Term
| When did life appear on earth? |
|
Definition
The Archean Ion 3.8-2.5 Billion Years Ago |
|
|
Term
|
Definition
| Life is defined as an organized genetic unit capable of metabolism, reproduction, and evolution or a self-sustained chemical system capable of undergoin Darwinian evolution. |
|
|
Term
| What are the minimal properties of life? |
|
Definition
| Metabolism, reproduction, and evolution. |
|
|
Term
| Organic Molecules are made by living organisms, so where did the first organic molecules come from? |
|
Definition
There are three theories: 1. On meteroties- organic molecules formed in interstellar clouds. Organic Molecules created by physicial processes outside of living cells came first. 2. Atmospheric reactions with lightning, solar and cosmic radiation (Reducing Atmosphere Hypothesis) 3. Underwater reactions with volcanic cents (Deep Sea Vent Hypothesis) |
|
|
Term
| Describe the Reducing Atmosphere Hypothesis: |
|
Definition
Earth's early atmosphere was anoxic, meaning withoutfree oxygen. Before about 1.9 billion years ago the Earth's atmosphere was a reducing mixture of N2, CH4, H2O, and possibly NH3. Solar radiation and lightning discharge into the reducing gas mixture are believed to have produced natural organic compounds and eventually life itself. |
|
|
Term
| According to the Reducing Atmosphere hypothesis, how did modern life come about? |
|
Definition
| A gradual building up of these complex organic molecules in the ocean would have formed a phospholipid bilayer. As these protobionts or protocells form they can perform (non-living) simple metabolic reactions which can become more complex through horizontal gne transfer. Suggests that protobionts formed spontaneously in the primordial soup. |
|
|
Term
| Whar are some criticisms of the reducing atmosphere hypothesis? |
|
Definition
-It has not been proven experimentally. That is, nucleic acids have never been shown to form through non-living processes. -Organic molecules may have been too dilute to be effectively incorporated into protobionts. -Organic molecules of the type useful for living cells are not that stable in water and probably broke down rapidly. -Chances of the right kinds of molecules forming randomly are very small. |
|
|
Term
| Describe the Deep Sea Vent Hypothesis (also known as the Iron-Sulfide World Hypothesis): |
|
Definition
Life first formed in tiny cavities in volcanic rock around underwater vents. -Energy supplied by reduced H2 and sulfur compounds (oxidation energy as a source for metabolism). -Catalysis was provided by iron compounds in the rocks, and simple organic molecules were produced. |
|
|
Term
| How did enzymes and DNA come about? |
|
Definition
RNA molecules called ribozymes can serve a enzyme-like catalysts that can self-replicate. -Energy for metabolic reactions may have been embedded in the cell membrane or captured by pigments; through oxidation of minerals like hydrogen sulfide. |
|
|
Term
| What was the nature of the energy crisis that developed during the earliest period of cellular evolution and how was it solved? |
|
Definition
Energy is required for cellular reactions. -The first organics took to chemoautotrophy and used energy from inorganic compounds to drive carbon fixation (carbon reduction). -CO2 is the universally accepted source of carbon. |
|
|
Term
| How long did it take to evolve from non-living systems? |
|
Definition
First fossil evidence of living cells is about 3.5 billion years old, and these were probably photosynthesizers. -Oxygen from photosynthetic begins to build up in the seas and atmospheres , aeorobic respiration evolves. -First eukaryotic cells show up around 2.1 billion years ago. -Life on land begins around 430 million years ago. |
|
|
Term
|
Definition
| layered rocks that form when certain prokaryotes bind thin films of sediment together. |
|
|
Term
| What are the three main branches of life? |
|
Definition
| Eubacteria, archaea, and eukarya |
|
|
Term
| What are common features of prokaryotic organisms (Bacteria and Archaea)? |
|
Definition
-Genes located on a single circular chromosome and sometimes on similar plastids. -Chromosomes not seperated into a membrane-bound nucleus. -No membrane-bound organelles or endoplasmic reticulum -Ribosomes embedded in the cytoplasm -No cytoskeleton -No mitosis, meiosis, or gametes -Flagella, if present, are a simple protein filament that rotates at its base. These cells reproduce by budding or binary fission (asexual) |
|
|
Term
| What are characteristics of bacteria? |
|
Definition
[image]
-Cell walls regulate the osmotic pressure
-The bacterial cell wall is made-up primarily of peptidoglycan.
-Pili allow bacteria to stick together to a substrate or each other. |
|
|
Term
| What is the difference between gram-positive and gram-negative bacteria? |
|
Definition
[image]
Gram-positive bacteria have a think wall of peptidoglycan while gram negative bacteria have a thinner wall with an additional outer phospholipid membrane. |
|
|
Term
| Why are internal membrane systems found in aerobic and photosynthetic bacteria? |
|
Definition
-Respiratory membrane folds the cytoplasm to expand the surface area needed for aerobic respiration.
-Thylakoid membranes also need an increase in surface area to perform reactions. |
|
|
Term
| Describe how bacteria occur as solitary cells, colonies, spores, or filaments: |
|
Definition
| Colonies occur when dividing cells remain embedded within a polysaccharide sheath. Filaments form when cells divide but remain connected together in long chains (found typically in photosynthetic cells). Bacteria may form spores under adverse conditions, spores are resting cells that typically have a hard dormant wall and ar useful for dispersal and survival. |
|
|
Term
| How do simple bacterial flagella work? |
|
Definition
| The basal body of the bacterial flagellum rotates, whipping the slender filament around like a propeller. |
|
|
Term
| Describe the three different ways bacteria can be exchanged (independent of reproduction or cell division): |
|
Definition
Transformation- bacteria can absorb DNA from remains of other bacteria.
Transduction- DNA transmitted from one bacterium to another via viruses (horizontal gene transfer).
Conjugation- two bacteria join together via specialized pili and exchange plasma (sex pili). |
|
|
Term
| How do prokaryotes exchange and obtain energy and raw materials? |
|
Definition
| Chemo and photo- hetero and autotrophs |
|
|
Term
| Describe nitrogen-fixation by bacteria and its importance to the ecosystem: |
|
Definition
Nitrogen-fixation is the reduction of nitrogen gas (N2) into ammonia (NH3) which can be used by plants to make amino acids.
This is an energy requiring process accomplished by specialized heterotrophic bacteria, such as rhizobium.
Some nitrogen-fixing bacteria are free-living in the soil, but rhizobium has a symbiotic relationship with members of the legume family. |
|
|
Term
| Describe the nitrogen cycle: |
|
Definition
| Chemoautotrophic bacteria obtain energy by oxidizing ammonia to nitrite to nitrate. Anaerobic bacteria use nitrate as an electron acceptor for respiration. |
|
|
Term
|
Definition
Photosynthestic bacteria that produce oxygen as a by product, just like higher plants.
Both photosynthetic and nitrogen fixing. Main sources of N2. 30% of all photosynthesis on the planet. |
|
|
Term
| Describe the branch of life Archaea: |
|
Definition
-No peptidoglycan -Branched hydrocarbons in membrane -Differents in RNA and protein synthesis -Histones associated with chromosomes (shared with Eukaryotes) -Called Extremophiles |
|
|
