1st Year Biology Guess Paper - Complete Answers
UNIT #1
Q: Differentiate between population & community.
Population: A group of organisms of the same species living in a specific area at a specific time. Example: All mango trees in a garden.
Community: A group of different populations living together in a specific area interacting with each other. Example: All plants, animals, and microorganisms in a garden.
---
Q: How does theory differ from the law?
Theory: A well-supported explanation of natural phenomena based on extensive observations and experiments. It explains why something happens. Example: Cell theory.
Law: A statement that describes a consistent natural phenomenon without explaining why it happens. It predicts what will happen. Example: Law of segregation.
---
Q: What is integrated disease management?
Integrated disease management is a comprehensive approach to control plant diseases by combining various methods including:
· Biological control (using natural enemies)
· Chemical control (using pesticides)
· Cultural practices (crop rotation, sanitation)
· Genetic resistance (using resistant varieties)
---
Q: Differentiate between chemotherapy, radiotherapy & gene therapy.
Chemotherapy: Treatment of diseases using chemical drugs that kill or inhibit disease-causing agents or cancer cells.
Radiotherapy: Treatment using high-energy radiation (X-rays, gamma rays) to destroy cancer cells or tumors.
Gene therapy: Treatment that involves introducing normal genes into a patient's cells to replace defective or missing genes causing genetic disorders.
---
Q: What is hydroponic technique? Give its importance.
Hydroponic technique: Growing plants without soil, using nutrient-rich water solutions to provide essential minerals directly to plant roots.
Importance:
· Plants grow faster and produce higher yields
· Can grow plants in areas with poor soil
· Saves water compared to traditional farming
· Controls nutrient supply precisely
· Reduces soil-borne diseases
---
Q: Write a note on vaccination.
Vaccination: The process of introducing weakened or dead pathogens (or their parts) into the body to stimulate the immune system to produce antibodies.
How it works:
1. Vaccine contains antigens that resemble the pathogen
2. Immune system recognizes these as foreign
3. Produces antibodies and memory cells
4. If actual pathogen enters later, body quickly fights it
Importance: Prevents infectious diseases, saves lives, and contributes to herd immunity.
---
Q: Define biome with an example.
Biome: A large geographical area characterized by specific climate conditions and dominant plant and animal communities.
Example: Desert biome - characterized by low rainfall, extreme temperatures, and adapted organisms like cacti and camels.
---
Q: Define phyletic lineage & biodiversity.
Phyletic lineage: A sequence of species that evolve from a common ancestor over time, showing evolutionary relationships.
Biodiversity: The variety of living organisms present in a particular area, including genetic diversity, species diversity, and ecosystem diversity.
---
Q: Differentiate between deductive reasoning & inductive reasoning.
Deductive reasoning: Moving from general principles to specific conclusions. It uses logical thinking to reach a specific conclusion from a general statement. Example: All humans are mortal; John is human; therefore John is mortal.
Inductive reasoning: Moving from specific observations to general conclusions. It uses patterns to form generalizations. Example: Observing many swans are white, concluding all swans are white.
---
UNIT #2
Q: Define biochemistry. Give its importance.
Biochemistry: The branch of biology that studies the chemical processes and substances occurring within living organisms.
Importance:
· Helps understand metabolic reactions in cells
· Essential for developing medicines and drugs
· Explains how nutrients are utilized
· Important in understanding genetic disorders
· Used in food science and agriculture
---
Q: Differentiate between glycosidic & peptide bond.
Glycosidic bond: A covalent bond formed between two monosaccharides through dehydration synthesis, joining them to form disaccharides or polysaccharides.
Peptide bond: A covalent bond formed between the carboxyl group of one amino acid and the amino group of another amino acid, releasing water, to form proteins.
---
Q: Define lipids. Give two roles of waxes.
Lipids: Organic compounds that are hydrophobic (insoluble in water) and include fats, oils, waxes, and steroids.
Two roles of waxes:
1. Provide waterproofing on plant leaves and fruits
2. Protect animal skin, feathers, and fur from water loss
---
Q: Differentiate between saturated & unsaturated fatty acid.
Saturated fatty acid: Contains no double bonds between carbon atoms; carbon chain is fully saturated with hydrogen atoms; solid at room temperature. Example: Butter, animal fats.
Unsaturated fatty acid: Contains one or more double bonds between carbon atoms; liquid at room temperature. Example: Olive oil, fish oil.
---
Q: Give the structure of lecithin.
Lecithin structure: A phospholipid composed of:
· Glycerol backbone
· Two fatty acid chains (hydrophobic tails)
· A phosphate group
· Choline (hydrophilic head)
---
UNIT #3
Q: What is the active site of an enzyme?
The active site is a specific region on the enzyme where the substrate binds. It has a unique three-dimensional shape complementary to the substrate. Enzymatic reactions occur here.
---
Q: Differentiate between apoenzyme & holoenzyme.
Apoenzyme: The protein portion of an enzyme without its cofactor; it is inactive.
Holoenzyme: The complete active enzyme consisting of apoenzyme plus its cofactor (coenzyme or metal ion).
---
Q: What are cofactor & activator of enzyme?
Cofactor: A non-protein component essential for enzyme activity. It can be inorganic (metal ions like Zn²⁺, Mg²⁺) or organic (coenzymes like vitamins).
Activator: A substance (usually a metal ion) that binds to an enzyme and increases its activity, often making the active site more effective.
---
Q: How does an enzyme accelerate a metabolic reaction?
Enzymes accelerate reactions by:
1. Lowering the activation energy needed
2. Providing an alternative reaction pathway
3. Bringing substrates close together in correct orientation
4. Stabilizing the transition state
5. Creating a favorable microenvironment at the active site
---
Q: Write four characteristics of enzymes.
1. Specificity: Each enzyme acts on a specific substrate
2. Reusability: Enzymes are not consumed during reactions
3. Catalytic efficiency: Speed up reactions millions of times
4. Sensitivity: Affected by temperature, pH, and inhibitors
---
Q: What is induced fit model? Who proposed this model?
Induced fit model: The model proposed by Daniel Koshland in 1958, suggesting that the active site of an enzyme changes shape when the substrate binds, becoming complementary to the substrate.
---
Q: How does high temperature affect enzyme activities?
High temperature:
· Increases reaction rate initially (up to optimum temperature)
· Above optimum temperature, causes denaturation of enzyme
· Breaks hydrogen bonds and hydrophobic interactions
· Alters the active site shape permanently
· Results in loss of enzyme activity
---
Q: What is the role of pH in enzyme action?
pH affects enzyme activity by:
· Changing the ionization state of amino acids at the active site
· Altering the three-dimensional structure of the enzyme
· Affecting substrate binding
· Extreme pH causes denaturation
---
Q: Give optimum pH values for any two enzyme actions.
1. Pepsin: Optimum pH 2.0 (stomach)
2. Trypsin: Optimum pH 8.0 (small intestine)
---
Q: What are enzyme inhibitors? Give two examples.
