Test: NEET 2015 Past Year Paper - NEET MCQ

Stratification is the occurrence of vertical zonation in the ecosystem & indicates the presence of favorable environmental conditions, for e.g., trees occupy top vertical strata or layer of a forest, shrubs the second. Herbs & grasses occupy the bottom layers. It is absent or poor where environmental conditions are unfavorable, e.g., desert ecosystems have very few trees & shrubs.

Transpiration causes water to rise in plants by pulling through xylem elements.Root pressure causes water to rise in plants by pushing water in xylem components.So, the rise of water in plants is done by pulling and pushing via transpiration and root pressure respectively.

Lac I gene produces an inhibitor or repressor and negative regulation of lac operon is induced. The repressor binds to the operator gene and stops its working. Repressor is meant to block the operator gene so that structural genes are unable to form mRNA thus stopping the transcription of genes.

High value of BOD (Biochemical Oxygen Demand) indicates that water is highly polluted.
- BOD measures the amount of oxygen required by microorganisms to decompose organic matter in water.
- When there is a high concentration of organic matter in water, such as sewage or other pollutants, microorganisms break down these substances and consume more oxygen.
- As a result, the BOD value increases, indicating a higher level of pollution in the water.
- Higher BOD levels can lead to a decrease in dissolved oxygen in the water, which can be harmful to aquatic life.
- A high BOD value is often associated with the presence of pollutants such as organic waste, fertilizers, and industrial effluents in the water.
- Therefore, a high BOD value indicates that the water is highly polluted and may require treatment or remediation measures to improve its quality.
- On the other hand, a low BOD value suggests that the water is less polluted, as there is less organic matter for the microorganisms to decompose and consume oxygen.

Initiation of parturition in humans
The initiation of parturition, or the process of childbirth, is a complex physiological event that involves various hormonal and biochemical changes in the body. While several components play a crucial role in the initiation of parturition, one of them is not as important as the others. Let's examine each component:
1. Increase in estrogen and progesterone ratio:
- Estrogen and progesterone are both hormones that are involved in regulating pregnancy and childbirth.
- As the pregnancy progresses, the ratio of estrogen to progesterone increases, which helps prepare the body for labor and delivery.
- This hormonal shift is a crucial component in the initiation of parturition.
2. Synthesis of prostaglandins:
- Prostaglandins are hormone-like substances that are involved in various physiological processes, including labor and delivery.
- The synthesis of prostaglandins increases towards the end of pregnancy, leading to uterine contractions and cervical ripening.
- Prostaglandins play a significant role in the initiation and progression of parturition.
3. Release of oxytocin:
- Oxytocin is a hormone that plays a crucial role in labor and delivery.
- It stimulates uterine contractions and promotes the release of milk during breastfeeding.
- The release of oxytocin is essential for the initiation and progression of parturition.
4. Release of prolactin:
- Prolactin is a hormone that is primarily involved in milk production and breastfeeding.
- While prolactin levels may increase during pregnancy, it is not a critical component in the initiation of parturition.
- Prolactin's main role comes into play after childbirth when it helps stimulate milk production.
Conclusion:
Among the given options, the release of prolactin is not an important component of the initiation of parturition in humans. While prolactin has its role in breastfeeding, it does not play a significant role in the onset and progression of labor and delivery.

The perinuclear space present between two membranes of nuclear envelope runs continuous with channels of the ER aiding in shrinkage or expansion of envelope. Nuclear envelope is a derivative of rough endoplasmic reticulum.

The crops engineered for glyphosate are resistant/tolerant to:

• Herbicides: Glyphosate-resistant crops are engineered to tolerate the herbicide glyphosate, which allows farmers to control weeds without harming the crop.


• Fungi: Glyphosate-resistant crops are not specifically engineered to be resistant to fungi. They are designed to withstand the effects of glyphosate-based herbicides.


• Bacteria: Glyphosate-resistant crops are not specifically engineered to be resistant to bacteria. Their resistance is focused on herbicides, not bacterial pathogens.


• Insects: Glyphosate-resistant crops are not specifically engineered to be resistant to insects. However, they may indirectly benefit from the use of glyphosate-based herbicides, as these herbicides can suppress weed growth, which can provide a habitat for insects.

