Scientific Theories and Characteristics of Life: Understanding Biological Concepts, Study notes of Biology

Download Scientific Theories and Characteristics of Life: Understanding Biological Concepts and more Study notes Biology in PDF only on Docsity! Chapter 1 Part II Scientific Theories  General explanation of important natural phenomena  Developed through extensive observations & experiments  Results are reproducible and reliable  Still subject to be modified  Nothing is carved in stone  New information & technology  new questions/experiments  Some Biological Theories  Atomic Theory =  Cell Theory =  Theory of Evolution = What is Life?  Not easily defined!  Dictionary definitions  “The quality that distinguishes a vital and functioning being from a dead body”   “The form of existence that distinguishes living organisms from dead organisms or inanimate matter …”   Biologists define life based on a combination of characteristics shared by all living organisms  Non-living organisms may have some, but not all What characteristics define life? 1) Composed of cells 2) Acquire & utilize materials and energy from the environment 3) Grow 4) Reproduce 5) Undergo homeostasis 6) Respond to stimuli 7) Evolve 1) Living Things Are Composed of Cells  Cells = basic unit of life  Cells are complex  Possess elaborate internal structures  Nucleus that contains necessary info  Organelles that carry out specific functions  Protected by a plasma membrane  Controls what goes in and out of cells  Living organisms can be:  Unicellular (single-celled)  Multicellular 2.) Living Things Acquire & Utilize Materials & Energy  Required to:  maintain a high level of complexity  Grow and reproduce  Maintain homeostasis  Acquisition of Materials  Materials = nutrients  Includes: minerals, oxygen, water & chemical building blocks for molecules  Obtained from:  Environment (water, ar, soil)  Other living organisms  Continuously exchanged and recycled  Energy = ability to do work  Necessary to perform various functions  Ex: grow leaves or walk across the room  Ultimately comes from sunlight  Plants & some single celled organisms  Undergo photosynthesis (Chapter 7)  Capture sunlight directly  Store it as energy-rich molecules (e.g. sugars)  Animals & fungi  ingest energy from other organisms (e.g. plants)  Flows through all life forms & released as heat 2.) Living Things Acquire & Utilize Materials & Energy SS 2.) Living Things Acquire & Utilize Materials & Energy 6) Living Things Respond to Stimuli  Necessity for survival  Stimuli arise from both external and internal environments  Animals  Sensory organs enable response to:  External stimuli: light, sound, touch, chemicals, etc.  Ex: A deer’s ears detect the approach of a mountain lion  Internal stimuli: temperature, pain, chemicals, etc.  Ex: Body can detect when blood sugar levels are low  Plants & bacteria  Also capable of responding to stimuli  Ex: Plants in window sill grow towards light  Ex: Intestinal bacteria will move away from harmful substances 7) Living Things Evolve  All about survival & adapting to an environment  Evolution = The genetic make-up of a population changes over time due to natural selection  Variations within populations enhance survival  Ex: Giraffes with longer necks can reach food sources that others cannot  Natural selection dictates which organisms survive  “Survival of the fittest”  Survival = Parent organisms pass down genes to offspring  Genes are segments of DNA  DNA is the molecule of heredity (=blueprint of the organism) BACTERIA ARCHAEA EUKARYA animals fungi plants protists  Evolution has led to a wide variety of organisms  3 domains of living organisms  Bacteria  Archaea  Eukarya  Domain criteria: 1) Cell type 2) Cell number 3) Energy acquisition Categorizing Life 3) Energy Acquisition: Autotroph vs Heterotroph  Autotrophs  “Self-feeding” These organisms make their own nutrients Ex: photosynthetic organisms  Heterotrophs  “Other-feeding” Cannot undergo photosynthesis Acquire energy from other sources by:  Absorbing food molecules from outside their body Or  Ingesting food partciles and digesting them , SS LULU Domain Comparison Table 1-1 Domain Kingdom Cell Type Cell Number Energy Acquisition Bacteria (Under discussion) Prokaryotic Unicellular Autotrophic or heterotrophic Archaea (Under discussion) Prokaryotic Unicellular Autotrophic or heterotrophic Eukarya Fungi Eukaryotic Multicellular Heterotrophic Plantae Eukaryotic Multicellular Autotrophic Animalia Eukaryotic Multicellular Heterotrophic “Protists’”* Eukaryotic Uni- and multicellular Autotrophic or heterotrophic *The “protists” are a diverse collection of organisms that includes several kingdoms under discussion.