Unit 2 Review

• Emergence


  Properties or behaviors that emerge only when parts interact as a whole
• Fitness


  Measure of survival and reproduction of a trait or genotype
• Phenotype


  Observable characteristic or trait
• Anthrocentrism is a human-centered perspective
• Fixation


  Permanent establishment of trait, gene, or genotype
• Convergent Evolution


  Appearance of similar traits NOT due to a common ancestor
• Microbial Mats are the earliest evidence of life on Earth (that more scientists agree on)
• Microbial Mats


  • Multilayered sheets of prokaryotes
  • Each layer is dominated by specific types of microorganisms
  • Creates food chain in the mat
• 3 Classes of Multicellularity in Bacteria: Filaments

  • Formation of long chains of cells, some of which elongate but do not divide
  • Linear or branched
  • Single or multiple layers
  • Many clonal in origin
• 3 Classes of Multicellularity in Bacteria: Aggregates


  • Cells embedded in self-produced extracellular matrix
  • Biofilm or swarms
  • Cells have distinct morphologies
  • Can be clonal or non-clonal
• 3 Classes of Multicellularity in Bacteria: Multicellular Magnetotactic Prokaryotes (MMP)


  • Magnetotactic-Orient themselves to Earth's magnetic field
  • Joined at tight intercellular junctions
  • Division by fission of entire structure
  • Only OBLIGATE multicellular bacteria
• All matter is subject to the physical laws of the universe
• Fitness


  An organism's ability to pass on its genetic material to the next generation
• Traits must allow an organism to survive and reproduce in its environment
• Life has additional constraints based on fitness compared to non-living matter
• Multicellularity enables new possibilities


  • Cell Differentiation
  • Division of labor to more efficiently use resources
  • Development of Structures at Different Times (Cells -> Tissues -> Organs > Organ Systems)
• Multicellularity has implications to intelligence and consciousness
• Advantages of Multicellularity

  • Resistance to Stress (temperature, pH, osmotic pressure)
  • Resistance to Predators (bigger-easier to resist engulfment)
  • Improved Nutrient Acquisition (better at catching and consuming prey)
  • Division of Labor (leads to cell specialization, more efficient use of resources)
• Disadvantages of Multicellularity


  • Energetic Costs (multicellular organisms can't get energy from just diffusion)
  • Physical Limitations (less freedom of movement)
  • Need to Resolve Conflict between Cells (what to do with "cheater" cells, need to make adhesive and communication molecules)
• Cell


  Basic structural and functional unit of life
• Tissue


  Ensemble of similar cells that together carry out a specific function
• Differentiation


  Cell or tissue specialization
• Adhesion


  Cells interact and adhere with neighboring cells
• Morphology


  Form and structure of organisms
• Simple Multicellularity


  • Adhesive molecules to maintain unified structure
  • Limited signaling and sharing of resources between cells
• Complex Multicellularity


  • Adhesive molecules to maintain unified structure
  • Organized signaling and resource sharing
  • Tissue differentiation (specialized tissues) and programmed cell death
• Unicellular organisms can only exchange gases through diffusion (passive) and are limited in size by ambient pressure of O₂
• How multicellular organisms transport oxygen

  1. Cells

  2. Tissues

  3. Organs

  4. Organ Systems
• Complex multicellular organisms require organized and hierarchical body plans
• Many plants and animals use bulk transport to transport oxygen
• Bilaterian animals mostly have well-developed circulatory and respiratory systems
• Tight junctions: form a seal that nothing, not even ions, can pass through
• anchoring junctions: hold adjacent cells together
• gap junctions: allow for direct chemical communication across cells
• the program of development is a genetic program that is a well defined network of genes that are activated in a specific order
• transcription factors tell which genes to be turned off and on
• lots of genes are needed for complex multicellularity
• need transcription to start at different parts of the body
• evolution can not predict the future
• ancestral; found in common ancestor and group of organisms