AHSEC Class 12 Biology Solved Question Paper 2023

2023

BIOLOGY

(Theory)

Full Marks: 70

Pass Marks: 21

Time: Three hours

The figures in the margin indicate full marks for the questions

Part - I (Botany)

1. Name the enzyme which help in unwind of the DNA helix. 1

Ans:- Helicases.

2. Where is occurred coleoptile? 1

Ans:- In grass plants.

3. What is cellular totipotency? 1

Ans:- Cellular totipotency is the inherent ability of a plant cell to give rise to an entire plant, an ability that is retained even after a single cell has undergone final differentiation in the plant body.

4. What is meant by speciation? 1

Ans:- Speciation is defined as the evolutionary formation of new biological species, usually by splitting the same species into two or more genetically distinct species. Speciation occurs with the help of genetic drift, migration, geographical isolation and natural selection.

5. What do you mean by Biofertilizer? 2

Ans:- Biofertilizers are biological preparations of efficient microorganisms that promote plant growth by improving the acquisition of nutrients. They increase soil productivity by fixing atmospheric nitrogen, solubilizing phosphorus in the soil, and stimulating plant growth.

6. Name the microbes used for production of curd and vinegar. 1+1=2

Ans:- Lactobacillus bacteria are helpful in making curd.

Acetic acid bacteria in vinegar.

7. How DNA isolated in purified from a bacterial cell? 2

Ans:- DNA is genetic material that is isolated in pure form by treating bacterial cells with enzymes such as lysozyme to remove the cell wall.

What is recombinant DNA? List the tools of genetic engineering. 2

Ans:- Recombinant DNA, often abbreviated as rDNA, is an artificially created DNA strand that is formed by combining two or more gene sequences. This new combination may or may not occur naturally, but it has been specifically engineered for the purpose of being used in one of the many applications of recombinant DNA.

(i) Restriction enzymes: Restriction enzymes, also known as restriction endonucleases, are proteins produced by bacteria that cut DNA at specific locations.

(ii) DNA ligase: DNA ligase is an enzyme that facilitates joining of DNA strands together by forming phosphodiester bonds.

(iii) Plasmids: Plasmids are small, circular pieces of DNA that are separate from the chromosomal DNA found in cells.

(iv) Gene guns: Gene guns are physical devices used to deliver DNA directly into cells.

(v) CRISPR-Cas9: CRISPR-Cas9 is a revolutionary genetic engineering tool that provides a more precise and efficient way to edit DNA.

(vi) Electroporation: Electroporation is a method used to introduce foreign DNA into cells.

8. Write briefly about application of electrophoresis. 2

Ans:- One of the most important applications of electrophoresis is DNA analysis and study of DNA fragments. DNA (or deoxyribonucleic acid), known for the stability of its negative charge, is affected by the presence of electric current.

Write brief account on ethical issues on biotechnology. 2

Ans:- Ethical issues in biotechnology are specific issues that are morally wrong. Such issues may affect fundamental moral principle which conflicts with the normal functioning of the society at large. We have divided the ethical issues related to biotechnology into specific subcategories. These groups are-

There are many principles related to ethics, medical ethics, scientific and technological ethics, justice and human dignity and its related ethics and many such ethical issues in biotechnology.

(i) Socio-economic issues: The scientific community and society promise significant advances in biotechnology, but never promise harmlessness with respect to socio-economic life.

(ii) Cultural issues: Different cultures have different ideas and values. These values are a reflection of his long-term vision. Sometimes biotechnology interferes with these cultural concepts.

9. Write the applications of mycorrhizae. 2

Ans:- Mycorrhizal fungi associated with plant roots increase the absorption of nutrients, especially phosphorus, and thus enhance the growth of crop plants and trees.

The level of mycorrhizal inoculum in the soil and their colonization in the roots of various forest plants, thereby reducing fertilizers, pathogen effects and fungicides and protecting the topsoil, soil erosion and water-logging.

10. Explain briefly: (any two) 2+2=4

(i) Cry protein

Ans:- Cry protein is a crystal protein that is toxic to insects and is expressed by the cry gene. Bacillus thuringiensis bacteria produce it in an inactive form. The alkaline pH in insects helps activate Rho proteins when they consume them.