Enzyme inhibitors: Substances that decrease or stop enzyme activity by binding to the enzyme.
Examples:
1. Cyanide - inhibits cytochrome oxidase in mitochondria
2. Penicillin - inhibits bacterial cell wall synthesis
---
Q: Differentiate between reversible & irreversible enzyme inhibitors.
Reversible inhibitors: Bind temporarily and can be removed, restoring enzyme activity. Includes competitive and non-competitive inhibitors.
Irreversible inhibitors: Bind permanently and covalently, permanently inactivating the enzyme. Cannot be removed.
---
Q: Differentiate between competitive & non-competitive enzyme inhibitors.
Competitive inhibitors: Resemble the substrate and compete for the active site; can be overcome by increasing substrate concentration.
Non-competitive inhibitors: Bind to a site other than the active site (allosteric site); change enzyme shape and cannot be overcome by increasing substrate concentration.
---
UNIT #4
Q: Write down salient features of cell theory.
1. All living organisms are composed of cells
2. Cell is the basic structural and functional unit of life
3. All cells arise from pre-existing cells (cell division)
4. Cells contain hereditary material (DNA)
5. All cells have similar chemical composition
---
Q: Differentiate between phagocytosis & pinocytosis.
Phagocytosis: "Cell eating" - engulfing solid particles by extending pseudopodia. Example: White blood cells engulfing bacteria.
Pinocytosis: "Cell drinking" - engulfing liquid droplets by forming small invaginations. Used to absorb fluids and dissolved substances.
---
Q: Give chemical composition of primary & secondary cell wall.
Primary cell wall:
· Cellulose (30%)
· Hemicellulose
· Pectin
· Proteins
· Water (up to 70%)
Secondary cell wall:
· Cellulose (40-80%)
· Lignin (in woody plants)
· Hemicellulose
· Less pectin
· More rigid and thicker
---
Q: Give three functions of smooth endoplasmic reticulum.
1. Synthesis of lipids (fats, phospholipids, steroids)
2. Detoxification of drugs and harmful substances
3. Calcium ion storage (especially in muscle cells)
4. Carbohydrate metabolism
---
Q: Define storage diseases with two examples.
Storage diseases: Genetic disorders caused by enzyme deficiencies leading to accumulation of undigested macromolecules in cells.
Examples:
1. Tay-Sachs disease - accumulation of lipids in neurons
2. Pompe disease - accumulation of glycogen
---
Q: What is location of centrioles in the cell & what is their role?
Location: Found in the centrosome near the nucleus in animal cells.
Role:
· Form spindle fibers during cell division
· Help in chromosome movement
· Organize microtubules
· Form basal bodies of cilia and flagella
---
Q: Differentiate between chromoplasts & leucoplasts.
Chromoplasts: Colored plastids containing pigments (e.g., carotenoids, xanthophylls); found in flowers and fruits; responsible for yellow, orange, red colors.
Leucoplasts: Colorless plastids storing starch (amyloplasts), lipids (elaioplasts), or proteins (proteinoplasts); found in roots and tubers.
---
Q: Differentiate between cisternae & cristae.
Cisternae: Flattened membrane-bound sacs found in Golgi apparatus and rough endoplasmic reticulum; arranged in stacks.
Cristae: Infoldings of the inner mitochondrial membrane; increase surface area for ATP production.
---
Q: What are peroxisome, polysome & ribosome?
Peroxisome: Small membrane-bound organelle containing oxidative enzymes; breaks down fatty acids and detoxifies hydrogen peroxide.
Polysome: A cluster of multiple ribosomes attached to a single mRNA molecule; allows simultaneous protein synthesis.
Ribosome: Small non-membranous organelle composed of rRNA and proteins; site of protein synthesis; present in all cells.
---
UNIT #5
Q: Define species & virology with examples.
Species: A group of organisms that can interbreed naturally to produce fertile offspring.
Example: Homo sapiens (humans), Felis catus (cats)
Virology: The study of viruses, their structure, classification, and effects on living organisms.
Example: Studying HIV virus
---
Q: Give biological classification of corn.
Kingdom: Plantae
Division: Magnoliophyta (Angiosperms)
Class: Liliopsida (Monocotyledons)
Order: Poales
Family: Poaceae (Grass family)
Genus: Zea
Species: Zea mays
---
Q: What is binomial nomenclature?
Binomial nomenclature: The system of naming organisms using two Latin words - the first word is the genus name (capitalized) and the second is the species name (lowercase). Both are italicized or underlined.
Example: Homo sapiens (humans), Rosa indica (rose)
---
Q: What are two rules of nomenclature?
1. Generic name starts with capital letter; specific epithet starts with small letter
2. Both names are written in italics or underlined when handwritten
3. The name must be in Latin form
4. Each organism has only one scientific name universally
---
Q: What are prions?
Prions: Infectious protein particles lacking nucleic acids. They cause neurodegenerative diseases by converting normal proteins into abnormal forms.
Examples: Causing mad cow disease (BSE), scrapie in sheep, and Creutzfeldt-Jakob disease in humans.
---
Q: Differentiate between lytic phage & lysogenic phage.
Lytic phage: A bacteriophage that causes immediate lysis (destruction) of the host cell after multiplication.
Lysogenic phage: A bacteriophage that integrates its DNA into the host genome and remains dormant (prophage) without killing the host; may enter lytic cycle later.
---
Q: Write down symptoms & prevention of hepatitis.
Symptoms:
· Jaundice (yellowing of skin and eyes)
· Fatigue and weakness
· Dark urine and pale stools
· Nausea and vomiting
· Abdominal pain
· Loss of appetite
Prevention:
· Vaccination (for Hepatitis A and B)
· Proper hand washing
· Safe drinking water
· Avoiding sharing needles
· Safe sex practices
---
Q: Write four postulates of germ theory.
1. The same microorganism must be present in every case of the disease
2. The microorganism must be isolated from the diseased host and grown in pure culture
3. The isolated microorganism must cause the same disease in a healthy susceptible host
4. The microorganism must be re-isolated from the experimentally infected host
---
UNIT #6
Q: What are mesosomes? Describe their function.
Mesosomes: Infoldings of the plasma membrane in prokaryotic cells (bacteria).
Functions:
· Increase surface area for cellular respiration
· Involved in DNA replication and cell division
· Help in secretion of substances
· Contain enzymes for respiration
---
Q: Write misuse of antibiotics.
1. Taking antibiotics without prescription
2. Not completing the full course of antibiotics
3. Using antibiotics for viral infections (ineffective)
4. Overuse in livestock and agriculture
5. Self-medication with antibiotics
Consequences: Leads to antibiotic resistance in bacteria.
---
Q: What are trichomes?
Trichomes: Hair-like epidermal outgrowths on plant surfaces (roots, stems, leaves).
Functions:
· Reduce water loss
· Protect from herbivores
· Reflect excess sunlight
· Secretion of substances
· Help in absorption (roots)
---
Q: Give the structure & function of Heterocysts.