Therefore, the correct answer is A, herbicides. Glyphosate-resistant crops are engineered to tolerate the herbicide glyphosate, allowing farmers to effectively control weeds without damaging their crops.

Explanation:
The vascular bundles in monocotyledons are considered closed because of the following reasons:
A: Xylem is surrounded all around by phloem:
- In monocotyledons, the xylem and phloem are arranged in a ring-like structure within the vascular bundles.
- The xylem is located towards the center, while the phloem surrounds it on the outside.
- However, this arrangement does not necessarily make the vascular bundles closed.
B: A bundle sheath surrounds each bundle:
- The presence of a bundle sheath in monocotyledons does not make the vascular bundles closed.
- The bundle sheath is a layer of cells that surrounds the vascular bundles and provides structural support.
- It does not affect the openness or closedness of the vascular bundles.
C: Cambium is absent:
- The absence of cambium, a meristematic tissue responsible for secondary growth, is one of the characteristics of monocotyledons.
- Without cambium, the vascular bundles in monocotyledons do not undergo significant secondary growth, which contributes to their closed nature.
D: There are no vessels with perforations:
- Monocotyledons lack vessels with perforations, which are typically found in the xylem of dicotyledons.
- Vessels with perforations allow for efficient water transport and are typically associated with open vascular bundles.
- The absence of vessels with perforations in monocotyledons contributes to their closed vascular bundles.
Therefore, the correct answer is option C: Cambium is absent. The absence of cambium in monocotyledons leads to closed vascular bundles.

To determine the correct statements, let's analyze each statement:
(A) Mosses and Lichens are the first organisms to colonize a bare rock.
This statement is correct. Mosses and lichens are pioneer organisms that can grow on bare rocks and initiate the process of primary succession.
(B) Selaginella is a homosporous pteridophyte.
This statement is correct. Selaginella is a genus of pteridophytes that exhibits homospory, producing only one type of spore.
(C) Coralloid roots in Cycas have VAM.
This statement is correct. Coralloid roots in Cycas, a type of gymnosperm, have a mutualistic association with vesicular-arbuscular mycorrhizal (VAM) fungi.
(D) Main plant body in bryophytes is gametophytic, whereas in pteridophytes, it is sporophytic.
This statement is correct. In bryophytes, such as mosses, liverworts, and hornworts, the dominant and independent stage is the gametophyte. In pteridophytes, such as ferns, the dominant and independent stage is the sporophyte.
(E) In gymnosperms, male and female gametophytes are present within sporangia located on the sporophyte.
This statement is correct. In gymnosperms, such as conifers and cycads, the male and female gametophytes are produced within the sporangia, which are located on the sporophyte.
Based on the analysis, the correct option is (D) (A), (D), and (E).

True nucleus is absent in:
- Anabaena
Explanation:
- True nucleus refers to a membrane-bound nucleus that contains genetic material in the form of chromosomes.
- In Anabaena, a cyanobacterium, the genetic material is not enclosed within a true nucleus.
- Instead, the genetic material is present in the form of a nucleoid, which is a condensed region within the cytoplasm.
- Anabaena belongs to a group of prokaryotes called bacteria, which lack a true nucleus.
- Unlike eukaryotic organisms, such as Volvox, Muco, and Vaucheria, which have cells with a well-defined nucleus enclosed within a nuclear membrane, Anabaena does not possess this feature.
Therefore, the correct answer is B: Anabaena.

The correct answer is A: Honey is made by bees by digesting pollen collected from flowers.
- Honey is not made by bees by digesting pollen collected from flowers. This is a common misconception. Here, the statement is not true.
The other options are true:
B: Pollen grains are rich in nutrients, and they are used in the form of tablets and syrups.
- Pollen grains are indeed rich in nutrients and are used in various forms, such as tablets and syrups, for their health benefits.
C: Pollen grains of some plants cause severe allergies and bronchial afflictions in some people.
- This is true. Pollen grains from certain plants can trigger allergies and respiratory issues in susceptible individuals.
D: The flowers pollinated by flies and bats secrete foul odor to attract them.
- Many flowers that are pollinated by flies and bats do indeed secrete foul odors to attract these specific pollinators.
In conclusion, option A is the statement that is not true.

