Biology: Characteristics of Living Things

Biology

• Study of living things

Characteristics of Living Things

• Need for energy (eating or making waste)
• Exchange of gases (respiration)
• Growth
• Movement
• Response to stimuli
• Reproduction

Where do Living Things Come From?

• Abiogenesis: theory that life can be made from non-living things (spontaneous generation)
• Biogenesis: theory that life is produced by other living things

Francesco Redi's Experiment

• Questioned spontaneous generation of maggots on meat
• Experiment on meat with three treatments:
  • Open air (control)
  • Sealed
  • Screened off
• Hypothesis: meat would decay in all jars, but maggots would only appear where there was contact with flies
• Result: maggots only appeared in the open container
• Conclusion: hypothesis supported ; maggots came from flies, not spontaneously from meat.

The Debate Continued

• John Needham
  • believed in abiogenesis
  • boiled chicken broth
  • bacteria grew, believed to favour his hypothesis
• Lazzaro Spallazani
  • believed in biogenesis
  • repeated Needham's experiment, but drew off air
  • nothing grew; favoured his hypothesis
• Louis Pasteur
  • designed an experiment to resolve the argument
  • boiled nutrient broth in three treatments:
    • Open
    • Closed
    • S-neck (open to air, but not atmospheric dust)
  • Prediction: no growth in S-neck flask
  • Result: no growth in S-neck flask
  • Conclusion: hypothesis supported; growth of microorganisms needs a source (external/atmosphere).

Microscopes and Cell Theory

• Magnification
  • Enlarges images
  • How many times bigger image compared to actual specimen
  • e.g., 5000X
• Resolution
  • Clarity of image under a microscope
  • Often depends on quality of lens
  • How far apart two objects need to be to be seen separately, not blurred
  • e.g., 10 µm

Types of Microscopes

• Modern Compound Microscope
  • Series of lenses producing a magnified image
  • Multiple objective lenses in a revolving nosepiece
• Dissecting Microscope (Stereoscope)
  • Two objectives and two eyepieces
  • Produces 3D images
  • Used for viewing larger, more opaque specimens
  • Lower Magnification
• Electron Microscopes
  • Use beam of electrons instead of light
  • Focused by magnetic fields
  • Produces 2D images or 3D images
  • Very powerful magnification (up to 1.2 million ×)
  • Transmission Electron Microscope (TEM)
    • Beam of electrons passes through very thin section (stained) specimen
    • Magnifications from 10,000 to 100,000 ×
  • Scanning Electron Microscope (SEM)
    • Specimen "painted" with electron-dense material (gold)
    • Electrons strike, reflected and sensor produces 3D image
    • Magnification of up to 300,000 x
• Confocal Laser Scanning Microscope (CLSM)
  • Laser beams direct through planes, creates 2D images
  • Images merged to create 3D images
  • Good for thick specimens.
• Scanning Tunneling Microscope (STM)
  • Greater magnification than electron microscope
  • Electron flow from tip to atoms on surface
  • 3D image from surface contours.

Cell Theory

• All living organisms are made of one or more cells.
• The cell is the most basic unit of life.
• All cells arise from pre-existing cells.

What have we discovered?

• Stem cells are used in creating treatments and cures for diseases
• Genes use DNA to direct cells' activities.
• Genetic sequencing can map genes which helps study cell activity and develop treatments for genetic disorders.
• Cancer and tumors are caused by damage to genes where cells grow uncontrollably.
• Scientists will study the sequences of cancer-causing genes to understand how they impact cell activity.
• Sub-cellular particles, like viruses and prions have been discovered which are not made up of cells.
  • Viruses are made of genetic material in a protein coat that invades cells' reproductive machinery
  • Prions are proteins which convert into deadly disease particles
• More has been discovered about cell components and how these components/processes allow the cell to function correctly.

