimen.
• A specimen is then chosen to serve as the description's type material; this specimen is known as the neotype.
• In contrast to lectotypes, neotypes have a holotype that was chosen by the name's original originator. But it is misplaced or silenced.
• As a result, the nomenclatural type for the initial description is a neotype.
• Neotypes can be chosen from any specimen that matches the traits of the specified type, despite the fact that there are some guidelines for their selection. As a result, the best specimen is chosen as the neotype.

Since species A's type had never been selected, while species B's type specimen for that species had been designated but was absent so both are neotypes according to the explanation above.

  hence the correct answer is option 2

Concept:

• Alternation of generations is a unique reproductive strategy observed in plants, where they exhibit alternating phases of gametophyte generation and a sporophyte generation.
• The plant life cycle transitions between these two distinct phases.

Gametophyte phase -

• It is the haploid phase, where the plant produces gametes through mitosis.
• These gametes fuse during fertilization to form a zygote, which develops into the sporophyte phase.

Sporophyte phase -

• This is the diploid phase, where the plant produces spores through meiosis.
• These spores are released and germinate to develop into new gametophytes, thereby completing the life cycle.

Important Points

Mosses -

• Mosses belong to Bryophyta, that are non-vascular plants i.e., lack true vascular tissues.
• They have a dominant gametophyte stage in their lifecycle, with the sporophyte stage being short-lived and dependent on the gametophyte.
• Mosses also reproduce through spores rather than seeds.

Ferns -

• Ferns belong to the Pteridophyta and possess all the given plant traits.
• They have a dominant sporophyte stage in their lifecycle, which is the larger and more conspicuous phase of the plant.
• Ferns also have well-developed vascular tissues, including xylem and phloem, which allow them to transport water, nutrients, and sugars throughout the plant.
• However, unlike seed plants, ferns reproduce via spores rather than seeds.

Cycads -

• Cycads are a group of Gymnosperms that are naked-seed plants and have a sporophyte-dominant lifecycle.
• They also possess vascular tissues for efficient nutrient transport.
• However, unlike ferns, cycads produce seeds, which are structures that enclose and protect the developing embryo.

Monocots -

• Monocots are a group of flowering plants or Angiosperms.
• They are characterized by having a single cotyledon in their embryo.
• While monocots possess vascular tissues and have a dominant sporophyte stage, they differ from ferns in that they reproduce through seeds.

Hence, the correct answer is option 2.

The correct answer is they are triploid and therefore seeds are not set.

Concept:

• Polyploidy refers to the condition of having more than two complete sets of chromosomes. In the case of bananas, they have three sets of chromosomes (triploid), denoted as 3n. In bananas, triploidy typically arises from the crossing of diploid (2n) and tetraploid (4n) plants. When these two different chromosome sets combine during reproduction, the resulting plant has three sets of chromosomes.
• During sexual reproduction, chromosomes need to pair up evenly during meiosis to form viable gametes (eggs and sperm). In diploid organisms, each chromosome has a homologous partner, facilitating this pairing.
• In triploid organisms like cultivated bananas, the odd number of chromosome sets (three of each chromosome instead of two or four) prevents proper pairing during meiosis. This results in the formation of unbalanced and non-functional gametes.

Explanation:

• Most cultivated varieties of bananas are sterile because they are triploid, that is, they contain three sets of chromosomes instead of the two found in most sexually reproducing organisms. During production of gametes (ovules and pollen) the odd set of chromosomes segregates unevenly, resulting in sterility.
• Cultivated bananas are produced asexually from sucker shoots at the base of the plant.

The correct answer is Option 4 i.e.A ‐ I and V ; B ‐ II, IV, and V

Key Points

• Bryophytes are terrestrial, non-vascular cryptogram that requires water for fertilisation, hence, they are also called amphibian plants. 
• They are advanced plants over the algae (Thallophyta) as they have multicellular jacketed sex organs i.e., antheridia (male) and archegonia (female). 
• They show distinct alternation of generations. 
• The plant body is called gametophyte and may be thallus (e.g., Riccia) or can be differentiated into rhizoids (root-like), cauloid (stem-like) and phylloid (leaves-like). 
• They lack a 'true' vascular system as their vascular system is not differentiated into xylem and phloem. 
• They can have a vegetative, asexual and sexual mode of reproduction.
• Vegetative reproduction is by te means of reproductive bodies like gemmae, tubers or adventitious buds. 
• Asexual reproduction is by the means of non-motile, wind-dispersed spores which are enclosed in a capsule of the sporophyte. The asexual spore germinates to give rise to a gametophyte. 
• Sexual reproduction is by the means of multicellular jacketed sex organs. 
  • Male sex organ produce male gametes that are biflagellate and coiled structures. 
  • Female sex organ produce female gametes called eggs that are non-motile. 
• Fertilization results in a zygote that develops into an embryo which later turns into sporophytes.
• Hence, Gametophyte is the dominant generation. It is autotrophic and independent. while sporophyte is small, parasite or semi-parasite on the gametophyte. 
• Bryophytes are divided into three classes :
  • Hepaticeae (Liverworts)
  • Anthocerotea (Hornworts)
  • Musci (mosses)

Explanation:

• Unicellular rhizoids are found in liverworts while multicellular rhizoids are found in mosses.
• Mosses and hornworts are the earlier known plant form that has stomata and their stomata are located on the sporangium of the sporophyte.
• Pyrenoids are proteins aggregates most exclusively consisting of Ribulose 1,5-bisphosphate carboxylase/oxygenase enzyme amongst other minor proteins. Pyrenoids are generally absent in bryophytes and only found in hornworts. 
• All bryophytes have gametophyte as their dominant generation.

