Biology: Characteristics of Life

Biology Study Notes

• Biology is the study of life
• Life has seven characteristics:
  • Maintain stable internal environment (homeostasis)
  • Evolve and adapt
  • Be made of cells
  • Use energy (metabolism)
  • Respond to external environment
  • Reproduce and pass on genetic traits (DNA)
  • Grow and change
• Cells are the smallest unit that can perform all life's processes.
• Two categories of cells:
  • Prokaryotes: Lack membrane-bound nucleus and organelles; Single-celled organisms
  • Eukaryotes: Have membrane-bound nucleus and organelles; Multicellular organisms
• Levels of organization in multicellular organisms:
  • Cells
  • Tissues (group of similar cells)
  • Organs (group of tissues working together)
  • Organ systems (group of organs working together)
  • Organism (collection of organ systems)
• Characteristic 2: Response to stimuli:
  • Stimulus (stimuli): A thing or event evoking a specific functional reaction in an organ or tissue
  • Example: Phototropism (plant growth in response to light)
• Characteristic 3: Homeostasis:
  • Homeostasis is the process by which living things maintain a stable internal environment.
  • All homeostasis involves response to stimuli; not all response to stimuli are for homeostasis
• Characteristic 4: Metabolism:
  • Metabolism is all chemical reactions that take in and transform energy/materials from the environment (to perform life functions)
• Major aspects of Metabolism:
  • Nutrition: The process of taking in materials from the environment
  • Transport: Moving substances within an organism (for example, through a circulatory system)
  • Use of Nutrients: For energy, synthesis of new materials, and maintaining homeostasis
  • Excretion: Removal of harmful substances and waste products
• Characteristic 5: Growth and development
  • Growth: Organisms and cells increase in size
  • Development: The process of becoming a mature adult
• Cell Differentiation:
  • Cell transformation from less specialized to more specialized cell types
  • Cell Specialization: Process where cells develop specialized functions
• Characteristic 6: Reproduction:
  • Reproduction: The process of creating offspring
  • DNA (deoxyribonucleic acid): A molecule that stores genetic information
  • Genes: A specific segment of DNA containing instructions for making a specific trait
  • Asexual reproduction: one parent produces offspring genetically identical to the parent
  • Sexual reproduction: Two parents produce offspring with a combination of genetic material
• Characteristic 7: Evolution:
  • Process of inherited characteristics of a population changing over generations
  • Genetic variations: variations in DNA
  • Natural selection: Organisms with advantageous traits pass them on to their offspring
  • Adaptations: Traits that improve an individual's chances of survival and reproduction

Cell Structure and Function

• Cells are the basic units of life. They carry out all life functions.
• Organelles are specialized structures within cells that perform specific functions.
• Plasma membrane: thin double layer of lipids and proteins - surrounds the cell and controls what enters and leaves.
• Cell wall: found in plants, fungi, and some bacteria, rigid outer layer that provides support and protection.
• Cytoplasm: a jelly-like substance that fills the cell, surrounds and supports organelles.
• Cytosol: the part of cytoplasm that is not contained within organelles
• Cytoskeleton: protein filaments that contribute to the shape and movement of cells
• Mitochondria: Convert the energy from food into a usable form of energy for the cell (ATP)
• Nucleus: Stores genetic information (DNA), controls cell activities.
• Ribosomes: Make proteins
• Endoplasmic Reticulum (ER): Internal membrane system for protein and lipid production, transport, and modification
  • Rough ER: has ribosomes attached, modifies proteins manufactured by ribosomes
  • Smooth ER: processes lipids, detoxifies harmful substances
• Golgi Apparatus: Modifies, sorts, packages, and transports proteins and lipids throughout the cell
• Lysosomes: Break down waste materials and cellular debris, use enzymes.
• Vacuoles: Storage compartments for water, nutrients, and waste products (large in plants)
• Vesicles: Small membrane-bound sacs used for transporting molecules within and between cells (in animals)
• Centrioles: Involved in cell division in animal cells.
• Cilia and Flagella: Hair-like projections that can help cells move.
• Chromosomes/Chromatin: Structures that contain DNA and genetic information

Classification and Taxonomy

• Classification: Arrangement of organisms in groups based on shared traits.
• Taxonomy: Scientific classification system from broad to specific groupings:
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Binomial nomenclature: Two-part naming system using genus and species (e.g., Homo sapiens)

Scientific Method

• The scientific method is a systematic approach to understanding the natural world.
  • Make observations, ask questions, formulate hypotheses, design and conduct experiments, analyze data, and draw conclusions.
  • Steps:
    • Observation
    • Question
    • Research
    • Hypothesis
    • Experiment
    • Data Analysis
    • Conclusion
    • Report results

Microscopy

• Microscopes are tools used to view small objects.
  • Magnification: enlarges the subject.
  • Resolution: how well details are distinguished
• Types: Light microscopes, Electron microscopes
• Magnifying systems (in compound microscopes):
  • Objectives (different magnifications)
  • Ocular lenses (usually 10x)

Chemistry

• Chemistry is the study of matter (anything that takes up space) includes elements and compounds
• Matter is made up of elements and compounds
• A chemical compound is a substance that forms when two or more elements are combined.
• Elements are substances made of only one type of atom.
  • Example: Carbon (C), Oxygen (O), Hydrogen (H), Nitrogen (N), etc.
• Atoms are the smallest units of an element. They are made up of three smaller particles: protons (positive), neutrons (neutral), electrons (negative).

Additional Info (from the document)

• Cell theory: All living things are made up of one or more cells, and all cells come from preexisting cells.
• Endosymbiotic theory: Explains how mitochondria and chloroplasts originated from simple prokaryotic cells.
• Unicellular organisms: organisms with one cell; multicellular organisms: organisms with more than one cell
• Spontaneous generation: the mistaken belief that living organisms can arise from nonliving matter.