The proximal convoluted tubule is involved in the active and passive absorption of solutes like sodium, potassium, bicarbonate, glucose, amino acids etc. present in the filtrate and passing it to the capillaries. Due to the solute absorption, water potential is lowered in the capillaries and so, the water from the filtrate also moves across the proximal convoluted tubule into the capillaries. Therefore, the removal of PCT will result in formation of highly dilute urine.

Hence, the correct answer is 'More diluted urine'

Vestibular apparatus is the sensory system th... moreat provides the leading contribution to the sense of balance and spatial orientation for the purpose of coordinating movement with balance.

In botany, a hilum (pronounced /ˈhaɪləm/) is a scar or mark left on a seed coat by the former attachment to the ovary wall or to the funiculus (which in turn attaches to the ovary wall). On a bean seed, the hilum is called the "eye".

The correct option is A: Blood = Plasma RBC WBC Platelets.
Explanation:
Blood is a vital fluid in the human body that plays numerous essential roles. It consists of different components, each with its specific functions. The given options describe the relationship between blood and its components. Let's analyze each option to determine the correct one:
A: Blood = Plasma RBC WBC Platelets
- This option correctly identifies the different components of blood, which include plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets.
B: Plasma = Blood - Lymphocytes
- This option suggests that plasma is the composition of blood excluding lymphocytes. However, this is incorrect as plasma is the liquid component of blood that carries various substances, including lymphocytes.
C: Serum = Blood Fibrinogen
- This option states that serum is the composition of blood and fibrinogen. However, serum is the liquid portion of blood that remains after clotting, and it does not contain fibrinogen.
D: Lymph = Plasma RBC WBC
- This option incorrectly states that lymph consists of plasma, red blood cells (RBCs), and white blood cells (WBCs). Lymph is a clear fluid that is derived from interstitial fluid and does not contain RBCs.
Therefore, the correct option is A: Blood = Plasma RBC WBC Platelets, as it accurately represents the components of blood.

The guts of cow and buffalo possess:
- Cyanobacteria: No, the guts of cow and buffalo do not possess cyanobacteria.
- Fucus spp.: No, the guts of cow and buffalo do not possess Fucus spp.
- Chlorella spp.: No, the guts of cow and buffalo do not possess Chlorella spp.
- Methanogens: Yes, the guts of cow and buffalo do possess methanogens.
Explanation:
- Methanogens are microorganisms that belong to the domain Archaea and are found in the guts of ruminant animals like cows and buffalos.
- These microorganisms play a crucial role in the digestion process of these animals by breaking down complex carbohydrates in the gut and producing methane gas as a byproduct.
- The presence of methanogens in the guts of cows and buffalos allows them to efficiently digest plant material, which is otherwise indigestible by the animals themselves.
- Methane produced by methanogens is released through the animal's belching and contributes to greenhouse gas emissions.
- The presence of methanogens in the guts of cows and buffalos is an example of a symbiotic relationship, where both the microorganisms and the animals benefit from each other's presence.

Explanation:
The correct answer is B: Geitonogamy.
Geitonogamy is a type of pollination in which the pollen is transferred from the anther of one flower to the stigma of another flower on the same plant. This requires the assistance of a pollinator, such as an insect or a bird, to carry the pollen between flowers.
Here is a detailed explanation of the options:
A: Cleistogamy - Cleistogamy is a type of self-pollination in which the flowers do not open, and the pollen is transferred within the closed flower. This does not require a pollinator and is genetically similar to autogamy.
B: Geitonogamy - Geitonogamy is a type of cross-pollination in which the pollen is transferred from one flower to another flower on the same plant. This requires a pollinator and is genetically similar to autogamy.
C: Xenogamy - Xenogamy is a type of cross-pollination in which the pollen is transferred from the anther of one flower to the stigma of another flower on a different plant. This requires a pollinator and is not genetically similar to autogamy.
D: Apogamy - Apogamy is a type of asexual reproduction in plants where the embryo develops without fertilization. It does not involve pollinators and is not genetically similar to autogamy.
In summary, geitonogamy is the option that requires pollinators but is genetically similar to autogamy.

