Holy Cross College Final Exam Short Responce

Accumulation of the SRQ from Exam 1-4. Biology 152 Spring 2026

Exam 1 SRQ27: How does a virus infect a host cell? Describe the lysogenic and lytic cycles.

A virus infects a host by binding to specific receptors on the host cell surface, entering the cell, and using the host cell machinery to replicate. In the lysogenic cycle, viral DNA integrates into the host genome as a prophage/provirus and replicates with the host without immediately killing it. In the lytic cycle, the virus rapidly replicates, assembles new viral particles, and lyses the host cell, releasing many new viruses.

Exam 1 SRQ28: What types of chemicals induce mutations in cells to cause cancer? Where are these chemicals found?

Carcinogens are chemicals or agents that induce mutations that can lead to cancer. They may be found in tobacco smoke, industrial chemicals, pollutants, radiation exposure, certain foods or environmental toxins, and other mutagenic substances. These agents can damage DNA, and if mutations affect oncogenes or tumor-suppressor genes, uncontrolled cell growth may result.

Exam 1 SRQ29: Describe a model for the action of enhancers and activators causing transcription initiation. Use terms such as promoter, RNA polymerase II, mediator proteins, etc.

Activator proteins bind to enhancer regions, which may be far from the gene. DNA bends so the bound activators can contact mediator proteins and general transcription factors at the promoter/TATA box. This helps assemble and position RNA polymerase II at the promoter, forming the transcription initiation complex and increasing transcription of the gene.

Exam 1 SRQ30: What is the Human Genome Project? When did it start and when was it completed? Who was in charge of the project?

The Human Genome Project was an international research effort to sequence and map the entire human genome. It officially began in 1990 and was largely completed in 2003. It was publicly led by scientists including Francis Collins through the NIH, while Craig Venter led a private sequencing effort through Celera Genomics.

Exam 1 SRQ31: What topic do you find most interesting in the class so far?

A strong answer should name one biology topic and explain why it is interesting using course concepts. Example: Viruses are interesting because they are not cells, yet they can hijack host cell machinery to reproduce. Their lytic and lysogenic cycles show how simple genetic material can have major effects on living cells.

Exam 1 SRQ32: Describe the multi-stage colorectal cancer progression and development through mutations or loss of tumor suppressor genes and oncogenes.

Colorectal cancer develops through the accumulation of multiple mutations over time. Proto-oncogenes may become oncogenes that overstimulate cell division, while tumor-suppressor genes may lose function and fail to stop the cell cycle or repair DNA. As these mutations accumulate, normal cells can form polyps and eventually malignant tumors with uncontrolled growth.

Exam 2 SRQ32: Describe indeterminate and determinate growth.

Indeterminate growth means a plant continues to grow throughout its life because meristems remain active and undifferentiated. Determinate growth means an organ or structure stops growing after reaching a certain size or stage, such as many flowers or leaves.

Exam 2 SRQ33: What are the differences between monocots and eudicots?

Monocots have one cotyledon, parallel leaf veins, fibrous roots, scattered vascular tissue in stems, and floral parts usually in multiples of three. Eudicots have two cotyledons, netlike leaf veins, a taproot system, vascular tissue usually arranged in a ring, and floral parts usually in multiples of four or five.

Exam 2 SRQ34: What are two ways in which new alleles can be produced in a population?

New alleles are produced mainly by mutation, which changes DNA sequence, and by gene duplication followed by mutation, which allows one copy of a gene to change while the other keeps its original function. Sexual recombination reshuffles existing alleles but does not create brand-new alleles.

Exam 2 SRQ35: Consider a population with allele frequencies p = 0.9 and q = 0.1. If the population is not evolving, use Hardy-Weinberg to predict genotype frequencies in the next generation.

Use p² + 2pq + q² = 1. With p = 0.9 and q = 0.1, p² = 0.81, 2pq = 2(0.9)(0.1) = 0.18, and q² = 0.01. Therefore, the genotype frequencies are 81% homozygous dominant, 18% heterozygous, and 1% homozygous recessive.

Exam 2 SRQ36: Descent with modification by natural selection explains three broad observations about nature. What is natural selection and what are these three broad observations?

Natural selection is the process in which individuals with heritable traits that improve survival or reproduction leave more offspring, causing those traits to become more common in a population over time. Descent with modification explains the unity of life, the diversity of life, and the match between organisms and their environments, or adaptation.

