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LIFE SCIENCES GRADE 10 NOTES

Compiled in compliance with CAPS documents and Life Sciences Examination guidelines. Author: ISRAEL ADEYANJU

ORIENTATION TO LIFE SCIENCES

  • What is Life Science?
    It is the scientific study of living things from molecular level to their interactions with one another and the environment.

  • Characteristics of Life:

    • Living systems exhibit levels of organization from molecules to biomes.
    • Life on Earth is dynamic, with homeostasis maintaining balance at every level of organization.
    • Life is characterized by changes over time.

  • Science Involves:

    • Contested knowledge and non-dogmatic inferences based on evidence and peer review.
    • Non-dogmatic conclusions: conclusions are not influenced by religious conviction.
    • Peer Review: scientists researching the same topic evaluate and contribute using their logic and data to confirm claims.

  • Strands in Life Sciences:

    • Life at the Molecular, Cellular, and Tissue Level
    • Life processes in Plants and Animals
    • Environmental Studies
    • Diversity, Change, and Continuity

MAKING DRAWINGS

  • Use a sharp HB pencil to draw.
  • Drawings must be an appropriate size so that all labelled parts are clearly visible.
  • Do not shade your drawings as it makes them unclear.
  • Labels and label lines must be written in pen.
  • Label lines must be drawn with a ruler and must not cross each other.
  • Label line must point to the exact labelled part and must not end in an arrowhead.
  • A drawing must have an appropriate heading that describes it.

VARIABLES IN EXPERIMENTATION

  • Independent Variable:
    The variable that you control and may change during the experiment; expected to affect the dependent variable.

  • Dependent Variable:
    The variable that is measured during the investigation, influenced by the change in the independent variable.

  • Fixed Variable (Controlled Variable):
    Remains constant to prevent influencing the investigation; not shown on a table or graph.

Example:

  • Investigating tomato growth:
    • Dependent variable: mass of tomatoes
    • Independent variable: how much light the tomato plants receive.

Fixed/Controlled Variables for Tomato Plants:

  • Same species of tomato
  • Type and amount of fertilizer
  • Type of soil
  • Type of container
  • Amount of water

HYPOTHESIS

  • A statement or prediction regarding the expected outcome of an investigation.
  • Should be:
    • Specific
    • Related directly to the question asked
    • Includes the cause and effect
    • Testable
    • Formatted as a prediction in the future tense.

Example:
"The more sunlight a tomato plant receives, the larger the tomatoes will grow."

EVALUATION OF RESULTS

  • Validity:
    Was it a fair test? Did it test what it set out to test?

  • Reliability:
    If the experiment were repeated, would similar results be obtained?

    • Ensure reliability by:
    • Repeating the experiment several times to obtain an average.
    • Increasing sample sizes.

PRESENTATION OF DATA

  • Scientific data can be represented in various ways:
    • Tables:
    • Appropriate heading
    • Different columns
    • Independent variables in the left column
    • Dependent variables in the right column
    • Line Graphs:
    • Two axes: x-axis (independent variable) and y-axis (dependent variable).
    • Correct scale and labeled axes.
    • Appropriate heading.
    • Bar Graphs and Histograms: Represent comparative data clearly with bars.
    • Pie Charts:
    • Visual representation of percentages; segments represent proportions of the total.

THE CHEMISTRY OF LIFE (PAPER 1 – 33 MARKS)

  • Molecules for Life:

    • Inorganic Compounds:
    • Do NOT contain carbon and are not produced by living organisms (e.g., water).
    • Exceptions: carbon dioxide, carbon monoxide, and carbonates.
    • Organic Compounds:
    • Contain carbon and are produced by living organisms.
    • Components: Carbon (C), Hydrogen (H), Oxygen (O), sometimes Nitrogen (N), Phosphorus (P), and Sulfur (S).
    • Include carbohydrates, lipids, proteins, nucleic acids, and vitamins.

  • Inorganic Compound – Water (H2O):

    • Most important for life; functions include:
    • Solvent for organic/inorganic compounds.
    • Medium for chemical reactions.
    • Transporting agent for nutrients and waste.
    • Lubricant in bodily processes.
    • Regulates body temperature.
    • Provides structure to cells (e.g., in plants).

  • Mineral Salts:
    Inorganic substances necessary for organisms.

    • Absorbed by plants from soil and animals from food.
    • Split into Macro-elements (needed in large quantities) and Micro-elements (needed in small quantities).

MACRO- & MICRO-ELEMENTS

  • Macro-elements:

    • Needed in large amounts (e.g., calcium, nitrogen).

  • Micro-elements:

    • Needed in small amounts (e.g., iron, copper).

FERTILISERS & EUTROPHICATION

  • Fertilisers enhance soil nutrients but can cause eutrophication:
    • Nutrients wash into water bodies, leading to rapid algal growth, blocking sunlight, depleting oxygen, leading to die-offs of aquatic life.

ORGANIC COMPOUNDS

  • Carbohydrates: Composition: C, H, O. Ratio of H:O is 2:1.