Explanation:
To determine the percentages of the other three bases in sea urchin DNA, we need to subtract the percentage of cytosine (17%) from 100% (total percentage of all bases).
The total percentage of all bases is 100%, and since DNA is double-stranded, each base will have a complementary base pairing partner. Therefore, the percentages of the other three bases are equal.
Here's how we can calculate the percentages:
1. Calculate the percentage of cytosine (C): 17%
2. Calculate the total percentage of the other three bases: 100% - 17% = 83%
3. Divide the remaining percentage equally among the other three bases:
- Guanine (G): 83% / 3 = 27.67% ≈ 27% (rounded to the nearest whole number)
- Adenine (A): 83% / 3 = 27.67% ≈ 27% (rounded to the nearest whole number)
- Thymine (T): 83% / 3 = 27.67% ≈ 27% (rounded to the nearest whole number)
Therefore, the expected percentages of the other three bases in sea urchin DNA are:
- G: 27%
- A: 27%
- T: 27%
Among the given answer choices, option D (G 17%, A 33%, T 33%) matches the expected percentages.

Capacitation is the penultimate step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte. This step is a biochemical event; the sperm move normally and look mature prior to capacitation. In vivo, this step typically occurs after ejaculation, in the female reproductive tract. In vitro, capacitation can occur by incubating sperms that have either undergone ejaculation or have been extracted from the epididymis in a defined medium for several hours.
The uterus aids in the steps of capacitation by secreting sterol-binding albumin, lipoproteins, proteolytic and glycosidasic enzymes such as heparin.

To determine which of the following had the smallest brain capacity, we need to compare the brain sizes of Homo habilis, Homo erectus, Homo sapiens, and Homo neanderthalensis.
Homo habilis:
- Brain capacity: Approximately 500 to 800 cubic centimeters (cc)
- Known as the earliest member of the Homo genus
- Lived between 2.8 and 1.5 million years ago
Homo erectus:
- Brain capacity: Approximately 650 to 1100 cc
- Evolved around 1.9 million years ago and existed until about 70,000 years ago
- Considered to have a larger brain size compared to Homo habilis
Homo sapiens:
- Brain capacity: Around 1300 to 1600 cc
- Refers to modern humans
- Emerged around 300,000 years ago
Homo neanderthalensis:
- Brain capacity: Approximately 1200 to 1700 cc
- Coexisted with Homo sapiens and became extinct around 40,000 years ago
- Had a larger brain size than Homo sapiens
Therefore, among the given options, Homo habilis had the smallest brain capacity, ranging from approximately 500 to 800 cc.

Viruses Transferred Through Semen:
- Ebola virus
- Hepatitis B virus
- Human immunodeficiency virus (HIV)
Virus Not Transferred Through Semen:
- Chikungunya virus
Explanation:
- The Ebola virus can be transmitted through semen, as the virus can persist in the reproductive organs of male survivors for several months after recovery.
- The Hepatitis B virus can also be transmitted through semen, as it can be present in high concentrations in the seminal fluid of infected males.
- The Human immunodeficiency virus (HIV) is primarily transmitted through sexual contact, including contact with infected semen.
- However, the Chikungunya virus is not known to be transmitted through semen. It is primarily transmitted to humans through the bite of infected mosquitoes.
Conclusion:
- Among the given options, the Chikungunya virus is the only virus that is not transferred through semen. Ebola virus, Hepatitis B virus, and Human immunodeficiency virus (HIV) can all be transmitted through semen.

In monocots there is no cambium in between xylem and phloem. so secondary growth is absent.

