The cell, the basic unit of life, was first discovered by Robert Hooke in 1665 while observing a cork slice under a microscope he designed. The term “cell” comes from the Latin word meaning “a little room.” A typical cell consists of three main parts:
- Cell (Plasma) Membrane – the selectively permeable outer boundary, made of lipids and proteins.
- Cytoplasm – the internal fluid containing organelles.
- Nucleus – the control center of the cell
Cell Biology Historical Contributions
- Robert Hooke (1665) discovered cells (dead) in cork.
- Leeuwenhoek (1674) discovered free-living cells in pond water.
- Robert Brown (1831) discovered the nucleus.
- Purkinje (1839) coined the term protoplasm.
- Schleiden & Schwann (1838–39) proposed the cell theory.
- Virchow (1855): Cells arise from pre-existing cells.
Type of organisms: Unicellular (e.g. amoeba, bacteria), Multicellular (e.g. plants, humans)
Diffusion and Osmosis
Diffusion is the passive movement of substances (like O₂ and CO₂) from a region of high concentration to low concentration. Osmosis is a type of diffusion where water molecules move across a selectively permeable membrane. Cells behave differently depending on the solution they are placed in:
- Hypotonic solution: Water enters the cell; it swells.
- Isotonic solution: No net water movement; cell remains the same.
- Hypertonic solution: Water exits the cell; it shrinks.
Plasma Membrane and Endocytosis
The plasma membrane is made of lipids and proteins, is flexible, and selectively allows substances in and out. The flexibility enables processes like endocytosis, where cells ingest external materials. Amoeba uses this method to capture food.
Cell Wall and Plasmolysis:
Plant cells have a rigid cell wall made of cellulose, which supports the plant and prevents bursting when water enters cells in hypotonic solutions. The phenomenon of plasmolysis, the shrinkage of the cell membrane from the wall when water is lost
The nucleus is a key organelle present in most eukaryotic cells. It is surrounded by a double-layered nuclear membrane that has pores to facilitate the exchange of substances with the cytoplasm. Inside the nucleus are chromosomes, which carry DNA, the genetic material of the cell. DNA is organized into genes, which govern hereditary traits and cellular functions.
Cells are broadly categorized into prokaryotes (without nuclear membrane or membrane-bound organelles, e.g., bacteria) and eukaryotes (with well-defined nucleus and organelles, e.g., plants, animals). The cytoplasm is a jelly-like substance that houses the organelles in eukaryotic cells. In prokaryotes, cytoplasmic functions occur without organelle membranes.
Viruses, though capable of replication, are not considered true living cells as they lack membranes and can only replicate inside a host cell.
Prokaryotic vs. Eukaryotic Cells
| Feature | Prokaryotic Cell | Eukaryotic Cell |
|---|---|---|
| 1. Size | Generally small (1–10 µm) | Generally large (5–100 µm) |
| 2. Nuclear region | Poorly defined, lacks nuclear membrane (nucleoid) | Well-defined, surrounded by nuclear membrane |
| 3. Chromosomes | Single circular chromosome | More than one linear chromosome |
| 4. Membrane-bound organelles | Absent | Present (ER, Golgi apparatus, mitochondria, etc.) |
| 5. Cell Type | Usually unicellular (e.g., bacteria) | Usually multicellular (e.g., plant, animal cells) |
Endoplasmic Reticulum (ER) is a network of membrane-bound tubules and sacs.
- Functions: Transport (Serves as channels for transport of materials like proteins and lipids.), Membrane Biogenesis: Proteins and lipids help in building the cell membrane. Framework: Acts as a structural framework in the cytoplasm. Production of Enzymes & Hormones: Some lipids/proteins act as hormones or enzymes.
Two types of Endoplasmic Reticulum (ER)
- Rough ER (RER): Has ribosomes attached, involved in protein synthesis.
- Smooth ER (SER): No ribosomes, involved in lipid synthesis.
