Biology Revision Notes

Characteristics of Living Organisms

  • Movement: Action by an organism causing a change of position or place.
  • Respiration: Chemical reactions in cells that break down nutrient molecules and release energy for metabolism.
  • Sensitivity: Ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.
  • Growth: Permanent increase in size and dry mass by an increase in cell number, cell size or both.
  • Reproduction: The process that makes more of the same kind of organism.
  • Excretion: Removal from organisms of waste products of metabolism, toxic materials, and excess substances.
  • Nutrition: Taking in materials for growth, energy, and development.

Binomial Naming System

  • A way to make classification standard.
  • Scientific name consists of Genus and Species.
    • Genus starts with a capital letter, species with a lowercase letter.
  • Scientific names are appropriate for humans and other organisms.

Why Classify Organisms?

  • To identify those at risk of extinction.
  • To understand evolutionary relationships.

How to Classify Organisms?

  • By studying morphology and anatomy.
    • Morphology: Study of the form or outward appearance of organisms.
    • Anatomy: Study of internal structure by dissection.
  • Sequences of DNA and amino acids in proteins are a more accurate way of classification.
  • Each species has a unique number of chromosomes and sequence of bases in DNA, making it different from other species (e.g., humans have 46 chromosomes).
  • Organisms with similar DNA are more closely related to recent ancestors.

All Living Things Classify Under

  • Kidgdom
  • Phylum
  • Class
  • Order
  • Genus
  • Species

Dichotomous Keys

  • Used to identify organisms.
  • Dichotomous means divided into two branches.
  • Early keys made of contrasting branches.

Viruses

  • Have a central core of RNA or DNA surrounded by a protein coat.
  • No nucleus, cytoplasm, cell organelles, or cell membrane.
  • Presence of cytoplasm, cell membrane, DNA (genetic material).
  • Do not feed, excrete, respire, or grow.
  • Ribosomes (in cytoplasm) floating freely or attached to membranes.
  • Virus PARTICLES are NOT cells.
  • Reproduce inside cells of living organisms using materials from the host cell.

Whittaker's Five Kingdom Scheme:

  • Animal
  • Plant
  • Fungus
  • Prokaryote
  • Protoctist

Animal

  • Multicellular
  • Divided into vertebrates and arthropods!

Plant

  • Multicellular
  • Cell wall made up of cellulose.
  • Contains chloroplasts with chlorophyll.
  • Can make their own food.
  • Divided into ferns and flowering plants.

Ferns

  • The zygote directly becomes the fern plant.
  • Fern plants have sporangia, which makes spores.

Flowering Plants

Fungus

  • Unicellular or multicellular organisms.
  • Made up of thread-like hyphae.
  • Many nuclei are distributed throughout the cytoplasm in their hyphae.
  • Examples: Yeast and Mushrooms.

Prokaryote

  • Bacteria and algae.
  • Chromosomes not organised into a nuclear membrane to form a nucleus.
  • Each bacterial cell contains a single chromosome, consisting of circular DNA strands.

Protoctist

  • Unicellular
  • Example: Amoeba

Eukaryotic Cells:

  • Have a nucleus and membrane-bound organelles.

Cell Structures in Bacterial Cells

  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Ribosomes
  • Circular DNA: DNA not in the nucleus, is in a loop.
  • Plasmids: Little rings of DNA, contain extra DNA.
  • Flagella: Helps them move around.
    Flagella (Plural)
    Flagellum (Singular)

Cell Structures in Both Animal and Plant Cells

  • Cell membrane: Selective control of what goes into and out of the cell.
  • Nucleus: Carries genetic material.
  • Cytoplasm: Jelly-like substance where all chemical reactions take place.
  • Ribosomes: Site of protein synthesis.
  • Mitochondria: Site of aerobic respiration (high metabolism cells to release energy).

Cell Structure in Plants Only

  • Cell wall: Structural support for plants.
  • Chloroplasts: Site of photosynthesis in plants.
  • Central Permanent Vacuoles: Stores/isolates harmful materials, stores nutrients, maintains water balance in the cell; structural support by applying turgor pressure.

Specialized Cells and Adaptations

  • Ciliated Cells: Allow movement of mucus in the trachea and bronchi.
  • Neurons/Nerve Cells: Conduction of impulses.
    • Long to reach different parts of the body.
    • Axon has a fatty sheath to insulate the cell and speeds up nerve impulse.
  • Root Hair Cells: Increase surface area to maximize absorption.
    • Walls are thin.
  • Red Blood Cells: Transport oxygen in blood.
    • Biconcave shape for increased surface area and flexibility.
    • No chloroplasts needed.
    • Contains haemoglobin, which joins with oxygen to transport it.
    • No nucleus increases oxygen capacity.
  • Palisade Mesophyll Cells: Allow for photosynthesis to occur.
    • Column shape to maximize sunlight absorption and fit many in the same layer.
    • Contains many chloroplasts to maximize photosynthesis.
  • Sperm and Egg Cells
    • Head contains haploid nucleus with genetic info.
    • Acrosome contains digestive enzymes to penetrate the egg.
    • Cell membrane changes after fertilization so that no more sperm can enter.
    • Tail allows the cell to swim.

