Biology: CUET Mock Test - 10 - CUET MCQ

The law of dominance states characters encoded by discrete units. Mendel called these factors, which he believed transferred from parents during progeny during fertilization. These are now known as genes.

The correct answer is A - (III), B - (IV), C - (I), D - (II)
Explanation:
A - Usage of bisexual flowers as female parents: This process involves (III) Emasculation, which is the removal of male parts from flowers to prevent self-pollination. This allows for controlled cross-pollination in breeding programs.
B - Incorporation of several desirable characters into a single variety: This goal is typically achieved through (IV) Hybridization, a method used to combine the desirable traits of two different varieties or species into a single offspring, which can then be selected for the combined traits.
C - Exploiting hybrid vigour for many generations: To maintain the benefits of hybrid vigour over many generations, (I) Clonal selection is used. Clonal selection could involve selecting individuals with desired traits from these hybrids and vegetatively propagating them, although it's more directly related to selecting the best individuals from a population of genetically similar organisms. Hybrid vigour (heterosis) is usually exploited in a single generation, after which the vigour tends to decrease in subsequent generations if those hybrids are bred.
D - Improving local varieties of self-pollinated crops: This is typically done through (II) Pure line selection, where plants from a population that shows desired characteristics and which are genetically uniform (homogeneous) are selected and self-pollinated over generations to develop a pure line.

Concept:

• Sperm and ovum are the male and female gametes respectively.
• Gametes fuse to form a zygote which undergoes cleavage to form an embryo and the embryo develops to form the fetus.

Explanation:
Option 1:

• The placenta is an organ that forms during pregnancy.
• It is important for the exchange of nutrients and oxygen between the mother and the fetus.
• Placenta secretes hormones such as human chorionic gonadotropin (hCG), relaxin, progesterone, etc.
• The major function of hCG is the maintenance of the corpus luteum that produces the progesterone required to keep the pregnancy.
• It also forms a basis for the counter pregnancy test as it can be detected in the body just after 1 week of fertilization.

Option 2:

• Zona pellucida is a layer that surrounds the ovum.
• It is important for the binding of single sperm to the ovum and thus prevents polyspermy.

Option 3:

• Bulbourethral glands are male accessory reproductive glands.
• They form the fluid part of semen and lubricate the penis.

Option 4:

• Leydig cells are found in testis, and they produce the male hormone testosterone or androgens.
• This hormone is important for spermatogenesis and the development of male secondary sexual characteristics.

So, the correct answer is option 2.

Concept:

• Evolution refers to the sequence of irreversible & gradual changes which took place in primitive organisms over millions of years to form present-day species.
• The scientific study of human evolution is called Paleoanthropology.
• Stages of human evolution are-
  • Dryopithecus 
  • Ramapithecus
  • Australopithecus
  • Homo habilis 
  • Homo erectus 
  • Neanderthalensis 
  • Homo Sapiens

Key Points
Homo habilis:

• This creature was called the first human-like being the hominid.
• The brain capacities were between 650-800cc.
• They did not eat the meat.

Homo erectus:

• The 1st fossil of homo erectus was found in Java in 1891.
• The brain capacities were 900cc.
• They probably eat the meat.

Neanderthal man:

• They lived in east, and central Asia.
• They used hides to protect their body and buried their dead.
• The brain capacities were 1400cc.

Thus the correct answer is A - II, B - III, C - I.

The correct answer is a-iii, b-i, c-ii, d-iv.​
Key Points

• Immunity is protection from various pathogens.
• It is an innate and acquired type.
• Innate is in-build and forms the first line of barriers against pathogens.

Physical barriers:

• It kills the pathogen that enters our body.
• The cells secrete mucus and entrap microbes.
• Mucus entrap microbes, then are expelled outside the body, thus pathogen does not invade inside the cells.

Physiological barrier:

• Tears consist of enzymes that kill the microbes.
• Enzymes from the stomach and saliva also kill the pathogen.

Cellular barriers:

• The cells such as Neutrophils, basophils, eosinophils, and lymphocytes kill germs.
• Neutrophils form the pseudopodia-linked structure and thus entrap germs inside it.
• It kills the germ by releasing various enzymes from lysosomes.

Cytokine barriers:

• It includes the interferon that kills the virus.
• Interferons are released by the infected cell, thus protecting the nearby cells.

Additional Information

• Adaptive immunity is acquired after birth.
• It is a highly specific immunity.
• It involves B and T B and T lymphocytes for protection.