Exam 2 SRQ37: Clock Question: Two days later we move our clock one hour forward and later back. These forward and backward time changes are not good for health. Provide two reasons.

Changing the clock can disrupt circadian rhythms, which regulate sleep-wake cycles, hormones, metabolism, and alertness. It can also cause sleep loss or poor-quality sleep, which may increase fatigue, reduce concentration, and temporarily raise risks related to accidents, stress, or cardiovascular strain.

Exam 2 SRQ38: What are your plans for spring break?

A strong answer should directly answer the personal prompt in complete sentences. Example: My plan for spring break is to rest, spend time with family or friends, and catch up on schoolwork so I can return prepared for the rest of the semester.

Exam 3 SRQ20: Understanding thermoregulation is important for understanding negative and positive feedback mechanisms. Describe a negative and positive feedback system and give one example of each.

Negative feedback reduces or reverses a stimulus to maintain homeostasis, such as sweating when body temperature rises or shivering when body temperature falls. Positive feedback amplifies a stimulus, such as oxytocin increasing uterine contractions during childbirth or milk release during nursing. Negative feedback stabilizes conditions, while positive feedback drives a process to completion.

Exam 3 SRQ21: Explain why endotherms require more energy than ectotherms. Describe how thermoregulation influences metabolic rate and energy demand.

Endotherms generate much of their body heat through metabolism, so they need more food and energy to maintain a stable internal temperature. Ectotherms rely more on external heat sources, so their metabolic energy demand is usually lower. Because thermoregulation in endotherms requires constant heat production, their metabolic rate is generally higher than that of ectotherms.

Exam 3 SRQ22: Describe a simple endocrine pathway.

In a simple endocrine pathway, an endocrine cell directly senses a stimulus and releases a hormone into the bloodstream. The hormone travels to target cells that have the correct receptors and causes a response. For example, low pH in the duodenum stimulates S cells to release secretin, which causes the pancreas to release bicarbonate to neutralize the acid.

Exam 3 SRQ23: Name and describe each of the four categories of animal tissues.

The four animal tissues are epithelial, connective, muscle, and nervous tissue. Epithelial tissue covers body surfaces and lines organs and cavities. Connective tissue supports, binds, and protects body parts. Muscle tissue contracts to produce movement. Nervous tissue detects stimuli and transmits signals through neurons.

Exam 3 SRQ24: Compare the osmotic challenges faced by marine and freshwater fish. Use hypoosmotic, hyperosmotic, dilute urine, and concentrated urine, and explain how each maintains water and ion balance.

Marine fish live in a hyperosmotic environment, so they lose water to the surroundings by osmosis. They drink seawater, excrete excess salts through gills and kidneys, and produce small amounts of concentrated urine. Freshwater fish live in a hypoosmotic environment, so they gain water by osmosis. They drink little or no water, take up salts through food or gills, and produce large amounts of dilute urine.

Exam 3 SRQ25: It is a cold spring morning and we want to stay warm. What feedback mechanism does our body follow? How do superficial blood vessels help maintain warmth?

The body uses negative feedback to maintain body temperature near a set point. In cold conditions, the hypothalamus triggers warming responses such as shivering and vasoconstriction. Superficial blood vessels constrict, reducing blood flow to the skin and decreasing heat loss to the environment, which helps conserve core body heat.

Exam 3 SRQ26: Explain how aquatic and terrestrial organisms differ in handling nitrogenous wastes. Compare ammonia, urea, and uric acid and relate these strategies to water availability and toxicity.

Aquatic organisms often excrete ammonia because it is very toxic but can be diluted quickly in water. Mammals and many amphibians convert ammonia to urea, which is less toxic and can be stored briefly but requires some water for excretion. Birds, reptiles, insects, and land snails often excrete uric acid, which is least soluble and conserves water but costs more energy to produce. The more limited the water supply, the more useful less-toxic, water-conserving wastes become.

Exam 3 SRQBonus: One hormone, such as epinephrine, has multiple effects depending on receptor type. Describe the 3 effects of epinephrine.

Epinephrine can have different effects depending on receptor type and target cell. In liver cells, it stimulates glycogen breakdown and increases blood glucose. In blood vessels supplying skeletal muscle, it causes dilation and increases blood flow. In blood vessels supplying the digestive tract, it causes constriction and reduces blood flow.

Exam 4 SRQ31: A patient has a tumor in the mammary gland. What type of functional imaging will the doctor use to determine growth and metabolism of the tumor? Why use this imaging?

