Question
Which of the following plant is monoecious? [NEET 2021]
(a) Carica papaya
(b) Chara
(c) Marchantia polymorpha
(d) Cycas circinalis
Answer/Explanation
Ans. (b)
When male and female reproductive structures are present on same plant it is called monoecious condition, whereas when both reproductive structures are present on different plants then this condition is called dioecious.
Chara is monoecious. It has oogonium (female organ) and antheridium (male organ)on the same plant. Other options are incorrect because Carica papaya(papayas) Marchantia polymorphaemel and Cycas circinalis (gymnosperm) are all dioecious plants.
Question
Which one of the following flowers only once in its lifetime? [NEET 2018]
(a) Mango
(b) Jackfruit
(c) Bamboo species
(d) Papaya
Answer/Explanation
Ans. (c)
Bamboo plants are perennial, monocarpic plants. They flower only once in their lifetime, usually after $50-100$ years. They produce large number of fruits and die. Mango, Jackfruit and Papaya are polycarpic plants, i.e. they flower repeatedly at regular intervals every year.
Question
Which one of the following generates new genetic combinations leading to variation? [NEET 2016, Phase II]
(a) Vegetative reproduction
(b) Parthenogenesis
(c) Sexual reproduction
(d) Nuclear polyembryony
Answer/Explanation
Ans. (c)
The sexual reproduction brings about variation through genetic recombinations. First of all genetic recombination occurs in non-homologous chromosomes during crossing over of pachytene stage in meiotic cell division.
Secondly, the random union of gametes also contributes in forming new combinations of characters. Other options (a), (b)and (d) do not contribute in the formation of progenies with new variations.
Vegetative reproduction occurs through vegetative parts of organisms (plants). Parthenogenesis is formation of new individual without fertilisation(e.g. frog).
Question
Match column I with column II and select the correct option using the codes given below [NEET 2016, Phase II]
Codes
A B C D
(a) 4 3 2 1
(b) 2 1 4 3
(c) 1 2 4 3
(d) 3 1 4 2
Answer/Explanation
Ans. (d)
(a) Pistils fused together – Syncarpous
(b) Formation of gametes – Gametogenesis
(c) Hyphae of higher ascomycetes Dikaryotic
(d) Unisexual female flower-Pistillate
Concept Enhancer Always remember, in Biology the latin word “Syn” signifies togetherness or fusion.
Question
Select the wrong statement. [NEET 2013]
(a) Isogametes are similar in structure, function and behaviour
(b) Anisogametes differ either in structure, function and behaviour
(c) In oomycetes female gamete is smaller and motile, while male gamete is larger and non-motile
(d) Chlamydomonas exhibits both isogamy and anisogamy and Fucus shows oogamy
Answer/Explanation
Ans. (c)
Oomycetes include water moulds, white rusts and downy mildews. In these, female gamete is larger and non-motile, whereas, male gamete is smaller and motile. Isogametes are found in algae like Ulothrix, Chlamydomonas, Spirogyra, etc., which are similar in structure, function and behaviour. Anisogametes are found in Chlamydomonas in which one gamete is larger and non-motile and the other one is motile and smaller. Dogamy is the fusion of non-motile egg with motile sperm. The gametes, differ both morphologically as well as physiologically. It occurs in Chlamydomonas, Fucus, Chara, Volvox, etc.
Question
Product of sexual reproduction generally generates [NEET 2013]
(a) longer viability of seeds
(b) prolonged dormancy
(c) new genetic combination leading to variation
(d) large biomass
Answer/Explanation
Ans. (c)
Sexual reproduction leads to new genetic combination leading to variation in new products. Longer viability of seeds, prolonged dormancy and large biomass are not related to sexual reproduction.
Question
Why is vivipary an undesirable character for annual crop plants? [CBSE AIPMT 2005]
(a) It reduces the vigour of the plant
(b) It adversely affects the fertility of the plant
(c) The seeds exhibit long dormancy
(d) The seeds cannot be stored under normal conditions for the next season
Answer/Explanation
Ans. (d)
Vivipary is the condition when seeds germinate on the plant. It is an undesirable character for annual crop plants because germinated seeds cannot be stored under normal conditions for the next season.
Question
In oogamy, fertilisation involves [CBSE AIPMT 2004]
(a) a small non-motile female gamete and a large motile male gamete
(b) a large non-motile female gamete and a small motile male gamete
(c) a large non-motile female gamete and a small non-motile male gamete
(d) a large motile female gamete and a small non-motile gamete
Answer/Explanation
Ans. (b)
In oogamous type of sexual reproduction, the female gamete (ovum/egg) is big, Passive while male gametes (spermatozoids)are smaller, active and motile.
Question
The process of series of changes from larva to adult after embryonic development is called [CBSE AIPMT 1999]
(a) regeneration
(b) metamorphosis
(c) growth
(d) ageing
Answer/Explanation
Ans. (b)
Metamorphosis (meta=change, morphe-form) is a process by which an animal under goes a comparatively rapid change from larval to adult form. Regeneration is regrowth of the part of body which has been removed due to the injury or other causes. Growth is an increase in dry mass of an organism. Ageing is progressive deterioration in activity of cell, tissues, organs, etc.
Question
A perennial plant differs from biennial in [CBSE AIPMT 1995]
(a) having underground perennating structure
(b) having asexual reproductive structures
(c) being tree species
(d) not dying after seasonal production of flowers
Answer/Explanation
Ans. (d)
Perennial plants have life span of more than two years, these may be herbs, shrubs or trees. Biennials are those plants which complete their life cycle in two years. These plants are usually herbs.
Question
Syngamy means [CBSE AIPMT 1991]
(a) fusion of gametes
(b) fusion of cytoplasms
(c) fusion of two similar spores
(d) fusion of two dissimilar spores
Answer/Explanation
Ans. (a)
Syngamy refers to the fusion of male and female gametes or compatible gametes. It is also known as fertilisation. In seed plants, fertilisation/syngamy occurs with the help of pollen tube and is known as siphonogamy.
Question
New banana plants develop from [CBSE AIPMT 1990]
(a) rhizome
(b) sucker
(c) stolon
(d) seed
Answer/Explanation
Ans. (b)
New banana plants develop through sucker, Sucker is the sub-aerial modification of stem which originates from the basal and underground portion of main stem. It grows obliquely upwards giving rise to leafy shoot or a new plant. It also occurs in mint, Chrysanthemum, etc.