(ii) Transgenesis

Ans:- Transgenesis can be defined as the uncontrolled transfer of foreign DNA into the germline of an animal species. Transgenesis became possible only after significant advances were made in the understanding of the developmental, reproductive, and molecular biological principles of the mammalian genome.

(iv) Bioreactor

Ans:- Bioreactors are vessels or tanks in which whole cells or cell-free enzymes convert raw materials into biochemical products and/or less undesirable by-products. The microbial cell itself is a miniature bioreactor; Other examples include shake flasks, petri dishes, and industrial fermenters.

11. Write the scientific name with their utility of the following plants: (1/2+1/2)x3=3

(i) Sarpagandha

Ans:- Rauvolfia serpentina is known for its medicinal importance. It is one of the best remedies that is widely used for high blood pressure and as a sedative and tranquilizing agent.

(ii) Beladona

Ans:- Belladonna, also known as Atropa belladonna or deadly nightshade, is a perennial herb in the nightshade family Solanaceae. Its roots, leaves and fruits contain hyoscyamine, scopolamine and mostly atropine. These alkaloids are naturally occurring muscarinic antagonists.

(iii) Arjun

Ans:- Terminalia arjuna, commonly known as arjuna, belongs to the Combretaceae family. Based on the observations of ancient physicians, decoctions of its bark have been used for centuries in the Indian subcontinent for chest pain, hypertension, congestive heart failure, and dyslipidemia.

(iv) Teak

Ans:- One such interesting plant is Tectona grandis L.f. (TG). It belongs to the Verbenaceae family. It is commonly called teak. It is a large deciduous tree and can reach a height of 30–40 meters with flutes and buttresses found at the base of older trees.

12. Write the characteristics of population. 2

Ans:- Population characteristics can be diverse and varied, but here are two key characteristics:

1.Size: The size of a population refers to the total number of individuals or entities within a defined area or group. It can range from small, localized populations to large, global ones.

2.Composition: Population composition includes factors such as age, gender, ethnicity, education level etc.

13. What are the major steps of gene cloning? Write briefly on each steps of gene cloning. 1+2=3

Ans:- Gene cloning involves several key steps. Here's a brief overview of each step:

1. Isolation of DNA: The first step is to extract the DNA containing the gene of interest from the source organism. This can involve breaking cell walls and membranes to release the DNA.

2.Amplification by Polymerase Chain Reaction (PCR): In this step, the specific gene is amplified using PCR. This process creates many copies of the target gene, making it easier to work with.

3.Insertion into a Vector: The target gene is inserted into a vector, which is typically a small, circular piece of DNA, such as a plasmid. This creates recombinant DNA.

These steps collectively allow for the creation of multiple copies of the desired gene, which can then be used for various purposes like gene expression studies or protein production.

Write an account of biotechnological application in agriculture. 3

Ans':- Biotechnology has made significant contributions to agriculture, improving crop yields, pest resistance, and overall sustainability. Here's an account of biotechnological applications in agriculture:

1.Genetically Modified Organisms (GMOs): Biotechnology has enabled the development of GMOs, which are crops that have been genetically altered to enhance their characteristics. For example, some GMOs are engineered to be resistant to pests or tolerant to herbicides, reducing the need for chemical pesticides and herbicides. This not only increases crop yield but also has environmental benefits by reducing chemical usage.

2.Crop Improvement: Biotechnology allows for the selective breeding of plants with desirable traits. Through techniques like marker-assisted breeding, scientists can identify and transfer specific genes associated with traits such as disease resistance, drought tolerance, or nutritional value. This accelerates the development of new crop varieties with improved characteristics.

3.Biological Nitrogen Fixation: Some biotechnological applications involve the use of nitrogen-fixing bacteria. These beneficial microorganisms can be introduced to crops, reducing the need for synthetic nitrogen fertilizers. This not only saves on fertilizer costs but also minimizes environmental pollution caused by nitrogen runoff into water bodies.