Levels of Organization

  • Cell
  • Tissue
  • Organ
  • System
  • Organism
  • Basic functional and structural unit in living organisms.
  • Groups of cells of similar structure working together to perform specific functions.
  • Made from different tissues working together to perform related functions.

Cell Division

  • Cells in the body need to divide to allow for growth and repair.
  • New cells are produced through the division of existing cells.

Calculations

  • Actual Image Size
    Magnification = \frac{Image : Size}{Actual : Size}
    Example:
  • Actual size = 2000 mm
  • Image size = 50 mm
    Magnification = \frac{50mm}{2000mm} = \frac{1}{40} = 0.025 units

Diffusion

  • Net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.
  • The steeper the gradient (big difference from high to low), the faster the diffusion.
  • Dissolved salts diffuse through root hair cells.

Osmosis

  • Net movement of water molecules from high water potential (dilute solution) to lower water potential (concentrated solution) through a partially permeable membrane.
  • Dilute solution has more water potential, and concentrated solution has less water potential.
  • Occurs in both plant and animal cells.

Importance of Osmosis

  • Plants gain water through osmosis from soil to roots.
  • Plants need water to stay firm.

Plant Cells in Different Solutions

  • If a plant cell is placed in distilled water (purified water), water molecules move from distilled water into plant cells.

If plant cell vacuoles aren't full, cell will become flaccid. If all the calls in leaf become flaccid whole leaf drops and plant wilts

  • If a plant cell is in a salt solution with low water potential, water moves from cell to solution, and the cell becomes plasmolysed.

Animal Cells in Different Solutions

  • If an animal cell is in water, excess water enters the cell by osmosis, and if water isn't expelled, the cell will burst (haemolysis).
  • If an animal cell is in a salt solution, water in cytoplasm osmoses out, and the cell becomes shrunken (crenated).

Isotonic Solutions

  • Similar amounts of sugars/salts to blood.

Hypotonic Solutions

  • Less sugars and salts than blood.
  • (Tissue fluid: liquid outside cells).

Active Transport

  • The movement of particles through a cell membrane from a lower concentration to a higher concentration using energy acquired from respiration.
  • Carrier proteins pick up specific molecules and take them through the cell membrane against the concentration gradient.
  • Substance combines with carrier molecule; using energy from respiration, carriers are given kinetic energy needed to change and move substance through the membrane.

Importance of Active Transport

  • Uptake of glucose by epithelial cells in the villi of the small intestines and by kidney tubules in the nephrons.
  • Uptake of ions from soil water by root hair cells in plants.

Biological Molecules

  • Carbohydrates, fats, and proteins.

Carbohydrates

  • All contain carbon, oxygen, and hydrogen.
  • Long chains of simple sugars.
  • Glucose is a simple sugar (monosaccharide).
  • When lots of glucose joins together, starch, glycogen, or cellulose can form, depending on the structure; these are polysaccharides.

Fats (Lipids)

  • Carbon, oxygen, and hydrogen.
  • Most fats (lipids) in the body are made up of triglycerides.
  • Basic unit of fat is one glycerol molecule chemically bonded with three fatty acid chains.
  • Lipids are divided into fats (solid at RTP) and oils (liquid at RTP).

GLYCEROL + 3 FATTY ACIDS = Triglyceride

Proteins

  • Carbon, oxygen, hydrogen, and nitrogen; some contain small amounts of other elements like sulphur.
  • Long chain of amino acids.
  • There are 20 different amino acids.
  • Same basic structure for all proteins, but the 'R' is different for each one.
  • Amino acids can be arranged in many patterns resulting in different proteins.

Structure of DNA Molecule

  • Deoxyribonucleic Acid (DNA).
  • Molecule contains the instruction for the growth and development of all organisms.
  • Consists of two strands of DNA wound around each other in what we call a double helix.
  • The individual units inside DNA are called nucleotides.
    • Phosphate forms the backbone of a DNA strand.
    • Deoxyribose.
    • Base (A, T, C, or G).
  • There are 4 different bases: Adenine (A), Cytosine (C), Thymine (T), and Guanine (G).
  • Bases always pair in the same way:
    • Adenine always with thymine (A-T).
    • Cytosine always with guanine (C-G).

Food Tests

Iodine Solution Test for STARCH

  • Add drops of iodine solution (orange-brown at start) to the food sample.
  • A positive test will make the iodine colour change to blue-black.
  • A negative test will show no colour change to blue.

Benedict's Solution Test for REDUCING SUGARS

  • Add Benedict's solution (blue colour at start) to the food sample.
  • Heat at 60-70 degrees Celsius in a water bath for 5 minutes.
  • Take test tube out and observe colour.
  • A positive test will show orange or brick red.
  • A negative test will show blue-green or yellow.

