Life 103-week 2
Life 103-week 2 LIFE 103
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This 4 page Class Notes was uploaded by Alexis Darling on Friday January 29, 2016. The Class Notes belongs to LIFE 103 at Colorado State University taught by Jennifer L Neuwald; Tanya Anne Dewey in Fall 2016. Since its upload, it has received 34 views. For similar materials see Biology of Organisms-Animals and Plants in Biology at Colorado State University.
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Date Created: 01/29/16
Week 2 Prokaryotes: Bacteria and Arachaea Eukaryotic cells of domain Eukarya, contains kingdoms protists, fungi, animals, and plants Prokaryotic cells of domains Bacteria and Archaea (the focus of this chapter) *Eukarya and Archaea more closely related than Bacteria Prokaryotes are remarkable in their ability to live in a pH of less than 1 or greater than 12 and temperatures above boiling or freezing. They can photosynthesize, convert N from2 he air into NH (4 king it available to plants), degrade many organic compounds, and utilize iron oxide for respiration, making oxygen unnecessary. Archaea are known as extremophiles because they prefer to live in extreme environments. Extreme halophiles live in super salty environments, and extreme thermophiles live in super hot environments. The most common prokaryotic cell shapes are spheres (“cocci”), rods (“bacilli”), and spirals. Most prokaryotic cells are .55µm, much smaller than eukaryotic cells of 10100µm. Because of their tiny size, we know little about prokaryotes compared to larger organisms. The best way to research them is to grow them in a lab by culturing, but less than 1% of prokaryotes grow artificially. Scientists have recently been studying them by analyzing their DNA. Bacteria make up the majority of prokaryotes that are known about. Physical characteristics of prokaryotes: ▪ Capsule sticky outer layer of sugar of protein which allows cell to adhere to environment, and it protects against immune response ▪ Cell wall for shape, protection, and strength to not explode in hypotonic environment o Bacterial cell walls are made of peptidoglycan chain of sugars interwoven with proteins o Archaea cell walls contain chains of sugars and proteins, but different and not peptidoglycan *Antibiotics target cell walls by keeping the enzyme in bacteria that makes peptidoglycan from producing, resulting in a weakened cell wall that lets membrane break, action called lysis. ▪ Fimbriae similar in appearance to cilia like little hairs off of capsule, allow for better adherence to other surfaces ▪ Nucleoid region where DNA resides ▪ Prokaryotic genome consists of a circular chromosome, and some also contain plasmids which are smaller rings of DNA which can be used for horizontal gene transfer through a sex pilus ▪ Bacterial endospores when cells encounter harsh environments or their nutrients become deficient, they condense their genetic material into endospores which can survive centuries because they remain metabolically inactive (do not require anything). These spores are the hardiest form of life as they remain dormant yet viable (able to reproduce). They ‘wake up’ when in the presence of water and a germination agent, continuing the lineage of that species. ▪ Flagella for motility can react to stimuli and direct their movement Reproduction: Because of the small size of single celled prokaryotes, these organisms can reproduce very quickly, some with a generation time of 20 minutes. They split by way of binary fission, which is an asexual process in which the original cell copies its chromosome and enlarges so that it can split its contents into two separate cells. As they have cell walls, the cells split by a protein band which forms between the divided chromosomes and other cell contents. Genetic Recombination: When DNA from two sources come together in one organism to create a new species. The movement of the DNA is called horizontal gene transfer. Prokaryotes do not give away their entire chromosome, but have plasmids, which replicate separately from the main chromosome, and can easily be released in three methods: ● Transformation when bare DNA fragments are released and taken up by different bacteria (what we did in lab last semester) ● Transduction when DNA is transferred through a bacteriophage (virus) ● Conjugation when one bacteria extends a sex pilus, pulls another bacteria closer and moves plasmid through the tube into the recipient *in order