Biotechnology in agriculture has the potential to address food security challenges, reduce the environmental impact of farming practices, and improve the nutritional content of crops. However, it also raises ethical and safety concerns that need to be carefully managed to ensure the sustainable and responsible application of these technologies.

14. Write brief account on organic evolution. 4

Ans:- Organic evolution is a foundational concept in biology that explains how life on Earth has changed over vast stretches of time. It encompasses the processes by which new species arise, adapt to their environments, and diversify from common ancestors. Here is a brief account of organic evolution:

Historical Context:

The concept of organic evolution has ancient roots, with early ideas proposed by philosophers like Empedocles and Anaximander. However, it gained scientific prominence in the 19th century, largely due to the work of Charles Darwin and Alfred Russel Wallace.

Darwin's seminal work, "On the Origin of Species," published in 1859, laid the foundation for our modern understanding of evolution. He proposed the theory of natural selection as the mechanism driving evolution.

Key Concepts:

Common Descent: Organic evolution posits that all living organisms share a common ancestor. Over time, these organisms have diverged and adapted to various environments, resulting in the diversity of life we observe today.
Natural Selection: This mechanism of evolution suggests that individuals within a population who possess advantageous traits are more likely to survive and reproduce. These advantageous traits are then passed on to the next generation, gradually altering the characteristics of the population.
Mutation: Genetic variation arises through mutations, which are random changes in an organism's DNA. Mutations can introduce new traits into a population and serve as the raw material for natural selection.
Speciation: The process of speciation occurs when one population of a species becomes isolated from another, leading to genetic divergence over time. Eventually, the isolated populations may become distinct species.

Supporting Evidence:

The fossil record provides tangible evidence of past life forms and how species have changed over time.
Comparative anatomy and embryology reveal similarities in the structures and developmental processes of organisms, indicating common ancestry.
Molecular biology, including DNA sequencing, demonstrates genetic relationships among species and supports the idea of a shared genetic code.

Modern Developments:

The modern synthesis of the mid-20th century combined Darwin's ideas with genetics, leading to the field of population genetics. It provided a comprehensive framework for understanding how genetic variation and selection interact to drive evolution.
Contemporary research continues to explore evolution at the genetic and molecular levels, uncovering the specific genes and mechanisms responsible for adaptation and speciation.

Evolutionary biology has expanded beyond just explaining the diversity of species to understanding broader processes, such as the evolution of complex traits and behaviors.

Implications:

The theory of organic evolution has far-reaching implications for our understanding of the natural world and our place in it.
It has applications in various fields, including medicine, agriculture, and conservation, as it helps us understand disease evolution, crop breeding, and biodiversity conservation.

What is coacervate? How do fossils evidence organic evolution? 1+3=4

Ans:- Coacervate:Coacervates are tiny droplets formed by certain molecules in water. They mimic some cell-like properties and might have played a role in the origin of life.

Fossils as Evidence for Organic Evolution: Fossils are crucial pieces of evidence for organic evolution. They provide a direct record of past life forms and how species have changed over geological time. Here's how fossils serve as evidence for organic evolution:
Transitional Forms: Fossils often reveal intermediate or transitional forms of organisms that exhibit characteristics of both ancestral and descendant species. These transitional fossils, such as the famous Tiktaalik, provide tangible evidence of evolutionary change within lineages.
Stratigraphy: The study of fossils in sedimentary rock layers (stratigraphy) allows scientists to determine the relative ages of different fossil species. By analyzing the sequence of fossils in rock layers, researchers can construct a timeline of evolutionary events and understand the order in which species appeared and disappeared.
Anatomical Changes: Fossils provide physical evidence of changes in the anatomy and morphology of species over time. For example, the fossil record documents the evolution of horse ancestors from small, multi-toed creatures to the larger, single-toed horses we see today.
Biogeography: Fossil evidence helps explain the distribution of species across continents and regions. Fossils of related species found on separate continents suggest that these species share a common ancestor and that continental drift played a role in their distribution.

