1.1 Properties of Life

• Eight characteristics that define life:

  • Order

    • Organisms are highly organized structures that consist of one or more cells.

    • Atoms make up molecules, molecules make up cell organelles, and cell organelles make up cells.

      • Multicellular organisms have an advantage over single-celled organisms since their cells can be specialized to perform specific functions.

    • Cells form tissues, tissues form organs (i.e. the heart, lungs, or skin), organs form organ systems which make up organisms

• Response to Stimuli (Sensitivity)

  • Living organisms respond to stimuli in the external environment.

  • They detect and respond to changes in light, heat, sound, and chemical and mechanical contact.

    • Example: Plants can bend toward a source of light or respond to touch; Bacteria can move toward or away from chemicals (chemotaxis) or light (phototaxis).

      • Movement toward a stimulus is considered a positive response, while movement away from a stimulus is considered a negative response.

• Reproduction

  • Single-celled organisms reproduce by first replicating their DNA, and then divide it equally to form two new cells.

    • Many multicellular organisms produce specialized reproductive cells that will form new individuals.

  • When reproduction occurs, DNA containing genes is passed along to an organism’s offspring.

•  Adaptation

  • Adaptation is the ability of an organism to adapt to its environment through the process of evolution

  • Favorable characteristics that are selected for and passed onto offspring are called adaptations.

    • It is driven by natural selection or survival of the fittest.

    • Adaptations enhance the reproductive potential of the individual exhibiting them (i.e. ability to survive and reproduce).

• Growth and Development

  • Growth occurs as the result of cell division and cell enlargement.

  • Development is the process by which an adult organism arises as a result of repeated cell divisions and cell differentiation.

  • Organisms grow and develop along a specific sequence based on the instructions present in their genes.

• Regulation/Homeostasis

  • All organisms are complex and require multiple regulatory mechanisms to coordinate internal functions, such as the transport of nutrients, response to stimuli, and coping with environmental stresses.

  • Homeostasis is the relatively stable internal environment required to maintain life.

    • Example: The digestive and circulatory systems perform specific functions such as carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body

  • Cells require appropriate conditions such as proper temperature, pH, and concentrations of diverse chemicals.

• Energy Processing

  • All organisms use a source of energy for their metabolic activities. 

  • Some organisms capture energy from the Sun and convert it into chemical energy in food (autotrophs).

    • Others use chemical energy from molecules they take in.

• Evolution 

  • The diversity of life on Earth is a result of mutations, or random changes in hereditary material over time.

    • Mutations allow the possibility for organisms to adapt to a changing environment.

    • An organism that is best suited to its environment will have a better chance at survival.

1.2 Levels of Organization of Living Things

• Living things are highly organized and structured, following this hierarchy from small to large:

  • Atom

    • The smallest and most fundamental unit of matter that retains the properties of an element.

      • Consists of a nucleus surrounded by electrons.

      • Atoms form molecules.

• Molecule 

  • A chemical structure consisting of at least two atoms held together by a chemical bond.

    • Many molecules that are biologically important are macromolecules, large molecules that are formed by combining smaller units called monomers.

      • Example: DNA is a macromolecule that contains the instructions for the functioning of the organism that contains it

• Organelles

  • Aggregates of macromolecules that are surrounded by membranes

    • Organelles are small structures that exist within cells and perform specialized functions

• Cell

  • The smallest fundamental unit of structure and function in living organisms.

    • All living things are made up of cells.

  • Some organisms consist of a single cell and others are multicellular.

    • Prokaryotes are single-celled organisms that lack organelles surrounded by a membrane, and do not have nuclei surrounded by nuclear membranes.

    • Eukaryotes are organisms that have membrane-bound organelles and nuclei.

• Tissues

  • Groups of similar cells carrying out the same function.

  • In most multicellular organisms, cells combine to make tissues.

• Organs

  • Collections of tissues grouped together based on a common function.

    • Organs are present in both animals and plants.

• Organ System

  • A higher level of organization that consists of functionally related organs.