Biuret Test for PROTEINS

  • Add drops of biuret solution (blue at start) to the sample solution in the test tube.
  • A positive test will show a colour change to violet/purple.
  • A negative test will show no colour change.

Ethanol Emulsion Test for FATS AND OILS

  • Food sample is mixed with 2 cm3 of ethanol and shaken.
  • Ethanol is added to equal volume of cold water.
  • A positive test will show a cloudy emulsion forming.
  • A negative test will show no change.

DCPIP Test for VITAMIN C

  • Add 1 cm3 of DCPIP solution (blue at start) to the food sample (as a solution).
  • A positive test will show the blue dye disappearing.
  • A negative test will show no change to the blue colour.

Enzymes

  • Enzymes are proteins.
  • Each enzyme has an active site.
    • Active site shape is specific as it ensures the substrate can fit, and bonds can form.
  • The substance on which the enzyme acts upon.
  • If the pH is too low or too high, the bonds holding the amino acids together in the enzyme may break, leading to denaturation.
    • Denaturation leads to a change of shape at the active site or a reduced rate of activity.
      Low temperatures don't denature enzymes; they just work slower.

Investigating Enzyme Actions

  • Investigating the effect of temperature on amylase.
  • Investigating the effect of pH level on amylase.

Limiting Factors in Photosynthesis

  • A factor in short supply that restricts the rate of a life process.
    Chlorophyll
  • Is a green pigment that is found in chloroplasts within plant cells.

Photosynthesis

  • The process in which plants synthesize carbohydrates.
  • End product: Glucose and Oxygen.
  • Glucose can be:
    • Converted to starch molecules and used as an energy store.

Plant Cell Structure

  • Stomata
  • Spongy mesophyll
  • Air spaces
  • Xylem & Phloem (vascular bundles)

How Photosynthesizing Cells Obtain CO2?

  • Atmosphere -> air spaces around spongy mesophyll -> leaf mesophyll cells -> chloroplast

Plant Labs

  • Investigating the need for Chlorophyll, Light & CO2.
  • Investigating the Rate of Photosynthesis.
  • Investigating Gas Exchange
  • Plants used are usually flodded or Cabomba -seaweed!
  • So net intake of carbon dioxide is found and net output of oxygen.
  • As photosynthesis occurs, oxygen will release into water.
  • Bubbles per minute can be counted to record rate.
  • Leaves can't be tested for glucose as it's quickly used, but starch is a reliable indicator of oxygen since starch is stored in chloroplasts where photosynthesis occurs.
  • This practical can be used to:
    • Investigate effect of changing light intensity.
    • Investigate effect of changing temperature.
    • Investigate effect of changing carbon dioxide concentration.
  • The leaf can be tested for starch, and this will prove that light is necessary for photosynthesis (production of starch).
  • We can investigate the effect of light on the net gas exchange using a pH indicator like hydrogen carbonate indicator.
  • Carbon dioxide is an acidic gas when dissolved in water.
  • One plant is placed in sodium hydroxide to absorb the carbon dioxide from the surrounding air.
  • Another plant is placed in beakers with beer.

Human Nutrition

  • A balanced diet needs the proper amount of carbs, protein, lipids, vitamins, minerals, dietary fiber, and water (food pyramid!).

Terms:

  • Ingestion: Intake of substances like food and water.
  • Digestion: The breakdown of food.
  • Absorption: Movement of nutrients from the intestines into the blood.
  • Assimilation: Uptake and use of nutrients by the cell.
  • Egestion: Removal of undigested food in the form of faeces.

Deficiencies

Scurvy

*Vitamin C deficiency
Symptoms:
*exhaustion
*Gum laceration
-Scurvy was commonly seen in Sailors between the 15th - 18th century
-treatment for rickets is to consume foods that are rich in calcium & Vitamin D, also vitamin D supplements can be prescribed

Rickets

*Vitamin D deficiency
Vitamin D is needed to absorb calcium into body and calcium is key component for bones and teeth. symptoms:
anemia & tooth loss
lack of bone growth
soft, weak bones (deformities)

Functions of Organs in Digestive System

## physical digestion **

  • breakdown of food into smaller pieces without chemical change to the food molecules
  • this process increases the surface area of food to make it easier for enzymes to digest in chemical digestion
    ( fatty acids & glycerol) ## chemical digestion*
  • breakdown of food into smaller molecules that can be absorbed & used by body
    ## Absorption **
  • movement of digested food molecules from the digestive system,in to the blood
  • Nutrients are absorbed in the small intestines

Enzymes in Digestion

Amylase, proteases.
produced in the mouth, pancreas and then secreted into the duodenum where amylase Digests starch into smaller sugars

  • maltase Digests maltose (a sugar) into glucose with the enzyme amylase.