Chapter 1 WHAT IS LIFE?

Life is a condition that distinguishes organisms from inorganic objects, i.e. non-life, and dead organisms. organismsinorganic non-lifedead

Why a Rabbit is not a Rock? All living things exhibit five characteristics in combination. 1. Organization 2. Energy use and metabolism 3. Maintenance of internal constancy 4. Reproduction, growth & development 5. Irritability and adaptation

A. Characteristics of Life 1. 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 & Development Asexual 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 maintained Organisms that successfully reproduce over several generations compose a species

Reproduction – Most obvious of Life’s Characteristics

5. Irritability & Adaptation Irritability - 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 & striking Vital 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.

Biodiversity Life 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 and archaea) are simple in form Eukaryotic cells (Plants, Animals, Fungi, Protists) have well defined nuclei and other internal membranous compartments

Taxonomy - how we name and classify 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: DomainEukarya KingdomAnimalia PhylumChordata ClassMammalia OrderPrimates FamilyHominidae Genus & speciesHomo 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 Life Scientists 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 theory Eg: The effects in animals of chemicals that resemble estrogen hormone Estrogen-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.