Structure: Specialized, thick-walled cells in cyanobacteria (blue-green algae).
Functions:
· Nitrogen fixation (converting atmospheric nitrogen to ammonia)
· Provide anaerobic environment for nitrogenase enzyme
· Transfer nitrogen to vegetative cells
---
Q: What are super blue-green algae? Give its importance.
Super blue-green algae: Genetically modified strains of cyanobacteria with enhanced nitrogen-fixing ability.
Importance:
· Increase soil fertility naturally
· Reduce need for chemical fertilizers
· Improve crop yield
· Environmentally friendly biofertilizers
---
UNIT #7
Q: What are choanoflagellates?
Choanoflagellates: Single-celled, flagellated protists with a collar of microvilli around the flagellum. They are considered the closest living relatives of animals (sponges).
---
Q: What are tritonymphs? Give their importance.
Tritonymphs: The third nymphal stage in the life cycle of mites and ticks.
Importance:
· Important developmental stage
· Some act as vectors for diseases
· Used in biological control studies
---
Q: Write two characteristics of ciliates.
1. Possess cilia (hair-like structures) for locomotion and feeding
2. Have two types of nuclei: micronucleus (genetic) and macronucleus (metabolic)
---
Q: Differentiate between micronucleus & macronucleus.
Micronucleus: Small, diploid nucleus; controls reproduction and genetic inheritance.
Macronucleus: Large, polyploid nucleus; controls metabolism and daily functions of the cell.
---
Q: Differentiate between foraminiferas & actinopods.
Foraminiferas: Marine protists with perforated calcareous shells; have pseudopodia extending through pores.
Actinopods: Marine protists with siliceous skeletons and radiating pseudopodia (axopodia).
---
Q: What are apicomplexans? Give one example.
Apicomplexans: Parasitic protists with an apical complex (specialized organelles) for penetrating host cells.
Example: Plasmodium (causes malaria)
---
Q: How algae differ from plants?
Algae:
· Lack true roots, stems, and leaves
· No vascular tissues
· Simple reproductive structures
· Most are aquatic
Plants:
· Have true roots, stems, and leaves
· Have vascular tissues
· Complex reproductive structures
· Mostly terrestrial
---
Q: What are red tides?
Red tides: Natural phenomena caused by rapid multiplication of certain dinoflagellates, turning seawater red or brown. They produce toxins harmful to marine life.
---
Q: Give structure & function of diatoms. Also write three characteristics of diatoms.
Structure: Unicellular algae with a silica cell wall (frustule) composed of two overlapping halves (valves) like a box.
Function: Major primary producers in aquatic ecosystems; produce oxygen.
Three characteristics:
1. Cell wall made of silica (glass-like)
2. Contain chlorophyll and carotenoids
3. Reproduce by binary fission
---
Q: What are kelps? Name the parts of thallus of a kelp.
Kelps: Large brown algae (macroalgae) found in cool ocean waters; form underwater forests.
Parts of thallus:
1. Holdfast: Root-like structure for attachment
2. Stipe: Stem-like structure
3. Blades: Leaf-like structures for photosynthesis
4. Pneumatocysts: Gas-filled bladders for buoyancy
---
Q: Green algae are considered ancestral organisms of green land plants, why?
1. They have chlorophyll a and b (same as plants)
2. Store starch as food reserve (same as plants)
3. Cell wall contains cellulose (same as plants)
4. Similar chloroplast structure
---
Q: What is chlorella? Give its significance.
Chlorella: A single-celled green alga.
Significance:
· Rich source of proteins and vitamins
· Used as food supplement
· Used in space research for oxygen production
· Used in wastewater treatment
· Used in biofuel production
---
Q: What is importance of algae?
1. Major oxygen producers (about 50% of Earth's oxygen)
2. Primary producers in aquatic food chains
3. Used as food (seaweed, spirulina, chlorella)
4. Source of agar and alginates (industry)
5. Used in biofuel production
6. Used as biofertilizers
7. Source of medicines and vitamins
---
UNIT #8
Q: What are lichens? Give their ecological importance.
Lichens: Symbiotic organisms consisting of a fungus and an alga (or cyanobacterium) living together.
Ecological importance:
· Pioneer species in ecological succession
· Sensitive indicators of air pollution
· Soil formation by breaking down rocks
· Food for reindeer and other animals
· Used in dye and perfume industry
---
Q: Differentiate between karyogamy & plasmogamy.
Karyogamy: Fusion of two haploid nuclei to form a diploid nucleus.
Plasmogamy: Fusion of cytoplasm of two cells without fusion of nuclei.
---
Q: Differentiate between rusts & smuts.
Rusts: Fungal pathogens causing reddish-brown pustules on plants; have complex life cycles.
Smuts: Fungal pathogens causing black masses of spores on plants; simpler life cycles.
---
Q: What is budding & parasexuality?
Budding: Asexual reproduction where a new organism develops from a small outgrowth on the parent.
Parasexuality: A process in some fungi where genetic recombination occurs without the typical sexual cycle.
---
Q: What are toad stools? Give example.
Toadstools: Poisonous or inedible mushrooms with umbrella-like caps.
Example: Amanita muscaria (fly agaric)
---
Q: What is histoplasmosis? Give its causes.
Histoplasmosis: A fungal infection affecting lungs.
Cause: Inhalation of spores of Histoplasma capsulatum found in soil contaminated with bird droppings.
---
Q: Give scientific name of yeast used in genetic research.
Saccharomyces cerevisiae (Baker's yeast)
---
Q: Define hyphae. Give their two types.
Hyphae: Thread-like filaments that make up the body (mycelium) of fungi.
Two types:
1. Septate hyphae: With cross walls (septa)
2. Coenocytic hyphae: Without cross walls (multinucleate)
---
Q: What is mycorrhiza? Give its importance.
Mycorrhiza: Symbiotic association between fungi and plant roots.
Importance:
· Helps plants absorb water and minerals (especially phosphorus)
· Protects roots from pathogens
· Improves plant growth
· Essential for many forest plants
---
Q: What are dikaryotic hyphae? Give example.
Dikaryotic hyphae: Hyphae containing two genetically different haploid nuclei in each cell.
Example: Found in basidiomycetes (mushrooms) during sexual reproduction
---
UNIT #9
Q: Why bryophytes plants are called amphibians of plant kingdom?
Bryophytes are called amphibians because:
1. They live on land but require water for reproduction
2. Their motile sperm need water for fertilization
3. They lack true vascular tissues
4. They are found in moist environments
---
Q: How spores of mosses differ from spores of liverworts?
Moss spores:
· Formed in a capsule with a peristome
· Dispersed by wind
· Germinate to form protonema
Liverwort spores:
· Formed in a capsule without a peristome
· Dispersed by elaters
· Germinate directly to form thallus
---
Q: What is alternation of generation? Give its significance.
Alternation of generation: Life cycle alternating between haploid gametophyte and diploid sporophyte generations.
