BIOL 191 Exam 2 ch. 24 - 29

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Hypothetical steps in the origin of simple cells

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Hypothetical steps in the origin of simple cells

  1. abiotic synthesis of small organic molecules

  2. joining of these small molecules into macromolecules packaging of molecules into protocols, membrane-bound droplets that maintain a consistent internal chemistry

  3. The packaging of these molecules into protocells, droplets with membranes that maintained an internal chemistry different from that of their surroundings

  4. The origin of self-replicating molecules that eventually made inheritance possible

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Miller and Urey experiment

in 1953, Miller and Urey showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible, or the first organic compounds may have been synthesized near volcanoes or deep-sea vents, or organic molecules have also been found in meteorites

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Proposed role of RNA in early life

The first genetic material was most likely RNA, not DNA. RNA plays a central role in protein synthesis, but it can also function as an enzyme-like catalyst. Such RNA catalysts are called ribozymes. Some ribozymes can make complementary copies of short pieces of RNA, provided that they are supplied with nucleotide building blocks.

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General characteristics of prokaryotes

Most prokaryotes are unicellular, although some species form colonies; Most prokaryotic cells have diameters of 0.5–5 μm, much smaller than the 10–100 μm diameter of many eukaryotic cells; Prokaryotic cells have a variety of shapes; The three most common shapes are spheres (cocci), rods (bacilli), and spirals

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Cell wall

maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment; Eukaryote cell walls are made of other materials: Plants – cellulose, Fungi - chitin

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peptidoglycan

a network of modified sugars cross-linked by polypeptides

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Gram-positive bacteria

have relatively simple walls composed of a thick layer of peptidoglycan

<p>have relatively simple walls composed of a thick layer of peptidoglycan</p>
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Gram-negative bacteria

have less peptidoglycan and an outer membrane that can be toxic; Gram-negative bacteria are more likely to be antibiotic resistant

<p>have less peptidoglycan and an outer membrane that can be toxic; Gram-negative bacteria are more likely to be antibiotic resistant</p>
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Capsule

The cell wall of many prokaryotes is surrounded by a sticky layer of polysaccharide or protein

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Endospores

Some bacteria can develop resistant cells; Dormant reproductive form of the bacterium

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Fimbriae

allow them to stick to their substrate or other individuals in a colony

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Pili

(sex pili) longer than fimbriae and allow prokaryotes to exchange DNA

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Taxis

the ability to move toward or away from a stimulus ex. Chemotaxis is the movement toward or away from a chemical stimulus (positive or negative)

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Internal organization

Prokaryotic cells lack the complex compartmentalization associated with the membrane- enclosed organelles found in eukaryotic cells. However, some prokaryotic cells do have specialized membranes that perform metabolic functions. These membranes are usually infolding of the plasma membrane.

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Nucleoid

unlike eukaryotes, prokaryotes lack a nucleus; their chromosome is located in the nucleoid, a region of cytoplasm that is not enclosed by a membrane

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Plasmids

in addition to its single chromosome, a typical prokaryotic cell may also have much smaller rings of independently replicating DNA molecules

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Nutritional modes

Photoautotrophy, chemoautotrophy, photoheterotrophy, and chemoheterotrophy

<p>Photoautotrophy, chemoautotrophy, photoheterotrophy, and chemoheterotrophy</p>
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Anaerobic respiration

Substances other than O2, such as nitrate ions(NO3-) or sulfate ions(SO4 2-), accept electrons at the "downhill" end of electron transport chains

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Nitrogen fixation

Some cyanobacteria and some methanogens (a group of archaea) convert atmospheric nitrogen (N2) to ammonia (NH3) Essential component of nitrogen cycles in ecosystems

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Heterocysts

In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocysts (or heterocytes) exchange metabolic products

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Biofilms

In some prokaryotic species, metabolic cooperation occurs in surface-coating colonies

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Reproduction

Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours Key features of prokaryotic biology allow them to reproduce quickly: They are small, They can reproduce by binary fission (asexual), They have short generation times Short generation times = relatively rapid evolution

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Transformation

A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process

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Transduction

the movement of genes between bacteria by bacteriophages (viruses that infect bacteria)

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Conjugation

the process where genetic material is transferred between prokaryotic cells Ex. Via a sex pilus

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Chlamydias

These parasites can survive only within animal cells, depending on their hosts for resources as basic as ATP

<p>These parasites can survive only within animal cells, depending on their hosts for resources as basic as ATP</p>
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Spirochetes

These helical gram-negative heterotrophs spiral through their environment by means of rotating, internal, flagellum-like filaments

<p>These helical gram-negative heterotrophs spiral through their environment by means of rotating, internal, flagellum-like filaments</p>
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Cyanobacteria

These gram-negative photoautotrophs are the only prokaryotes with plantlike, oxygen-generating photosynthesis

<p>These gram-negative photoautotrophs are the only prokaryotes with plantlike, oxygen-generating photosynthesis</p>
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Gram-positive bacteria

Gram-positive bacteria rival the proteobacteria in diversity

<p>Gram-positive bacteria rival the proteobacteria in diversity</p>
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Extremophiles

The first prokaryotes assigned to domain Archaea live in environments so extreme that few other organisms can survive there

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Extreme halophiles

live in highly saline environments, such as the Great Salt Lake and the Dead Sea

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Extreme thermophiles

thrive in very hot environments

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Methanogens

archaea that release methane as a by-product of their unique ways of obtaining energy. Many methanogens use CO2 to oxidize H2, a process that produces both energy and methane waste

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Decomposers

breaking down dead organisms and waste products

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Symbiosis

an ecological relationship in which two species live in close contact: a larger host and smaller symbiont

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Mutualism

an ecological interaction between two species in which both benefit

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Commensalism

an ecological relationship in which one species benefits while the other is not harmed nor helped in any significant way

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Parasitism

an interaction in which a parasite eats the cell contents, tissues, or body fluids of its host

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Pathogens

Parasites that cause disease are known as pathogens, many of which are prokaryotic.