to make a pilus, the cell must have the F factor DNA, which is transferred as part of the plasmid through the pilus so that the recipient can then make a pilus also and continue spreading the gene Nutrition and Metabolism: I: For energy ● phototrophs use sunlight as energy source through photosynthesis ● chemotrophs consume (in various ways) organic molecules and chemical compounds from which they extract energy II: For Carbon ● autotrophs take CO (i2 rganic) from air ● heterotrophs must consume an organic nutrient/carbon from other living things *There can be any combination of these methods of obtaining energy and carbon. Oxygen ● Obligate aerobes are ‘obligated’/must use oxygen in respiration ● Obligate anaerobes absolutely cannot have oxygen, in fact would be poisoned by oxygen, and instead use fermentation as anaerobic respiration ● Facultative anaerobes can use oxygen, but are not dependant on it as they can also complete anaerobic respiration Examples: Methanogens archaea anaerobes, therefore cannot live with oxygen but live in swamps and marshes. They produce methane as a waste product, so we can attribute the past warming of the earth so that it could be inhabitable to them. Pathogens bacteria some cause disease while others have positive effects in humans. Note: it is bad if any of them or any other bacteria became resistant to antibiotics because they could spread the resistance gene and our antibiotics against harmful bacteria would no longer have an effect Eukaryotes: Protista and Algae Most eukaryotes are single celled organisms, but all have organelles surrounded by a membrane with the same structure as the cellular membrane is made of. They also have cytoskeletons that assists in movement and allows them to control their shape. Four Supergroups of Eukarya: 1) Excavata ● Structure includes a groove (think “excavated”/dug out like a trench) which is useful for feeding ● Three monophyletic groups: ○ diplomonads Mitochondria reduced in size and no plastids ○ parabasalids Parasitic (ex: Giardia intestinalis, Thrichomas vaginalisuce Hydrogen gas as byproduct ○ euglenozoans flagella 2) “SAR” clade Grouped because of DNA similarities Made up of: o Stramenophiles= “straw hair”, seen from hairy flagella Includes diatoms (unicellular algae with glass walls), Gold, and Brown Algae (form bigger organisms, therefore more complex) *Huge importance with photosynthesis on Earth o Alreolates= membrane sacs called alveoli lie just under the outer membrance Includes Dinoflagellates (“armored” cells which bloom when proper nutrients are available, causing red tides), Apicomplexans (all have important structure to attack host cells, therefore parasites), and Ciliates (paramecium) o Rhizarians=(think “Rhiz” frizz because many threadlike extensions that look like frizzy hair off of the cells), use pseudopodia and cytoplasmic streaming Includes (in large part) amoebas, cercozoans, radiolarians, forams 3) Archaeplastida All photosynthesize their food Unified by common ancestor that attained a cyanobacteria through endosymbiosis which became a chloroplast Made up of: o Red algae can be found very deep in oceans because they utilize blue light which penetrates farther through the water o Green algae contain nearly the same pigments as land plants, divided into the subgroups of Charophytes (closest to land plants) and Chlorophytes *Algae is crucial as they make up the foundation in the aquatic food web o Land plants probably came from green algae 4) Unikonta Made up of animals, fungi, and most animallike and funguslike protists Contain unreduced mitochondria Divided into o Opisthokonts (the animallike and funguslike protists, and even humans) o Amoebazoans Protists: Any living organism that is not a plant, animal, fungus, or prokaryote “junk drawer of taxonomy” but is being clarified by DNA sequencing, which actually ended the kingdom of Protista. Most are single celled, but all are eukaryotes Symbiotic protists have mutual relationships to benefit and live in other organisms Ex: the symbionts in termites’ digestive system, dinoflagellates in coral Photosynthetic protists extremely important for the photosynthesis on Earth (make up about a third) Additional Vocab: Monophyletic group ancestral species plus all descendants Paraphyletic group ancestral species plus some of descendants Polyphyletic group ancestral species plus all descendants plus other distantly related species
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