Golgi apparatus (Post office of the cell), discovered by Camillo Golgi, is made of membrane-bound flattened sacs called cisterns. It is connected to the endoplasmic reticulum and is involved in modifying, packaging, and transporting substances like proteins and lipids. It also helps form lysosomes.
Lysosomes are membrane-bound vesicles filled with digestive enzymes made by RER. They break down worn-out organelles, foreign substances, and cellular waste. Lysosomes act as the clean-up system of the cell and are capable of self-destruction during cell damage (hence called suicide bags).
Mitochondria – Known as the powerhouse of the cell, they release energy in the form of ATP (Adenosine Triphosphate). They have a double membrane, with the inner membrane folded to increase surface area. They also have their own DNA and ribosomes, so they can make some of their own proteins.
Plastids – Found only in plant cells. Two types:
- Chloroplasts (green) – Contain chlorophyll, conduct photosynthesis, also have DNA & ribosomes.
- Leucoplasts (colorless) – Store starch, proteins, and oils. Like mitochondria, plastids have their own DNA.
Vacuoles – Store liquid or solid materials. In plant cells, they are large and help maintain turgidity. In animal cells, vacuoles are small. In Amoeba, food vacuoles store ingested food. Some vacuoles help in waste removal and water balance.
| Feature | Plant Cell | Animal Cell |
|---|---|---|
| Cell wall | Present (made of cellulose) | Absent |
| Plastids | Present (e.g., chloroplasts) | Absent |
| Vacuole | One large central vacuole | Small or absent |
| Shape | Generally rectangular or rigid | Generally round or irregular |
| Centrosome/Centrioles | Absent (except in lower plants) | Present |
| Energy storage | Stores starch | Stores glycogen |
| Mode of nutrition | Autotrophic (photosynthesis in chloroplasts) | Heterotrophic |
Cell Division – Important for growth, repair, and reproduction. Two types:
- Mitosis – For growth & repair (identical cells).
- Meiosis – For formation of gametes (half chromosome number).
| Feature | Mitosis | Meiosis |
|---|---|---|
| Cell division rounds | 1 | 2 (Meiosis I and II) |
| Number of cells formed | 2 | 4 |
| Chromosome number | Same as mother cell (2n → 2n) | Half of mother cell (2n → n) |
| Type of cells formed | Body (somatic) cells | Sex cells (gametes) |
| Genetic identity | Identical to parent | Genetically different from parent |
Tissues are groups of similar cells specialized to perform specific functions efficiently in multicellular organisms. In unicellular organisms, one cell does all tasks, while in multicellular ones, division of labour is seen—different cells perform different roles.
Plant vs Animal Tissues:
- Plants: Stationary, require support → more dead supportive tissue; growth limited to regions (meristematic tissue).
- Animals: Move around, need more energy → mostly living tissues; uniform growth; complex organs and organ systems.
Meristematic tissues are responsible for plant growth and are located only at specific regions such as root tips, shoot tips, and nodes. These are classified into:
- Apical Meristem: Found at root and shoot tips – increases length.
- Lateral Meristem (Cambium): Found on sides – increases girth.
- Intercalary Meristem: Found near nodes – helps in elongation
Meristematic Tissue
- Highly active cells with dense cytoplasm, thin cell walls, prominent nuclei.
- Lack vacuoles → because they are not involved in storage, only division & growth.
Permanent Tissue
-
Formed by differentiation of meristematic cells → take specific shape, size, function & lose ability to divide.
Simple Permanent Tissues
Parenchyma – Living, unspecialised cells Thin walls, large intercellular spaces, Function: storage Types:
-
- Chlorenchyma (with chlorophyll) – does photosynthesis
- Aerenchyma (in aquatic plants) – air cavities help in floating
Collenchyma – Living, elongated cells, Thickened corners, very little intercellular space, Function: Flexibility + mechanical support, Found below epidermis (e.g. leaf stalks)
Sclerenchyma is a simple permanent tissue consisting of dead, long, narrow cells with thick lignified walls and no intercellular spaces. These cells provide mechanical strength and are found in stems, seed coverings, and around vascular bundles.
