Standard Biology
Unit 1
Study Guide
A. Introduction to Biology
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Biology is the study of life.
An organism is anything that has or once had all the characteristics of life.
There are 8 characteristics of life:
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Made of one or more cells- all organisms are made of one or more cells. The cell is the basic unit of life.
(A one celled organism is called unicellular and organisms made of many cells are multicellular.
Displays organization- levels of organization begin small and increase in complexity. (Ex. Cells make up
tissues, tissues make up organs, organs make up organ systems, and organ systems make up the
organism).
 Each structure in an organism also has a specific function (Ex. Human eyes are for seeing; ears
are for hearing, etc.)
 Organization means they are arranged in an orderly way.
Grows and develops- every living organism grows and develops.
 Growth-the addition of mass to an organism by the formation of new cells and new structures.
 Development- the process of natural changes that take place during the life of an organism.
 Example: You were not always the same size you are now, you started off as a baby and then
with the formation of new cells you grow each year; you also were not always able to walk so
you have developed that ability over time.
Reproduces- pass along traits from one generation to the next by producing offspring (child or baby).
 Species- a group of organisms that can breed with one another and produce fertile offspring.
Responds to stimuli- all living organisms react to internal and external stimuli.
 Stimulus- anything that is part of either environment and causes some sort of reaction by the
organism.
 Response- the reaction to a stimulus
 Example: if you put a plant near the window it will grow towards the sun in response to the
stimulus of the sun; if you get poked with something sharp you respond to the touch.
Requires energy- living things need sources of energy to fuel their life functions and thus get their
energy from food.
 Example: plants take in sunlight and carbon dioxide to photosynthesis to make their own food;
humans consume other organisms to get energy.
Maintains homeostasis- if anything happens within or to an organism that affects its normal state,
processes to restore the normal state begin (if homeostasis is not restored, death might occur)
 Homeostasis- regulation of an organism’s internal conditions to maintain life.
 Example: humans sweat to cool down the temperature of the body when they are hot; dogs
pant when they are trying to lower their body temperature; some reptiles’ sunbath to increase
their body temperatures.
Adaptations evolve over time- any inherited characteristic that results from changes to a species over
time.
 Example: tropical orchids have roots that are adapted to life in a soil-less environment; humans
were not always able to walk on two legs but over time they have adapted to do this in order to
run away from predators and climb.
B. The Nature of Science:
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Science is a body of knowledge based on the study of nature.
o Relies on evidence- scientific explanations combine what is already known with consistent evidence
gathered from many observations and experiments.
 Theory- an explanation of a natural phenomenon supported by many observations and
experiments over time.
 Examples in biology are the cell theory and the theory of evolution.
o Expands scientific knowledge- science fields are guided by research that results in a constant
reevaluation of what is known which leads to new knowledge that scientists then evaluate.
o Challenges accepted theories- scientists welcome debates about one another’s ideas, disagreements
occur often, and additional investigations and/or experiments are done to either prove or disprove
claims.
o Questions results- observations and data that are not consistent with current scientific understanding
are of interest to scientists which often lead to further investigations.
o Tests claims- scientists make claims based on a large amount of data and observations obtained from
unbiased investigations and carefully controlled experiments.
o Undergoes peer review- science-based information is reviewed by other scientists that are working in
the same field.
 Peer review- process in which procedures and results of an experiment are evaluated by
scientists who are in the same field.
o Uses the metric system- use units in divisions that are powers of ten.
 Makes communication easier since most scientists use the metric system when collecting data
and performing experiments.
 SI- the International System of Units:
 Length- meters
 Mass- grams
 Time- seconds
 Temperature- Celsius
C. Methods of Science:
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Steps of the scientific method:
o Ask a question
o Research or make observations to learn more about the question
o Form a hypothesis
o Design an experiment
o Collect, record, and analyze the data
o Make a conclusion
Observation is a direct method of gathering information in an orderly way.
Inference is a logical conclusion of combining what you know with what you have learned.
Hypothesis is a testable explanation of a situation.
Experiment is an investigation of a phenomenon in a controlled setting to test a hypothesis.
Control group is a group used in an experiment for comparison.
Experimental group is the group exposed to the factor being tested.
An independent variable is the tested factor which could affect the outcome of the experiment.
The dependent variable results from or depends on changes to the independent variable.
A constant is a variable that remains fixed throughout the experiment.
Data is the information gained from observations: quantitative or qualitative.
o Quantitative data is data collected as numbers.
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Qualitative data are descriptions of what our senses detect.
D. The Origin of Life:
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Big bang theory is a theory of how the earth was created.
o The earth is approximately 4.6 billion years old.
o Starts off as an infinitesimal speck (very small) and something (like a meteorite) crashed into it causing it
to expand. The earth is still expanding today.
o Gravity pulled the densest elements to the center of the planet.
o Early history of life is that it was hostile, extremely hot, and no free oxygen.
Spontaneous generation- the idea that life arises from nonlife.
Mid 1800s replaced by the theory of biogenesis- living things can produce other living organisms.
o Pasteur designed an experiment using a curved-neck flask and letting the air in.
Theories of how the first life formed:
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Extraterrestrial origin: meteorites brought the first organic molecules to Earth.
o Asteroid hits bringing amino acids.
Oparin and Haldane: earth’s early atmosphere had gases and molecules could have formed from simple
reactions between the gases and the early oceans.
o UV light and electrical discharge from lightening might have been the primary energy source.
o Primordial soup: Miller and Urey first ones to show simple organic molecules could be made from none
living matter. Gases (elements) + Energy = Amino Acids (the building blocks to proteins)
o CHNOPS: the components that make up 97% of living organisms.
 These are all the ingredients to make “life.”
Hydrothermal volcanic vents theory- some scientists believe that the reactions that created life began in the
deep blue sea where sulfur forms a unique food chain.
Life began about 3.5- 3.8 billion years ago based on the earliest fossils that we have.
Prokaryotic cells- first cells that were unicellular
Eukaryotic cells- didn’t show up until 1.8 billion years ago. Can be unicellular or multicellular and is a more
complex cell
Endosymbiont theory- proposed by Lynn Margulis in 1966 ancestors of eukaryotic cells lived in association with
prokaryotic cells.
o Prokaryotes (act like parasite) might have lived inside eukaryotes and relationship was mutually
beneficial so the prokaryotes became organelles in the eukaryotic cells.