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A View of Life

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• The Human Genome Project mapped the complete set of human genes

• Genomics analyses the DNA sequence of an organism

• While genomics will lead to breakthroughs in science, it also raises ethical concerns–Safeguarding the privacy of

genetic information, for example

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•Living organisms composed of cells–Unicellular organisms•Single cell

–Multicellular organisms•Many cells organized to form tissues, organs, and organ systems

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•Cells–Plasma membrane regulates passage of materials

–Specialized molecules (usually DNA) contain genetic instructions

– Internal structures called organelles perform specific functions

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•Types of cells–Prokaryotic cells, exclusive to bacteria and microscopic organisms

–Eukaryotic cells contain a variety of organelles, including a nucleus, which houses DNA

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•Biological Growth– Increase in the size of cells, the

number of cells, or both•Development– Includes all the changes that take

place during an organism’s life–Structures and body form are

adapted to an organism’s functions

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•Metabolic processes–Chemical reactions and energy transformations

–Essential to nutrition, growth and repair of cells, and conversion of energy

–Regulation of metabolic processes maintains homeostasis

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• Stimuli–Physical or chemical changes in

the internal or external environment

–The organism responds to, for example, changes in•Light•Temperature, pressure, or sound•The chemical composition of soil

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• Locomotion–Simpler organisms•Amoeboid movement•The beating of cilia or flagella

–Animals•Move by contracting muscles•Some are sessile and have cilia or flagella

–Plants respond to light, water, etc.

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Asexual and Sexual Reproduction

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• Adaptation–Populations evolve to better

survive–Adaptations•Characteristics that enhance an organism’s ability to survive in a particular environment•May be structural, physiological, behavioral, or a combination

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Biological Organization

Hierarchy

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•The cell–Consists of atoms and molecules

– Is the basic unit of life– In multicellular organisms, associates to form tissues

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• Tissues– In animals, an example is

muscle– In plants, an example is

epidermis• Tissues are organized into

organs• Tissues and organs form

organ systems

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• Population–Members of a species that live in

the same area at the same time• Community–Populations that live together

and interact• Ecosystem–A community and the

environment

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• To carry on life processes, an organism must have–Precise instructions–Communication among cells

• This information is coded and delivered by–Chemical substances–Electric impulses

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•DNA is the large molecule that makes up genes

•Genes specify instructions for making every living organism

•Watson and Crick worked out structure of DNA in 1953

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DNA consists of

twochains of

atomstwisted into

a helix

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•DNA contains “recipe” for proteins

•Proteins determine structure and function of cells and tissues

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• In multi-cellular organisms, communication with and among cells is critical

•Some proteins are important in this communication

•Cell-to-cell communication is a complex process called cell signaling

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• Information transmitted from one part of the body to another is important in regulating life processes

• Information is transmitted by–Hormones–Neurotransmitters and their receptors

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•Evolution is the unifying concept of biology

•Biology–Hierarchical classification scheme

– Identifies the approximately 1.7 million species of living organisms

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•Systematics studies the diversity of organisms and their evolutionary relationships–Taxonomy is the science of naming and classifying organisms

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• Binomial system of nomenclature–Developed in the 18th century by

Linnaeus, a Swedish botanist–Names and classifies organisms–Basic unit is a species–Each species assigned a two-part

name–Genus species

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•Binomial system of nomenclature uses a series of taxonomic categories from species to domain

•Domain, Kingdom, Phylum, Class, Order, Family, Genus, species

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•Each category is more general andmore inclusivethan the onebelow it

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•Natural selection–Theory of evolution developed by Darwin and Wallace

–The Origin of Species by Natural Selection published in 1859

–Sometimes called “survival of the fittest”

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• Natural selection based on four observations–Members of a species show

variation–Organisms produce many more

offspring than will survive–Organisms compete–Only some survive to

reproduce

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Egg masses ofthe wood frog—Many more produced thancan survive

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• Variation among individuals–Result of different varieties of

genes that code each characteristic

–Ultimate source of variation is random mutation•Chemical or physical changes in DNA that can be inherited•Modifies genes

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•Every cell of an organism requires nutrients

•Certain nutrients are used as fuel for cellular respiration

•Virtually all cells carry on cellular respiration

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•A self-sufficient ecosystem contains three types of organisms–Producers–Consumers–Decomposers

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•Ecosystems depend on continuous input of energy

•Organisms can neither create energy nor use it with complete efficiency

•During every energy transaction, some is lost to the environment as heat

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EnergyFlow in an

ecosystem

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•The scientific method involves systematic thought–Deductive reasoning draws conclusions from premises

– Inductive reasoning begins with observations and draws conclusions or extrapolates

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The scientificmethod involvesordered steps:–Observation–Hypothesis–Experimentation (data)

–Conclusion

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