15. Write an account on the development of dicotyledonous embryo with labelled diagram. 5

Ans:- The development of a dicotyledonous embryo involves a series of stages from fertilization to the formation of a mature seed. Dicotyledonous plants are characterized by having two cotyledons or seed leaves in their embryos. Here is an account of the development of a dicotyledonous embryo along with a simplified labeled diagram:

Development of Dicotyledonous Embryo:

Fertilization:The process begins with fertilization when a pollen grain lands on the stigma of a flower and produces a pollen tube that carries the male gametes (sperm cells) to the ovule.
The male gametes fuse with the female gametes (egg cell and central cell) in the ovule to form a zygote and a triploid cell called the endosperm nucleus.

Formation of Zygote:

The zygote is the first cell of the new plant and is deployed, meaning it has two sets of chromosomes (one from each parent).

Embryogenesis:

The zygote undergoes several rounds of cell division and differentiation to form an embryo.
The first division produces two cells: the terminal cell (will become the embryo) and the basal cell (will develop into the suspensor, providing nutrients to the embryo).
The terminal cell further divides to form the globular embryo stage.

Cotyledon Formation:

The globular embryo then elongates and forms the heart-shaped or torpedo-shaped embryo stage.
During this stage, the two cotyledons, or seed leaves, develop.

Radicle and Plumule Formation:

As the embryo continues to develop, the radicle (embryonic root) and plumule (embryonic shoot) become distinct structures.
The radicle will grow into the main root of the mature plant, while the plumule will develop into the shoot system.

Maturation:

The embryo matures as additional tissues and structures, such as the hypocotyl (the region between the cotyledons and the radicle) and the epicotyl (the region above the cotyledons), become well-defined.
The embryo is surrounded by protective seed coats.

Seed Formation:

The mature embryo, along with the endosperm and sometimes other seed parts, becomes encased in a seed coat.
The endosperm stores nutrients that will nourish the developing embryo as it germinates into a new plant.

Labeled Diagram of Dicotyledonous Embryo:

Write an account on the structure of a typical ovule with labeled diagram. 5

Ans:-

Ovule is an integumented megasporangium.Ovules are enclosed within the ovary in angiosperms.

An ovule consists of a female gametophyte (embryo sac), nutrient rich tissue (nucellus) and a jacket of cell layers (integuments). On fertilisation , the ovule ripens into a seed and the integuments form the seed coat.

Description

An ovule has following parts

(i) Attachment points:

Funicle is the stalk that attaches the ovule to placenta.

Hilum is the point where funicle is attached to the ovule body.

Raphe is a ridge-like structure formed, where funicle fuses with the body of ovule.

(ii) Integuments:

Integuments are the covering layer that protects the developing embryo.

(iii) Nucellus:

A mass of cells that lies enclosed within the integuments is called the nucellus. Cells of nucellus have abundant reserves of food material.

(iv) Embryo sac/ female gametophyte:

Female gametophyte covered by a thin membrane is called embryo sac. It is located in the nucellus. An ovule generally has a single embryo sac formed from the megaspore through reduction division(meiosis).

PART - II (Zoology)

1. Fill in the blanks: (any two) 1x2=2

(a) Ovulation is induced by luteinizing hormone (LH).

(b) DNA fingerprinting is first discovered by Sir Alec Jeffreys.

(d) AIDS is caused by HIV (Human Immunodeficiency Virus).

2. Answer any two: 1x2=2

(a) What is a transgenic animal?

Answer: A transgenic animal is an organism that has had foreign genes (genes from another species) deliberately introduced into its genome through genetic engineering techniques.

(b) What is menopause?

Answer: Menopause is a natural biological process that marks the end of a woman's reproductive years. It occurs when a woman's ovaries stop producing eggs, leading to the cessation of menstruation and a range of hormonal and physical changes

Answer: DNA fingerprinting, also known as DNA profiling or genetic fingerprinting, is a forensic technique used to identify and analyze an individual's unique DNA pattern. It is often employed in criminal investigations, paternity testing, and determining genetic relationships.

(d) Mention one cause of sound pollution.

Ans:- One cause of sound pollution is excessive noise from sources such as traffic, industrial machinery, construction activities, and loud music.