Significance:
· Allows genetic recombination
· Increases genetic diversity
· Essential for plant evolution
· Provides evolutionary advantage
---
Q: Why sphenopsida are called arthropytes?
Sphenopsida (horsetails) are called arthropytes because:
· They have jointed (articulated) stems
· Stems have distinct nodes and internodes
· The stem resembles an arthropod leg with joints
---
Q: Differentiate between microphylls & megaphylls.
Microphylls: Small, simple leaves with a single vein; found in club mosses.
Megaphylls: Large, complex leaves with multiple veins; found in ferns and seed plants.
---
Q: Define double fertilization in angiosperms. Give its importance.
Double fertilization: Process where one sperm fertilizes the egg to form a zygote (2n) and the other sperm fuses with polar nuclei to form endosperm (3n).
Importance:
· Ensures food reserve for developing embryo
· Unique to angiosperms
· Provides nutrients for seed germination
· Evolutionary advantage over gymnosperms
---
Q: Differentiate between monocot stem & dicot stem.
Monocot stem:
· Scattered vascular bundles
· No secondary growth
· No distinct cortex and pith
· Epidermis with cuticle
Dicot stem:
· Vascular bundles arranged in a ring
· Secondary growth present
· Distinct cortex, pith, and medullary rays
· Epidermis with cuticle
---
UNIT #10
Q: Write the importance of sponges.
1. Provide habitat for small organisms
2. Used commercially for bath sponges
3. Important in marine food chains
4. Produce chemicals for medical research
5. Help in maintaining water quality
---
Q: Define polymorphism with example.
Polymorphism: The occurrence of different forms or stages in the life cycle of the same species.
Example: In hydra and jellyfish, exists in two forms - polyp (sessile) and medusa (free-swimming).
---
Q: Write down the importance of corals.
1. Form coral reefs (rich biodiversity habitats)
2. Protect coastlines from erosion
3. Provide shelter for marine organisms
4. Source of calcium carbonate
5. Used in jewelry and ornaments
---
Q: Differentiate between infestation & disinfestation.
Infestation: Presence of harmful pests (insects, mites) in large numbers on a host or environment.
Disinfestation: Process of removing or destroying pests from an infested area or organism.
---
Q: Write names and uses of any two useful insects.
1. Honey bee (Apis mellifera): Produces honey and wax; pollinates crops
2. Silkworm (Bombyx mori): Produces silk
---
Q: Define nymph & metamorphosis.
Nymph: Immature stage of insects that undergo incomplete metamorphosis; resembles the adult but smaller and without wings.
Metamorphosis: The process of transformation from immature form to adult form.
---
Q: Give three characteristics of chordates.
1. Presence of notochord (at some stage)
2. Dorsal hollow nerve cord
3. Pharyngeal gill slits (at some stage)
---
Q: Give the role of swim bladder in bony fishes.
1. Maintains buoyancy (helps fish float)
2. Controls depth without swimming
3. Acts as a respiratory organ in some fish
4. Helps in sound production and hearing
---
Q: Give two commercial importance of sharks.
1. Shark meat is used for food
2. Shark fins are used in soup
3. Shark liver oil is used in cosmetics and medicine
4. Skin used for leather
---
Q: Define regeneration & madreporite.
Regeneration: The ability of organisms to regrow lost body parts.
Madreporite: The sieve-like opening in starfish (echinoderms) through which water enters the water vascular system.
---
Q: Write names and harms of any two harmful molluscs.
1. Snails: Damage crops and garden plants; act as intermediate hosts for parasites
2. Shipworms (Teredo): Bore into wooden ships and structures, causing damage
---
Q: Differentiate between polyps & medusae.
Polyps: Sessile (attached) body form with a cylindrical body and tentacles at one end. Example: Hydra.
Medusae: Free-swimming, umbrella-shaped form with tentacles hanging downward. Example: Jellyfish.
---
Q: Differentiate between coelomates & acoelomates.
Coelomates: Animals with a true coelom (body cavity lined by mesoderm). Example: Earthworm, humans.
Acoelomates: Animals without a coelom; solid body. Example: Flatworms.
---
Q: Differentiate between diploblastic & triploblastic animals.
Diploblastic: Animals with two germ layers (ectoderm and endoderm). Example: Cnidarians (hydra, jellyfish).
Triploblastic: Animals with three germ layers (ectoderm, mesoderm, and endoderm). Example: All higher animals.
---
UNIT #11
Q: What is compensation point? Where it occurs?
Compensation point: The light intensity at which the rate of photosynthesis equals the rate of respiration, so net gas exchange is zero.
Occurs: In plants during early morning or late evening when light intensity is moderate.
---
Q: Write down the molecular formula for chlorophyll "a" and "b".
Chlorophyll a: C₅₅H₇₂O₅N₄Mg
Chlorophyll b: C₅₅H₇₀O₆N₄Mg
---
Q: What are necessary pigments in plants? Give their importance.
Necessary pigments:
1. Chlorophyll a (primary pigment)
2. Chlorophyll b (accessory pigment)
3. Carotenoids (accessory pigments)
Importance:
· Capture light energy for photosynthesis
· Transfer energy to reaction centers
· Protect chlorophyll from photodamage
· Give color to plants (attract pollinators)
---
Q: Differentiate between absorption & action spectrum.
Absorption spectrum: A graph showing the amount of light absorbed by pigments at different wavelengths.
Action spectrum: A graph showing the rate of photosynthesis at different wavelengths of light.
---
Q: Differentiate between photosystem I and photosystem II.
Photosystem I:
· Absorbs light at 700 nm (P700)
· Reduces NADP⁺ to NADPH
· Involved in non-cyclic and cyclic phosphorylation
Photosystem II:
· Absorbs light at 680 nm (P680)
· Splits water (photolysis) to release oxygen
· Produces ATP through electron transport
---
Q: What is Z-scheme? Why is it called so?
Z-scheme: The electron transport pathway in photosynthesis showing the flow of electrons from water to NADP⁺, with energy changes.
Why called so: The pathway is shaped like the letter "Z" when drawn, with electrons moving uphill in energy at two light-dependent steps (photosystems I and II).
---
Q: What is fermentation? Explain its types.
Fermentation: Anaerobic breakdown of organic compounds (especially glucose) to produce energy without oxygen.
Types:
1. Alcoholic fermentation: Glucose → Ethanol + CO₂ + ATP (by yeast)
2. Lactic acid fermentation: Glucose → Lactic acid + ATP (by bacteria and muscles during exercise)
---
UNIT #12
Q: Distinguish between nutrients & nutrition.
Nutrients: The chemical substances present in food that provide energy and building materials. Example: Carbohydrates, proteins, vitamins.
Nutrition: The process of obtaining and utilizing nutrients by living organisms.
---
Q: Write components & functions of saliva.
