Punjab Biology 2017 Paper 1 — Solved MCQs

Question 1

The category of plants that have adaptation of small and thick leaves to limit water loss is called

Accepted Answer

B. xerophytes — Xerophytes have the adaptations for reduced rate of transpiration. Many xerophytes possess small, thick leaves to limit water loss by reducing surface area proportional to the volume. Their cuticle is thick, waxy and leathery. Stomata are on lower surface of leaves and located in depression. Some as cacti, during the driest season, shed their leaves to restrict transpiration completely, thus stems are the photosynthetic organs. In rainy season, stem stores water for use in dry conditions

Question 2

The reabsorption of water in collecting tubules is under the control of

Accepted Answer

B. ADH — ADH, or antidiuretic hormone, acts on the kidneys to increase water reabsorption. It does so by altering the permeability of the collecting ducts and distal tubules, allowing them to absorb more water back into the bloodstream. This mechanism helps regulate body fluid balance by conserving water and reducing urine volume, particularly in response to dehydration or low blood volume situations.

Question 3

Turgor pressure is generated by osmotic pressure of

Accepted Answer

B. cell vacuole — Turgor pressure is generated by the osmotic pressure exerted by the cell vacuole. When the vacuole accumulates solutes, water enters the vacuole via osmosis, creating a hydrostatic pressure that pushes against the cell wall, contributing to cell rigidity and plant support.

Question 4

Skeletal muscles are called striated (stripped) because of the presence of

Accepted Answer

C. alternating dark and light band — Skeletal muscles appear striated due to the alternating pattern of light and dark bands, known as striations, under a microscope. These bands are caused by the arrangement of contractile proteins actin and myosin within the muscle fibers, giving rise to the sarcomere structure. The precise alignment and overlap of these proteins result in the striated appearance, indicative of the functional organization necessary for muscle contraction.

Question 5

Fruit ripening is associated with the burst of respiratory activity called

Accepted Answer

D. climacteric — Fruit ripening triggers a burst of respiratory activity known as the climacteric phase, marked by increased ethylene production. This surge in respiration leads to elevated levels of carbon dioxide and heat, driving metabolic changes such as sugar breakdown and flavor development. The climacteric phase is a crucial stage in fruit ripening, facilitating softening, color changes, and aroma enhancement.

Question 6

Evolution of the pollen tube parallels the evolution of

Accepted Answer

D. seed — The evolution of the pollen tube parallels the evolution of seeds due to their interdependent roles in reproduction and dispersal. Both structures evolved to improve the efficiency of fertilization and seed formation, ensuring successful reproduction and offspring survival. The development of pollen tubes allowed for the direct delivery of sperm cells to ovules, enhancing the chances of fertilization and subsequent seed development, contributing to the reproductive success of seed plants.

Question 7

Each chromosome when visible consists of two unseparated replicas

Accepted Answer

D. chromatids — Each visible chromosome consists of two identical replicas called chromatids, which are held together by a centromere. These chromatids contain identical genetic information and are formed during DNA replication in the S phase of the cell cycle. The chromatids separate during cell division, ensuring that each daughter cell receives a complete set of chromosomes.

Question 8

The sex chromosomes of the person affected with klinefelter's syndrome are

Accepted Answer

C. XXY — Contrary to popular belief, individuals with Klinefelter syndrome do not have the karyotype XXY. Instead, they typically have one or more additional X chromosomes, resulting in variations such as XXY, XXYY, or XXXY. These extra X chromosomes can lead to a range of developmental and physiological differences, including infertility and various physical and cognitive traits.

Question 9

Neuroglial cells provide the neuron with

Accepted Answer

D. all — Neuroglial cells, also known as glial cells, play crucial roles in supporting and maintaining the function of neurons within the nervous system. They provide neurons with essential nutrients, regulate their chemical environment, and remove debris and waste products. Additionally, neuroglial cells provide physical support and insulation for neurons, contributing to the structural integrity of the nervous tissue. Overall, these supportive functions are essential for the proper functioning and survival of neurons, highlighting the importance of neuroglial cells in neural physiology.

Question 10

Apical dominance in plants occurs due to higher concentration of

Accepted Answer

D. auxin — Apical dominance in plants occurs due to the higher concentration of auxin produced by the apical bud. This auxin inhibits the growth of lateral buds, promoting the vertical growth of the main stem. As a result, the apical bud maintains dominance over lateral branches, regulating the overall growth pattern of the plant.

Question 11

The number of histone protein molecules in a single nucleosome are

Accepted Answer

C. 08 — The number of histone protein molecules in a single nucleosome is 8. Together, they form a protein complex around which approximately 200 base pairs of DNA are wrapped, contributing to the structural organization of chromatin within the cell nucleus.

Question 12

Deuteranopia is a colour blindness of

Accepted Answer

C. green — Deuteranopia is a form of color blindness characterized by a reduced sensitivity to green light. Individuals with this condition have difficulty distinguishing between different shades of green and red. Deuteranopia is caused by the absence or malfunction of green cone cells in the retina.

Question 13

The first restriction enzyme was isolated by

Accepted Answer

B. hamilton — In 1970, Hamilton O. Smith, at Johns Hopkins University, isolated the first restriction enzyme

Question 14

The endosymbiont hypothesis was proposed by

Accepted Answer

C. lynn margulis — The endosymbiont hypothesis, proposed by Lynn Margulis in the 1960s, suggests that eukaryotic organelles such as mitochondria and chloroplasts originated from free-living prokaryotic organisms that were engulfed by ancestral eukaryotic cells. Margulis's groundbreaking theory provided a compelling explanation for the evolutionary origins of these organelles and has since become widely accepted in the field of biology.

Question 15

Who proposed the term niche in ecology

Accepted Answer

D. Josph Grinnel — The term "niche" in ecology was indeed proposed by Joseph Grinnell, an American zoologist, in the early 20th century. Grinnell introduced the concept to describe the specific ecological role and habitat requirements of a species within its environment.

Question 16

Alpine coniferous forests are found on high

Accepted Answer

C. altitude — Coniferous forests located at high altitude are called alpine

Question 17

The decline in thickness of the ozone layer is caused by an increasing level of

Accepted Answer

C. chloroflorocarbon — The decline in thickness of the ozone layer is indeed caused by an increasing level of CFC (chlorofluorocarbon) emissions. CFCs released into the atmosphere break down ozone molecules in the stratosphere, leading to ozone depletion. This process allows more harmful ultraviolet (UV) radiation to reach the Earth's surface, posing risks to human health and the environment.

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