3. Answer any four: 2x4=8

(a) What is sex linked inheritance? Give one example.

Ans:- Sex-Linked Inheritance: Genes on sex chromosomes (X and Y). Example: Hemophilia, a disorder where faulty X-linked genes cause bleeding issues, mainly in males.

(b) Write the scientific name of Muga silk worm. Mention one host plant of Muga silk worm.

Ans:- Muga Silk Worm: Scientific name - Antheraea assamensis. Host plant - Som and sualu trees found in Assam.

Ans:- CuT (Contraceptive Technology): Copper T, an intrauterine device (IUD) for contraception. It prevents pregnancy by releasing copper ions that are toxic to sperm.

(d) What is world heritage site? Mention one world heritage site of Assam.

Ans:- World Heritage Site: A place recognized by UNESCO for cultural, historical, or natural significance. Example in Assam: Kaziranga National Park, known for rhino conservation.

(e) Define drug. Write one Psychotropic drug.

Ans:- Drug: Chemical substance affecting the mind or body. Psychotropic drug example: Prozac (fluoxetine), used to treat conditions like depression and anxiety.

4. Write the differences between: (any two) 2x2=4

(a) Morula and blastula

Ans:- The differences between Morula and blastula :-

Morula	Blastula
It is solid sphere of 8-16 blastomeres	It contains about 64 cells and is hollow inside due to the development of blastocoel cavity.
Zona-pellucida remains intact	As the blastocyst enlarges, zona-pell- ucida disintegrates.

(b) Parturition and lactation

Ans:- The differences between Parturition and lactation :-

Category	Parturition	Lactation
Definition	Process of giving birth to offspring, involving contractions and the expulsion of the fetus.	Process of producing and secreting milk from mammary glands.
Timing	Occurs during labor and childbirth	Typically begins after childbirth.
Purpose	Allows the delivery of the offspring	Provides nourishment to the newborn through breast milk

Ans:- The differences between Incomplete dominance and codominance:-

Category	Incomplete Dominance	Codominance
Gene Expression	Neither allele is completely dominant, resulting in an intermediate phenotype.	Both alleles are expressed fully, leading to the simultaneous presence of both traits.
Example	Cross between a red flower (RR) and a white flower (WW) results in pink flowers (RW)	Cross between a black chicken (BB) and a white chicken (WW) results in black and white speckled chickens (BW)
Phenotype	Phenotype is a blend or mixture of the two alleles	Phenotype shows both traits distinctly

(d) Active Immunity and Passive Immunity

Ans:- The differences between Active Immunity and Passive Immunity:-

Category	Immunity	Passive Immunity
Source of Immunity	Acquired through exposure to pathogens or vaccines, where the immune system generates its own immune response, including the production of antibodies.	Transferred from an external source, such as antibodies from mother to fetus through the placenta or via breast milk, or through the administration of pre-formed antibodies like immunoglobulin injections.
Duration	Generally long-lasting, as the immune system "remembers" how to respond to the specific pathogen	Temporary, as it relies on the presence of transferred antibodies and does not confer lasting protection
Examples	Getting vaccinated against a disease like measles	Receiving antibodies to treat a snakebite or a newborn acquiring maternal antibodies through breastfeeding

(e) Transcription and Translation

Ans:- The differences between Transcription and Translation:-

Category	Transcription	Translation
Process	The process of copying genetic information from DNA into a complementary RNA molecule	The process of decoding the RNA message to build a polypeptide chain (protein)
Location	Occurs in the nucleus of eukaryotic cells.	Takes place in the cytoplasm, specifically on ribosomes.
End Product	Produces a messenger RNA (mRNA) molecule	Results in the synthesis of a polypeptide chain, which folds into a protein

5. Draw a labelled diagram of the matured human sperm. 3

Ans:- The human sperm mainly consists of the head, neck, middle piece and tail. The tail helps in the movement of the sperm. The head contains a cap-like structure called the acrosome. The acrosome is filled with enzymes that help fertilisation of the ovum. The middle piece helps in the production of energy due to the presence of numerous mitochondria in it. This energy helps in sperm motility needed for fertilization.

