Biology Combined Science Notes

BIOLOGY - COMBINED SCIENCE NOTES

CELLS AND LEVELS OF ORGANIZATION

  • Specialized Cells: Different types of cells perform specific functions. Collaboration among cells supports life processes.
      - Each cell relies on others, functioning collectively.
      - Specialized cells develop distinct shapes related to their functions.

Examples of Specialized Cells:

  1. Red Blood Cell (Erythrocyte):
       - Function: Transports oxygen from lungs to body tissues and carbon dioxide from tissues to lungs.
       - Lacks nucleus to increase surface area for oxygen absorption.
       - Biconcave shape provides flexibility to navigate through capillaries.
       - Contains hemoglobin (red pigment) for oxygen transport needed during cellular respiration.

  2. Muscle Cell:
       - Responsible for contraction in response to nerve stimulation for movement.
       - Long and thin structure enables shape changes during contraction.
       - Contains numerous mitochondria for energy production during muscle contraction.

  3. Palisade Cell:
       - Function: Photosynthesis food production.
       - Rich in chloroplasts that contain chlorophyll for light absorption.
       - Columnar shape and close packing optimize surface area for sunlight and CO₂ absorption.

  4. Root Hair Cell:
       - Absorbs water and salts from soil.
       - Thin cell walls facilitate easy movement of water and nutrients.
       - Numerous in number to enhance absorption surface area.
       - Hair-like projections penetrate soil particle spaces, maximizing absorption.
       - Large vacuole aids in water absorption and storage.

ECOSYSTEMS

  • An Ecosystem: A self-contained system comprising interdependent organisms and their physical environment.
      - Ecosystem Components:
        - Physical (Abiotic) Components: Non-living factors e.g., humidity, temperature, air, soil, water, light.
        - Biological (Biotic) Components: Living organisms e.g., fungi, plants, animals, bacteria.

Natural Ecosystem:

  • Influences on organisms’ survival by the environment's role.

  • Interactions between plants and animals maintain natural balance.

  • Adaptation determines survival and reproduction of species.

  • Nutrients recycled through decomposes.

  • No control measures for pests and diseases in natural ecosystems.

Food Chain:

  • Nutritional sequence showing energy transfer through organisms.

  • Begins with producers (green plants).

  • Example: extgrass<br>ightarrowextinsects<br>ightarrowextdragonfly<br>ightarrowextfrog<br>ightarrowextsnake<br>ightarrowexteagleext{grass} <br>ightarrow ext{insects} <br>ightarrow ext{dragonfly} <br>ightarrow ext{frog} <br>ightarrow ext{snake} <br>ightarrow ext{eagle}.

Food Web:

  • Interconnected feeding relationships among plants and animals.

  • Organisms may feed on multiple sources and provide food for various predators.

Pyramid of Biomass:

  • Biomass: Amount of living material present.

  • In a balanced ecosystem, the biomass hierarchy is:
      - Producers > Herbivores > Carnivores.

  • Energy availability decreases up the trophic pyramid.

Energy Loss in Food Chains and Food Webs:

  1. The sun is the primary energy source for ecosystems.

  2. Producers capture 100% energy via photosynthesis.

  3. Energy loss occurs due to metabolic processes, averaging about 90% at each trophic level, with only 10% passed on.

  4. Decomposers play a crucial role in recycling nutrients.

NUTRIENT CYCLES
Carbon Cycle:

  1. Carbon dioxide is essential in all organic compounds.

  2. Photosynthetic plants absorb CO₂, converting it into organic compounds.

  3. Animals ingest organic materials, obtaining carbon.

  4. Respiration and decay processes return CO₂ to the atmosphere.

  5. Human activities (e.g., burning fossil fuels) release CO₂, exacerbating the cycle.

Nitrogen Cycle:

  1. Nitrogen is vital in proteins for both plants and animals.

  2. Decay by fungi and bacteria produces nitrates utilized by plants.

  3. Soil organisms convert dead wastes to ammonium compounds.

  4. Nitrifying bacteria (e.g., Nitrosomonas, Nitrobacter) convert ammonium to nitrites and then to nitrates.

  5. Approximately 79% of the atmosphere consists of nitrogen; limited conversion through lightning and nitrogen-fixing bacteria (e.g., Rhizobium).

