1 What is the approximate date of the origin of life on Earth 4 6 GA What is the approximate date of the earliest evidence for life on Earth 3 77 4 32 Ga billion years What is the earliest evidence for life on Earth not sure Some of oldest evidence of life on Earth from microbialites eastern shore of Hudson Bay Canada Microbialites Microbialites benthic deposits formed from microbes precipitated calcium carbonate chalk limestone What is the approximate date for the origin of eukaryotes on Earth 2 1Ga What are microbialites Why are they important for understanding the evolution of life on Earth benthic deposits formed from microbes precipitated calcium carbonate chalk limestone By studying microbialites scientists gain a better understanding of the origins of life early biosphere development and the long term impact of microorganisms on Earth s environment What is a stromatolite type of microbialite What are biofilms Why are they important in terms of the evolution of life on Earth exchange nutrients of microorganisms which adhere to each other on a surface Cooperative interactions in bio lms thought to have aided survival of early prokaryotes in harsh conditions How do biofilms form and what are their characteristics Biofilms are structured communities of microorganisms encased in a self produced extracellular matrix that adheres to surfaces 1 Reversible attachment free oating microorganisms attach toa surface 2 Irreversible attachment extracellular matrix creates irreversible attachment 3 4 Maturation 1 maturation 2 colony grows through cell division addition of other free oating microorganisms multiple layers develop 5 Dispersal bio lm spreads colonizes new surfaces Are biofilms present on Earth today If so give some examples kombucha SCOBY What are the characteristics of prokaryotes In Domains Bacteria Archaea Lack membrane bound organelles Unicellular organisms although can form colonies bio lms etc Smaller than eukaryotic cells Cell walls differ in structure from eukaryotes not all Archaea have cell walls In the history of life on Earth when did prokaryotes evolve Prokaryotes evolved approximately 3 5 to 3 8 billion years ago making them the earliest known forms of life on Earth Fossil evidence such as stromatolites layered structures created by microbial communities suggests that microbial life was already present around 3 5 billion years ago Molecular and genetic evidence indicates that bacteria and archaea the two main domains of prokaryotes diverged early in Earth s history These organisms played a crucial role in shaping Earth s atmosphere particularly through photosynthesis by cyanobacteria which contributed to the Great Oxygenation Event around 2 4 billion years ago Are prokaryotes a monophyletic group No prokaryotes are not a monophyletic group because they do not include all the descendants of a common ancestor Instead they are considered paraphyletic because the group excludes eukaryotes which share a common ancestor with archaea Explain the ubiquity of prokaryotes Prokaryotes bacteria and archaea are the most widespread and abundant organisms on Earth found in virtually every environment from extreme conditions to common ecosystems Their ubiquity is due to their adaptability metabolic diversity and rapid reproduction How do prokaryotes reproduce Prokaryotes reproduce through binary fission Asexual reproduction What are pathogens organisms that cause disease How do Archaea differ from bacteria not sure Cell Membrane Composition Cell walls cell membranes differ chemically from bacteria What are extremophiles What are some specific examples of extremophiles Organisms that can live in extreme environments Thermophiles tolerate extremely high heat Acidophiles tolerate acidic environments Halophiles tolerate high saline environments Methanogens in mammal gut in outside environment produce methane gas e g in flatulence How do Archaea acquire their carbon based nutrition Archaeans can be heterotrophic or autotrophic and Mixotrophic but not photosynthetic Explain why Archaea are important in the human body Plays important role in digestion of polysaccharides e g starch Removes hydrogen from gut to produce methane methanogen aids our extraction of energy from food Major component of human feces Methanobrevibacter smithii Describe the ecological roles of bacteria as outlined in lecture Decomposers decompose organic matter Primary producers photosynthetic bacteria Mutualistic beneficial relationship with other species What are cyanobacteria Are a group of photosynthetic bacteria that live in a variety of environments Photosynthetic bacteria most abundant taxon to have ever existed on Earth first photosynthetic organisms Why are cyanobacteria so important to life on Earth Cyanobacteria produce O 2 as by products of photosynthesis Explain how cyanobacteria are used or have been used as a food source not sure Spirulina as food source for indigenous people Spirulina dihe is important food source for the Kanembu in Chad What was the Great Oxygenation Event Cyanobacteria the Great Oxygenation Event 2 5 Ga Cyanobacteria produced O 2 as byproduct of photosynthesis Explain the difference between autotrophs photoautotrophs chemoautotrophs and heterotrophs Autotrophs create their own food e g photoautotrophs Heterotrophs obtain carbon organic compounds by consuming other organisms also calledchemoheterotrophs Photoautotrophs photosynthetic autotrophs Chemoautotrophs use chemical compounds e g sulfur ammonia as energy sources to synthesize carbohydrates Heterotrophs obtain carbon by consuming other organisms e g decomposers Give an example of autotrophic bacteria and heterotrophic bacteria e g photoautotrophs auto e g decomposers heter What is plankton Describe the types of plankton covered in lecture Plankton diverse group of organisms found in water or air that are unable to propel themselves against a current Marine plankton bacteria archaeans microscopic eukaryotes small drifting animals in ocean plankton can also be in freshwater What is horizontal gene transfer HGT Briefly explain the three ways that HGT can occur Horizontal gene transfer HGT is the movement of genetic material between organisms without reproduction Unlike vertical gene transfer from parent to offspring HGT allows genes to be transferred between unrelated species playing a crucial role in microbial evolution and genetic diversity Transformation introduction uptake expression of foreign genetic material