chapter 1 what is life?. life is a condition that distinguishes organisms from inorganic objects,...
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Chapter 1
WHAT IS LIFE?
Life is a condition that distinguishes organisms from inorganic objects, i.e. non-life, and dead organisms.
Why a Rabbit is not a Rock?
All living things exhibit five characteristics in combination.
1. Organization2. Energy use and metabolism3. Maintenance of internal constancy4. Reproduction, growth & development5. Irritability and adaptation
A. Characteristics of Life1. Organization (organisms-
dynamic organization)• chemical (atom -> molecule ->
macromolecule)• organelle• cell• tissue• organ• organ system• multicellular organism
Characteristics of Living Things
Biological organization beyond individual organisms• Population: two or more members
of the same species living in the same place at the same time
• Community: Populations of different species in a particular area
• Ecosystem: The living and nonliving components of an area
• Biosphere: the parts of the planet that can sustain life and the organisms that live there
Levels of biological organization
Chemicals – uniquely in cells-Biochemicals – DNA.
Structure- related to function
Each level of biological organization exhibits emergent properties.
Ex. Capillaries transport blood (property not exhibited by individual endothelial cells).
Functions arise as complexity grows – Emergent Properties
2. Energy Use & Metabolism(All organisms use energy)
Metabolism - biochemical reactions that acquire & use energy.
Why do organisms need energy?• to combat entropy (the tendency
towards disorder)• to build new structures• to repair/break down old
structures• to reproduce
How do organisms obtain energy?
• By extracting energy from the environment
• Producers: get energy from non-living sources
• Consumers: get nutrients made by other organisms
• Decomposers: get nutrients from dead organisms
Life is connected
3. Maintenance of Homeostasis• Homeostasis - the ability of an
organism to maintain its internal environment despite conditions in the external environment.
• Failure to maintain homeostasis can have drastic consequences including death
Ex. Human body temperature is ~98.6ºF• if body temperature rises, you sweat.• if body temperature lowers, you shiver
4. Reproduction, Growth & DevelopmentAsexual reproduction - involves a
single parent; progeny are genetically identical to the parent.
• Often used in unicellular organisms
Sexual reproduction - involves 2 parents; progeny are genetically diverse. Results in diversity in a population.
Continuity of Life in the Environment
Is it essential for an individual to reproduce?
• Not necessarily . . . • The population needs to be
maintainedOrganisms that successfully
reproduce over several generations compose a species
Reproduction – Most obvious of Life’s Characteristics
5. Irritability & AdaptationIrritability - immediate response to
a stimulus. Rapid-transient.
Organisms respond to the Environment
Adaptation - an inherited behavior or characteristic that enables an organism to survive & reproduce.
Diverse & strikingVital to all organisms
Over time, adaptations are modified by natural selection.
Trees with adaptation eventually predominate in the population.
Evolution – essential to life• Genetic change within a
population• Natural selection is one of the
driving forces• Mutations in DNA provide genetic
variation upon which natural selection acts
• An ongoing process
Natural Selection - the enhanced survival & reproductive success of individuals whose inherited traits better adapt them to a particular environment.
Eliminates inherited traits that decrease the chance of survival and reproduction in a certain environment.
BiodiversityLife on earth is diverse, yet similar.
Taxonomists place organisms into groups based upon evolutionary relationships.
Broadest, most inclusive group (taxon) is the domain.
Domain Kingdom Phylum or Division Class Order Family Genus Species
Genus & species refer to the organism’s binomial (name).
Domains & Kingdoms Categorize Life’s Diversity
The Three Domains: (Differences in cellular constituents and organization)
• Bacteria - unicellular prokaryotes• Archaea - unicellular prokaryotes• Eukarya - eukaryotes
• Kingdom Protista• Kingdom Plantae• Kingdom Fungi• Kingdom Animalia
Cell complexity, mode of energy use and acquisition and reproductive mechanisms distinguish the kingdoms.
Cells• All living things are made of cells• All cells come from other cells• Prokaryotic cells (bacteria andarchaea) are simple in form• Eukaryotic cells (Plants, Animals,Fungi, Protists) have well definednuclei and other internal membranouscompartments
Taxonomy - how we name andclassify living things• Species - Felis concolor (mountain lion – America)
– Always two parts to the name– Always italicized or underlined
• Genus - Felis• Family - Felidae• Order - Carnivora• Class - Mammalia• Phylum - Chordata• Kingdom - Animalia• Domain - Eucarya
Human classification scheme:Domain EukaryaKingdom AnimaliaPhylum ChordataClass MammaliaOrder Primates Family HominidaeGenus & species Homo sapiens
Classification
Of gray wolf
•Theories change as knowledge accumulates.
•As knowledge increases, the strength of evidence for theory grows and becomes as law.
•Controlled experiments verify theories.
Scientific Inquiry
C. The Study of LifeScientists study life by using the
scientific method.
OBSERVATION
BACKGROUND KNOWLEDGE
HYPOTHESIS
EXPERIMENT
RESULTS
What is difference between hypothesis, theory & law?
• Hypothesis - “an educated guess”; a tentative explanation of phenomena which is experimentally tested.
• Theory - a widely accepted explanation of natural phenomena; has stood up to thorough & continual testing.
• Law - a statement of what always occurs under certain conditions.
Development of scientific theoryEg: The effects in animals of chemicals
that resemble estrogen hormoneEstrogen-like chemicals in pesticides cause reproductive abnormalities. A. DDT sprayed on crops. B. Birds exposed to this develop malformed beak.
C. Egg shells too fragile to bear the weight during incubation.
Validity can be influenced by:• Sample size• The appropriate use of controls
• A control group is treated like the experimental group except for the one variable being tested
• Placebos are a form of control• Use of double blind studies
SUMMARY
LIFE – five distinct characteristics (organization, energy use and metaboilsm, maintenance of homeostasis, growth, reproduction and development, adaptation)
EVOLUTION- natural selection – driving force
Biodiversity & Taxonomy- classification of living organisms
Study of Life
HOME WORK
1. Write the classification scheme of Jasmine and Banana.
2. What is species?
3. The presence of ___ provides the raw material for evolution.
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