Epidermis, which forms the outer protective covering of the plant. It consists of a single layer of flat cells with thicker outer walls. The epidermis prevents water loss, protects against mechanical injury and fungal infection. In dry regions, it may be thicker. The epidermis also contains stomata—tiny pores guarded by two kidney-shaped guard cells—that allow gas exchange and transpiration.
Photosynthesis requires carbon dioxide, while transpiration helps in cooling, water movement, and mineral transport in plants.
In roots, epidermal cells have hair-like extensions to increase water absorption. In desert plants, the thick waxy cutin layer on the epidermis prevents water loss. As plants age, the outer epidermis is replaced by cork, made by secondary meristem. Cork cells are dead, compact, and contain suberin, which makes them waterproof and gasproof.
Complex permanent tissues like xylem and phloem contain different types of cells working together for transportation. Xylem carries water and minerals with the help of tracheids and vessels, while xylem parenchyma stores food, and xylem fibres offer support. Phloem transports food via sieve tubes, supported by companion cells. Phloem parenchyma stores food, and phloem fibres are the only dead component.
Animal tissues are classified as:
- Epithelial (covering/protection) Forms lining of body surfaces (e.g., skin, lungs, kidneys, blood vessels)
Types: Tissu – Squamous, Columnar, Cuboidal, Glandular - Connective (support & transport) (e.g., Blood, Bone, Ligament, Tendon, Cartilage, Areolar, Adipose)
- Muscular (movement)
Types: Striated – Skeletal, Voluntary, Smooth- Involuntary, Visceral, Cardiac – Heart muscles - Nervous (impulse conduction)
Connective tissue connects and supports various parts of the body. Its cells are loosely packed and suspended in a matrix which varies in composition based on function. For example, blood
Nervous Tissue Transmits messages (nerve impulses) rapidly across the body Main, Unit: Neuron
Neuron Parts: Dendrite – receives signal, Cell Body – contains nucleus, Axon – sends signal away
Heredity refers to the transmission of traits from one generation to the next. Reproduction produces similar but slightly different individuals. Asexual reproduction leads to minimal variation (due to DNA copy errors).
Sexual reproduction introduces greater genetic variation. Inheritance includes both: Basic body structure (from parents) Minor changes (new traits) Variations accumulate over generations and cause diversity. Not all variations survive equally; natural selection favors beneficial traits. Example: Sugarcane shows little variation (asexually reproduced); humans show high variation (sexually reproduced).
Diversity in sexually reproducing species results from combining traits of two parents and new mutations.
Variations help organisms adapt to the environment. Example: Heat-resistant bacteria survive heat waves better. Natural selection of beneficial traits drives evolution.
Heredity
- Reproduction creates individuals with similar design and inherited traits.
- Traits: Characteristics passed from parents to offspring.
- Variation: Differences among individuals (even among siblings).
A child inherits basic human features but does not look exactly like parents. Human traits (e.g., earlobes) show variation: Free earlobes vs Attached earlobes These are inherited through parental genes.
Rules of Inheritance – Mendel’s Work
- Gregor Mendel (Father of Genetics) discovered rules of inheritance through pea plant experiments.
- Key Finding: Both mother and father contribute equally to the child’s genes. Each child has two versions (alleles) of every trait – one from each parent. These versions determine dominant or recessive traits.
Mendel studied science and math but failed his teaching exam; continued research in monastery. Used pea plants to study inheritance with a scientific and mathematical approach. Focused on contrasting traits: Round vs wrinkled seeds Tall vs short plants White vs violet flowers Crossed tall plants (TT) with short plants (tt): F1 generation: All tall (no medium height) – only one trait expressed. F2 generation: When F1 self-pollinated, offspring were 3 tall:1 short. Conclusion: Traits controlled by pairs of factors (genes) — two copies in sexually reproducing organisms. One copy could be dominant (T for tall), the other recessive (t for short). Tall (T) is dominant; short (t) is recessive. Mendel’s Laws of Inheritance based on these observations.