Draw a labelled diagram of Watson and Crick model of semiconservative replication of DNA. 3

Ans:- Watson-Crick Structure of DNA

Watson and Crick presented a model for the DNA’s double-helix structure.
A nucleotide polymer makes up the DNA molecule.
A nitrogenous base, a five-carbon sugar (deoxyribose), and a phosphate group are found in each nucleotide.
There are two purines (adenine and guanine) and two pyrimidines in the DNA (cytosine and thymine).

Given below is the diagram for the Watson-Crick Structure Of DNA

6. What do you mean by biodiversity hotspot? Write the name of biodiversity hotspot of India. 1+2=3

Ans:- A biodiversity hotspot refers to a biogeographic region with significant levels of biodiversity, which means it is home to a large number of different species, many of which are found nowhere else on Earth. These regions are characterized by high species richness and often face threats such as habitat destruction and species extinction due to human activities.

In India, one of the most prominent biodiversity hotspots is the Western Ghats. The Western Ghats is a mountain range along the western coast of India and is known for its rich and diverse flora and fauna. It is home to numerous endemic species, which means they are found exclusively in this region and nowhere else in the world. The Western Ghats is also recognized as a UNESCO World Heritage Site due to its ecological significance. However, like many biodiversity hotspots, it faces various conservation challenges due to habitat loss, deforestation, and other human activities. Efforts are being made to protect and preserve this vital hotspot and its unique biodiversity.

What is transcription unit? Write about types of RNA. 1+2=3

Ans:- A transcription unit is a segment of DNA that serves as a functional unit for the process of transcription. Transcription is the first step in the central dogma of molecular biology, where the information stored in DNA is transcribed into RNA. A transcription unit typically includes three key components:

Promoter: The promoter is a region of DNA located upstream (towards the 5' end) of the transcription start site. It contains specific DNA sequences recognized by RNA polymerase, the enzyme responsible for catalyzing transcription. The promoter initiates the binding of RNA polymerase to the DNA strand, marking the beginning of transcription.
RNA-Coding Region: This is the actual segment of DNA that is transcribed into RNA. It includes the coding sequences for the RNA molecule to be synthesized. In eukaryotes, this region can contain both exons (coding sequences) and introns (non-coding sequences). After transcription, the introns are typically removed, and the exons are joined together through a process called splicing to form mature RNA.

Terminator: The terminator is a sequence of DNA that marks the end of transcription. It signals RNA polymerase to release the newly synthesized RNA molecule and detach from the DNA strand.

Types of RNA:

Messenger RNA (mRNA): mRNA is a type of RNA molecule that carries genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm, where protein synthesis (translation) occurs. It serves as a template for protein synthesis by specifying the order of amino acids in a protein.
Ribosomal RNA (rRNA): rRNA is a structural component of ribosomes, which are cellular organelles responsible for protein synthesis. Ribosomes consist of both protein and rRNA, and they play a crucial role in reading the mRNA and catalyzing the assembly of amino acids into proteins.
Transfer RNA (tRNA): tRNA is involved in protein synthesis and acts as an adaptor molecule. Each tRNA molecule carries a specific amino acid to the ribosome and has an anticodon region that can base-pair with the complementary codon on the mRNA. This ensures that the correct amino acid is added to the growing protein chain.

7. What is gene migration? Write about the genetic drift. 1+2=3

Ans:- Gene migration, also known as gene flow or allele flow, refers to the movement of genes from one population to another within a species. It occurs when individuals or their gametes (reproductive cells) move from one population to another, leading to the exchange of genetic material between these populations. Gene migration can have significant effects on the genetic diversity and composition of populations.

Key points about gene migration:

Introduction of New Genetic Variation: When individuals from one population migrate and interbreed with individuals from another population, they bring with them their unique genetic traits. This introduces new genetic variation into the recipient population.
Reduction of Genetic Differences: Over time, gene migration tends to reduce genetic differences between populations. If gene flow is extensive, it can homogenize the genetic makeup of different populations, making them more similar to each other.
Role in Evolution: Gene migration is a fundamental process in evolution, as it can introduce new alleles or genetic variants into a population. These new alleles can undergo natural selection, genetic drift, or other evolutionary forces, leading to changes in the genetic composition of populations.

