Chapter 1.1- 2.1

Four Questions of Biology

  1. What are the shared properties that make something alive"?

  2. How do those living things function?

  3. When faced with the remarkable diversity of life, how do we organize the different kinds of organisms so that we can better understand?

  4. What biologists ultimately seek to understand- how did diversity arise and how is it continuing?

Properties of life

When together these eight characteristics serve to define life

  1. Order

    1. Highly organized structures that consist of one or more cells (every cell is remarkably complex)

    2. In each cell, atoms make up molecules to make cell components and organelles

    3. Multicellular organisms can have specialized cells to perform specific functions

  2. Sensitivity/ response to stimuli

    1. Organisms respond to diverse stimuli

    2. Ex. plants can bend toward a source of light or respond to touch

    3. Bacteria can move toward or away from chemicals (chemotaxis) or light (phototaxis)

    4. Movement toward a stimulus is considered a positive response

    5. Movement away froma stimulus is considered a negative response

  3. Reproduction

    1. Single- celled organisms reproduce first by duplicating their DNA (genetic material), then divided equally as cell prepares to form two new cells

    2. Multicellular organisms produced specialized reproductive cells that form new individuals

    3. DNA containing genes are passed onto offspring after reproduction

  4. Adaptation

    1. All living organisms exhibit a “fit” to their environment

    2. Consequence of evolution by natural selection

    3. Enhance reproductive potential of individual exhibiting them (ability to survive to reproduce)

    4. Adaptations are not constant

    5. Environment changes causes characteristics of individuals in a population to track changes

  5. Growth and Development

    1. Organisms grow and develop by specific instructions coded for by their genes

    2. Genes provide instructions so species young will grow up to exhibit many of the same characteristics as its parents.

  6. Regulation/ homeostatsis

    1. Refers to the relatively stable internal environment required to maintain life

    2. Ex. digestive or circulatory systems perform specific functions like carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body

    3. To function properly cells require a proper temperature, pH, and concentration of diverse chemicals

    4. Organisms are able to maintain homeostatic internal conditions within a narrow range almost constantly, despite environmental changes, by activation of regulatory mechanisms

    5. Ex. many organisms regulate their body temperature in a process known as thermoregulation

    6. Ex. Polar bear has body structure that help withstand low temperatures and conserve heat

  7. Energy Processing

    1. All organisms use a source of energy for their metabolic activites

    2. Some organisms se sun and convert to chemical energy in food

    3. Some organisms use chemical energy from molecules they take in

  8. Evolution

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

    2. Allow the possibility for organisms to adapt to a changing environment

    3. Organism that evolves characteristics fit for the environment will have greater reproductive success

Levels of Organization of Living Things

Living things are highly organized and structured

  1. Atom- smallest

    1. Most fundamental unit of matter that retains the properties of an element

    2. Consists of a nucleus surrounded by electrons

    3. Atoms form molecules

  2. Molecule

    1. Chemical structure consisting of at least two atoms held together by a chemical bond

    2. Molecules that are biologically important are macromolecules (large molecules that are typically formed by combining smaller units called monomer)

    3. Ex. Deoxyribonucleic acid

  3. Organelles

    1. Cells contain aggregates of macromolecules surrounded by membranes

    2. Small structures that exist within cells and perform specialized functions

  4. Cells

    1. All living things are made of cells; the cell itself is the smallest fundamental unit of structure and function in living organisms- viruses are not considered living because they are not made of cells

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

    3. Eukaryotes- do have membrane-bound organelles and nuclei

  5. Tissues

    1. Cells combine to make tissues

    2. Groups of similar cells carrying out the same function

  6. Organs

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

    2. Present in animals and in plants

  7. Organ System

    1. Higher level of organization that consists of functionally related organs

    2. Ex. circulatory system that transports blood throughout the body and to and from the lungs; it includes organs such as the heart and blood vessels