Dihybrid Cross and Independent Inheritance
When pea plants differing in two traits (e.g., tall/short and round/wrinkled seeds) are crossed: F1 generation: All progeny show dominant traits (tall and round seeds). F2 generation: Shows a variety of combinations: Tall with round seeds Short with wrinkled seeds Tall with wrinkled seeds (new combination) Short with round seeds (new combination) This shows traits are inherited independently (Mendel’s Law of Independent Assortment).
How Traits are Expressed
Traits depend on proteins produced by genes (DNA sections coding for proteins). Example: Plant height depends on hormones, which depend on enzymes coded by genes. Efficient enzyme → more hormone → tall plant. Less efficient enzyme → less hormone → short plant. Each parent contributes one copy of each gene to offspring. Offspring have two sets of genes (one from each parent). Germ cells (gametes) have only one set of genes (haploid) due to reduction division (meiosis). This separation allows independent assortment of genes, explaining Mendel’s F2 results.
Chromosomes and Sex Determination
Genes are located on chromosomes, which exist in pairs—one from each parent. Germ cells carry one chromosome from each pair, maintaining chromosome number after fertilization. Sex determination varies: environmental in some animals, genetic in humans. Humans have 22 pairs of autosomes and 1 pair of sex chromosomes (XX in females, XY in males). All offspring inherit an X chromosome from the mother. The sex of the child depends on the chromosome inherited from the father: X from father → Female (XX) Y from father → Male (XY) This explains the roughly 1:1 sex ratio in humans.
Recape
- All living organisms are made up of cells, the basic unit of life.
- Cell membrane (plasma membrane) controls what enters and leaves the cell; made of lipids and proteins.
- Cell wall gives rigidity and protection, especially in plant, fungal, and bacterial cells.
- Plant cells have a cell wall (mainly cellulose) outside the membrane — gives shape and protection.
- Nucleus controls cell activities and contains DNA in chromosomes.
- Endoplasmic Reticulum (ER) helps in transport and synthesis (RER = protein, SER = lipids).
- Golgi apparatus: modifies, stores, and packages materials for secretion.
- Plastids (in plants): Chloroplasts (chromoplasts): photosynthesis Leucoplasts: store starch, oils, proteins
- Lysosomes: Contain digestive enzymes; called “suicide bags”.
- Mitochondria: Powerhouse of the cell; produce ATP.
- Vacuoles: store substances; large in plant cells, small in animal cells.
- Mitosis: For growth and repair. Meiosis: For reproduction, forms gametes with half chromosomes.
Q. Who discovered the cell and in which year? (A) Anton van Leeuwenhoek, 1674 (B) Robert Hooke, 1665 (C) Schleiden, 1838 (D) Schwann, 1839
Q. Who discovered free-living cells in pond water? (A) Robert Hooke (B) Robert Brown (C) Leeuwenhoek (D) Virchow
Q. Who discovered the nucleus in the cell? (A) Hooke (B) Virchow (C) Robert Brown (D) Schleiden
Q. Who proposed that all cells come from pre-existing cells? (A) Schleiden (B) Schwann (C) Virchow (D) Leeuwenhoek
Q. Which of these is not a basic cell organelle? (A) Nucleus (B) Plasma membrane (C) Ribosome (D) Heart
Q. Which process is responsible for gaseous exchange in cells? (A) Respiration (B) Osmosis (C) Diffusion (D) Filtration
Q. Which of the following is a selectively permeable membrane? (A) Nucleus (B) Cytoplasm (C) Plasma Membrane (D) Cell Wall
Q. Which type of solution causes a cell to gain water? (A) Isotonic (B) Hypertonic (C) Hypotonic (D) Neutral