Key Points

• Asexual reproduction in plants is also called vegetative propagation.
• It is a form of reproduction where only one parent is required.
• There is no fertilization of gametes and so are called asexual.
• A single parent can produce a progeny or clone of itself by vegetative propagation.
• Units of vegetative propagation such as runner, rhizome, sucker, tuber, offset, and bulb are all capable of giving rise to new offspring.
• Many plants are capable of vegetative reproduction.
• Vegetative propagules in angiosperms.
  1. Eyes of potato
  2. Rhizome of ginger
  3. Bulbil of Agave
  4. Leaf buds of Bryophyllum
  5. Offset of water hyacinth
  6. Rhizome of banana

Hence the correct option is ,A - III, B - II, C - IV, D - I
Additional Information

• Rhizome
  • Rhizomes are modified stems.
  • They are horizontal underground plant stem capable of producing the shoot and root systems of a new plant.
  • They store starches and proteins and enable plants to perennate unfavorable season.
  • Example - bamboos, ginger, banana.
• Offset
  • Offset is a modification of the stem.
  • It is a lateral branch with a short internode and each node bears a rosette of leaves and a tuft of roots.
  • These nodes can separate and form a separate plant.
  • Example - Tulips, lilies, strawberries, water hyacinth.
• Leaf bud
  • Leaf buds are adventitious buds that arise from the notches present at the margins of leaves.
  • Example - Bryophyllum, Begonia.
• Bulbil
  • A bulbil is a small, young plant that is reproduced vegetatively from axillary buds on the parent plant's stem.
  • They are produced in place of a flower on an inflorescence.
  • They can detach and form a new plant.
  • Example - Agave, Colocasia.
• Eyes
  • Tubers are modified stem.
  • Each of the tubers comprises several notches on their surface, known as 'eyes'.
  • Eyes are axillary buds that can detach and form a new potato plant.
  • Example - potato.

(A) Correct: The pollen grain is the male gamete in plants, carrying the sperm cell for fertilization.
(B) Correct: The egg cell is the female gamete in plants, located within the ovule.
(C) Incorrect: The ovule develops into a seed, not a fruit. The fruit develops from the ovary.
(D) Incorrect: The ovary develops into the fruit after fertilization, not the seed. The seed develops from the fertilized ovule.
(E) Correct: Pollinators like bees assist in transferring pollen between flowers, promoting cross-pollination.

(A) Correct: Pollination is indeed necessary for fertilization to occur, as it involves transferring the pollen grain to the stigma for fertilization.
(B) Incorrect: Plants can reproduce sexually without pollinators, especially in self-pollinating species.
(C) Correct: Some plants have both self-pollination and cross-pollination abilities, which increases their chances of reproduction.
(D) Incorrect: The male part of the flower is the stamen, not the pistil. The pistil is the female reproductive part.
(E) Correct: Fertilization results in the formation of the embryo, which eventually develops into a new plant.

Population attributes include birth rate, death rate, and sex ratio, but organismal behavior is not considered a defining characteristic of a population.

An age pyramid visually represents the distribution of different age groups in a population, which helps indicate whether the population is growing, stable, or declining.

The sex ratio in a population indicates the proportion of males and females in the population at any given time.

Death rate is a key population attribute that reflects the number of deaths per capita in a population during a specific period.

Age distribution, which is shown through an age pyramid, helps assess whether a population is growing, stable, or declining, which directly influences its stability.

Life history traits are influenced by a combination of biotic and abiotic factors, including the availability of resources, environmental conditions, and interactions with predators and competitors.

Species like Pacific salmon reproduce only once in their lifetime, which is known as a semelparous strategy.

Darwinian fitness refers to an organism's ability to survive and reproduce, passing on its genes to the next generation.

Producing fewer, larger offspring can maximize survival and reproductive success, especially in environments with high predation or limited resources.

R-strategy involves producing many offspring with minimal parental investment, commonly seen in species like fish and insects.

The correct answer is (a), (b), and (d) only.
Key Points

• The flower is the reproductive organ of a flower.
• It consists of male and female organs and is stamen and carpel.
• Pollen grains are formed inside anther.
• Pollen grain consists of vegetative cells and generative cells.
• The vegetative cells act as a food source for pollen grains.
• The generative cell fuses with the egg to form an embryo or seed.
• The embryo sac is 8-nucleated and 7-celled.
• The embryo sac consists of 3 antipodal cells,2 synergid cells, 1 egg cell, and 1 central cell.
• The central cell comprises two polar nuclei.
• Dicot seed consists of two cotyledons.
• Cotyledons provide food to the developing embryo.

Additional Information

• The endosperm, which forms after double-fertilization is triploid.
• It is formed by the fusion of male gamete and polar nuclei.

