Biology- The study of life
A Hierarchy of Organization
Emergent Properties- Novel properties that emerge as each step up the hierarchy of biological order is taken. Reductionism- Reducing complex systems to simpler components that are more manageable to study. Cells- The lowest level of structure capable of performing all the activities of life, all organisms are composed of cells which are the basic units of structure and function. The cell theory- The ability of cells to divide to form new cells is the basis for all reproduction and for the growth and repair of multicellular organisms, including humans. Two Major Kinds of Cells
Eukaryotic cells- Membrane enclosed organelles in which DNA is organized along with certain proteins into structures called chromosomes contained within a nucleus, the largest organelle of most eukaryotic cells. Around the nucleus is a cytoplasm in which are suspended the various organelles that perform most of the cells functions. Plants eukaryotic cells have tough cell walls external to their membranes, while animal eukaryotic cells do not. Prokaryotic cells- DNA is not separated from the rest of the cell in a nucleus, prokaryotic cells lack the cytoplasm organelles typical of eukaryotic cells. Almost all prokaryotic cells have tough external walls. DNA- The substance of genes. The units of inheritance that transmit information from parents to offspring. Nucleotides- Four chemical building blocks that make up strands of DNA. Genome- The entire “library” of genetic instructions that an organism inherits. Open System- An entity that exchanges materials and energy with its surroundings. Energy Conversion- The exchange of energy between an organism and its surroundings involves the transformation of one form of energy to another. Negative Feedback (Feedback inhibition)- slows or stops processes. Positive Feedback- Speeds up a process.
Diversity- Biologists have identified and named about 1.5 million species. Taxonomy- The branch of biology that names and classifies species, formalizes this hierarchical ordering which includes kingdoms and domains. Natural Selection- An editing process, with heritable variations exposed to environmental factors that favor the reproductive success of some individuals over others.
Matter- Anything that takes up space and has mass.
Element- A substance that cannot be broken down to other substances by chemical reactions. Compound- A substance consisting of two or more elements combined in a fixed ratio. Trace elements- Elements required by an organism in only minute quantities, yet indispensible for life. Compound - A pure substance composed of two or more elements combined in a fixed ratio.
Atom- the smallest unit of matter that still retains the properties of an element. Subatomic particles
The three most stable subatomic particles are:
1. Neutrons (neutral)
2. Protons [+1 electrostatic charge].
3. Electrons [-1 electrostatic charge].
Atomic number - Number of protons in an atom of a particular element. Mass number - Number of protons and neutrons in an atom.
Isotopes - Atoms of an element that have the same atomic number but different mass number.
Radioactive isotope - Unstable isotope in which the nucleus spontaneously decays, emitting subatomic particles and/or energy as radioactivity.
Half life - Time for 50% of radioactive atoms in a sample to decay. Dating geological strata and fossils
-Radioactive decay is at a fixed rate.
-By comparing the ratio of radioactive and stable isotopes in a fossil with the ratio of isotopes in living organisms, one can estimate the age of a fossil.
-The ratio of 14C to 12C is frequently used to date fossils less than 50,000 years old.
Electrons - Light negatively charged particles that orbit...