Q. Plasma membrane is made of ? (A) DNA and RNA (B) Lipids and proteins (C) Carbohydrates (D) Water and salts
Q. Which process explains water movement through a semi-permeable membrane? (A) Endocytosis (B) Osmosis (C) Diffusion (D) Filtration
Q. What is the main component of the plant cell wall? (A) Protein (B) Cellulose (C) Lipids (D) DNA
Q. What is plasmolysis? (A) Cell wall bursting (B) Cell shrinking (C) Cell swelling (D) Cell division
Q. What is the nucleus surrounded by? (A) Plasma membrane (B) Cell wall (C) Nuclear membrane (D) Chromatin
Q. What are functional segments of DNA called? (A) Nucleus (B) Chromosomes (C) Genes (D) Ribosomes
Q. What is the fluid content inside the plasma membrane called? (A) Nucleus (B) Cytoplasm (C) Vacuole (D) Cell wall
Q. Which organelle is responsible for protein synthesis? (A) Lysosome (B) Mitochondria (C) Ribosome on RER (D) Golgi
Q. Which of the following is absent in prokaryotic cells? (A) Plasma membrane (B) Ribosomes (C) Membrane-bound organelles (D) Cytoplasm
Q. What is the function of endoplasmic reticulum? (A) Photosynthesis (B) Digestion (C) Transport of materials (D) Cell movement
Q. Which ER is responsible for lipid synthesis? (A) Rough ER (B) Smooth ER (C) Golgi body (D) Ribosomes
Q. Which organelle is involved in membrane biogenesis? (A) Mitochondria(B) Endoplasmic reticulum (C) Nucleus (D) Lysosomes
Q. What is the function of ribosomes on rough ER? (A) Lipid synthesis (B) Cell wall formation (C) Protein synthesis (D) Waste disposal
Q. Golgi apparatus was discovered by? (A) Robert Hooke (B) Camillo Golgi (C) Rudolf Virchow (D) Anton van Leeuwenhoek
Q. Which cell organelle is called the “suicide bag” of the cell? (A) Nucleus (B) Mitochondria (C) Lysosome (D) Golgi apparatus
Q. Lysosomal enzymes are produced by? (A) SER (B) RER (C) Golgi body (D) Mitochondria
Q. Which of these helps in detoxifying drugs in the liver? (A) Smooth ER (B) Golgi body (C) Lysosome (D) Ribosome
Q. What is the primary function of the Golgi apparatus? (A) Photosynthesis (B) Detoxification (C) Modification and packaging of proteins (D) Protein synthesis
Q. Which of the following organelles is called the ‘Powerhouse of the cell’? (A) Lysosome (B) Mitochondria (C) Ribosome (D) Nucleus
Q. Plastids are found in which type of cells? (A) Animal cells (B) Fungal cells (C) Plant cells (D) Bacterial cells
Q. Which organelle helps in storing food, wastes and water in plant cells? (A) Mitochondria (B) Lysosome (C) Vacuole (D) Golgi body
Q. Which two organelles have their own DNA? (A) Ribosome and Nucleus (B) Lysosome and Vacuole (C) Mitochondria and Plastids (D) Golgi and ER
Q. What is stored in leucoplasts? (A) Chlorophyll (B) Starch and fats (C) Enzymes (D) Oxygen
Q. Which process results in the formation of gametes? (A) Mitosis (B) Meiosis (C) Diffusion (D) Photosynthesis
Q. What is the result of one mitotic cell division? A) Four daughter cells B) Two daughter cells C) One daughter cell D) Eight daughter cells
Q. In meiosis, the number of daughter cells formed is: A) 2 B) 4 C) 6 D) 1
Q. Which cell division maintains the same chromosome number? A) Meiosis B) Mitosis C) Binary fission D) Fusion
Q. Meiosis occurs in: A) Skin cells B) Liver cells C) Reproductive cells D) Muscle cells
Q. Which organelle stores starch in plant cells? (A) Chloroplast (B) Leucoplast (C) Golgi body (D) Ribosome
Q. Which of the following tissues in plants is responsible for growth? (A) Permanent Tissue (B) Structural Tissue (C) Meristematic Tissue (D) Parenchyma
Q. Which of the following is an example of a tissue? (A) Heart (B) Blood (C) Brain (D) Liver