Below is the diagrammatic representation of embryo-sac

Key Points

• Statement (A) - CORRECT
  • Standing crop refers to the mass of living material at each trophic level at a particular time.
  • It is measured as the biomass or number of organisms in that area.
• Statement (B) - INCORRECT
  • As discussed above, standing crop denotes the mass of living material and NOT any particular crop.
• Statement (C) - INCORRECT
  • The amount of nutrients present in the soil at any given time in known as the standing state.
  • The nutrients include carbon, nitrogen, phosphorus, calcium, etc.
  • On the other hand, biomass denotes the organic matter that constitutes living organisms.
• Statement (D) - INCORRECT
  • The ecosystem is defined as a functional unit of nature, that consists of both biotic and abiotic components.
  • The organisms interact among themselves as well as with the physical environment.
  • The flow of energy leads to clearly defined trophic structures, biodiversity and nutrient cycles.
• Statement (E) - CORRECT
  • Planktons are the diverse collection of microorganisms found in water.
  • They are usually classified as Phytoplanktons and Zooplanktons.
  • The phytoplanktons commonly include many green algae and blue-green algae.

Hence, the correct answer is option 1: (A) and (E) only.

The correct answer is 1, 2 and 3 only.
Important Points

• Loss of Biodiversity
  • ​While it is doubtful if any new species are being added (through speciation) into the earth’s treasury of species, there is no doubt about their continuing
    losses.
    • Speciation is the evolutionary process by which populations evolve to become distinct species. 
  • The biological wealth of our planet has been declining rapidly and the accusing finger is clearly pointing to human activities.
  • The colonisation of tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds.
  • The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years.
    • Some examples of recent extinctions include
      • The dodo (Mauritius),
      • Quagga (Africa),
      • Thylacine (Australia),
      • Steller’s Sea Cow (Russia)
      • Three subspecies (Bali, Javan, Caspian) of Tiger. Hence, statements 1, 2 and 3 are correct.
    • Snow leopards live in the mountainous regions of central and southern Asia.
      • In India, their geographical range encompasses a large part of the western Himalayas including the states of Jammu and Kashmir, Himachal Pradesh, Uttarakhand and Sikkim and Arunachal Pradesh in the eastern Himalayas.
      • The snow leopard is listed as Vulnerable on the IUCN-World Conservation Union’s Red List of the Threatened Species. Hence, statement 4 is incorrect.
  • In general, loss of biodiversity in a region may lead to
    • The decline in plant production,
    • Lowered resistance to environmental perturbations such as drought,
    • Increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycles.

Concept:
DNA (Deoxyribonucleic acid):

• DNA is a nucleic acid made up of nucleotides.
• It is a long polymer of deoxyribonucleotides.
• DNA was first identified by Fredrich Meischer in 1869. He named it Nuclein.
• DNA acts as the genetic material in most organisms.
• It is a double-helix structure of protein and nucleic acid which carry all the genetic information in the form of genes.
• A nucleotide has 3 components: a nitrogenous base ( A, T, G, C), a pentose sugar, and a phosphate group.

RNA (Ribonucleic acid):

• RNA is a polymer of nucleotides.
• It is made up of ribose sugar, phosphate, and bases.
• It is a single-helix structure.
• There are 3 types of RNA :
  • rRNA (ribosomal)
  • tRNA (transitional)
  • mRNA (messenger)

Explanation:

• According to Chargaff’s Rule, the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine. Hence, statement A is correct.
• • Adenine formed two hydrogen bonds with Thymine (A=T).
  • Guanine is bonded with Cytosine with 3 H-bonds (G ≡ C).
• DNA is made up of two polypeptide chains, where the backbone is constituted by sugar-phosphate and bases project inside.
  • Two chains have anti-parallel polarity (5'→ 3' and 3' → 5'.
• RNA is a nucleic acid messenger between DNA and ribosomes.
  • So, Thymine in DNA is replaced by uracil in RNA. Hence, statement C is correct.
• Adenine and guanine base pair are purine while Cytosine and thymine are pyrimidines.

Therefore, we can say that B and D are incorrect statements.

The principle of dominance does not state the segregation of factors. This is stated by the law of segregation or separation.

The phenotypic ratio is the ratio of different phenotypes observed in the progeny. In the F2 generation of a Mendelian cross, there are 75% plants with dominant phenotype and 25% plants with a recessive phenotype. This gives a phenotypic ratio of 3:1.

The genotypes of a progeny can be studied using Punnett square. The ratio of different genotypes is called the genotypic ratio.

In the Punnett square, the boxes are filled with the offsprings that can be produced, in principle, from the combinations of gametes of both parents. This can be used to determine the genotypic and phenotypic ratios of the progeny.

The Punnett square was discovered by a British scientist named Reginald Punnett. Its importance aligns with Gregor Mendel’s earlier work on inheritance.

Emasculation is the process of removal of anthers. This is carried out to carry out pollination in a controlled manner and avoid self-pollination.

True-breeding plants are taken as parental plants in crosses. Hence offsprings produced by the crossing of these true-breeding plants are F1 progeny.

Tall plants are dominant over dwarf plants. Being true-breeding parents, the offsprings will all be heterozygous. Moreover, hence phenotypically, all of them will be tall.