LECTURE 2- Know the timeline of events; see book and power point for detailed chart!1) Describe the timing of the emergence of life on earth, and the relevant physical and chemical features of the planet before and after the origination of life forms.1) Extant species are the currently living species, species in which we can still see in our planet today; see evidence that they have been around for a long time. Ancient are those that have exited for a long time they may be extant or extinct. The formation of the Earth came about 4.6 billion years ago. This includes terrestrial environment, hydrosphere and atmosphere where the organisms interact with all these levels in different ways. During theformation of Earth we think there was a heavy bombardment of meteors and comets, which could have created the structures of the layers of the core, develop some water and some of the destructive temperature. The consequence was that there was no O2, no ozone layer and a higher concentration of CO2. The emergence of life came at about 3.8 billion years ago. After this occurred, there were early life of prokaryotic, photosynthetic and marine organisms that we see with the evidence of the fossil record and chemical evidence.2) Explain the origin of oxygenic photosynthesis from earlier examples of autotrophy.1) Autotrophy is synthesizing your own nutrients that are light dependent that suggests photosynthesis but no evidence that is needs oxygen. Oxygenic photosynthesis is where water in the electron donor and oxygen is released. Earlier photosynthesis may have had the release of sulfur.3) Describe the impact of oxygenic photosynthesis on the atmosphere.1) There wasn’t oxygen in the environment meaning there wasn’t an ozone layer. The ozone layer can block certain UV lights effectively. UV-C is effectively blocked by ozone layer. Organisms are susceptible when there is no ozone layer. Evidence suggests that most organisms were unicellular and aquatic to tolerate these conditions. At 3.5 billion years ago, there were changes in oxygen accumulation so this is where we believe was the introduction of oxygenic photosynthesis. 4) Describe the direct and indirect evidence used to support the current understanding of plant evolution and the origins of early life.1) Acritarch fossils were where apparent diversification was noticed, so slow diversification process but they don’t look like the things that are alive today. Bangiomorpha was when wesaw something that appeared to look like something today. The Cambrian period is when we see huge diversification period. The first land plants came about during the Ordovician period. See figure 1-11 in book. 5) Explain the endosymbiont theory, including the important events associated with it and the evidence supporting it, and describe how this theory relates to the origin of eukaryotic heterotrophs and autotrophs.1) Earliest life forms didn’t have the nucleus so they were prokaryotes. The origin of eukaryotic organisms came from the acquisition of mitochondria and chloroplasts. With the rapid decrease in carbon dioxide, we could see a potential for heterotrophy and other opportunities similar to that. The evidence for eukaryotes was the heterotroph. The evidence is that there is multiple membranes, mitochondrial genomes, tend to look like a line of bacteria and the inner membrane is what was expected. Primary chloroplast endosymbiosis was the evidence where there was a eukaryotic cell and all evidence suggests it came from cyanobacteria. The evidence expected: own DNA, genes in nucleus transferred from endosymbiosis event, photosynthesis and multiple membranes. LECTURE 31) Discuss the transition of plant life from water to land, and explain the evidence that land plants descended from algal-like ancestors.1) More oxygenic photosynthesis lead to more changes in the environment. The Cambrian explosion led to the emersion of many different species as well as more marine animals dueto more oxygen in the water. The first angiosperms were in the cretaceous period. Evidencefrom DNA sequence, morphological features such as cellulose in cell walls, phragmoplast and plasmodesmata but isn’t necessarily supported by fossil record. 2) Describe the features that distinguish plants from their algal ancestors.1) They have plastids. Land plants have a multicellular sporophyte, embryo, gametangia, sporangium and cuticle. Evidence comes from the cellulose. Evolutionary trends in green algae: have unicells (single cell that goes under asexual reproduction), others grow in colonies where there is a sheet of them that have aggregated (different form multicellular because they don’t grow next to each other), some in chains or filaments which is what evidence suggests is shared by the most common ancestor. Have blades and giant cells.4) List the major taxa that compose the group referred to as the protists, and describe the evolutionary relationships of those taxa.1) Charales: look like mosses, cell division, complex reproductive structures, big egg, and small sperm. Closest relative to land plants; chlorophyta, red algae, glaucophytes, diatoms, dinoflagellates and brown algae. 4) Define the features that distinguish the bryophytes, eutracheophytes, and embryophytes.1) A retained embryo is what all organisms share so that they are called embroyphytes and this came about 450 million years ago. Vascular tissue developed around 400 million years ago, which are the eutracheophytes (xylem and phloem, lignin roots, cuticle and stomates with function guard cells). The bryophytes are common with vascular plants and not present in green algae. They were terrestrial plants and the sporopollenin results in the new individual plant and there is a resistant to decay. There is evidence of signaling pathways, which are predominant in land plants to modify so it doesn’t lose a lot of water. They aren’t adapted for completely dry habitats, which causes them to grow in wet locations. One reason is the sperm needs to be able to swim. They have rhizoids, which are for anchorage and are real roots. See power point for different types of bryophytes. Eutracheophytes are where megaphylls emerged and have no leaves, they grow usually in one direction (example from power point) 5) Explain the difference between monophyletic and polyphyletic taxa, and both provide and recognize examples of each.1) Protists that do not have a common ancestor and may not contain all of the descendants are
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