Living Things
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Biology: defined as “the study of life”
I. Complex Organization
 All living things are complex & highly ordered; from simplest to most complex
 Atom…..molecule…macromolecule…organelle…cell…tissue….organ….organ system
…. organism …. population ….community …. ecosystem ….biosphere
II. Cell: Basic Unit of Structure and Function
 cell is the lowest level of organization capable of performing all activities of life
 all living organisms are composed of cells
o bounded by a plasma membrane (cell membrane) and filled with cytoplasm
o all cells have DNA as the chemical material of genes, our unit of inheritance
 unicellular – single-celled organism, seen only with a microscope
o bacteria, many protists
 multicellular – organism with many cells, each cell an independent living unit
o plants, most fungi, animals
 2 main types of cells:
o Prokaryotic Cell (Prokaryote)
 Lack internal membranes….no nucleus, no membrane-bound organelles
 Contains “loose” DNA (not in a nucleus)
 Unicellular, microscopic……bacteria only
 All have tough external cell walls
o Eukaryotic Cell (Eukaryotes)
 Have a membrane-bound nucleus and membrane-bound organelles
 DNA is found inside of the nucleus
 Some eukaryotes have a cell wall
 Plants have a cell wall; animals do not
III.
Correlation Between Structure and Function
 “Form fits function” : all parts of an organism have specific structures that allow them to
perform their jobs most efficiently
o neurons: have long processes to transmit nervous impulses quickly
IV. Unity and Diversity
 Diversity is enormous….taxonomy - branch of biology that names & classifies organisms
 Ranked from most general to most specific
o Domain …. Kingdom …. Phylum …Class …Order …Family …Genus…..species
 Domain Bacteria – most of common prokaryotes (bacteria)
 Domain Archae – prokaryotes that live in extreme environments (extreme bacteria)
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Living Things
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Domain Eukarya – all eukaryotes
o Protists (multiple kingdoms) - mainly unicellular eukaryotes and their simple
multicellular relatives
 Amoeba, paramecium, euglena
o Kingdom Plantae – multicellular eukaryotes, autotrophic feeding (photosynthesis)
 Plants, grass, some algae
o Kingdom Fungi – multicellular eukaryotes, heterotrophic, absorptive decomposers
 Mold, mushroom, yeast
o Kingdom Animalia – multicellular eukaryotes, heterotrophic, ingestive nutrition
 Animals, humans
Unity is evident at lower levels of organization
o Universal genetic code…….all living things need DNA to reproduce
NOTE: Viruses are not considered by biologists as living things. They are acellular particles
that lack the properties of living things, but do have the ability to replicate inside living cells:
o No cell….no plasma membrane; no energy metabolism; no growth; no waste
products; no response to stimuli; no independent reproduction
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Living Things
V.
Metabolism
 Involves all of the chemical processes within the living organism
 We are a “bag of chemicals” and chemical reactions
 What do we use for energy? food
VI.
Responsiveness
 All living things respond to stimuli in the external environment
 E.g. changes to light, heat, sound, chemical and mechanical stimuli
 To detect stimuli, organisms must have a nervous system and sensory equipment
 To respond to stimuli, an organism must coordinate its responses
o Uses nerves, hormones, glands, muscles, brain
o Energy is used in the process
VII. Growth and Development
 Requires an organism to take in material from the environment and transform it into its
own structures
 To accomplish this, the organism must use some of the energy it has acquired during
metabolism
 Instructions for growth and development: encoded in DNA
VIII. Reproduction
 Biogenesis, which means that “life comes from life”
 Sexual reproduction: two parents contribute to the formation of a new individual
o During this process, a combination of new traits can be produced
 Biological instructions are encoded in the nucleotide “alphabet” of DNA
(deoxyribonucleic acid)……..A, T, C, and G
o DNA found in every living cell, except mature RBC
 Inheritance is based on copying the DNA, passing the info from parents to offspring;
DNA sections carry the secret code for protein production by being “transcribed” or
copied into RNA and then “translated” into the appropriate proteins.
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Living Things
VIII. Regulation
 Feedback mechanisms regulate biological systems; done to maintain homeostasis
o Keeping internal systems the same or steady state
o Kidneys; shivering; sweating
 Can have both positive or negative feedback; negative feedback….turns off a process
o Positive feedback….continues a process
X. Evolution
 All life connected; traced back to primitive/old bacteria – more than 3 billion years ago
 Life evolves (changes) to be better adapted to their environment
 Puts us on a branching “tree of life”…..species very similar share a common ancestor at
recent branch points; e.g. horse and zebra
 Father of Evolution : Charles Darwin (1859); Published the book “On the Origin of
Species by Means of Natural Selection”
 5 characteristics of evolution
o variation, overpopulation, competition, survival of fittest/camouflage.....now
called natural selection, reproduction/inheritance.........now called natural selection
 Evolutionary change – species change over time
o Darwin called this “descent with modification”; this point has been proven
 Natural selection – being best suited to the environment; thought to be the mechanism of
evolutionary change (often called “survival of the fittest" or camouflage)
o Different reproductive success (those who are best suited to their environment
will live long enough to reproduce & put their genes into the next generation of
the population)…Note: Only populations can evolve; this point can’t be proven
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Living Things
Nuevo Vallarta, Mexico, 2012..........sand crab
XI. Scientific Process…..Involves hypothetico-deductive method
 Hypothesis: educated guess……uses inductive reasoning
o Go from specific observations to general conclusions
o “It rained today, Monday, and last Monday; therefore, it must rain every
Monday”
 Deductive reasoning......used to make predictions; “If….then” logic; go from general
ideas to specific predictions; “If it’s cloudy, then it will rain today”
o After repeatedly testing and having test support hypothesis, the hypothesis may
become a “Theory”
 5 steps to a systematic approach to answering questions:
o observe
o hypothesize
o experiment
o gather data
o conclude
Evolutionary adaptation: The Spanish dancer moves through ocean water by “dancing”…..it is
actually undulating the bright red ruffles that run along its body. What is it? It is actually a sea
slug.
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