Q. Which tissues in plants divide throughout life? (A) Permanent tissue (B) Meristematic tissue (C) Muscle tissue (D) Phloem
Q. What is the function of apical meristem? (A) Increase in girth (B) Healing of wounds (C) Increase in length (D) Photosynthesis
Q. Which type of meristem increases the thickness of the stem? (A) Apical meristem (B) Lateral meristem (C) Intercalary meristem (D) Epidermis
Q. Intercalary meristem is found at which location? (A) Root tip (B) Leaf tip (C) Node (D) Stem base
Q. What is the function of meristematic tissue in plants? (A) Photosynthesis (B) Support (C) Growth by cell division (D) Transport of food
Q. What is the function of parenchyma tissue? (A) Conduction (B) Flexibility (C) Storage (D) Protection
Q. Which permanent tissue provides flexibility to plant parts? (A) Parenchyma (B) Collenchyma (C) Sclerenchyma (D) Xylem
Q. Which type of parenchyma helps aquatic plants to float? (A) Chlorenchyma (B) Collenchyma (C) Aerenchyma (D) Sclerenchyma
Q. The process by which meristematic cells become permanent tissue is called: (A) Photosynthesis (B) Transpiration (C) Differentiation (D) Germination
Q. Parenchyma with air spaces in aquatic plants is called: (A) Chlorenchyma (B) Aerenchyma (C) Collenchyma (D) Sclerenchyma
Q. What type of cells are present in sclerenchyma tissue? (A) Living and thin-walled (B) Dead and thick-walled (C) Living and loosely packed (D) Photosynthetic cells
Q. What is the function of epidermis in plants? (A) Water conduction (B) Providing strength (C) Protection and water retention (D) Photosynthesis
Q. What is the role of lignin in sclerenchyma? (A) Increases flexibility (B) Provides strength and thickening (C) Helps in photosynthesis (D) Aids in water transport
Q. What is the role of cutin in desert plants? (A) Helps in food storage (B) Increases flexibility (C) Prevents water loss (D) Absorbs sunlight
Q. What makes cork cells impermeable to water and gases? (A) Lignin (B) Suberin (C) Cellulose (D) Cutin
Q. Which of the following phloem cells is dead? (A) Companion cell (B) Phloem fibre (C) Sieve tube (D) Phloem parenchyma
Q. Which tissue transports minerals in plants? (A) Phloem (B) Collenchyma (C) Parenchyma (D) Xylem
Q. Which cells in phloem are dead at maturity? (A) Sieve tubes (B) Companion cells (C) Phloem parenchyma (D) Phloem fibres
Q. Which tissue covers body surfaces and internal cavities in animals? (A) Connective (B) Muscular (C) Epithelial (D) Nervous
Q. Name the types of simple permanent tissues. (A) Parenchyma, Collenchyma, Sclerenchyma (B) Xylem, Phloem, Epidermis (C) Cork, Phloem, Parenchyma (D) Collenchyma, Guard cells, Xylem
Q. Where is apical meristem found? (A) In the veins of leaves (B) At tips of roots and shoots (C) In the bark (D) Inside phloem
Q. Which tissue forms the husk of coconut? (A) Parenchyma (B) Collenchyma (C) Sclerenchyma (D) Phloem
Q. Which of the following is a component of phloem? (A) Xylem parenchyma (B) Guard cells (C) Sieve tube (D) Tracheid
Q. Which type of tissue lines the inner walls of organs and vessels? (A) Connective tissue (B) Muscular tissue (C) Epithelial tissue (D) Nervous tissue
Q. What is the function of simple squamous epithelium? (A) Secretion (B) Filtration and diffusion (C) Contraction (D) Sensation
Q. Which epithelial tissue type secretes substances and forms glands? (A) Squamous (B) Glandular (C) Ciliated (D) Cuboidal
Q. Which tissue type has loosely packed cells in an intercellular matrix? (A) Muscular (B) Connective (C) Nervous (D) Epithelial
Q. What is the function of cuboidal epithelium in kidney tubules? (A) Gas exchange (B) Mechanical support (C) Absorption (D) Protection