To determine when blood pressure in the mammalian aorta is maximum, we need to understand the cardiac cycle and the events that occur during it. The cardiac cycle consists of two main phases: diastole and systole.
During diastole, the heart is relaxed and filling with blood. In contrast, during systole, the heart is contracting and pumping blood out. In this context, we can analyze the given options and determine the correct answer.
Option A: Diastole of the right atrium
During this phase, the right atrium is filling with blood from the body. However, the blood pressure is not maximum in this phase.
Option B: Systole of the left atrium
During this phase, the left atrium contracts to push blood into the left ventricle. However, the blood pressure is not maximum in this phase either.
Option C: Diastole of the right ventricle
During this phase, the right ventricle is filling with blood from the right atrium. However, the blood pressure is not maximum in this phase.
Option D: Systole of the left ventricle
During this phase, the left ventricle contracts forcefully to pump blood into the aorta. This contraction generates the highest pressure in the cardiovascular system, leading to maximum blood pressure in the mammalian aorta.
Therefore, the correct answer is option D: Systole of the left ventricle.

Explanation:
The conversion of the Bt toxin present in plant tissue as a pro-toxin into an active toxin in Bt cotton occurs due to the alkaline pH of the insect gut. Here is a detailed explanation:
1. Bt Cotton and Bt Toxin:
- Bt cotton is a genetically modified crop that produces a toxin called Bacillus thuringiensis (Bt) toxin.
- The Bt toxin is derived from the bacterium Bacillus thuringiensis, which naturally produces this toxin.
2. Pro-toxin:
- In Bt cotton, the Bt toxin is initially present as an inactive form called the pro-toxin.
- The pro-toxin is harmless to the cotton plant itself but becomes toxic to specific insect pests.
3. Insect Gut Environment:
- When an insect feeds on Bt cotton, the pro-toxin is ingested along with plant tissue.
- The insect gut environment plays a crucial role in converting the pro-toxin into an active toxin.
4. Alkaline pH:
- The insect gut has an alkaline pH, which is higher than neutral pH.
- The alkaline pH of the insect gut triggers the activation of the pro-toxin.
5. Activation Process:
- In the alkaline environment of the insect gut, the pro-toxin is cleaved by specific proteases present in the gut.
- This cleavage process converts the pro-toxin into an active toxin.
6. Mode of Action:
- The active Bt toxin binds to specific receptors in the insect gut lining.
- This binding disrupts the integrity of the gut lining, leading to the formation of pores or channels.
7. Toxic Effects:
- The formation of pores or channels in the gut lining causes the leakage of gut contents.
- This leads to the disruption of normal gut functions, ultimately resulting in the death of the insect.
Therefore, the conversion of the Bt toxin from pro-toxin to active toxin in Bt cotton occurs due to the alkaline pH of the insect gut.

The rate of production of organic matter during photosynthesis is termed as gross primary productivity.
Explanation:
Gross primary productivity refers to the total amount of organic matter produced by plants through photosynthesis in an ecosystem. It is the rate at which energy is captured and stored by plants in the form of organic compounds. Here is a detailed explanation of the terms mentioned in the question:
1. Net productivity:
- Net productivity is the amount of energy or biomass remaining after subtracting the energy lost through respiration.
- It represents the energy available to the next trophic level.
2. Net primary productivity (NPP):
- NPP is the energy or biomass available to the primary consumers (herbivores) after subtracting the energy lost through respiration by the plants.
- It is the difference between the gross primary productivity and the energy used by plants for their own metabolic needs (respiration).
- NPP is an important measure of the energy available for the growth and reproduction of primary consumers.
3. Gross primary productivity (GPP):
- GPP is the total rate of photosynthesis in an ecosystem.
- It represents the total amount of organic matter produced by plants through photosynthesis.
- GPP includes all the energy captured by plants, regardless of whether it is used for growth, reproduction, or respiration.
4. Secondary productivity:
- Secondary productivity refers to the rate at which consumers convert the organic matter of their food into their own biomass.
- It represents the energy or biomass stored in the consumers, such as herbivores, carnivores, and omnivores.
- Secondary productivity is dependent on the amount of energy available from primary producers (plants) and the efficiency of energy transfer through the food chain.
In conclusion, the correct term for the rate of production of organic matter during photosynthesis is gross primary productivity (GPP). It represents the total amount of organic matter produced by plants through photosynthesis in an ecosystem.

In a ring girdled plant, the root dies first. A ring of bark is cut from the stem. It also removes phloem. Nutrients collect above the ring where the bark also swells up and may give rise to adventitious roots.