Components:
· Water (99%)
· Salivary amylase
· Mucus
· Lysozyme
· Electrolytes
Functions:
· Moistens food for easy swallowing
· Begins starch digestion (by amylase)
· Lubricates the mouth
· Antibacterial action (lysozyme)
· Dissolves food for taste perception
---
Q: Name various types of the salivary gland in man.
1. Parotid gland: Largest; located near the ears
2. Submandibular gland: Located under lower jaw
3. Sublingual gland: Located under the tongue
---
Q: Differentiate between peristalsis & anti-peristalsis.
Peristalsis: Wave-like contractions of smooth muscles that push food forward in the digestive tract.
Anti-peristalsis: Reverse wave-like contractions that move contents backward (causes vomiting).
---
Q: How hunger pangs are caused?
Hunger pangs are caused by:
1. Empty stomach contractions
2. Low blood glucose levels
3. Signals from the hypothalamus
4. Hormones like ghrelin
---
Q: What is heart burn or pyrosis?
Heart burn (pyrosis): A burning sensation in the chest caused by backflow of gastric acid into the esophagus (acid reflux).
---
Q: Name types of cells present in gastric glands.
1. Chief cells: Produce pepsinogen
2. Parietal cells: Produce HCl and intrinsic factor
3. Mucous cells: Produce mucus
4. G cells: Produce gastrin hormone
---
Q: What prevents the wall of stomach from being digested?
1. Thick mucus layer protects the epithelium
2. Bicarbonate ions neutralize acid
3. Tight junctions between cells prevent leakage
4. Rapid cell renewal
---
Q: How secretion is produced in man? What is its effects on pancreas in man?
Secretion production: Stimulated by:
· Sight, smell, or thought of food
· Presence of food in stomach (gastrin hormone)
· Distension of stomach
Effect on pancreas: Gastrin stimulates the pancreas to release pancreatic juice rich in digestive enzymes.
---
Q: What is the role of liver in the digestion of food?
1. Produces bile (emulsifies fats)
2. Stores and releases glucose as glycogen
3. Detoxifies harmful substances
4. Produces urea from amino acids
5. Synthesizes proteins (albumin, clotting factors)
6. Stores vitamins and minerals
---
UNIT #13
Q: Differentiate between organismic and cellular respiration.
Organismic respiration: The exchange of gases (oxygen and carbon dioxide) between an organism and its environment (breathing).
Cellular respiration: The biochemical process in cells that breaks down glucose to produce ATP using oxygen.
---
Q: How is air better respiratory medium than water?
1. Air contains more oxygen (21%) than water (less than 1%)
2. Oxygen diffuses faster in air
3. Air is less dense and easier to move
4. Less energy required to obtain oxygen from air
5. Air has higher oxygen concentration
---
Q: What is photorespiration? Name organelles involved in it. Write the names of its products.
Photorespiration: A wasteful process where RuBisCO fixes oxygen instead of carbon dioxide, reducing photosynthesis efficiency.
Organelles involved: Chloroplast, Peroxisome, Mitochondria
Products: Glycolate, Glycine, Serine, Carbon dioxide, Ammonia
---
Q: What is rubisco. Write its importance.
Rubisco: RuBP carboxylase/oxygenase - the most abundant enzyme on Earth.
Importance:
· Catalyzes first step of carbon fixation in photosynthesis
· Can function as carboxylase (CO₂ fixation) or oxygenase (photorespiration)
· Essential for converting CO₂ into organic compounds
---
Q: Define respiratory surface. Give three properties.
Respiratory surface: The surface where exchange of gases occurs between an organism and its environment.
Three properties:
1. Large surface area for efficient exchange
2. Thin and moist to allow diffusion
3. Well-supplied with blood vessels for transport
---
Q: Differentiate between cutaneous & pulmonary respiration in frog.
Cutaneous respiration: Gas exchange through the skin; occurs when frog is in water or during hibernation.
Pulmonary respiration: Gas exchange through lungs; occurs when frog is on land.
---
Q: What are counter current exchange and parabranchi?
Counter current exchange: Mechanism where blood flows in the opposite direction to water flow, maximizing oxygen uptake (found in fish gills).
Parabranchi: The respiratory organs in some aquatic insects; gills located along the sides of the body.
---
Q: Differentiate between diaphragm and pleura.
Diaphragm: A dome-shaped muscular sheet separating thoracic cavity from abdominal cavity; involved in breathing.
Pleura: A double-layered membrane surrounding the lungs; reduces friction during breathing.
---
Q: Name some respiratory disorder and explain one.
Respiratory disorders:
1. Asthma
2. Emphysema
3. Pneumonia
4. Bronchitis
5. Tuberculosis
Asthma: A chronic condition causing inflammation and narrowing of airways; symptoms include wheezing, coughing, and shortness of breath.
---
Q: What is emphysema? Write its symptoms.
Emphysema: A respiratory disease where alveoli walls are damaged, reducing surface area for gas exchange.
Symptoms:
· Shortness of breath
· Persistent coughing
· Wheezing
· Fatigue
· Bluish skin (cyanosis)
---
Q: What is diving reflex? What changes occur in animal during diving reflex.
Diving reflex: A physiological response in aquatic animals when submerged in water.
Changes during diving reflex:
1. Heart rate slows down (bradycardia)
2. Blood flow is redirected to vital organs
3. Peripheral blood vessels constrict
4. Oxygen is conserved
5. Breathing stops (apnea)
---
UNIT #14
Q: Differentiate between water potential & solute potential.
Water potential: The tendency of water to move from one area to another; influenced by pressure and solute concentration.
Solute potential: The component of water potential due to dissolved solutes; always negative (decreases water potential).
---
Q: Differentiate between plasmolysis & deplasmolysis.
Plasmolysis: Shrinkage of protoplast from cell wall due to water loss in hypertonic solution.
Deplasmolysis: Swelling of protoplast to original state when placed in hypotonic solution (water enters).
---
Q: Differentiate between apoplast & symplast pathway.
Apoplast pathway: Movement of water through cell walls and intercellular spaces (non-living parts).
Symplast pathway: Movement of water through cytoplasm of living cells connected by plasmodesmata.
---
Q: Differentiate between single & double circuit heart.
Single circuit heart: Blood passes through heart once per complete circulation (found in fish).
Double circuit heart: Blood passes through heart twice per complete circulation - once to lungs (pulmonary) and once to body (systemic) (found in mammals, birds).
---
IMPORTANT LONG QUESTIONS
Q: (a). How study of biology helped mankind to improve the production of food.
Biology helped improve food production through:
1. Plant breeding: Developing high-yielding, disease-resistant varieties
2. Genetic engineering: Creating GMOs with better traits
3. Fertilizer development: Understanding nutrient requirements
4. Pest control: Biological and chemical methods
5. Irrigation techniques: Understanding water requirements
6. Hydroponics: Soil-less cultivation
7. Animal breeding: Better livestock for meat and milk
8. Disease control: Vaccines and treatments for livestock
9. Food preservation: Understanding microorganisms
10. Green Revolution: Development of high-yield wheat and rice
(b). Define cloning. Discuss its types & importance.