  8. Organisms

    1. Individual living entities

    2. Ex. each tree in a forest is an organism

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

  9. Population

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

    2. Ex. the forest with the pine trees includes populations of flowering plants

  10. Community

    1. The set of populations inhabiting a particular area

    2. Ex. all of the trees, flowers, insects, and other populations in a forest form the forest’s community

  11. Ecosystem

    1. Living organisms and the environment in which they live

  12. Biosphere- largest

    1. Encompasses all the ecosystems on Earth

Diversity of Life

The source of this diversity is evolution, the process of gradual change during which new species arise from older species

  1. Carl Linnaeus proposed organizing species of organisms into hierachical taxonomy

  2. Current taxonomic system has eight levels

    1. Species, genus, family, order, class, phylum, kingdom, domain (lowest to highest)

  3. Domain

    1. Eukarya contains organisms that have cells with nuclei

    2. Includes the kingdoms of fungi, plants, animals, and several kingdoms of protists

  4. Archaea

    1. Single-celled organisms without nuclei

    2. Include many extremophiles that live in harsh environments like hot springs

  5. Bacteria

    1. Different group of single-celled organisms without nuclei

    2. Prokaryotes

Scientific Inquiry

  1. Inductive reasoning

    1. A form of logical thinking that uses related observations to arrive at a general conclusion

    2. Reasoning is common in descriptive science

    3. Data can be qualitative (descriptive) or quantitave (consisting of numbers)

      1. Raw data can be supplemented with drawings, pictures, photos, or videos

    4. Formulating generalizations inferred from careful observation and large amount of data

  2. Deductive reasoning

    1. A form of logical thinking that uses a general principle or law to predict specific results

    2. Deduce and predict the specific results that would be valid as long as the general principles are valid

    3. Ex. a prediction would be that if the climate is becoming warmer in a region, the distribution of plants and animals should change

  3. Descriptive science

    1. Aims to observe, explore, and discover

  4. Hypothesis- based science

    1. a specific question or problem and a potential answer or solution that can be tested

Matter

Life is made up of matter

  1. Occupies spaces and has mass

  2. Matter is composed of elements- substances that cannot be broken down or transformed chemically into other substances

  3. Each element is made of atoms with a constant number of protons

Atoms

  1. Smallest component of an element that retains all of the chemical properties

  2. Ex. one hydrogen atom has all of the properties of the element hydrogen, such as it exists as a gas at room temperature, and it bonds with oxygen to create a water molecule.

  3. Hydrogen atoms cannot be broken down into anything smaller while still retaining the properties of hydrogen- it would no longer have the properties of hydrogen

  4. Most common isotope of hydrogen (H) is the only exception and is made of one proton and one electron with no neutrons

  5. Proton is a positively charged particle that resides in the nucleus (has mass of 1 and charge of +1)

  6. Electron is a negatively charged particle that travels in the space around the nucleus (negligible mass and has a charge of -1)

  7. Neutrons reside in the nucleus (mass of 1 and no charge)

  8. Since protons and neutrons each have a mass of 1, the mass of an atom is equal to the number of protons and neutrons of that atom (electons do not factor into the overal mass because their mass is so small)

    Illustration of an atom showing two neutrons and two protons in the center, with a circle labeled as the nucleus around them. Another circle shows an orbit with two electrons outside of the nucleus

    1. The atomic number is equal to the number of protons

    2. The mass number is number of protons + nuetrons

      1. It is possible to determine the number of neutrons by subtracting the atomic number from the mass number

    3. Isotopes are different forms of the same element that have the same number of protons, but a different number of neutrons.