  6. Denitrification occurs under anaerobic conditions, releasing nitrogen gas back into the atmosphere.

ARTIFICIAL ECOSYSTEMS

  • Heavily influenced by humans (e.g., monoculture, agricultural practices).

  • High control measures on pests.

  • Nutrient augmentation via fertilizers.

  • Grazing strategies employed to mitigate overgrazing issues.

BIODIVERSITY

  • Refers to variability within and among species across different ecosystems.

  • Benefits of Biodiversity:
      - Broad food sources.
      - Ecosystem self-sustenance.
      - Interdependence among species.
      - Reduced disease incidence.
      - Provides shelter, medicinal resources, and ecological stability.

  • Problems from Limited Biodiversity:
      - Pest issues and disease outbreaks.
      - Ecosystem instability.
      - Soil infertility.
      - Pollution and resource overutilization.

NUTRITION
Plant Nutrition - PHOTOSYNTHESIS

  1. Leaf Structure:
       - Waxy cuticle prevents water loss; protects the leaf.
       - Veins transport materials in and out.
       - Stipulates leaf attachment to stem via petioles for optimal light exposure.
       - Thin, flat shape enhances sunlight absorption.

  2. Internal Leaf Structure:
       - Cuticle: Waxy layer preventing water loss.
       - Epidermis: Transparent protective layer allowing light penetration.
       - Palisade Cells: Main site for photosynthesis; rich in chloroplasts.
       - Spongy Mesophyll: Less dense, containing chloroplasts and air spaces for gas exchange.
       - Vascular Bundle: Comprises xylem (water transport) and phloem (sugar transport).
       - Stomata & Guard Cells: Regulate gas exchange.

  3. Adaptations for Photosynthesis:
       - Broad, flat shape for sunlight and CO₂ absorption.
       - Thin structure for efficient diffusion of gases.
       - High density of chloroplasts in palisade cells.
       - Air spaces maximize CO₂ diffusion.
       - Optimal stomata density for gas exchange.
       - Vascular networks ensure hydration and nutrient supply.

Factors Affecting Photosynthesis Rate

  1. Light Intensity:
       - Higher intensity enhances photosynthetic rates.
       - Experiment: Vary light distances to measure oxygen bubble production.

  2. Carbon Dioxide Concentration:
       - Increased CO₂ levels boost bubbling rates.
       - Experiment: Record oxygen bubble production with varying sodium hydrogen carbonate concentrations.

  3. Water Availability:
       - Necessary for photosynthesis; lack thereof closes stomata.

  4. Chlorophyll Presence:
       - Essential for capturing light energy.

  5. Temperature:
       - Directly correlates with photosynthesis rate; moderate increases enhance enzymatic activities involved in carbohydrate production.

HUMAN NUTRITION

  • A Balanced Diet consists of all essential nutrients in required proportions:

  1. Carbohydrates:
       - Provide energy and dietary fiber.
       - Found in potatoes, rice, bread, and sweets.

  2. Lipids (Fats & Oils):
       - Supply energy, absorb vitamins, and form cell membranes.
       - Found in animal fats and plant oils.

  3. Proteins:
       - Facilitate growth, repair, and immune function.
       - Sources include meat, fish, dairy, and legumes.

  4. Vitamins & Minerals:
       - Key for metabolic processes, bone health, and disease prevention.
       - Specific vitamins (A, C, D) important for various bodily functions.

  5. Dietary Fiber:
       - Aids digestion, softens stool, and prevents constipation.

  6. Water:
       - Essential for cellular reactions and temperature regulation.

Nutrition Needs Across Life Stages

  • Toddler:
       - Needs proteins for tissue development, varied fruits and vegetables for vitamins.

  • Adolescents:
       - Higher nutritional requirements for growth.

  • Manual Workers:
       - Require higher energy intake due to physical labor.

  • Sedentary Workers:
       - Need a diet low in high-energy foods to prevent obesity.