Cloning: Production of genetically identical organisms or cells from a single ancestor.
Types:
1. Reproductive cloning: Producing a whole organism
2. Therapeutic cloning: Producing embryonic stem cells
3. Gene cloning: Producing copies of genes (DNA)
Importance:
· Medical research and drug production
· Preserving endangered species
· Producing genetically identical animals for research
· Understanding gene functions
· Organ transplantation research
Q: (a). Discuss the role of the study of biology in the protection and conservation of the environment.
Role of biology in environmental conservation:
1. Understanding ecosystems: How organisms interact
2. Biodiversity conservation: Protecting species and habitats
3. Pollution control: Developing bioremediation methods
4. Climate change: Understanding carbon cycles
5. Endangered species: Conservation breeding programs
6. Habitat restoration: Recreating natural environments
7. Sustainable practices: Agriculture, forestry, fishing
8. Waste management: Using organisms to treat waste
9. Biological indicators: Monitoring environmental health
10. Environmental education: Creating awareness
(b). Explain different types of polysaccharides.
Polysaccharides: Complex carbohydrates made of many monosaccharide units linked by glycosidic bonds.
Types:
1. Starch: Storage polysaccharide in plants
· Consists of amylose and amylopectin
· Found in potatoes, rice, wheat
2. Glycogen: Storage polysaccharide in animals
· Highly branched; stored in liver and muscles
· Also called animal starch
3. Cellulose: Structural polysaccharide in plants
· Made of β-glucose units; rigid and insoluble
· Main component of cell walls
4. Chitin: Structural polysaccharide in arthropods and fungi
· Contains nitrogen; forms exoskeleton
· Found in insects, crustaceans
5. Pectin: Found in plant cell walls
· Forms gels; used in jam-making
· Provides fruit texture
6. Peptidoglycan: Found in bacterial cell walls
· Provides structural support
Q: (a). Describe the importance of water in life.
Importance of water:
1. Universal solvent: Dissolves many substances for transport
2. Chemical reactions: Participates in hydrolysis and photosynthesis
3. Temperature regulation: High specific heat stabilizes temperature
4. Transport medium: Carries nutrients and waste
5. Lubrication: Reduces friction in joints and organs
6. Photosynthesis: Essential reactant
7. Hydrolysis: Breaks down complex molecules
8. Protection: Cushions organs and tissues
9. Habitat: Supports aquatic life
10. Turgor pressure: Maintains plant shape
(b). Describe acylglycerols in detail.
Acylglycerols (glycerides): Lipids formed by esterification of glycerol with fatty acids.
Types:
1. Monoglycerides: One fatty acid attached to glycerol
2. Diglycerides: Two fatty acids attached to glycerol
3. Triglycerides: Three fatty acids attached to glycerol (most common)
Properties:
· Hydrophobic (water-insoluble)
· Store more energy than carbohydrates
· Provide insulation
· Found in adipose tissue (animals) and seeds (plants)
Structure:
· Glycerol backbone (3-carbon alcohol)
· Fatty acid chains (long hydrocarbon chains)
· Ester bonds connect glycerol and fatty acids
Functions:
· Energy storage
· Thermal insulation
· Protection of organs
· Transport of fat-soluble vitamins
Q: (a). Describe primary & secondary structure of protein.
Primary structure:
· Linear sequence of amino acids
· Held by peptide bonds
· Determines higher-order structures
· Unique for each protein
Secondary structure:
· Folding of polypeptide into regular structures
· Held by hydrogen bonds
· Two main types:
· α-helix: Right-handed spiral
· β-pleated sheet: Zigzag arrangement
· Stabilized by hydrogen bonds
(b). Compare DNA and RNA. Explain different types of RNA.
Comparison of DNA and RNA:
Feature DNA RNA
Sugar Deoxyribose Ribose
Bases A, T, G, C A, U, G, C
Strands Double-stranded Single-stranded
Function Genetic material Protein synthesis
Location Nucleus Nucleus and cytoplasm
Types of RNA:
1. mRNA (Messenger RNA): Carries genetic information from DNA to ribosomes
2. tRNA (Transfer RNA): Transfers amino acids to ribosomes during protein synthesis
3. rRNA (Ribosomal RNA): Forms part of ribosomes
4. snRNA (Small nuclear RNA): Involved in RNA splicing
---
(c). Explain Watson and Crick model of DNA.
Watson and Crick model (1953):
1. DNA is a double helix
2. Two strands are antiparallel (run in opposite directions)
3. Strands are held by hydrogen bonds between complementary bases
4. Base pairing: A=T (2 H-bonds), G≡C (3 H-bonds)
5. Sugar-phosphate backbone on outside
6. Bases on inside like rungs of a ladder
7. Helix has a diameter of 2 nm
8. One turn has 10 base pairs (3.4 nm)
9. Distance between base pairs is 0.34 n
Q: (a). Write a note on Endoplasmic reticulum.
Endoplasmic reticulum (ER): A network of membrane-bound tubules and flattened sacs (cisternae) extending from the nuclear envelope.
Types:
1. Rough ER (RER):
· Has ribosomes on surface
· Involved in protein synthesis and modification
· Produces secretory proteins
· Forms transport vesicles
2. Smooth ER (SER):
· No ribosomes
· Synthesizes lipids and steroids
· Detoxifies drugs and toxins
· Stores calcium ions
· Involved in carbohydrate metabolism
Functions:
· Protein synthesis and modification (RER)
· Lipid synthesis (SER)
· Transport of molecules within cell
· Detoxification (SER)
· Calcium storage (SER)
(b). What are plastids? Explain the structure & function of chloroplast.
Plastids: Double-membrane organelles found in plant cells.
Types:
· Chloroplasts (green)
· Chromoplasts (colored)
· Leucoplasts (colorless)
Chloroplast structure:
· Outer membrane (permeable)
· Inner membrane (selectively permeable)
· Stroma (fluid matrix)
· Thylakoids (flattened sacs)
· Grana (stack of thylakoids)
· Lamellae (connecting thylakoids)
· DNA and ribosomes
Chloroplast functions:
· Photosynthesis (light reaction in thylakoids, dark reaction in stroma)
· Carbon fixation
· Oxygen production
· ATP and NADPH production
· Starch synthesis
Q: (a). Describe the structure and function of mitochondria.
Mitochondria structure:
· Double membrane:
· Outer membrane: Smooth, permeable
· Inner membrane: Folded into cristae, impermeable
· Cristae: Increase surface area
· Matrix: Fluid inside inner membrane, contains enzymes
· Intermembrane space: Between outer and inner membranes
· Contains DNA and ribosomes (semi-autonomous)
Functions:
· Site of cellular respiration (Krebs cycle in matrix, electron transport on cristae)
· ATP production (aerobic respiration)
· Fatty acid oxidation
· Calcium ion storage
· Apoptosis regulation
· Heat production
---
(b). Differentiate between prokaryotic & eukaryotic cells.