      1. Some isotopes are unstable and will lose protons, other subatomic particles, or energy to form more stable elements (radioactive isotopes)

Chemical Bonds

  1. How elements interact with another is dependent on how the electrons are aligned and how many openings there are

    1. The closest shell can hold up to two (filled first)

    2. The second and third energy levels can hold up to 8 (four pairs)

  2. Atom is at its most stable when all of the electron positions in the outermost shell are filled

  3. If there are empty spots on the outermost shells, chemical bonds form

  4. To be more stable atoms tend to completely fill outer shells by bonding with other elements

  5. Because the outermost shells of the elements with low atomic numbers (up to calcium, with atomic number 20) can hold eight electrons (octet rule)

    1. An element can donate, accept, or share electrons with other elements to fill its outer shell and satisfy the octet rule

  6. An ion is when an atom does not contain equal numbers of protons and electrons

    1. The number of electrons does not equal the number of protons (each ion has a net charge)

  7. Positive ions are formed by losing electrons (cations)

  8. Negative ions are formed by gaining electrons (anions)

    1. Ex. Sodium only has one electron in its outermost shell. It takes less energy for sodium to donate that one electron than it does to accept seven more electrons to fill the outer shell. If sodium loses an electron, it now has 11 protons and only 10 electrons, leaving it with an overall charge of +1. It is now called a sodium ion.

  9. The movement of elctrons from one element to another is referred to as electron transfer

    1. Ex. The chlorine atom has seven electrons in its outer shell. Again, it is more energy-efficient for chlorine to gain one electron than to lose seven. Therefore, it tends to gain an electron to create an ion with 17 protons and 18 electrons, giving it a net negative (–1) charge. It is now called a chloride ion.

Ionic Bonds

  1. Ionic and covalent bonds are strong interactions that require a larger energy input to break apart

  2. SInce positive and negative charges attract the ions stay together and form an ionic bond

  3. The elements bond together with the electron from one element staying predominantly with the other element

    1. Ex. When Na+ and Cl– ions combine to produce NaCl, an electron from a sodium atom stays with the other seven from the chlorine atom, and the sodium and chloride ions attract each other in a lattice of ions with a net zero charge

  4. Dissociate in water

Covalent Bonds

  1. Strong chemical bond between two or more atoms

  2. These bonds form when an electron is shared between two elements

    1. Strongest and most common form of biological molecules in our cells

  3. Do not dissociate in water

  4. Nonpolar covalent bonds

    1. Form between two atoms of the same element or between different elements that share electrons equally

    2. Ex. an oxygen atom can bond with another oxygen atom to fill their outer shells

      1. Nonpolar because electrons are equally distributed between each oxygen atom

  5. Polar covalent bonds

    1. Electrons shared by the atoms spend more time closer to one nucleus than to the other nucleus

    2. Unequal distribution of electrons between the different nuclei, a slightly positive (δ+) or slightly negative (δ–) charge develops.

      1. Ex. covalent bonds between hydrogen and oxygen atoms in water are polar covalent bonds

        Diagram depicting polar and nonpolar covalent bonds

Hydrogen Bonds

  1. Attractions that occur between positive and negative charges that do not require much energy to break

  2. Weaker bond than ionic and covalent

    1. Forms when H is covalently bonded to a highly electronegative atom (O, N, F)

    2. The more electronegative atom pulls the shared electrons closer, leaving hydrogen electron-poor and slightly positive (δ+)

    3. That δ+ hydrogen is attracted to δ– regions (usually lone pairs on O, N, or F atoms in nearby molecules)

    4. Results in a hydrogen bond, which is weaker than a covalent bond but stronger than most other intermolecular forces

      1. Ex. the liquid nature of water is caused by the hydrogen bonds between water molecules. Hydrogen bonds give water the unique properties that sustain life. If it were not for hydrogen bonding, water would be a gas rather than a liquid at room temperature.

      Diagram showing hydrogen bonds formed between adjacent water molecules.

      1. Hydrogen bonds can form between different molecules and they do not always have to include a water molecule

      2. Hydrogen atoms in polar bonds within any molecule can form bonds with other adjacent molecules

Van der Waals Interactions

  1. Weak attractions or interactions between molecules

  2. Occur between polar, covalently bonded atoms in different molecules

  3. Weak attractions are caused by temporary partial charges formed when electrons move around a nucleus