Class 10 Biology (NCERT)

Cheatsheet Content

### Life Processes - **Definition:** Basic functions performed by living organisms to maintain their life on Earth. - **Key Processes:** - **Nutrition:** Intake of food and its utilization. - **Autotrophic:** Organisms make their own food (e.g., plants, cyanobacteria). Photosynthesis: $6CO_2 + 6H_2O \xrightarrow{\text{Sunlight, Chlorophyll}} C_6H_{12}O_6 + 6O_2$. - **Heterotrophic:** Organisms depend on others for food (e.g., animals, fungi). - **Holozoic:** Ingestion, digestion, absorption, assimilation, egestion (e.g., Amoeba, humans). - **Saprophytic:** Feed on dead and decaying matter (e.g., fungi, bacteria). - **Parasitic:** Obtain nourishment from a host (e.g., Cuscuta, tapeworm). - **Respiration:** Process of releasing energy from food. - **Aerobic:** Requires oxygen. $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}$. Occurs in cytoplasm (glycolysis) and mitochondria (Krebs cycle, electron transport chain). - **Anaerobic:** Without oxygen. - **Yeast:** Glucose $\rightarrow$ Ethanol + $CO_2$ + Energy. - **Muscle cells (during strenuous activity):** Glucose $\rightarrow$ Lactic acid + Energy. - **Transportation:** Movement of substances from one part of the body to another. - **Plants:** - **Xylem:** Transports water and minerals from roots to leaves. Unidirectional. - **Phloem:** Transports food (sugars) from leaves to other parts. Bidirectional. - **Humans:** - **Blood:** Connective tissue responsible for transport. - **Plasma:** Fluid matrix. - **RBCs (Erythrocytes):** Oxygen transport (Hemoglobin). - **WBCs (Leukocytes):** Immunity. - **Platelets:** Blood clotting. - **Heart:** Pumping organ. Double circulation (Pulmonary and Systemic). - **Blood Vessels:** Arteries (away from heart), Veins (towards heart), Capillaries (exchange). - **Lymphatic System:** Lymph (tissue fluid), Lymph vessels, Lymph nodes. Role in immunity and fat absorption. - **Excretion:** Removal of metabolic waste products from the body. - **Plants:** Oxygen (photosynthesis), excess water (transpiration), other wastes stored in vacuoles or shed leaves. - **Humans:** - **Kidneys:** Filter blood to produce urine. Nephron is the functional unit. - **Ureters:** Carry urine from kidneys to bladder. - **Urinary Bladder:** Stores urine. - **Urethra:** Carries urine out of the body. - **Other excretory organs:** Lungs ($CO_2$), Skin (sweat), Liver (bile pigments). ### Control and Coordination - **Definition:** The ability of living organisms to respond to stimuli and coordinate body activities. - **Animals:** - **Nervous System:** - **Neurons:** Structural and functional unit. Transmit nerve impulses. - **Dendrite:** Receives information. - **Cell body (Cyton):** Contains nucleus. - **Axon:** Transmits impulse away from cell body. - **Synapse:** Gap between two neurons. - **Reflex Action:** Quick, involuntary response to a stimulus (e.g., touching a hot object). - **Reflex Arc:** Pathway of nerve impulse in a reflex action (Receptor $\rightarrow$ Sensory neuron $\rightarrow$ Spinal cord $\rightarrow$ Motor neuron $\rightarrow$ Effector). - **Brain:** Main coordinating center. - **Forebrain:** Cerebrum (thought, memory, voluntary actions), Hypothalamus (hunger, thirst, sleep). - **Midbrain:** Relays sensory information. - **Hindbrain:** Cerebellum (balance, posture), Medulla (involuntary actions: heart rate, breathing), Pons (respiration). - **Spinal Cord:** Connects brain to nerves, controls reflex actions. - **Endocrine System (Hormonal Control):** Glands secrete hormones directly into blood. - **Pituitary:** Master gland (growth hormone, TSH, etc.). - **Thyroid:** Thyroxine (metabolism). - **Pancreas:** Insulin, Glucagon (blood sugar regulation). - **Adrenal:** Adrenaline (fight or flight). - **Testes:** Testosterone (male secondary sexual characteristics). - **Ovaries:** Estrogen, Progesterone (female secondary sexual characteristics, menstrual cycle). - **Plants:** - **Phytohormones (Plant Hormones):** - **Auxins:** Cell elongation, root growth, phototropism, geotropism. - **Gibberellins:** Stem elongation, seed germination. - **Cytokinins:** Cell division, breaking dormancy. - **Abscisic Acid (ABA):** Growth inhibitor, stomatal closure, dormancy. - **Ethylene:** Fruit ripening. - **Tropic Movements:** Directional growth responses to stimuli. - **Phototropism:** Towards light (shoot). - **Geotropism:** Towards gravity (root). - **Hydrotropism:** Towards water (root). - **Chemotropism:** Towards chemicals (pollen tube growth towards ovule). - **Thigmotropism:** Towards touch (tendrils). - **Nastic Movements:** Non-directional responses (e.g., touch-me-not plant leaves folding). ### How Do Organisms Reproduce? - **Definition:** Process by which living organisms produce new individuals of their own kind. - **Asexual Reproduction:** Single parent, no gamete formation, offspring genetically identical to parent. - **Fission:** - **Binary:** Parent divides into two (e.g., Amoeba, Paramecium). - **Multiple:** Parent divides into many (e.g., Plasmodium). - **Budding:** Outgrowth forms a new individual (e.g., Hydra, Yeast). - **Spore Formation:** Spores develop into new individuals (e.g., Rhizopus - bread mould). - **Fragmentation:** Body breaks into pieces, each piece grows into a new individual (e.g., Spirogyra). - **Regeneration:** Ability of an organism to regrow lost body parts (e.g., Planaria, Hydra). Not true reproduction. - **Vegetative Propagation (Plants):** New plants from vegetative parts (root, stem, leaf). - **Natural:** Roots (sweet potato), Stem (potato, ginger), Leaves (Bryophyllum). - **Artificial:** Cutting, Layering, GraftingTissue culture. - **Sexual Reproduction:** Involves two parents (usually), fusion of male and female gametes, offspring genetically different. - **In Flowering Plants:** - **Flower:** Reproductive organ. - **Sepals:** Green, protective. - **Petals:** Colorful, attract pollinators. - **Stamen (Male):** Anther (produces pollen - male gamete), Filament. - **Pistil/Carpel (Female):** Stigma (receives pollen), Style, Ovary (contains ovules - female gamete). - **Pollination:** Transfer of pollen grains from anther to stigma. - **Self-pollination:** Within same flower or same plant. - **Cross-pollination:** Between different plants. - **Fertilization:** Fusion of male gamete (from pollen) with female gamete (in ovule). Forms zygote. - **Post-fertilization:** Ovary develops into fruit, ovules into seeds. - **In Humans:** - **Male Reproductive System:** Testes (sperm production, testosterone), Scrotum, Vas deferens, Urethra, Penis, Accessory glands (seminal vesicles, prostate gland). - **Female Reproductive System:** Ovaries (egg production, estrogen, progesterone), Oviducts/Fallopian tubes (fertilization site), Uterus (implantation, fetal development), Vagina. - **Menstrual Cycle:** Monthly cycle in females involving egg maturation and shedding of uterine lining if no fertilization. - **Fertilization:** Fusion of sperm and egg in fallopian tube. - **Implantation:** Zygote develops into embryo and implants in uterine wall. - **Gestation:** Period of development of embryo/fetus in uterus (approx. 9 months). - **Placenta:** Connects fetus to uterine wall for nutrient and waste exchange. - **Reproductive Health:** Importance of contraception methods (barrier, oral pills, IUDs, surgical methods) and preventing STIs. ### Heredity and Evolution - **Heredity:** Transmission of traits from parents to offspring. - **Genetics:** Study of heredity and variation. - **Chromosomes:** Thread-like structures in nucleus, carry genetic information (DNA). - **Genes:** Segments of DNA, functional unit of heredity. - **Alleles:** Different forms of a gene (e.g., T for tall, t for dwarf). - **Dominant Trait:** Expressed even in presence of recessive allele. - **Recessive Trait:** Expressed only in absence of dominant allele. - **Genotype:** Genetic makeup (e.g., TT, Tt, tt). - **Phenotype:** Observable characteristic (e.g., Tall, Dwarf). - **Mendel's Laws:** - **Law of Dominance:** In a cross of parents with contrasting traits, only one form of the trait will appear in the first filial (F1) generation. - **Law of Segregation:** Alleles for each gene segregate during gamete formation. - **Law of Independent Assortment:** Alleles of different genes assort independently of one another during gamete formation. - **Sex Determination:** In humans, determined by sex chromosomes (XX for female, XY for male). - **Variation:** Differences among individuals of a species. - **Sources:** Mutation, recombination during sexual reproduction. - **Importance:** Basis of evolution, allows adaptation to changing environment. - **Evolution:** Gradual change in living organisms over successive generations. - **Evidence for Evolution:** - **Homologous Organs:** Similar structure, different function (e.g., forelimbs of human, whale, bat). Indicates common ancestry. - **Analogous Organs:** Different structure, similar function (e.g., wings of bird and insect). Indicates convergent evolution. - **Fossils:** Preserved remains of ancient life. Provide direct evidence of past organisms. - **Embryology:** Similar embryonic development patterns. - **Molecular Biology:** Similarities in DNA and protein sequences. - **Mechanism of Evolution (Natural Selection by Darwin):** - **Overproduction:** Organisms produce more offspring than can survive. - **Variation:** Individuals in a population show variations. - **Struggle for Existence:** Competition for resources. - **Survival of the Fittest:** Individuals with favorable variations survive and reproduce. - **Inheritance of Favorable Traits:** Favorable traits are passed to offspring. - **Speciation:** Formation of new species from existing ones due to isolation and natural selection. - **Human Evolution:** Tracing human ancestry through fossil records and genetic studies. ### Our Environment - **Ecosystem:** A community of living organisms (biotic components) interacting with their non-living environment (abiotic components). - **Biotic Components:** - **Producers:** Autotrophs (plants) that make food. - **Consumers:** Heterotrophs that feed on others. - **Primary (Herbivores):** Eat producers. - **Secondary (Carnivores/Omnivores):** Eat primary consumers. - **Tertiary:** Eat secondary consumers. - **Decomposers:** Fungi, bacteria that break down dead organic matter. - **Abiotic Components:** Non-living factors like sunlight, temperature, water, soil, air. - **Food Chain:** Sequence of organisms through which energy is transferred (e.g., Grass $\rightarrow$ Deer $\rightarrow$ Tiger). - **Food Web:** Interconnected food chains. - **Energy Flow:** Unidirectional, 10% law (only 10% of energy is transferred to next trophic level). - **Environmental Problems:** - **Ozone Layer Depletion:** Ozone ($O_3$) protects Earth from harmful UV radiation. Depleted by CFCs (Chlorofluorocarbons). Causes skin cancer, cataracts. - **Waste Management:** - **Biodegradable:** Decomposed by microbes (e.g., vegetable peels). - **Non-biodegradable:** Cannot be decomposed (e.g., plastics, glass). - **Methods:** Segregation, Recycling, Composting, Landfills, Incineration.