Prokaryotic cells:
· No true nucleus (nucleoid)
· No membrane-bound organelles
· Smaller (1-10 μm)
· 70S ribosomes
· Binary fission reproduction
· Cell wall present (peptidoglycan)
· Single circular DNA
· Example: Bacteria, Archaea
Eukaryotic cells:
· True nucleus with nuclear membrane
· Membrane-bound organelles
· Larger (10-100 μm)
· 80S ribosomes
· Mitosis/meiosis reproduction
· Cell wall (plants, fungi) or no cell wall (animals)
· Linear DNA with histones
· Example: Plants, animals, fungi, protists
Q: (a). Describe life cycle of a bacteriophage.
Lytic cycle:
1. Attachment: Phage attaches to bacterial cell wall
2. Penetration: DNA injected into bacterium
3. Biosynthesis: Host machinery produces phage components
4. Maturation: Assembly of new phages
5. Lysis: Cell bursts, releasing new phages
Lysogenic cycle:
1. Phage DNA integrates into bacterial genome (prophage)
2. Replicates with bacterial DNA
3. Can remain dormant
4. May enter lytic cycle under stress conditions
---
(b). How HIV is transmitted? Give a sketch of the infection cycle of HIV.
HIV Transmission:
· Unprotected sexual contact
· Contaminated needles (drug use)
· Blood transfusion
· Mother to child (during birth or breast-feeding)
· Contact with infected body fluids
HIV Infection Cycle:
1. Attachment: HIV binds to CD4 receptors on T-cells
2. Entry: Virus enters cell
3. Reverse transcription: RNA → DNA
4. Integration: Viral DNA integrates into host genome
5. Transcription: Viral genes expressed
6. Translation: New viral proteins made
7. Assembly: New viruses assembled
8. Budding: New viruses released
Q: (a). Define hepatitis. Describe its symptoms, causes & types.
Hepatitis: Inflammation of the liver.
Symptoms:
· Jaundice (yellow skin/eyes)
· Fatigue
· Dark urine
· Nausea and vomiting
· Abdominal pain
· Loss of appetite
· Fever
Causes:
· Viral infection (Hepatitis A-E)
· Alcohol abuse
· Drug toxicity
· Autoimmune disorders
· Metabolic disorders
Types:
1. Hepatitis A: Fecal-oral transmission; preventable by vaccine
2. Hepatitis B: Blood and body fluids; vaccine available
3. Hepatitis C: Blood-borne; no vaccine yet
4. Hepatitis D: Requires Hepatitis B; rare
5. Hepatitis E: Fecal-oral; common in developing countries
(b). Describe different classes of bacteria on the basis of flagella.
Classes based on flagella arrangement:
1. Atrichous: No flagella
2. Monotrichous: Single flagellum at one end
3. Lophotrichous: Multiple flagella at one end
4. Amphitrichous: Flagella at both ends (one or multiple)
5. Peritrichous: Flagella all over the surface
Q: (a). Discuss the process of nutrition in bacteria.
Nutrition in bacteria can be:
1. Autotrophic:
· Photoautotrophs: Use light energy (e.g., cyanobacteria)
· Chemoautotrophs: Use chemical energy (e.g., nitrifying bacteria)
2. Heterotrophic:
· Saprophytes: Feed on dead organic matter
· Parasites: Feed on living hosts
· Symbionts: Mutual benefit with host
Process:
· Absorption: Nutrients enter through cell wall
· Extracellular digestion: Enzymes secreted outside
· Transport: Active transport and diffusion
(b). Describe different physical & chemical methods to control bacteria.
Physical methods:
1. Heat: Autoclaving (steam under pressure)
2. Radiation: UV rays, gamma rays
3. Filtration: Removing bacteria from liquids
4. Dessication: Drying
5. Osmotic pressure: Salt/sugar solutions
6. Cold storage: Low temperatures
Chemical methods:
1. Antibiotics: Inhibit bacterial growth
2. Disinfectants: Kill bacteria on surfaces
3. Antiseptics: Safe for living tissues
4. Phenols: Protein denaturants
5. Halogens: Iodine, chlorine
6. Alcohols: Denature proteins
7. Heavy metals: Mercury, silver
8. Detergents: Disrupt cell membranes
Q: (a). Give adaptations of fungi on land.
Fungal adaptations to land:
1. Mycelium network: Extensive branching for nutrient absorption
2. Spore production: Asexual and sexual spores for dispersal
3. Septate hyphae: Cell walls with septa for support
4. Thick-walled spores: Survival in harsh conditions
5. Symbiotic relationships: Mycorrhizae with plants
6. Enzymes: Secrete enzymes for digestion
7. Chitinous cell walls: Provide structural support
8. Resistance to desiccation: Survive dry conditions
(b). Describe land adaptations of bryophytes.
Bryophytes adaptations to land:
1. Cuticle: Waxy layer prevents water loss
2. Rhizoids: Root-like structures for attachment
3. Stomata: Gas exchange (in some)
4. Reproductive structures: Protected in gametangia
5. Water requirement: Still need water for reproduction
6. Desiccation tolerance: Can survive drying
7. Storage organs: Store food and water
8. Spores: Dispersal by wind
Q: (a). What is alternation of generation? Give its significance.
Alternation of generation: A life cycle alternating between haploid gametophyte (n) and diploid sporophyte (2n) generations.
Significance:
· Provides genetic diversity
· Allows adaptation to different environments
· Essential for plant evolution
· Increases survival chances
· Facilitates sexual reproduction
· Gene flow and variation
(b). How the evolution of leaf took place?
Evolution of leaf:
1. Origin from stems: Leaves evolved as flattened branches
2. Microphylls: Simple leaves (club mosses) - evolved from outgrowths
3. Megaphylls: Complex leaves (ferns and seed plants) - evolved from branch systems
4. Enation theory: Leaves from small outgrowths
5. Telome theory: Leaves from flattened branch systems
6. Vascularization: Development of veins for transport
Q: (a). Enlist steps involved in the evolution of seed.
Steps in seed evolution:
1. Heterospory: Two types of spores (microspores and megaspores)
2. Retention of megaspore: Megaspore retained in sporangium
3. Reduction of gametophyte: Smaller, dependent female gametophyte
4. Development of integuments: Protective layer around ovule
5. Pollen production: Male gametophyte transported by wind or insects
6. Embryo development: Within protected ovule
7. Seed formation: Ovule becomes seed with embryo and food reserve
(b). Describe in detail cyclic & non-cyclic phosphorylation.
Non-cyclic phosphorylation:
· Involves both photosystem I and II
· Electrons flow from water to NADP⁺
· Produces ATP and NADPH
· Water splits (photolysis), releasing oxygen
· Electron flow is linear
Cyclic phosphorylation:
· Involves only photosystem I
· Electrons return to photosystem I (cycle)
· Produces only ATP
· No NADPH production
· No water splitting
· Electron flow is circular
Q: (a). Draw and describe Calvin cycle in photosynthesis.