ALIMENTARY CANAL

  • Functions of Parts:
      1. Ingestion: Intake food and masticate to increase surface area for enzymes.
      2. Digestion:
         - Mechanical Digestion: Physical breakdown through chewing and churning; emulsification by bile for fats.
         - Chemical Digestion: Enzymes breakdown nutrients into absorbable forms.
      3. Absorption: Transport of digested nutrients from intestine into bloodstream and lymphatic system.
      4. Assimilation: Use of absorbed nutrients in metabolic pathways.
      5. Egestion: Removal of undigested substances.

DIGESTION PROCESSES

  • Mouth: Chewing and saliva (amylase) initiates starch digestion.

  • Stomach: Churns food; Hydrochloric acid and enzymes (pepsin) digest proteins.

  • Small Intestine: Major site for chemical digestion; pancreatic juices continue breakdown.

  • Absorption in Ileum:
      - Extensive villi and capillary networks facilitate nutrient uptake; water absorbed in large intestines.

MALNUTRITION

  • Result of unbalanced diet; can be under or over-nutrition leading to health issues (e.g., obesity, anorexia).

DISEASES CAUSED BY DEFICIENCY

  1. Kwarshiorkor: Due to protein deficit; results in swollen abdomen.

  2. Goitre: Caused by iodine deficiency; leads to thyroid enlargement and stunted growth.

  3. Scurvy: Vitamin C deficiency; causes bruising and joint pain.

  4. Anemia: Resulting from iron deficiency; fatigue and weakness.

  5. Night Blindness: Caused by vitamin A deficiency.

  6. Beriberi: Resulting from lack of vitamin B1.

FOOD TESTS

  1. Starch: Positive test with blue-black color using iodine.

  2. Reducing Sugar: Red precipitate forms using Benedict's solution upon heating.

  3. Proteins: Purple color with sodium hydroxide and copper sulfate.

  4. Fats: Cloudy emulsion forms using ethanol and water mix.

RESPIRATORY SYSTEM

  • Gaseous Exchange in alveoli facilitated by:
      - Thin, moist walls and extensive capillary networks for efficient gas diffusion.

  • Inhaled vs Exhaled Air:
      - Composition differences: O₂ and CO₂ levels, moisture content, temperature.

RESPIRATION

  1. Aerobic Respiration:
       - Uses extO2ext{O}_2 for glucose breakdown; yields energy, CO₂, and water.
       - Requires oxygen to fully oxidize glucose.

  2. Anaerobic Respiration:
       - Glucose breakdown without oxygen; produces lactic acid or alcohol.

TRANSPORT SYSTEM

  • Plant Transport:
      - Transpiration: Water vapor loss affecting nutrient uptake.
      - Factors: Temperature, humidity, air movement, stomata density influence rates.

REPRODUCTIVE SYSTEM

  1. Human Male Reproductive System:
       - Testes: Produce sperm and hormones (testosterone).
       - Scrotum: Regulates testes temperature for optimal sperm production.
       - Epididymis: Stores sperm until maturation.
       - Prostate, Cowper's Gland, Seminal Vesicle: Secrete fluids during ejaculation.

  2. Female Reproductive System:
       - Ovaries: Produce ova and hormones (oestrogen and progesterone).

MENSETRUAL CYCLE

  • Involves changes in uterine walls due to hormone regulation; lasts about 28 days.

HEALTH AND DISEASES
STIs

  • Chancroid: Ulcers on genitals; treated with antibiotics.

  • Gonorrhea: Caused by Neisseria gonorrhoea; serious if untreated.

  • Syphilis: Develops in stages; penetrative treatment required to avoid severe consequences.

  • HIV/AIDS: Immunodeficiency due to CD4 T-cell destruction by HIV; anti-retroviral therapies available.

INFECTIOUS DISEASES

  1. Malaria: Caused by Plasmodium; transmitted by Anopheles mosquito.

  2. Cholera: Vibrio cholerae; resulting in severe dehydration.

  3. Ebola: High mortality rate; transmission via bodily fluids.

  4. Typhoid: Salmonella typhi; high infection risk in unsanitary c