A doctor could use PET imaging to examine tumor metabolism because PET uses radioactive glucose to show areas of high metabolic activity. Tumors often consume more glucose than normal tissues, so PET can help locate cancer activity, evaluate growth or spread, and assess how metabolically active the tumor is. fMRI is mainly used to detect brain activity through blood oxygen changes, so PET is the stronger answer for tumor metabolism.

Exam 4 SRQ32: Describe the neuronal circuit/path responsible for pain in a human. Include sensory receptors and brain.

Pain begins when sensory receptors detect tissue damage or another painful stimulus. Sensory neurons carry the signal into the spinal cord and central nervous system. Interneurons process the information, and the brain interprets the signal as pain. If a response is needed, motor neurons can send signals to muscles to withdraw from the stimulus.

Exam 4 SRQ33: What is an axon of a neuron? What structure causes an axon to regenerate? Give a real-life situation where axonal regeneration is needed.

An axon is the long extension of a neuron that carries nerve impulses away from the cell body to other neurons, muscles, or glands. In the PNS, Schwann cells form the neurilemma, which helps guide axon regeneration after injury. Axon regeneration may be needed after a cut, burn, crush injury, or nerve damage that disrupts sensation or movement.

Exam 4 SRQ34: Explain how a signal is transmitted across a synapse. Include neurotransmitters and receptors.

A nerve impulse travels down the axon to the terminal bouton of the presynaptic neuron. This causes neurotransmitters to be released into the synaptic cleft. The neurotransmitters diffuse across the cleft and bind to specific receptors on the postsynaptic cell, triggering either stimulation or inhibition of a new nerve impulse or response.

Exam 4 SRQ35: Describe one disease that negatively affects bone and/or joint health in humans.

Osteoporosis is a disease in which bone mass decreases because bone breakdown exceeds bone formation, often due to aging, inactivity, low calcium intake, or hormonal changes. The bones become weaker and more porous, increasing the risk of fractures. Another acceptable example would be arthritis, which causes inflammation, pain, and reduced joint movement.

Exam 4 SRQBonus: Explain how the introduction of the Arctic fox to Arctic islands imposed a selective force on plant communities. Use soil, nutrients, natural selection, differential success.

The introduction of Arctic foxes reduced seabird populations because foxes preyed on the birds. Fewer seabirds meant less guano, so the soil received fewer nutrients. This changed the plant environment and created a selective pressure: plants better adapted to lower-nutrient soil had greater differential success, while plants requiring nutrient-rich soil declined. Over time, natural selection shifted the plant community toward species better suited to the changed soil conditions.

Final Practice SRQ46: Describe the four mechanisms of evolution and give an example of each.

The four mechanisms of evolution are natural selection, genetic drift, gene flow, and mutation. Natural selection occurs when pesticide-resistant insects survive and reproduce more. Genetic drift is random allele frequency change, such as a storm randomly killing many individuals in a small population. Gene flow occurs when alleles move between populations, such as pollen moving between plant populations. Mutation creates new alleles through DNA sequence changes.

Final Practice SRQ47: Describe the composition of the human genome and what it reveals about gene regulation.

Only a small percentage of the human genome codes for proteins, while much of it consists of noncoding DNA such as introns, regulatory sequences, repetitive DNA, and transposable elements. This shows that gene regulation is complex and depends not only on protein-coding genes but also on enhancers, promoters, chromatin modification, RNA processing, and noncoding RNAs.

Final Practice SRQ48: Compare and contrast strategies for thermoregulation in endotherms and ectotherms.

Endotherms generate body heat through metabolism and can maintain a relatively stable body temperature, but this requires high energy intake. Ectotherms rely mostly on external heat sources and often regulate temperature behaviorally, such as basking in sun or seeking shade. Both must balance heat gain and heat loss, but endotherms spend more metabolic energy doing so.

Final Practice SRQ49: Explain how antibiotics influence natural selection in microbes.

Antibiotics create a selective pressure on bacterial populations. Bacteria with resistance traits are more likely to survive and reproduce, while susceptible bacteria die. Over generations, resistance alleles become more common in the population, showing evolution by natural selection.

Final Practice SRQ50: Discuss how an allelopathy experiment relates to natural selection.

Allelopathy occurs when one plant releases chemicals that affect the growth or survival of other plants. In an experiment, plants that tolerate the chemical may survive and reproduce better than sensitive plants. If tolerance is heritable, natural selection can cause tolerant traits to become more common over generations.