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Endosymbiosis

a symbiotic relationship in which one organism lives inside the body or cell of another organism

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Endosymbiont theory

proposes that mitochondria and plastids were formerly small prokaryotes that began living within larger cells

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Excavata

Some members of this supergroup have an "excavated" groove on one side of the cell body

<p>Some members of this supergroup have an &quot;excavated&quot; groove on one side of the cell body</p>
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Euglenozoa

A diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, and parasites The main feature distinguishing them as a clade is a spiral or crystalline rod inside their flagella Some species can be both autotrophic and heterotrophic

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SAR

The “SAR”clade is a diverse supergroup named for the first letters of its three major clades, stramenopiles, alveolates, and rhizarians

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Stramenopiles

Some of the most important photosynthetic organisms on Earth

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Diatoms

highly diverse, unicellular algae; have a unique two-part, glass-like wall of silicon dioxide (SiO2)

<p>highly diverse, unicellular algae; have a unique two-part, glass-like wall of silicon dioxide (SiO2)</p>
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Brown algae

largest and most complex algae All are multicellular, and most are marine

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Alveolates

subgroup of the SAR clade that have membrane-bounded sacs (alveoli) just under the plasma membrane ex. Dinoflagellates and ciliates

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Dinoflagellates

have two flagella, and each cell is reinforced by cellulose plates

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Ciliates

a large varied group of protists, are named for their use of cilia to move and feed

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Rhizarians

Subgroup of SAR clade. many species of amoebas, most of which have pseudopodia that are threadlike in shape

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Forams

Threadlike pseudopodia extend through the pores in the test

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Tests

porous shells

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Archaeplastida

the supergroup that includes red algae, green algae, and land plants

<p>the supergroup that includes red algae, green algae, and land plants</p>
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Red algae

reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll

<p>reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll</p>
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Green algae

a structure and pigment composition much like the chloroplasts of plants

<p>a structure and pigment composition much like the chloroplasts of plants</p>
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Unikonta

This supergroup of eukaryotes includes amoebas that have lobe- or tube-shaped pseudopodia, as well as animals, fungi, and non-amoeba protists that are closely related to animals or fungi

<p>This supergroup of eukaryotes includes amoebas that have lobe- or tube-shaped pseudopodia, as well as animals, fungi, and non-amoeba protists that are closely related to animals or fungi</p>
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Amoebozoans

amoebas that have lobe- or tube-shaped pseudopodia

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Protists

Protists can be single or multi-celled; Most are unicellular Protists are found in diverse moist environments Some protists reproduce asexually, while others reproduce sexually; All three* sexual life cycles found in protists Protists show a wide range of nutritional diversity; Can be photoautotrophs, heterotrophs, or mixotrophs

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Derived traits of land plants

Alternation of generations life cycle Multicellular, dependent embryos Walled spores produced in sporangia Apical meristems

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Alternation of generations life cycle

each generation gives rise to the other; this type of reproductive cycle evolved in various groups of algae but does not occur in the charophytes, the algae most closely related to plants

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Embryophytes

The multicellular, dependent embryo of plants is such a significant derived trait that plants

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Sporangia

multicellular organs that produce spores; Spore walls contain sporopollenin

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Apical meristems

localized regions of cell division at the tips of roots and shoots

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Cuticle

a waxy covering of the epidermis that functions in preventing water loss and microbial attack

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Stomata

specialized pores that allow the exchange of CO2 and O2 between the outside air and the plant

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Chitin

a strong but flexible polysaccharide

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Yeasts

single cells

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Mycelia

networks of branched hyphae

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Hyphae

filaments adapted for absorption

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Haustoria

allow them to extract or exchange nutrients with plant hosts

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Mycorrhizae

mutually beneficial relationships between fungi and plant roots

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Ectomycorrhizal fungi

form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex

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Arbuscular mycorrhizal fungi

extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane

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Chytrids

found in freshwater and terrestrial habitats Chytrids have flagellated spores and are thought to have diverged early in fungal evolution

<p>found in freshwater and terrestrial habitats Chytrids have flagellated spores and are thought to have diverged early in fungal evolution</p>
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Zygomycetes

include fast-growing molds, parasites, and commensal symbionts Produce a resistant zygosporangium

<p>include fast-growing molds, parasites, and commensal symbionts Produce a resistant zygosporangium</p>
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Glomeromycetes

form arbuscular mycorrhizae with plant roots About 80% of plant species have mutualistic relationships with glomeromycetes

<p>form arbuscular mycorrhizae with plant roots About 80% of plant species have mutualistic relationships with glomeromycetes</p>
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Ascomycetes

live in marine, freshwater, and terrestrial habitats Called the sac fungi Produce spores in sacs called asci

<p>live in marine, freshwater, and terrestrial habitats Called the sac fungi Produce spores in sacs called asci</p>
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Basidiomycetes

important decomposers and ectomycorrhizal fungi Ex. mushrooms Produce spores on basidia

<p>important decomposers and ectomycorrhizal fungi Ex. mushrooms Produce spores on basidia</p>
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Lichen

a symbiotic association between a photosynthetic microorganism and a fungus

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Vascular tissue

cells joined into tubes that transport water and nutrients throughout the plant body

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Vascular plants

most plants have vascular tissue for the transport of water and nutrients

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Bryophytes

nonvascular plants; an informal name for plants that lack an extensive transport system

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Seedless vascular plants

The plants in these clades lack seeds, which is why collectively the two clades

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