Ancient Organisms

9/9/2019

Ancient Organisms

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How do we know how old things are?

Radiometric Dating: The use of radioactive isotopes as a
measure for determining the age of a rock or fossil

Radioactive isotope: an unstable form of an element that decays
into another element by radiation, that is, by
emitting energetic particles

Half-Life: the amount of time it takes for one half of a substance to decay

Uranium-238: has a half life of 4.5 billion years

Potassium-40: has a half life of 1.3 billion years

Stromatolites: are about 3.5 billion years old, calcareous mound built up
  of layers of lime-secreting cyanobacteria and trapped
  sediment, found in Precambrian rocks as the earliest known
  fossils, and still being formed in lagoons in Australasia.

Prokaryotes: about 3.5 billion years ago, a microscopic single-celled
  organism that has neither a distinct nucleus with a
  membrane nor other specialized organelles.

Prokaryotes include the bacteria and cyanobacteria.

Unicellular organism who lacks membrane bound organelles
DNA not in a nucleus, it just floats around in cytoplasm
much smaller than eukaryotic cells
a prokaryote is about the size of a mitochondria in a eukaryote
single DNA loops

Bacteria and Archaea are prokaryotes, the two domains of prokaryotic life.

Types of Bacteria

Cyanobacteria are a phylum of bacteria that obtain their energy through photosynthesis and are the only photosynthetic prokaryotes able to produce oxygen.

Round bacteria are referred to as cocci (singular: coccus),
- an example is Streptococcus

Cylindrical, capsule-shaped bacteria are named bacilli (singular: bacillus),
- bacteria that make yogurt: Lactobacillus bulgaricus

Spiral bacteria are called spirilla (singular: spirillum)
- Lyme disease and syphillis are caused by this type of bacteria

Flagella: whip-like appendages used to move around, like arms

Pili: short, hair-like appendages extending from the surface, used to stick to surfaces

Capsule: sticky coating, used to stick to surfaces

Cyanobacteria in Fossils

https://www.smithsonianmag.com

https://sciencestruck.com/what-are-stromatolites-how-do-they-form

Pathogenic Bacteria?

Some but not all bacteria are pathogens: a disease causing agent

Some bacteria are purely beneficial and help with symbiosis: the relationship in which two different organisms live together, often interdependently.

Nitrogen Fixation:

Converting atmospheric nitrogen into a form that plants can use to grow
- Two types of bacteria do this job: non-symbiotic bacteria in the soil and symbiotic bacteria that live in the roots of plants.
- Bacteria in the genera Clostridium and Azotobacter are non-symbiotic nitrogen-fixing bacteria.
- The genus Rhizobium are symbiotic bacteria.

Cell Division in Bacteria is Called Binary Fission

https://simple.wikipedia.org/wiki/Binary_fission

Archaea

The other domain of prokaryotic life, tend to live in extreme environments

Grouped according to where they live (pg 371):

Halophiles: live in very salty places
Hyperthermophile: extremely high temperatures (80 to 100 Celcius), (176 to 212 Fahrenheitt)

Archaea in hydrothermal vents:

The sea floor is an anaerobic environment, no oxygen

Serpentinization: H2, hydrogen is formed when mantle rock is exposed to seawater, the rock columns that are formed as gases emerge from the earth's crust in hydrothermal chimneys

Methanogens: archaea that produce methane as a by-product of converting energy from carbon dioxde, using hydrogen H2 as an energy source

Anaerobic Archaea: eat methane

The beginnings of life in hydrothermal vent

The heated fluids rise back to the surface through openings in the seafloor. Hydrothermal fluid temperatures can reach 400°C (750°F) or more, but they do not boil under the extreme pressure of the deep ocean.

As they pour out of a vent, the fluids encounter cold, oxygenated seawater, causing another, more rapid series of chemical reactions to occur. Sulfur and other materials precipitate, or come out of solution, to form metal-rich towers and deposits of minerals on the seafloor.

https://www.whoi.edu/know-your-ocean/ocean-topics/seafloor

Deep Sea Research Affects Engineering today:

https://www.reuters.com/article/us-norway-deep-sea-minerals/

https://www.theguardian.com/environment/2010/aug/31/greenland-greenpeace-arctic-oil-rig

Life in Hydrothermal Vents

Endosymbiotic Theory

Evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms.

That prokaryotes ate a mitochondria and kept it around, some ate a chloroplast and became plants (pg. 391)

Endosymbiotic theory deals with the origins of mitochondria and chloroplasts, two eukaryotic organelles that have bacteria characteristics. Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria, specifically alpha-proteobacteria and cyanobacteria, respectively.

Mitochondria: an organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. It has a double membrane, the inner layer being folded inward to form layers (cristae).

Makes ATP

Mitochondria origin: The endosymbiotic hypothesis for the origin of mitochondria (and chloroplasts) suggests that mitochondria are descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm.

SO Mitochondria and Chloroplasts were bacteria billions of years ago.

They have their own DNA

Mitochondria and chloroplasts have striking similarities to bacteria cells.

They have their own DNA, which is separate from the DNA found in the nucleus of the cell.
And both organelles use their DNA to produce many proteins and enzymes required for their function.

Mitochondrial DNA (mtDNA or mDNA): is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP).

Mitochondrial DNA is double-stranded like cellular DNA in prokaryotes. However it is circular and similar in size and structure to the single DNA loops found in prokaryotes like bacteria.
Mitochondria and Chloroplasts can no longer live outside the eukaryotic cell, and cells cannot live without mitochondria or chloroplasts because that is how they get ATP.

Over millions of years of evolution, mitochondria and chloroplasts have become more specialized and today they cannot live outside the cell.

They are now interdependent/codependent

Cells would only be able to obtain energy from anaerobic respiration (in the absence of oxygen)

So mitochondria helped get archaea out of the hydrothermal vents

Evidence obtained so far indicates that the Bacteria and Archaea diverged from a common ancestor about 3.7 billion years ago, and somewhat later the Archaea diverged from the lineage that would become the Eukarya.

Evidence was found by comparing nucleic acid sequences to discover the evolutionary relationships among microorganisms.
The more alike the rRNA sequences were between two microbes, the more recently they shared an ancestor.
Read more:
http://www.biologyreference.com/ArBi/Archaea.html#ixzz5cZWeYzkr

Around 2 billion years ago, archaea and bacteria found a way to share genes or merge some of their material and a third kingdom of life, eukaryotes, was born.

Mitochondria know both aerobic and anaerobic respiration: When oxygen is present, the mitochondria will undergo aerobic respiration which leads to the Krebs cycle.

However, if oxygen is not present, fermentation of the pyruvate molecule will occur.

Eukaryote

An organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus.
Eukaryotes include all living organisms other than the eubacteria and archaebacteria.