Cell Structures and their functions

• Nucleus
  • Controls cell activities
  • Contains DNA
  • Surrounded by a nuclear envelope
  • Contains the nucleolus
• Nucleolus
  • Center of the nucleus
  • Synthesizes ribosomes
• Ribosomes
  • Turn DNA into proteins, responsible for growth and cell reproduction activities.
• Mitochondria
  • Powerhouse of the cell
  • Uses oxygen to make cell energy (ATP)
  • Performs cellular respiration
• Lysosome
  • Vesicles containing enzymes that break down particles and dispose of waste.
• Vacuole
  • Stores food and water
  • Transport
  • Plants generally have a large central vacuole whereas animals have many small vacuoles.
• Endoplasmic Reticulum & Ribosomes
  • Attached to nucleus
  • Rough ER (RER) has ribosomes which transport DNA
  • Smooth ER (SER) has no ribosomes which synthesizes lipids (fats) required by the cell
• Golgi Apparatus
  • Modifies and repackages lipids and proteins.
  • Disposes of waste products.
• Centrioles
  • Involved in cell division
• Cytoskeleton
  • Supports the structure of the cell
  • Facilitate transport
  • Intricate network of fiber-like structures - only present in animal cells
• Cell Membrane
  • Protective barrier around the cell
  • Semi-permeable (regulates movement of substances in and out)
  • Made of phospholipids, proteins, carbohydrates, and cholesterol
  • Role: to maintain equilibrium
• Cell Wall
  • Rigid, supportive structure
  • Shapes plant cells (along with large vacuole)
  • Enclosed membrane
  • Made of cellulose
• Chloroplasts
  • Site of photosynthesis (plant cells)
  • Solar energy converted into chemical energy (glucose)
  • Made up of two membranes
  • Contains chlorophyll

Cell Transport

• Passive Transport
  • Diffusion: particles move away from high concentration regions toward lower concentration regions. (e.g., O2 and CO2)
  • Osmosis: Water moves from higher to lower water concentration.
  • Facilitated diffusion: transport proteins help polar molecules and ions diffuse passively down a concentration gradient (e.g., aquaporins and carrier proteins)
• Active Transport:Requires energy to move solutes against a concentration gradient using carrier proteins (e.g, sodium-potassium pump)
• Bulk Transport:
  • Exocytosis: cells excrete molecules using vesicles (that fuse with the membrane)
  • Endocytosis
    • Phagocytosis: cells take in large materials to be digested
    • Pinocytosis: cells take in fluid and small solutes
    • Receptor-mediated endocytosis: uses receptors to identify specific materials.

Dialysis

• Method to filter waste and regulate material concentration using dialysis tubing (permeable membranes)
• Used to treat those with damaged kidneys
• Involves use of machines that circulate blood past membranes in a fluid (solute) mix.

Plant Organization

• Cells → Tissues → Organs → Organ Systems → Organisms
• An organism is a complex of interacting dependent systems

Organ Systems (Plant)

• Shoot systems include everything above the ground involved in capturing energy from sunlight
• Root systems are mostly below ground and involved in obtaining water and nutrients and anchoring the plant.

Specialized Plant Cells

• Xylem: non-living cells that conduct water and minerals up from the roots to leaves.
• One-way transport.
• Phloem: form sieve tubes and connected to companion cells that transport sugars from the leaves to other parts of the plant.
• Two-way transport

Plant Adaptations/Growth

• Plants adapt via features or behaviors in their environment for survival or reproduction.
  • Larger leaves increase surface area which allows them to capture sunlight.
  • Dark leaves can absorb more light
  • Wax cuticle and thick epidermis reduces water loss in plant
• Tropisms (Directional Growth):
  • Phototropism: growth towards/away from light
  • Gravitropism: growth towards/away from gravity
    • Roots grow toward, shoots grow away.
  • Thigmotropism: growth towards/away from physical object.

Calculating Surface Area & Volume Ratios

• Area and volume calculations help determine efficient cell/plant structure which allows for survival & reproduction.
• The surface area often increases rapidly compared to volume in smaller cells, which contributes to efficient nutrient uptake and waste removal in plants/cells.

This quiz explores the foundational concepts of biology, focusing on the characteristics that define living things and the origins of life theories including abiogenesis and biogenesis. Additionally, it discusses Francesco Redi's experiment that challenged spontaneous generation, providing insights into scientific inquiry and debate.