BIO NOTES

Chapter 1: Studying Life

LIVING ORGANISMS HAVE A COMMON ORIGIN AND SHARE SIMILARITIES

BIOLOGY: The scientific study of organisms (living and fossils)

  • The goal of biological study is discovering/ understanding the unity and diversity of the processes that make up life on Earth.

  • Life formed about 4 billions years ago

  • The common features living organisms share proves that all life has common ancestry.

    • Evolution has generated enormous diversity of life

Levels of Biological Organization:

Atoms, small molecules, large molecules, cells, tissues, organs, organ systems, organism, population, community, ecosystem, biosphere.

Levels of Biological Organization

  • Life on Earth is diverse, yet all life forms share common features that separate them from the nonliving.

    • Made of a common set of chemical compounds

    • Made up of CELLS (smallest living unit that can carry out life process)

    • Use molecules from the environment to synthesize new molecules

    • Extract energy from the environment and use it to do work (Using Sun)

    • Contain genetic information

    • Respond to stimuli (Stimulus: an environmental condition that causes an organism to react to and adjust)

    • Regulate their internal environments (Homeostasis: Same state)

    • Exist in populations that evolve over time

GENETICS AND EVOLUTION ARE FUNDAMENTAL PRINCIPLES OF BIOLOGY

Gregor Mendel showed that inherited traits exist in discrete units which were later termed genes.

  • The discovery of DNA and it's functions transformed biological science.

Charles Darwin compiled factual evidence for evolution and proposed that all organisms are descended from a common ancestor and are therefore related.

  • Best known for the evolutionary mechanisms of Natural Selection

  • Evolution is the major unifying principle of biology

Genus: Group of species that share a recent common ancestor

Species: Base unit of taxonomic classification. A group of populations of evolutionarily closely related organisms capable of interbreeding.

  • Each species has a distinct scientific name, a binomial (genus and species)

  • Written in one of two ways

    • Homo sapiens OR Homo sapiens

    • Escherichia coli OR Escherichia coli OR E. coli

BIOLOGISTS INVESTIGATE LIFE THROUGH EXPERIMENTS THAT TEST HYPOTHESES

INFO

UNDERSTANDING BIOLOGY IS IMPORTANT FOR HEALTH, WELL-BEING AND PUBLIC POLICY DECISIONS

  • Understanding biological principles is essential for us to lead healthy productive lives and to be good stewards of our planet

    • agriculture and medical practices require the application of biological knowledge in order to serve human beings

    • human activities are resulting in unprecedented rates of change in Earth’s systems

  • Public policy

  • our newfound scient






  • ific abilities raise ethical and policy issues

    • biologists are called on to advice government agencies on many issues


Chapter 2: Small Molecules and the Chemistry of Life

Matter: Anything that has mass and occupies space; all matter is composed of atoms
Atom: smallest unit of chemical element; physical and chemical properties of atoms depend on the number of particles the atoms contain

  • Proton: subatomic particle, positive electrical charge, located in nucleus

  • Neutron: subatomic particle, no charge, located in nucleus

  • Electron: subatomic particle, negative charge, located in orbits around the nucleus

    • the further an electron is from the nucleus the more energy it has

    • Electrons determine how atoms will combine with other atoms to form stable associations (molecules)

Valence shell: an atom’s outermost energy shell (fixed distance)

  • Valence electrons: Involved in chemical reactivity

Element: a substance that cannot be converted to a simpler substance

  • Living organisms’ tissues are made up of six elements

    • Carbon (C), Oxygen (O), Hydrogen (H), Nitrogen (N), Phosphorus (P), Sulfur (S)

Compound:

Molecule:

No other element is as versatile as carbon; carbon is present everywhere in nature.

  • Carbon has four valence electrons so the ability to form four bonds as well as the ability to bond itself which creates very strong bonds

ATOMS BOND TO FORM MOLECULES

  • The energy level of an electron is higher in a shell farther from the nucleus

  • The valence shell electrons determine how the atom combines with other atoms

    • atoms with unpaired electrons in their valence shells are unstable and will undergo reactions to fill the shell

  • Reactive atoms attain stability:

    • by sharing electrons with other atoms

    • by losing or gaining one or more electrons

      • either activity can form a chemical bond (an attractive force that links two atoms together)

      • Covalent bonds are the strongest

  • Electronegativity: the attraction of a given atom for the electrons of a covalent bond; the more electronegative an atom is, the more strongly it pulls shared electrons toward itself; this can cause an unequal sharing of electrons

    • depends on:

      • its positive charge

      • the distance between the nucleus and the valence shell electrons

  • Oxygen has the highest electronegativity

    • higher proton count

    • electrons are closer to nucleus

    • smaller bond

Covalent Bond: forms when two atoms attain stable electron numbers in their shells by sharing (equally or unequally) a pair of electrons

  • VERY STRONG and stable. Much energy is needed to break them

Polar covalent bond (unequal sharing of electrons)

  • One atom has greater electronegativity, so electrons are drawn more to that atom

  • The bond has a slightly negative charge on one end (pole) and a slightly positive charge on the other (pole)

  • Water is a polar molecule

Nonpolar covalent bond (equal sharing of electrons)

  • atoms have similar or equal electronegativities

Ion: Electrically charged particle that forms when an atom gains or loses one or more electrons

  • Cation: Positively charged ion

  • Anion: Negatively charged ion

Ionic Bond: a chemical bond resulting from the electrical attraction between oppositely charged ions

Hydrogen Bond: a weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another reigion of the same molecule; form between water molecules; DNA and proteins.

  • Polar molecules that form hydrogen bonds with water are considered to be hydrophilic (water-loving); hydrophilic substances dissolve in water

  • Nonpolar molecules such as hydrocarbons (molecules containing only hydrogen and carbon atoms) are hydrophobic (water-fearing); hydrophobic don’t dissolve

CHEMICAL REACTIONS TRANSFORM SUBSTANCES

The bonding of atoms to form molecules is not necessarily permanent. Molecular interactions— how they break up and how they find new partners— occur constantly

Chemical Reactions: occur when atoms collide with enough energy to combine or change their bonding partners; the making and breaking of chemical bonds leads to changes in the composition of matter

  • Reactant:

  • Product:

Energy: capacity to do work or the capacity for change, energy usually changes form during chemical reactions

THE PROPERTIS OF WATER ARE CRITICAL TO THE CHEMISTRY OF LIFE

Water has special properties:

  • polar molecule, forms hydrogen bonds and has a tetrahedral shape

These special properties allow for these characteristics of water:

  • Water molecules are farther away from one another in ice than in liquid water. There are cavities between molecules.

Soluble compounds mix completely with water.

Solution is a substance (solute) that dissolved in a liquid (solvent)

Acid: substance that releases H+ in aqueous solution

Base: substance that accepts H+ from an aqueous solution

pH scale: quantitative means for stating the [ ] of H+ in solutions

Buffer: substance that minimizes changes in the [ ] of H+ and OH- in a solution maintains a relatively constant pH.