    • Types:
    • Monosaccharides: Single sugars like glucose, fructose.
    • Disaccharides: Two sugars; e.g., maltose, sucrose, formed via condensation reaction.
    • Polysaccharides: Long chains; e.g., starch (plant storage), glycogen (animal storage), cellulose (plant structure).

  • Importance of Carbohydrates:

    • Source of energy and reserve energy.
    • Component of cell walls.

  • Lipids (Fats and Oils): Consist of C, H, O; ratio is much higher for H.

    • Soluble in ether/alcohol; hydrophobic.
    • Types:
    • Saturated Fats: Solid at room temp; from animals.
    • Unsaturated Fats: Liquid at room temp; from plants.

  • Importance of Lipids:

    • Energy reserve, insulation, shock absorption, waterproofing.

  • Proteins: Composed of amino acids (CO, H, N; sometimes P and Fe).

    • Building blocks: amino acids form peptides and proteins.
    • Functionality: shape determines activity; enzymes are proteins that act as catalysts for reactions.

NUCLEIC ACIDS

  • Types:
    • DNA: Carries hereditary information; found in the nucleus.
    • RNA: Involved in protein synthesis; present in nucleus and cytoplasm.

VITAMINS

  • Essential for metabolism and development; classified as water-soluble (excreted) or fat-soluble (stored).

FOOD TESTS

  • Carbohydrates:

    • Glucose: Benedict’s solution.
    • Starch: Iodine turns blue-black.

  • Lipids: Ether test for fats.

  • Proteins: Biuret test; blue indicates absence, purple indicates presence.

CELLS: BASIC UNITS OF LIFE (PAPER 1 – 19 MARKS)

  • Microscopy:

    • Antonie van Leeuwenhoek: first simple microscope; first to observe bacteria (father of microscopy).
    • Cell Theory:
    • All living organisms are composed of cells.
    • Cells are the smallest unit of life.
    • Cells arise from other cells.

  • Cell Structure and Function:

    • Prokaryotic Cells: No true nucleus; e.g., bacteria.
    • Eukaryotic Cells: Have a true nucleus; includes plant and animal cells.

  • Components of Cells:

    • Cytoplasm: Site of metabolic processes.
    • Cell Membrane: Selectively permeable boundary.
    • Nucleus: Control center; carries genetic material.

TYPES OF CELLS

  • Plant Cells: Have cell wall, chloroplasts, and large vacuoles.
  • Animal Cells: No cell wall, have small vacuoles and include lysosomes.

CELL DIVISION – MITOSIS (PAPER 1 – 19 MARKS)

  • Mitosis:

    • Division of somatic cells; produces two identical daughter cells from one mother cell.
    • Phases of Mitosis:
    • Prophase, Metaphase, Anaphase, Telophase.

  • Cancer: Uncontrolled mitosis leading to tumors.

    • Treatment Options:
    • Surgery, chemotherapy, radiotherapy.

PLANT AND ANIMAL TISSUES (PAPER 1 – 28 MARKS)

  • Plant Tissues:

    • Meristematic (actively dividing) vs. Permanent (differentiated).
    • Types of permanent tissue include skin, parenchyma, collenchyma, sclerenchyma.

  • Animal Tissues:

    • Epithelial, connective, muscle, nerve tissues.

TRANSPORT SYSTEMS IN MAMMALS (PAPER 2 – 32 MARKS)

  • Circulatory System:

    • Composed of the heart, blood vessels, and blood.
    • Closed circulatory system with two main circulations: pulmonary and systemic.

  • Heart Structure:

    • Composed of four chambers and valves; responsible for pumping oxygenated and deoxygenated blood.

  • Blood Vessels:

    • Three types: Arteries (oxygenated), veins (deoxygenated), capillaries (exchange).

ENVIRONMENTAL STUDIES (PAPER 2 – 54 MARKS)

  • Biosphere: Region of Earth where life exists; includes atmosphere, lithosphere, hydrosphere.

  • Biomes: Areas with particular climates and ecosystems; e.g., savannah, grassland, forests.

  • Ecosystems: Interaction of biotic and abiotic factors; comprised of producers, consumers, and decomposers.

  • Nutrient Cycles: Includes oxygen, nitrogen, and carbon cycles, involving transfers between living organisms and the environment.

BIODIVERSITY AND CLASSIFICATION (PAPER 2 – 21 MARKS)

  • Biodiversity: Variety of life forms; includes species, genetic, and ecosystem diversity.

  • Classification of Organisms: Based on shared characteristics; includes taxonomy systems (Linnaean and five kingdoms).

  • Naming of Species: Binomial nomenclature system by Carl Linnaeus gives each species a unique name (genus and species).

HISTORY OF LIFE ON EARTH (PAPER 2 – 43 MARKS)

  • History: Life began 3.8 billion years ago; the study involves fossils and geological events.

  • Mass Extinctions: Significant events leading to biodiversity loss; current concerns regarding human impact on species.

  • Fossil Dating: Radiometric and relative dating methods used to determine the age of fossils and the history of life on Earth.