Biology

Characteristics of Living Organisms

  • MRS C GREN: Movement, Respiration, Sensitivity, Control, Growth, Reproduction, Excretion, Nutrition.

    • Movement: Organisms can move voluntarily or involuntarily and show internal movements such as blood circulation.

    • Respiration: The process of converting glucose into energy, involving the intake of oxygen and release of carbon dioxide.

    • Sensitivity: Organisms respond to changes in their environment through various stimuli.

    • Control: Homeostasis is the maintenance of stable internal conditions despite external changes.

    • Growth: A permanent increase in size or mass as a result of cell division.

    • Reproduction: The biological process through which new individual organisms are produced, which is vital for the continuation of a species.

    • Excretion: The process of removing waste products of metabolism from the body, critical for maintaining internal balance.

    • Nutrition: The intake of necessary substances for energy, growth, and cellular repair.

The Variety of Living Organisms

  • Kingdoms:

    • Plants: Multicellular, contain chloroplasts for photosynthesis, have cellulose-based cell walls.

    • Animals: Multicellular, lack cell walls, characterized by nervous coordination and ability to move.

    • Fungi: Have chitin in cell walls, absorb nutrients via saprotrophic nutrition; can be unicellular or multicellular.

    • Bacteria: Single-celled prokaryotes, some are pathogenic while others are beneficial.

    • Protoctists: Mostly unicellular, can exhibit characteristics of both plants and animals.

    • Viruses: Non-living, parasitic entities that require a host cell for replication.

Biological Molecules

  • Carbohydrates: Provide energy; examples include starch and glycogen, composed of simple sugars.

  • Proteins: Made of amino acids; serve multiple functions, including as enzymes, antibodies, and hormones.

  • Lipids: Composed of glycerol and fatty acids; store energy and provide insulation.

  • Testing for Molecules:

    • Starch: Iodine test (blue-black indicates presence).

    • Glucose: Benedict’s test (brick red indicates presence).

    • Proteins: Biuret test (purple indicates presence).

    • Lipids: Ethanol emulsion test (cloudy white indicates presence).

Enzymes

  • Definition: Biological catalysts that speed up chemical reactions without being consumed in the process.

  • Lock and Key Model: The specificity of enzymes to substrates based on the shape of the active site.

  • Factors Affecting Enzyme Activity:

    • Temperature: Enzymes have an optimal temperature for activity, and extreme heat can denature them.

    • pH: Each enzyme has an optimal pH and values outside this range can reduce activity or denature the enzyme.

Movement of Substances

  • Diffusion: Movement of particles from an area of higher concentration to an area of lower concentration.

  • Osmosis: The diffusion of water across a semi-permeable membrane; crucial for maintaining cellular turgor.

  • Active Transport: The movement of substances against their concentration gradient, requiring energy (ATP).

Nutrition

  • Plants:

    • Photosynthesis Equation: Carbon dioxide (CO2) + water (H2O) → glucose (C6H12O6) + oxygen (O2).

    • Limiting Factors: Light intensity, carbon dioxide concentration, and temperature affect the rate of photosynthesis.

    • Essential Minerals: Nitrate for protein synthesis, magnesium for chlorophyll production.

  • Humans:

    • Balanced Diet: Composed of carbohydrates, proteins, fats, vitamins, minerals, water, and fiber.

    • Digestive System: Mouth → esophagus → stomach → small intestine → large intestine (with nutrient absorption in the small intestine).

Respiration

  • Aerobic Respiration: Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP).

  • Anaerobic Respiration:

    • In humans: Glucose → Lactic Acid + Energy (less efficient).

    • In yeast: Glucose → Ethanol + Carbon Dioxide + Energy (used in fermentation).

Gas Exchange

  • Plants: Gas exchange occurs through stomata; guard cells control their opening and closing.

  • Humans: Alveoli enable efficient exchange of oxygen and carbon dioxide, facilitated by a large surface area and thin walls.

Transport Systems

  • Plants:

    • Xylem: Transports water and minerals from roots.

    • Phloem: Transports sugars produced during photosynthesis.

  • Humans:

    • Circulatory System: Heart pumps blood through arteries, veins, and capillaries.

    • Blood Components:

      • Red blood cells: Carry oxygen.

      • White blood cells: Immune defense.

      • Platelets: Blood clotting.

      • Plasma: Liquid medium for transport of nutrients, hormones, and waste.

Excretion

  • Plants: Excrete oxygen (byproduct of photosynthesis) and carbon dioxide (byproduct of respiration).

  • Humans: Excrete waste through lungs (CO2), kidneys (urea), and skin (sweat).

Homeostasis

  • Definition: Maintenance of a stable internal environment for optimal functioning (e.g., temperature, pH).

  • Mechanisms:

    • Temperature control via sweating or shivering.

    • Blood glucose level regulation through insulin release.

Coordination and Response

  • Nervous System: Comprises brain, spinal cord, and nerves, responsible for reflexes and coordinated responses.

  • Reflex Arc: Pathway of a reflex action: Stimulus → Receptor → Sensory Neuron → Relay Neuron → Motor Neuron → Effector.

  • Hormones: Chemical messengers that regulate bodily functions (e.g., adrenaline, insulin).

Reproduction

  • Plants:

    • Pollination: Transfer of pollen from anther to stigma.

    • Fertilization: Fusion of pollen with ovule.

  • Humans:

    • Male: Produces sperm in testes.

    • Female: Ovaries release eggs; fertilization occurs in the uterus.

  • Menstrual Cycle: Typically lasts 28 days with ovulation around day 14.

  • Asexual Reproduction: Offspring produced from one parent and are genetically identical.

Inheritance

  • DNA Structure: Double helix made of nucleotides (A-T, C-G pairing).

  • Genes: Sequences of DNA that determine traits.

  • Alleles: Different variants of a gene (dominant or recessive).

  • Punnett Squares: Useful for predicting genetic trait inheritance.

Ecology

  • Levels of Organization: Individual → Population → Community → Ecosystem.

  • Food Chains: Energy flow from producers to consumers.

  • Carbon Cycle: Includes processes like photosynthesis, respiration, and decomposition.

  • Human Impact: Effects of deforestation, pollution, and climate change on ecosystems.

Genetic Modification & Biotechnology

  • Selective Breeding: Choosing parents with desired traits for future generations.

  • Genetic Engineering: Involves altering an organism's DNA (e.g., insulin production in bacteria).

  • Biotechnology: Use of organisms for technical applications (e.g., yeast in baking and fermentation).

  • Cloning: Producing genetically identical organisms.

Practical Works

  • Key Experiments:

    • Investigating osmosis using potato strips.

    • Studying enzyme activity with variations in temperature/pH.

    • Observing photosynthesis by measuring oxygen production in aquatic plants (e.g., pondweed).