Chapter 1

Biology, the Study of Life

Scientific Method

• 1. Observation• Using senses• Learning from other scientists in the field

• 2. Create Hypothesis• Based on existing knowledge• If not supported, it can be

– Modified– Rejected

• Must be testable– Morals and religious beliefs are not always testable

• 3. Experiments and more observations• Experimental variable

– What is changed in experiment

• Test groups– Exposed to experimental variable

• Control group– Not exposed to experimental variable

• Model– Sometimes used in place of actual object

» Computer software» Mice instead of humans

• Data– Results of experiments and observations– Correlation does not indicate causation

• 4. Conclusion• Is hypothesis supported by data or not• If not supported, propose new hypothesis• CANNOT prove anything in science, only support• Experiments and observations must be repeatable

by other scientists

• Scientific Theory• Ultimate goal of science• Accepted explanations for how the world works

Observation

Hypothesis

Experiment/

Observation

Conclusion

Scientific Theory

Sample Experiment – Growing plants in presence of salt

• Observation – Previous research, fields irrigated with saltwater are lifeless

• Hypothesis – As the concentration of salt in the soil increases, the amount of plant growth will decrease

• Experiment – Include replicates Control Pots Test Pots I Test Pots II Water Only 5% Saltwater 10% Saltwater

• Results

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Control 5% Saltwater 10% Saltwater

Treatment

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Average Growth of Plants watered with Varying Salt Concentrations

• Conclusion – Hypothesis is supported. Data illustrates that as salt concentration of water increased, plant growth decreased.

• Follow-up Experiment – Perform the same experiment with plants that live along the ocean shore.

• Follow-up Results

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Control 5% Saltwater 10% Saltwater

Average Growth of Plants watered with Varying Salt Concentrations

Treatment

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mm

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• Follow-up Conclusion – Possible that different plants are affected in different ways when exposed to salt. Native environment may play a large role.

Five Basic Theories of Biology

Theory• Cell

• Gene

• Evolution

• Homeostasis

• Ecosystem

Concept• All organisms are composed of cells, and

new cells only come from preexisting cells• All organisms contain coded information that

dictates their form, function, and behavior• All organisms have a common ancestor, but

each is adapted to a particular way of life• All organisms have an internal environment

that must stay relatively constant within a range protective of life

• All organisms are members of populations that interact with each other and with the physical environment within a particular locale

Levels of Biological Organization

• Atom– Smallest unit of an element (protons, electrons, neutrons)

• Molecule– Two or more atoms of same or different elements

• Cell– Structural and functional unit of all living things

• Tissue– Group of cells with a common structure and function

• Organ– Tissues functioning together for a specific purpose

• Organ System– Several organs working together

• Organism– Individual complex individual containing organ

systems

• Population– Organisms of same species in particular area

• Community– Interacting populations in a particular area

• Ecosystem– Community plus physical environment

• Biosphere– Crust, water, and atmosphere inhabited by living

things

Cells are the Fundamental Unit of Living Things

• Cell Theory– Cells are the fundamental unit of living things– Cells come from other cells

• Split• Sexual reproduction

– Cells use materials and energy• Sun is the ultimate source of energy – allows

plants to grow, which provides animals with food

Organisms have a Genetic Inheritance

• Gregor Mendel– Father of genetics– Performed experiments with pea plants and

inheritance– Genes – units of heredity

• James Watson and Francis Crick

– Genes are composed of DNA

• Gene Theory– Genes are hereditary units composed of DNA– Genes control the structure and function of

cells and organisms

• Gene theory applications– Study metabolism at molecular level– Who is related to whom– Species conservation– Genetic testing for diseases

Organisms Regulate their Internal Environment

• Theory of Homeostasis– Cells and organisms have an internal

environment– Cells regulate this environment so that it stays

fairly constant

• Examples– Body maintaining blood sugar levels– Reptiles using sun to regulate temperature– Plants bending towards sunlight

• Response to stimuli – this ability assists the homeostatic ability of organism– Vulture detecting carcass

• For food

– Monarch butterfly sensing fall• Time to migrate

– Plant bending towards sun• For photosynthesis

– Animal running away from danger• For survival

The Biosphere is Divided into Ecosystems

• Theory of Ecosystems– Organisms form units in which they interact

with the biotic (living) and abiotic (nonliving) components of the environment

• Biosphere– Climate (temperature and precipitation)

determines where ecosystems are found in biosphere

• Ecosystems characterized by – Chemical cycling

• Chemicals move from one population to another in a food chain

• Death and decomposition return nutrients back to the soil to be used by plants again

– Energy flow• From sun to plants to other members of the food

chain• Gradually dissipates, does not cycle• Photosynthesizers required to absorb energy

The Ancestry of Species can be Determined

• Theory of Evolution– Organisms have shared characteristics due to common descent– Evolutionary tree

• Traces the ancestry of a group to a common ancestor

– Ways to trace evolution• Molecular data• Fossil record• Anatomy and physiology of organism• Embryonic development of organism

Remember: species evolve, not individuals

Evolutionary Relationships help Biologists Group Organisms

• Organizing Diversity– Taxonomy

• Identifying and grouping organisms according to certain rules

– Classification categories• Least inclusive to most inclusive• Species, genus, family, order, class, phylum,

kingdom, and domain

• Domains – 3 domains– Archaea

• Live in harsh environments• Prokaryotes

– Bacteria• Live in more common

environments• Prokaryotes

– Eukarya• Eukaryotes• Protists, fungi, plants, and animals

• Scientific Names– Binomial nomenclature

• 2 part name• Genus and specific epithet (descriptive term)• Phoradendron tomentosum or P. tomentosum• Scientific names are Latin and universally used to

avoid confusion

Evolution through Natural Selection Results in Adaptation to the Environment

• Charles Darwin– Father of evolution– Concluded that natural selection

is the process that makes modification

(adaptation) possible

• Natural selection– Some aspects of the environment selects which traits

are more apt to be passed on to the next generation– Mutations fuel natural selection because they produce

variation

Plant typically produces smooth leaves

Mutation causes leaves to be covered with hairs

Deer prefer to eat smooth leaves

Hairy leaves have an advantage

Generations later, most of those plants produce hairy leaves

Evolution’s Many Applications

• Agriculture– Artificial selection of crops and livestock for high yield

in a short amount of time– Pesticide use selects for resistant insects

• Medicine– Antibiotic use selects for resistant bacteria

• Conservation– Bacteria converting corn to ethanol, select for most

efficient– Endangered species breeding

Evolution from a Common Ancestor Accounts for the Characteristics of Life

1. Life is organized

2. Life uses materials and energy

3. Life reproduces

4. Life is homeostatic

5. Life responds to stimuli

6. Life forms ecosystems

7. Life evolves