Cell, Tissues and Classification of Living Things
Cell, Tissues and Classification of Living Things
The cell is the basic unit of life, tissues are groups of similar cells doing one job, and classification sorts living things into groups. NTPC asks the function of each cell organelle, plant and animal tissues (xylem and phloem above all), and the scientists and kingdoms of classification.
1. The Cell
| Organelle | Function |
|---|---|
| Cell membrane | Selectively permeable boundary |
| Cell wall | Cellulose wall in plant cells; gives shape and strength |
| Nucleus | Contains DNA; controls the cell |
| Mitochondria | Powerhouse; aerobic respiration makes ATP |
| Chloroplast | Photosynthesis; only in plant cells |
| Ribosome | Protein synthesis |
| Endoplasmic reticulum | Transport channels; rough ER has ribosomes |
| Golgi apparatus | Packaging and secretion |
| Lysosome | Digestive enzymes; called suicide bags |
| Vacuole | Storage; large in plant cells |
| Centrosome | Helps cell division in animal cells |
| Fact | Detail |
|---|---|
| Discovery of cells | Robert Hooke (1665), in cork |
| Living cells first seen | Anton van Leeuwenhoek |
| Nucleus discovered | Robert Brown (1831) |
| Cell theory | Schleiden and Schwann |
| Prokaryotes | No true nucleus: bacteria |
| Mitosis | Growth and repair; two identical cells |
| Meiosis | Forms gametes; chromosome number halves |
2. Tissues
| Tissue | Job |
|---|---|
| Meristematic | Dividing tissue at root and shoot tips |
| Xylem | Carries water and minerals upward from roots |
| Phloem | Carries food (sugars) made in leaves to other parts |
| Epithelial | Covers and lines organs; skin, lining of mouth |
| Connective | Binds and supports: bone, cartilage, blood, tendons (muscle to bone), ligaments (bone to bone) |
| Muscular | Striated (voluntary), smooth (involuntary), cardiac (heart) |
| Nervous | Neurons carry messages |
3. Classification
| Item | Fact |
|---|---|
| Binomial nomenclature | Carolus Linnaeus; genus then species, such as Homo sapiens |
| Five-kingdom system | R.H. Whittaker (1969): Monera, Protista, Fungi, Plantae, Animalia |
| Hierarchy | Kingdom, phylum, class, order, family, genus, species |
| Fungi | Heterotrophs with chitin cell walls; yeast, mushroom |
| Viruses | Not placed in the five kingdoms; living only inside a host cell |
✗ Xylem carries food and phloem carries water | ✓ Xylem carries water and minerals; phloem carries food
✗ Ligaments join muscle to bone | ✓ Tendons join muscle to bone; ligaments join bone to bone
हिंदी नोट: माइटोकॉन्ड्रिया कोशिका का ऊर्जा घर और लाइसोसोम आत्मघाती थैली है। जाइलम जल और खनिज ऊपर ले जाता है, फ़्लोएम पत्तियों में बना भोजन पौधे के अन्य भागों तक पहुँचाता है। पाँच जगत वर्गीकरण आर.एच. व्हिटेकर ने और द्विनाम पद्धति लिनियस ने दी।
Exam Pointer: Verified NTPC pattern: the function of phloem (March 2021 CBT-1). Organelle and classification questions are tagged syllabus-based.
Pariksha Pattern: Every Way NTPC Asks This Topic
Pattern 1: Plant and animal tissues
[PYQ: NTPC CBT-1 27-Mar-2021 Shift-2]
EXAM LEVEL
Q. Which plant tissue carries water from roots to leaves?
Xylem.
Answer: Xylem
EXAMATLAS LEVEL
Q. Match the tissue with its job: phloem, tendon, cardiac muscle, meristem.
Phloem carries food made in the leaves. A tendon joins muscle to bone. Cardiac muscle makes the heart beat without tiring. Meristem divides to make the plant grow at its tips.
Answer: Food transport; muscle to bone; heartbeat; growth
Pattern 2: Cell organelles and their functions
[Pattern: syllabus-based, PYQ-style]
EXAM LEVEL
Q. Which organelle is called the powerhouse of the cell?
The mitochondrion, where aerobic respiration releases energy as ATP.
Answer: Mitochondria
EXAMATLAS LEVEL
Q. Which organelle makes proteins, which is called the suicide bag, and which two structures are found in plant cells but not animal cells?
Ribosomes make proteins. Lysosomes are suicide bags because their enzymes can digest the cell itself. Plant cells have a cell wall and chloroplasts, which animal cells lack.
Answer: Ribosome; lysosome; cell wall and chloroplast
Pattern 3: Classification and nomenclature
[Pattern: syllabus-based, PYQ-style]
EXAM LEVEL
Q. Who proposed the five-kingdom classification?
R.H. Whittaker, in 1969.
Answer: R.H. Whittaker
EXAMATLAS LEVEL
Q. In Homo sapiens, which word is the genus? Name the five kingdoms and the kingdom of bacteria.
Homo is the genus and sapiens the species. The kingdoms are Monera, Protista, Fungi, Plantae and Animalia; bacteria belong to Monera.
Answer: Homo; Monera
Pattern 4: Discoveries and cell division
[Pattern: syllabus-based, PYQ-style]
EXAM LEVEL
Q. Who first discovered cells, and in what material?
Robert Hooke, in a thin slice of cork, in 1665.
Answer: Robert Hooke, cork
EXAMATLAS LEVEL
Q. A cell with 46 chromosomes divides by meiosis. How many chromosomes will each gamete have, and which type of division repairs a wound?
Meiosis halves the number, so each gamete has 23. Wounds are repaired by mitosis, which makes identical cells.
Answer: 23; mitosis
60-Second Revision
- Mitochondria powerhouse; ribosome protein; lysosome suicide bag; chloroplast photosynthesis.
- Xylem water up; phloem food; tendon muscle-bone; ligament bone-bone.
- Hooke cells 1665; Brown nucleus; Schleiden-Schwann cell theory.
- Whittaker five kingdoms; Linnaeus binomial names.