Cells 1.2

• Eukaryotic cells


  Bigger and more elaborate than prokaryotic cells
• Eukaryotes


  • Have the capacity to form more complex structures
  • Unlike the prokaryote which exists mostly as unicellular organisms
• Infoldings of the outer membranes of bacteria

  Extend into the cytoplasm and serve as passageways to the surface
• Endoplasmic reticulum (ER)


  Network of internal membranes in eukaryotes, thought to have evolved from infoldings of bacterial membranes
• Nuclear envelope


  Extension of the ER network that isolates and protects the nucleus
• Endosymbiotic theory


  Suggests mitochondria and chloroplasts in eukaryotic cells were derived from prokaryotic organisms living inside another cell as a symbiont, that eventually evolved to be a part of the eukaryote cell
• Energy-producing bacteria may have come to reside within larger bacteria, eventually evolving into mitochondria
• Photosynthetic bacteria may have come to live within other larger bacteria, leading to the evolution of chloroplasts, the photosynthetic organelles of plants and algae
• Mitochondria and chloroplasts


  • Have their own DNA and ribosomes, which are remarkably similar to those found in bacteria in terms of size and character
• Comparison of structures of a eukaryotic and a prokaryotic cell

  • Size
  • Nucleus
  • Organelles
  • Cell wall
  • Plasma membrane
  • Cytoplasm
  • Ribosomes
  • DNA
• All living things are classified into groups where all individuals share a set of characteristics
• Within each group, living organisms are further divided into smaller groups where individuals have more specific similarities
• Seven levels of classification of living things

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Five recognized kingdoms


  • Monera
  • Protista
  • Fungi
  • Plantae
  • Animalia
• Kingdom Monera


  Prokaryotic organisms under Archaea (lack a peptidoglycan cell wall) and Bacteria with a peptidoglycan cell wall
• Kingdom Protista


  Eukaryotic, primarily unicellular (although algae are multicellular), photosynthetic or heterotrophic organisms
• Kingdom Fungi


  Eukaryotic, mostly multicellular (although yeasts are unicellular), heterotrophic, usually non-motile organisms, with cell walls of chitin
• Kingdom Plantae


  Eukaryotic, multicellular, non-motile, usually terrestrial, photosynthetic organisms
• Kingdom Animalia


  Eukaryotic, multicellular, motile, heterotrophic organisms
• Kingdoms are broken down into phyla, each phylum has a specific set of shared characteristics for its members
• The shared features suggest common ancestry among these organisms
• The universe, in its unfathomable expanse, holds only one planet where life is readily perceived - planet Earth
• The planet Earth is endowed with the perfect recipe to conceive and accommodate life
• Living things on Earth are remarkably diverse
• Living things can be self-sufficient or dependent on other living things for survival
• Living things can flourish on land or underwater
• Living things can reproduce swiftly in seconds or take years to bear offspring
• Despite these dissimilarities, living things are classified as such because they all manifest characteristics of life
• Characteristics of life


  • Orderly structure
  • Organized into basic units called cells
  • Use energy
  • Irritable
  • Develop
  • Reproduce
  • Coded by genes
  • Evolve and adapt to environments
• Cell


  Packet of highly organized living material enclosed by a membrane, basic unit of structure, function, and reproduction in living organisms
• Most organisms depend, directly or indirectly, on energy from the sun
• Green plants use the sun's energy to make food, which supports the plants themselves and all organisms that eat plants
• Organisms use energy to maintain and increase the degree of orderliness of their bodies, to grow, and to reproduce
• Irritability


  Living things respond to external and internal stimuli
• Development


  Living organisms change as they grow in particularly complex ways, directed by heritable programs in genes
• Reproduction


  New cells arise only from the division of other cells, new organisms arise only from the reproduction of other, similar, organisms
• Genes


  Organism's genetic material containing information specifying the possible range of the organism's development, structure, function, and response to its environment
• Evolution


  Descent and modification of organisms from more ancient forms of life, allowing living things to adapt and thrive in changing environments
• Possibilities for the origin of life

  • Special Creation
  • Panspermia
  • Spontaneous Origin
• Special Creation


  Life may have been placed on earth by supernatural/divine forces