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BI Midterm 2 Study Guide Part 1
Terms in this set (23)
Larger in size (multicellular), more complex, larger ribosomes, flagella with a different structure, and membrane-bound organelles (organized structure within a cell with a specialized function and are membrane bound with a lipid bilayer). The most notable organelle is the nucleus which has a double membrane called the nuclear envelope. Other notable organelles are the mitochondria (all eukaryotes have) and chloroplasts (some eukaryotes have - plants). All eukaryotes do mitosis and meiosis, which are both divisions of eukaryotic cells (almost always include cytokinesis - mitosis results in genetically identical daughter cells and meiosis is required for sexual reproduction ONLY).
Why are Ribosomes not Organelles
Ribosomes are not membrane-bound and serve multiple functions. They move freely around in and outside of the cell are not usually bound to one location (the cell). To be an organelle, it must not be able to leave the cell.
The Endosymbiont Hypothesis
The theory that says that mitochondria and chloroplasts most likely originated on their own many years ago by entering an ancestral cell. Mitochondria is likely from proteobacteria and chloroplasts are likely from cyanobacteria. They realized this because both mitochondria and chloroplasts contained small ribosomes, circular DNA (similar sequences to prokaryotic DNA), and both duplicated via binary fission. All of these are features show that mitochondria and chloroplasts were more closely related to prokaryotes than eukaryotes and likely evolved from them.
Ancestral eukaryote with nucleus > bacterium is engulfed > over time the symbiotic relationship was so helpful to both cases that it became an obligate interior structure and had the inability to leave and is what we now know as mitochondria > animals, fungi, etc.
Prokaryotic vs. Eukaryotic DNA
Prokaryotic DNA - Chromosomes are in the nucleoid, genome smaller, and one, circular chromosome.
Eukaryotic DNA - Chromosomes are in the nucleus, genome larger (3x-30000x), and multiple, linear chromosomes.
Mitosis vs. Meiosis
Mitosis - 1 division producing 2 identical diploid cells. Asexual reproduction. Much more common than meiosis. Responsible for growth, differentiation, repair, and almost all divisions in multicellular eukaryotes. Solves the distribution problem (both daughter cells have to have the same type and same amount of chromosomes as the parent cell) for eukaryotes.
Interphase (DNA is replicated) > Prophase (chromosomes condense - DNA is a lot easier to move in a small structure) > Metaphase (chromosomes line up at the equator) > Anaphase (chromatids are pulled to opposite poles - as soon as those chromatids break apart, they are considered their own chromosomes) > Telophase (cells complete division) > Cytokinesis (cells get cut into 2 and complete division).
Meiosis - 2 divisions producing 4 nonidentical haploid cells. Sexual reproduction. Only happens in specialized cells. Reductional division occurs in meiosis I, meaning that there is a change in ploidy (diploid > haploid). In meiosis, the 2 homologous chromosomes find each other and pair up = 4 chromatids = tetrad. Meiosis increases heritable variation because it reduces ploidy (diploid to haploid).
Purpose of Sex
Sexual reproduction increases genetic variation, because the sperm and egg that are produced contain different combinations of genes than the parent organisms. Some ways to promote genetic variation during meiosis are fertilization (different individuals may have different versions of the same gene which is why we all look different) and independent assortment (the chromosomes line up in the middle of the cell randomly and are then pulled into 2 new cells).
Eukaryotic Sexual Reproduction (sex) vs. Prokaryotic Asexual Reproduction (binary fission)
Sex - Eukaryotic daughter gametes do not have identical DNA as their parent cell.
Binary Fission - Prokaryotic daughter cells have identical DNA a their parent cell.
Eukaryotes that are not animals, plants, or fungi. Some groups are among the oldest eukaryotes. A lot of protists are unicellular, but some are aggregate, colonial, or multicellular (algae). Vast majority are aerobic, a few anaerobic which lack true mitochondria. Phototrophic, chemotrophic or mixotrophic (combination - don't see in bacterial cells). Protists are aquatic producers - organisms that use light to produce organic molecules from carbon dioxide. They like moist environments, freshwater, and salt water. They produce up to ¼ of the world's photosynthesis. They are the base of many aquatic food webs. Major eukaryotic clades (supergroups) are archaeplastida, SAR, amphorea (previously unikonta), and excavata. The deep relationships between these clades is unclear. Some research today shows that there are a lot more than 4. 1977 "grab-bag" kingdom. Protista is not a kingdom anymore because it is not a monophyletic group. They do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor (paraphyletic).
Secondary Endosymbiosis for Brown Algae
Get chloroplast with 2 membranes during primary endosymbiosis. During secondary endosymbiosis, the entire red algae cell was absorbed into another cell, creating a brown algal cell. This makes a cell with a chloroplast that has 4 membranes. Similar event in euglenids.
Contains Stramenopiles, Aleovates, and Rhizarians.
Have two flagella (one hairy and one smooth). Includes diatoms, golden algae, and brown algae.
Diatoms - Glass-like cell wall made of silica called a frustule, kind of marine plankton that do 50% of the worlds photosynthesis (plankton are free-floating aquatic microorganisms, diatoms are also called phytoplankton) Diatoms prefer colder water which is why they bloom in winter.
Brown Algae - Chloroplast with 4 membranes, multicellular, largest algal species.
Have membrane-bound sacs called alveoli. There are apicomplexans, dinoflagellates, and ciliates.