Genetic Drift:

Genetic drift is a random process of allele frequency change within a population due to chance events. Unlike natural selection, which is driven by the adaptive advantage of certain traits, genetic drift is driven by random sampling error. It is particularly significant in small populations where chance events can have a more pronounced impact on allele frequencies.

Key points about genetic drift:

Random Sampling: Genetic drift occurs because, in small populations, the individuals that contribute their genes to the next generation are a random sample of the current population. As a result, the frequency of alleles in the offspring generation may differ from that in the parent generation purely by chance.
Effects on Allele Frequencies: Genetic drift can lead to the fixation of one allele (where it becomes the only allele at a particular gene locus) or the loss of an allele within a population. These changes in allele frequencies can happen relatively quickly in small populations.
Impact on Genetic Diversity: Genetic drift reduces genetic diversity within populations and increases genetic differences between populations. In small, isolated populations, genetic drift can have a more pronounced effect, potentially leading to the fixation of deleterious alleles or the loss of beneficial ones.

8. Describe the Miller's experiment to provide idea about the origin of life. 5

Ans:- Miller's Experiment and the Origin of Life:

Miller's experiment, conducted by chemist Stanley Miller in 1953, was a pioneering laboratory simulation that aimed to provide insight into the possible origin of life on Earth. Here are the key points of Miller's experiment:

Purpose: The experiment aimed to replicate the conditions of early Earth, hypothesized to be rich in gases like methane (CH4), ammonia (NH3), water vapor (H2O), and hydrogen (H2).

Setup: Miller created a closed system consisting of a flask containing water, representing Earth's oceans, and a second flask containing these gases, simulating Earth's early atmosphere. The two flasks were connected, allowing vapor and gases to cycle through a loop.

Energy Source: To mimic the energy sources present on early Earth, Miller used sparks to simulate lightning strikes. These sparks provided energy to the system.

Results: Over a period of several days, Miller observed that the gases in the system underwent chemical reactions driven by the energy from the simulated lightning. Amino acids, the building blocks of proteins and essential for life, were formed in the experiment. This was a significant discovery because it suggested that the basic building blocks of life could have originated from simple organic compounds and energy in the early Earth's environment.

Implications: Miller's experiment provided experimental evidence supporting the idea that the conditions on early Earth could have facilitated the synthesis of organic molecules necessary for life. While it did not directly prove the origin of life, it demonstrated that life's basic building blocks could have formed naturally under prebiotic conditions.

Describe the process of energy flow in different trophic level in the ecosystem. 5

Ans:- Energy Flow in Trophic Levels in Ecosystems:

Energy flow in ecosystems follows a hierarchical structure, with different trophic levels representing distinct positions in the food chain. Here's a simplified explanation of this process:

Producers (Trophic Level 1): Producers, typically green plants or photosynthetic microorganisms, are at the base of the energy pyramid. They convert sunlight, water, and carbon dioxide into energy-rich organic molecules through photosynthesis.

Primary Consumers (Trophic Level 2): Primary consumers are herbivores that feed on producers. They obtain energy by consuming plant material and converting it into their own biomass.

Secondary Consumers (Trophic Level 3): Secondary consumers are carnivores or omnivores that feed on primary consumers. They obtain energy by consuming herbivores.

Tertiary Consumers (Trophic Level 4): Tertiary consumers are carnivores that feed on secondary consumers. They obtain energy by consuming other carnivores.

Decomposers (Detritivores) and Detritus (Trophic Level 5): Decomposers, such as bacteria and fungi, break down dead organic matter and waste materials, returning nutrients to the environment. Detritus, which includes dead plants and animals, serves as their primary food source.

Energy Transfer: As energy moves up the trophic levels, there is a loss of energy at each step due to metabolic processes, heat production, and inefficiencies in energy transfer. This is known as the 10% rule, which means that only about 10% of the energy from one trophic level is transferred to the next.

