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.