    • Example: Vertebrate animals have many organ systems, such as the circulatory system that includes multiple organs like the heart and blood vessels.

• Organisms

  • Individual living entities.

    • Example: Each tree in a forest is an organism.

  • Single-celled prokaryotes and single-celled eukaryotes are also considered organisms and are typically referred to as microorganisms.

• Population

  • All the individuals of a species living within a specific area.

    • Example: A forest may include many white pine trees; all of these pine trees represent the population of white pine trees in this forest.

• Community

  • The set of populations inhabiting a particular area.

    • Example: All of the trees, flowers, insects, and other populations in a forest form a community.

• Ecosystem

  • Consists of all the living things in a particular area together with the abiotic (nonliving) parts of that environment such as nitrogen in the soil or rainwater.

• Biosphere

  • The collection of all ecosystems; represents the zone of life on Earth.

  • Highest level of organization.

  • It includes land, water, and portions of the atmosphere.

1.3 The Diversity of life

• Three major domains:

1. Bacteria

2. Archaea

3. Eukarya

• Domains:

  • Humans belong in the eukarya domain.

  • Domain is further divided into kingdoms, phylum, class, order, genus, and species.

• Naming Organisms Scientifically:

  • Linnaeus was the first to name organisms using two unique names, now called the binomial naming system.

  • This system uses the genus and the specie name, where the first letter of the genus is capitalized and the specie name is all lowercase.

  • You must underline when writing and italicize when typing a scientific name.

    • Example: The scientific name for humans is Homo sapiens.

1.4 Scientific Method

• Why follow this?

  • Scientific Method

    • A universal way to generate knowledge in Science.

    • The goal of this is to answer questions based on observations and logical reasoning in our findings.

      • Understanding this method is important since it is used by all branches of natural and social sciences to answer questions and to validate data to support conclusions.

• Steps of the Scientific Method

1. Making observations.

2. Asking questions.

3. Hypothesis: possible explanations you can test, needs to be both falsifiable and testable.

4. Make a prediction: It is a specific expectation. An if-then statement as an outcome expected from our hypothesis if it is correct. 

5. Scientific Theory (law): an explanation that has been tested and supported by evidence many times

6. Methodology: Collecting data for testing the hypothesis. Conducting the experiment.

7. Analysis of results

8. Conclusion 

9. Publication

*Good experiments repeat the process multiple times

• For an experiment to be valid, the following criteria need to be met:

1. Big sample size when conducting experiment

2. Random assignments of subjects in experimental vs control group

3. Double blind. Researchers do not know in which group subjects are placed and subjects do not know in which group they are placed. This removes bias from the experiment.

4. Repeatable results when experiments conducted by other researchers.

5. Research published and peer reviewed.  

1.5 Variables

• Variable

  • Any part of the experiment that can vary or change during the experiment.

• Three Types of Variables

  • Independent Variable

    • A variable that is being tested or manipulated.

  • Dependent Variable

    • A variable that is being measured.

  • Control variable

    • A variable that is constant and does not change.

      • Example: The effects of drug X on blood pressure.

        • Independent variable is drug X.

        • Dependent variable is blood pressure measurement.

        • Control variable is the age of subjects, health status, etc.

• Graphs And Data

  • Graphs and charts are visual diagrams that help you interpret data.

• Typical layout for graphs:

  • X-axis (horizontal axis) 

    • Includes the independent variable

  • Y-Axis (vertical axis)

    • Includes the dependent variable

1.6 Sciences

• Types of sciences

  • Natural Sciences

    • Field of science related to the physical world and its phenomena and its processes.

    • Includes diverse fields of astronomy, chemistry, computer science, biology, etc.

• Life Sciences

  • Study of living things (i.e. biology).

• Physical Sciences

  • Study of nonliving matter.

  • Includes astronomy, chemistry, and physics.

• Applied Science

  • Aims to use science to solve real life problems.

    • Example: Finding a cure for a disease, development of vaccine, etc.