9. Describe the chromosomal theory of inheritance. 5

Ans:- The chromosomal theory of inheritance is a fundamental concept in genetics that explains how genes are located on chromosomes and how they are passed from one generation to the next. This theory, developed by Walter Sutton and Theodor Boveri in the early 20th century, established a link between the behavior of chromosomes during cell division and the patterns of inheritance observed in Mendelian genetics.

The Following are five key points that describe the chromosomal theory of inheritance:

Genes Are Located on Chromosomes: The theory posits that genes, which are the units of heredity responsible for transmitting traits from one generation to the next, are located on chromosomes. Chromosomes are long, thread-like structures made of DNA and associated proteins, and they exist in the cell nucleus.
Chromosome Segregation: During the process of cell division, specifically during meiosis, chromosomes segregate and are distributed into daughter cells. Each parent contributes one set of chromosomes to the offspring, with one member of each homologous pair coming from the mother and the other from the father. This explains Mendel's law of segregation, where alleles (different forms of a gene) separate during gamete formation.
Chromosome Assortment: The chromosomal theory also explains Mendel's law of independent assortment. This principle states that genes located on different chromosomes assort independently during meiosis. This means that the inheritance of one gene does not influence the inheritance of another gene located on a different chromosome.
Recombination: The chromosomal theory accounts for genetic recombination, which is the process by which new combinations of alleles are generated in offspring. Recombination occurs during meiosis when chromosomes exchange genetic material through a process called crossing over. This leads to genetic diversity among offspring.
Sex Chromosomes Determine Sex: The chromosomal theory clarifies how sex is determined in many species. In humans, for example, individuals with two X chromosomes (XX) are females, while individuals with one X and one Y chromosome (XY) are males. The presence or absence of specific sex chromosomes determines an individual's sex and the inheritance of sex-linked traits.

Describe the Hardy-Weinberg principle. 5

Ans:- The Hardy-Weinberg principle, also known as the Hardy-Weinberg equilibrium or law, is a fundamental concept in population genetics that describes the relationship between the frequencies of alleles in a population and predicts how these frequencies will remain constant from generation to generation under specific conditions. This principle is named after British mathematician and biologist G. H. Hardy and German physician Wilhelm Weinberg, who independently formulated it in the early 20th century. The Hardy-Weinberg principle is based on several key assumptions and equations:

Large Random Mating Population: The principle assumes that the population is large enough to prevent random genetic drift, and individuals mate randomly within the population. This means that there is no preferential selection of mates based on genotype.
No Mutation: The principle assumes that there are no new mutations occurring in the gene pool of the population. In other words, the genetic makeup of the population remains stable with regard to the studied gene or genes.
No Migration: There is no migration of individuals into or out of the population. This implies that the gene pool of the population is closed, and there is no gene flow with other populations.
No Natural Selection: The principle assumes the absence of natural selection, meaning that none of the genotypes offer a reproductive advantage or disadvantage. In other words, all genotypes have equal fitness in terms of survival and reproduction.
Two Alleles: The gene under consideration must have only two alleles, typically referred to as the dominant (usually represented by "A") and recessive (usually represented by "a") alleles.

The mathematical equation for the Hardy-Weinberg principle is as follows:

p^2 + 2pq + q^2 = 1

Where:

p^2 represents the frequency of homozygous dominant individuals (AA genotype).
2pq represents the frequency of heterozygous individuals (Aa genotype).
q^2 represents the frequency of homozygous recessive individuals (aa genotype).
The sum of these three terms equals 1, indicating that the frequencies of all possible genotypes in the population add up to 100%.

The Hardy-Weinberg principle is a useful tool for understanding how genetic variation is maintained or changes within populations over time. If the actual genotype frequencies in a population deviate from those predicted by the Hardy-Weinberg equilibrium, it suggests the presence of evolutionary forces such as mutation, migration, natural selection, or non-random mating within the population. Thus, the principle serves as a baseline for identifying and studying the mechanisms of evolution.

-00000-

The Treasure Notes

AHSEC Class 12 Biology Solved Question Paper 2023 | HS 2nd Year Biology Solved Question Paper 2023