Calvin cycle (C₃ cycle):
Three phases:
1. Carbon fixation:
· CO₂ + RuBP (5C) → 2 PGA (3C)
· Catalyzed by RuBisCO
2. Reduction:
· PGA → PGAL using ATP and NADPH
· PGAL is the product
3. Regeneration:
· Some PGAL used to regenerate RuBP
· Requires ATP
Summary: 6 CO₂ + 18 ATP + 12 NADPH → 1 glucose + 18 ADP + 12 NADP⁺
Location: Stroma of chloroplast
(b). What is glycolysis? Sketch its various steps.
Glycolysis: Breakdown of glucose (6C) into two pyruvate (3C) molecules.
Steps:
1. Energy investment phase (Steps 1-5):
· Glucose → Glucose-6-P
· Glucose-6-P → Fructose-6-P
· Fructose-6-P → Fructose-1,6-bisphosphate
· Fructose-1,6-bisphosphate → DHAP + G3P
· DHAP → G3P
2. Energy payoff phase (Steps 6-10):
· G3P → 1,3-bisphosphoglycerate
· 1,3-bisphosphoglycerate → 3-PGA
· 3-PGA → 2-PGA
· 2-PGA → PEP
· PEP → Pyruvate
Net yield: 2 ATP (produced), 2 NADH, 2 pyruvate
Location: Cytoplasm
Q: (a). Draw the sketch and explain Krebs cycle.
Krebs cycle (Citric acid cycle):
1. Citrate formation: Acetyl-CoA + Oxaloacetate → Citrate
2. Isocitrate formation: Citrate → Isocitrate
3. Oxidative decarboxylation: Isocitrate → α-ketoglutarate + CO₂ + NADH
4. Decarboxylation: α-ketoglutarate → Succinyl-CoA + CO₂ + NADH
5. GTP formation: Succinyl-CoA → Succinate + GTP
6. FADH₂ formation: Succinate → Fumarate + FADH₂
7. Hydration: Fumarate → Malate
8. Regeneration: Malate → Oxaloacetate + NADH
Products per cycle:
· 3 NADH
· 1 FADH₂
· 1 GTP (ATP)
· 2 CO₂
Location: Mitochondrial matrix
(b). Give digestion in the cockroach.
Cockroach digestion:
1. Mouth: Chewing
2. Crop: Food storage
3. Gizzard: Grinding food with chitinous teeth
4. Midgut: Digestion and absorption
· Gastric caeca secrete enzymes
· Amylase for starch
· Protease for proteins
· Lipase for fats
5. Malpighian tubules: Excretion
6. Hindgut: Water absorption and waste elimination
(c). Explain the process of digestion in hydra.
Hydra digestion:
1. Extracellular digestion: Tentacles capture prey, enzymes secreted into gastrovascular cavity
2. Intracellular digestion: Food particles engulfed by endodermal cells
3. Absorption: Nutrients diffuse into cells
4. Waste elimination: Undigested material expelled through mouth
Q: (a). Describe digestion in oral cavity of man.
Digestion in oral cavity:
1. Mechanical digestion:
· Teeth chew food (mastication)
· Tongue mixes and moves food
· Food becomes bolus
2. Chemical digestion:
· Saliva secreted by salivary glands
· Salivary amylase breaks starch → maltose
· Lingual lipase begins fat digestion
3. Taste perception: Tongue detects tastes
4. Swallowing: Food passes to esophagus
(b). Describe absorption of digested food in small intestine.
Absorption in small intestine:
1. Location: Mainly in jejunum and ileum
2. Adaptations:
· Villi (increase surface area)
· Microvilli (brush border)
· Rich blood supply
3. Absorption of different nutrients:
· Monosaccharides: Active transport into blood
· Amino acids: Active transport into blood
· Fatty acids and glycerol: Form micelles; absorbed into lacteals (lymph)
· Vitamins and minerals: Various mechanisms
4. Transport:
· To blood: capillaries → hepatic portal vein → liver
· To lymph: lacteals → lymphatic system
Q: (a). Write a note on (i) Anorexia nervosa (ii) Bulimia nervosa (iii) Obesity.
(i) Anorexia nervosa:
· Eating disorder characterized by:
· Intense fear of gaining weight
· Severe restriction of food intake
· Distorted body image
· Extremely low body weight
· Excessive exercise
(ii) Bulimia nervosa:
· Eating disorder characterized by:
· Binge eating followed by purging
· Vomiting, laxative use, or excessive exercise
· Fear of gaining weight
· Normal body weight usually
· Dental erosion, electrolyte imbalance
(iii) Obesity:
· Condition of excessive body fat
· BMI ≥ 30
· Causes: Overeating, genetic factors, lack of exercise
· Health risks: Diabetes, heart disease, hypertension
(b). Why transpiration is necessary evil?
Transpiration as necessary evil:
Necessary because:
· Creates transpiration pull for water movement
· Cools the plant
· Maintains turgor pressure
· Absorbs minerals
· Opens stomata for CO₂ uptake
Evil because:
· Causes water loss
· Can lead to wilting
· Stresses plant in hot conditions
· Reduces growth during drought
Q: (a). Explain various functions of human blood.
Functions of blood:
1. Transport:
· Oxygen (RBCs)
· Carbon dioxide (plasma and RBCs)
· Nutrients (glucose, amino acids, fats)
· Waste products (urea, uric acid)
· Hormones
2. Protection:
· White blood cells (immunity)
· Antibodies
· Clotting (platelets)
3. Regulation:
· Body temperature
· pH balance
· Water balance
· Blood pressure
4. Storage:
· Nutrients
· Hormones
· Ions
---
(b). Describe lymphatic system. Explain its functions and components.
Lymphatic system:
Components:
1. Lymph: Fluid containing white blood cells
2. Lymphatic vessels: Capillaries and larger vessels
3. Lymph nodes: Filter lymph
4. Spleen: Filters blood; stores lymphocytes
5. Thymus: T-cell development
6. Tonsils: Immune defense in throat
7. Bone marrow: Produces lymphocytes
Functions:
· Returns interstitial fluid to blood
· Transports fats from digestive system
· Immune defense (filters pathogens)
· Produces lymphocytes
· Removes waste products
(c). Define immunity. Give its types.
Immunity: The ability of the body to resist and fight against pathogens and foreign substances.
Types:
1. Innate (Non-specific) immunity:
· Present at birth
· Physical barriers (skin, mucous membranes)
· Chemical barriers (enzymes, stomach acid)
· Phagocytes
· Inflammatory response
2. Acquired (Specific) immunity:
· Active immunity:
· Natural: After infection
· Artificial: Vaccination
· Passive immunity:
· Natural: Maternal antibodies (through placenta/milk)
· Artificial: Antibody injection
· Humoral immunity: B-cells produce antibodies
· Cell-mediated immunity: T-cells destroy infected cells