Q. The main function of ciliated columnar epithelium is ? (A) Protection (B) Absorption (C) Secretion (D) Mucus movement
Q. Which epithelial tissue is found in the alveoli of lungs and blood vessels? (A) Stratified squamous (B) Simple squamous (C) Cuboidal (D) Columnar
Q. Which epithelial tissue has cilia? (A) Cuboidal (B) Simple squamous (C) Ciliated columnar (D) Stratified squamous
Q. Where is stratified squamous epithelium found? (A) Alveoli (B) Skin and mouth (C) Intestine (D) Kidney
Q. Which connective tissue connects bones to bones? (A) Tendon (B) Ligament (C) Cartilage (D) Areolar
Q. The matrix of bone is made up of: (A) Protein and sugar (B) Fat and collagen (C) Calcium and phosphorus (D) Water and salt
Q. Which connective tissue helps in repair and fills space between organs? (A) Cartilage (B) Blood (C) Areolar tissue (D) Adipose tissue
Q. Adipose tissue is mainly responsible for: (A) Transport (B) Insulation and fat storage (C) Protection of joints (D) Oxygen exchange
Q. What is the function of adipose tissue? (A) Blood production (B) Fat storage and insulation (C) Muscle contraction (D) Bone repair
Q. Which connective tissue is present in ear and nose? (A) Bone (B) Cartilage (C) Ligament (D) Areolar tissue
Q. Which tissue connects muscles to bones? (A) Ligament (B) Cartilage (C) Tendon (D) Blood
Q. Which muscle type is involuntary and found in internal organs like the alimentary canal? (A) Skeletal (B) Smooth (C) Cardiac (D) Voluntary
Q. Which muscle is striated, branched, and works throughout life involuntarily? (A) Smooth (B) Skeletal (C) Cardiac (D) Voluntary
Q. Nervous tissue is made up of which main type of cell? (A) Nephron (B) Neuron (C) Myocyte (D) Chromatin
Q. Which muscle contains multinucleated cells? (A) Cardiac (B) Smooth (C) Skeletal (D) Involuntary
Q. What is the function of axon in a neuron? (A) Receiving signals (B) Sending signals (C) Storing signals (D) None of the above
Q. Which part of a neuron receives signals? (A) Axon (B) Nucleus (C) Dendrite (D) Synapse
Q. What causes variation in asexual reproduction? (A) Environmental factors (B) DNA copying errors (C) Sexual fusion (D) Mutation from parents
Q. Which type of reproduction increases the chance of variation the most? (A) Asexual reproduction (B) Cloning (C) Sexual reproduction (D) Budding
Q. Which organism is used as an example for asexual reproduction? (A) Human (B) Sugarcane (C) Bacterium (D) Cow
Q. Who formulated the basic rules of inheritance? (A) Darwin (B) Mendel (C) Newton (D) Watson
Q. Earlobe type (free or attached) is an example of: (A) Acquired trait (B) Environmental trait (C) Inherited trait (D) Artificial trait
Q. What was the observed ratio in Mendel’s F2 generation? (A) 1:1 (B) 3:1 (C) 2:2 (D) 4:0
Q. Which term refers to a trait that is masked in the F1 generation? (A) Dominant (B) Recessive (C) Hybrid
Q. What do we call the pair of factors controlling traits, as per Mendel? (A) Chromosomes (B) Genes (C) Cells (D) Organs
Q. How many copies of each chromosome do body cells have? (A) One copy (B) Two copies (C) Three copies (D) Four copies
Q. What are the sex chromosomes of a female? (A) XY (B) YY (C) XX (D) YX
Q. Which of the following is true about male sex chromosomes? (A) Both are X chromosomes (B) One X and one Y chromosome (C) Both are Y chromosomes (D) No sex chromosomes
Q. How many pairs of chromosomes do humans have excluding sex chromosomes? (A) 21 (B) 22 (C) 23 (D) 2
Q. Which chromosomes determine human sex? (A) Autosomes (B) X and Y chromosomes (C) Mitochondrial DNA (D) Chromosome 21