Apicomplexans - Have an apical complex, which are organelles specialized for penetration. They also have parasitic symbiosis with animals. Some apicomplexans cause human disease such as malaria. A common apicomplexan is plasmodium (the one that causes malaria). They are unicellular but have complex life cycles: sexual and asexual, two or more hosts.
Dinoflagellates - Have an armor of cellulose plates, have 2 flagella in armor grooves, and are abundant in marine and freshwater plankton. Dinoflagellates have a mutualistic symbiosis with coral reefs (polyps, the calcium carbonate base), as the dinoflagellates provide photosynthesis and 90% of the energy it generates for the polyp. A big problem is coral bleaching due to stress (temperature, UV radiation, etc.). When this happens, corals lose their dinoflagellates are photosynthetic pigments, and the polyp will die.
Ciliates - Have cilia used for movement and/or feeding. Also have 2 types of nuclei in the same cell, the macronucleus is the larger one (has 50 copies of each chromosome that provide everyday functions) and the micronucleus is the smaller one (can be 1-80 per cell, only function is in sexual reproduction/meiosis, which works in a way called conjugation where there is an exchange of micronuclei after meiosis).
Amoebas characterized by threadlike pseudopodia.
An organism that can use both photosynthesis to get energy (autotrophic) and digest organisms to get energy (heterotrophic).
Compare and contrast the life cycles of Plasmodium (an Apicomplexan), plasmodial slime molds, cellular slime molds and Chlamydomonas.
Plasmodium Life Cycle - (malaria) Single cell. Can infect many different types of cells. As it infects each different type of cell, it has a different morphology. Forms gametes by mitosis not meiosis (only in this).
Slime molds are decomposers. There are two types: plasmodial and cellular.
Plasmodial Slime Mold Life Cycle - Decomposers, multinucleate (mitosis without cytokinesis). Stress triggers reproduction, then makes sporangium (sexually) and spores. STRESS TRIGGERS REPRODUCTION
Cellular Slime Mold Life Cycle - Primarily haploid and unicellular, have a positive chemotaxis, meaning they move towards a chemical that they produce themselves, and stress causes the cells to aggregate into a multicellular organism. Then they migrate and form a fruiting body, for asexual reproduction. STRESS TRIGGERS REPRODUCTION
Chlamydomonas Life Cycle - A genus of green algae consisting of about 325 species all unicellular flagellates (have 2 flagella), found in stagnant water and on damp soil, in freshwater, and seawater. After fertilization, the zygote soon goes through meiosis and produces four haploid flagellated spores (zoo-meiospores), which develop to haploid unicellular individuals. STRESS TRIGGERS REPRODUCTION
Kinds of Symbiosis
Parasitic Symbiosis - One organism benefits from the relationship but the other (often called the host) is harmed.
Mutualistic Symbiosis - Both organisms benefit from the relationship.
Thought synapomorphy was a feeding groove, but it turns out they were only in some, so it might not be a true synapomorphy. Contains diplomonads, parabasalids, and euglenozoans. Diplomonads and parabasalids are anaroebic (every other eukaryote is aerobic), and have degenerate mitochondria.
Diplomonads - Have 2 nuclei and the degenerate mitochondria called mitosomes (iron and sulfur metabolism but not sure)
Parabasalids - Have degenerate mitochondria called hydrogenosomes (produce ATP + H2).
Euglenozoans - Have a cystalline rod with a flagella.
Have lobe-shaped pseudopodia used for movement and feeding. Contains free-living ones (tubulinids), parasites (entamoebas), and slime molds. All are heterotrophs. All feed by phagocytosis, which is a process by which a cell engulfs another cell or particle, usually for digestion.
This monophyletic group, which includes red algae, green algae (2 types), and plants, descended from an ancient protist ancestor that engulfed a cyanobacterium (cyanobacterial endosymbiosis).
Rhodophyta - Red algae. Contains phycoerythrin in chloroplast that emits a red pigment. This helps them absorb the blue/green pigment that is abundant underwater to the best of its ability. Abundant at coastal tropics.
Chlorophyta - Type of green algae. Plant-like chloroplast pigments. No real synapomorphies. There are unicellular, multicellular, and colonial ones. Volvox is a colonial organism, meaning multiple cells form a single structure, but can live as single cells if seperated. Some cell differentiation (baby cells inside only focus on reproduction). Complex Life Cycle of Chlorophyta: + strain and - strain recognize stress (no nutrients or water) and join together to form a gamete, then fertilization happens to form a diploid cell, then during a great time and after some dormancy, they undergo mitosis.
Charophyta - Type of green algae. Closest living relatives to land plants. Shared derived characters between land plants and charophytes are: 1) cellulose synthesis by enzymes with 'rosette' structure 2) similar cytokinesis with a phragmoplast 3) DNA sequence. An example of a charophyte is chara, a pond dwelling species.
Benefits/Obstacles/Adaptations of Algae Colonizing Land
Benefits - More sunlight, more CO2, less competition, less water pressure, soil has lots of nutrients, herbivores.
Obstacles - Drying out, no more buoyancy, no anchors, no structural support, harmful radiation, need to find new dispersal method because there is no water.
Adaptations - Embryos, spores with sporopollenin, cuticles (a waxy covering on the surface of stems and leaves that acts as an adaptation to prevent desiccation in terrestrial plants and allowed for more surface area for more photosynthesis), and stomata (small openings on leaves opens and closes pores to o2 exit and co2 intake - may close off co2 when not needed).
Who can generate gametes directly through meiosis?
Only animals can do that, no one else.
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