Hence, the correct answer is Option 4.

 Additional Information

1. Liverworts 
   • The plant body is a thallus, dorsoventrally flattened and dichotomously branched. 
   • The dorsal surface is marked by grooves while the ventral surface consists of unicellular rhizoids. 
   • Vegetative reproduction takes place by gemmae.
2. Mosses
   • The plant body is differentiated into rhizoids, cauloid and phylloids.
   • They have multicellular rhizoids. 
   • Reproduction is mainly by sexual and asexual modes, and a few times vegetative reproductions is seen. 

Concept:

• Zoogeography refers to the geographic distribution of animal life or fauna.
• The concept was originated by naturalists like A. R. Wallace in the 19th 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.

Important Points

• Earth is broadly divided into 3 realms - Megagea, Neogea and Notogea.
• These realms are again divided into several regions.
• The land masses can be classified as given below:

Explanation:

• The Indian subcontinent is covered in the Oriental region of tropical Asia.
• The Oriental region is included in the Megagea realm.
• Therefore, the Indian subcontinent belongs to the Megagea realm.

The correct answer is A, C, and D

Explanation:

A flower is considered a modified shoot because it originates from a shoot apex and shows morphological modifications of typical shoot structures. Floral organs such as sepals, petals, stamens, and carpels are homologous to leaves, showing modification of leaf structures in a reproductive context.

• Statement A: Correct. Flowers develop in the axils of bracts similar to axillary shoots, indicating their origin as modified shoots.
• Statement B: Incorrect. The floral pedicel is not an elongated node, rather, the floral axis is typically condensed and does not elongate like a normal shoot.
• Statement C: Correct. Floral parts (calyx, corolla, androecium, gynoecium) are morphologically modified leaves, reinforcing the concept of flower as a modified shoot.
• Statement D: Correct. Floral buds generally develop into reproductive structures; modification into vegetative buds or bulbils is rare. In some cases, floral buds can modify into vegetative buds or bulbils, as seen in plants like Agave and Dioscorea.

The correct answer is A - II, B - III, C - I

Explanation:

• Bugun liocichla (Liocichla bugunorum) - Northeast India (II): This rare bird was discovered in Arunachal Pradesh, Northeast India, and is endemic to this region's subtropical forests. It is named after the Bugun tribe of Arunachal Pradesh.
• Grey-headed Bulbul (Pycnonotus priocephalus) - Western Ghats (III): This bird is endemic to the Western Ghats, a biodiversity hotspot in peninsular India, primarily inhabiting evergreen forests at mid to high elevations.
• Brooks's Leaf-Warbler (Phylloscopus subviridis) - High Altitude Western Himalayas (I): This species is found in the higher altitude forests and scrub areas of the Western Himalayas, adapted to cooler climates and elevation.

The correct answer is A-II, B-IV, C-I, D-III

Explanation:

Snakes - Heat sensing pits (A-II):

• Many snakes, such as pit vipers, have specialized heat-sensing pits located between their eyes and nostrils.
• These pits allow snakes to detect infrared radiation emitted by warm-blooded prey, helping them locate and hunt effectively in darkness.

Spiders - Spinnerets (B-IV):

• Spiders have spinnerets, which are specialized organs used to produce silk.
• Silk is used for various purposes, including building webs, creating egg sacs, and capturing prey.

Fishes - Lateral Line (C-I):

• Fishes possess a lateral line system, which is a sensory organ that detects vibrations and movement in the water.
• This adaptation helps fishes sense nearby objects, predators, and prey, even in murky or dark environments.

Dolphins - Echolocation (D-III):

• Dolphins use echolocation to navigate and hunt in underwater environments.
• By emitting sound waves and analyzing the echoes that bounce back, dolphins can determine the location, size, and shape of objects around them.

The correct answer is Thar desert of India

Explanation:

• Saara hardwickii, commonly known as the spiny-tailed lizard, is a diurnal (active during the day), ground-dwelling reptile.
• This species is primarily herbivorous but may occasionally consume insects or other small prey.
• It is endemic to arid and semi-arid regions of the Indian subcontinent, with its primary habitat being the Thar Desert.
• The Thar Desert, also known as the Great Indian Desert, is characterized by arid conditions, sandy landscapes, and sparse vegetation. It provides the perfect habitat for Saara hardwickii.
• The spiny-tailed lizard thrives in the hot and dry climate of the Thar Desert, where it can bask in the sun during the day and retreat to burrows for protection from predators and extreme temperatures.
• These lizards are often found in sandy areas with scattered shrubs and grasses, which provide both shelter and food sources.