Life 121 - Exam 2
Life 121 - Exam 2 Life Science 2: Cells, Tissues and Organs
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Life Science 2: Cells, Tissues and Organs
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This 14 page Class Notes was uploaded by Abby Mangefrida on Tuesday January 5, 2016. The Class Notes belongs to Life Science 2: Cells, Tissues and Organs at University of Nebraska Lincoln taught by Chad Brassil in Spring 2016. Since its upload, it has received 56 views. For similar materials see Life 121 in Biological Sciences at University of Nebraska Lincoln.
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Date Created: 01/05/16
24.1 Hypothesized steps in the formation of life: 1) Abiotic synthesis of small molecules from extra – terrestrial 2) Small molecules to macromolecules 3) Protocell formation 4) Self – replicating molecules Bacteria profoundly impacted earths atmosphere when they started producing oxygen, this was done by organisms that could photosynthesize, this happened around 2.25 billion years ago What is the fundamental molecule that enabled self-replicating protocells to transmit heritable information and thus evolve? RNA, because RNA can form ribosomes and they don’t just form the double helix of RNA, they can assemble another RNA that is similar to themselves 24.2 Diverse structural and metabolical adaptations have evolved in prokaryotes Differentiate among prokaryote morphological structures based on function Gram positive – Gram negative - Parts of cell: Capsule – attachment & resistance, substance around cell that can attach to other substances but can also protect cell from environment Pili – pulls bacteria cells together Fimbriae – attachment Endospore – resting & resistance, help resist harsh environmental conditions Flagella - movement Categorize metabolic diversity in prokaryotes ENERGY CARBON Photo – from light Auto – CO2 or bicarbonate (from atmosphere) Chemo – non-carbon chemicals or Hetero – carbon compound from carbon compounds some other organic compound (sugars) So…photoautotroph gets energy from light and carbon from the atmosphere in the form of CO2 or bicarbonate Photoheterotrophs use organic compounds for carbon, Phototrophs get energy from light Chemotrophs get energy from not light Autotrophs get carbon from carbon dioxide or related Heterotrophs get carbon from organic carbon compounds Autotrophs get energy from light or non-carbon chemicals Heterotrophs get energy from light or non-carbon chemicals 24.4 Prokaryotes have radiated into a diverse set of linages Revolution of evolutionary understanding: Ribosomal RNA divides them into the three domains Lots of old taxonomical groupings of bacteria are not monophyletic Lots of prokaryotes only known from DNA sequences Horizontal gene transfer: origin of 75% of genes Proteobacteria Gram – negative Metabolically diverse, ex: o Photoautotrophs, chemoautotrophs, heterotrophs o Anaerobic and aerobic o Nitrogen – fixers & nitrogen cycle in soils o Sulfur as energy source Ex: salmonella, e. coli, legionella Chlamydias Gram – negative o No peptidoglycan at al Obligate to animal cells o Use ATP from host cell Chlamydia trachomatis o Most common cause of worldwide blindness o Most common STS in united states Spirochetes Gram-negative Heterotrophs Spiral shaped Free-living or parasitic Ex: syphilis, lymes disease Cyanobacteria Gram-negative Photoautotrophs o The source of chloroplasts Some specialized nitrogen fixing cells Gram-positive Gram positive Diverse Some form branched colonies A few cause diseases: tuberculosis, leprosy Most are in the soil: decompose Some are sources of antibiotics One group lacks cell walls, small: mycoplasmas Archaea Environmentally diverse Extreme halophiles high salt concentrations Extreme thermophiles extreme heat, source of polymerase in modern PCR Methanogens use H2 instead of O2 (deep sea vents, marshes) 25.1 – The Origin and Diversification of Eukaryotes Eukaryotes Nucleus Membrane bound organelles o Mitochondria o Golgi apparatus Cytoskeleton – proteins that give structure to the cell and allow it to take on all different shapes Hybrids of bacteria and archaea Early Evolution of Eukaryotes Eukaryote-like lipids: 2.7 billion years ago Eukaryotes: 1.8 billion years before present Eukaryote multicellularity: 1.3 billion years before present Large Eukaryotes: 635-535 million years ago Endosymbiont Theory: Historically o Archaeal cell engulfs bacteria cell o Bacteria cell becomes organelle Key event in eukaryotes evolution Generally origin of mitochondria and plastids photosynthetic engulfed second bc not all are photosynthetic Inferred Origins of Key Eukaryotic Features: Feature Original Source DNA Replication enzymes Archaeal Transcription enzymes Archaeal Translation enzymes Mostly archaeal Cell division apparatus Mostly archaeal Endoplasmic Reticulum Archaeal and bacterial Mitochondrion Bacterial Metabolic Genes Mostly Bacterial Serial Endosymbiosis: 1. Ancestral archaea Membrane infolding: nucleus & endoplasmic reticulum 2. Proteobacteria Engulfed to form mitochondria (happened once, all mitochondria have single origin) All eukaryotes have mitochondria 3. Lineages separate some carry on, some go on to other lineage (cyanobacteria) 4. Cyanobacteria Engulfed to form plastids (happened once, all plastids have single origin) Organelles and Prokaryotes: Proof organelles came from prokaryotes Similar enzymes in plasma membranes Similar fission process with circular DNA Both have ribosomes and can DNA replicate Ribosomes of similar size and structure to those inside bacteria Further plastids evolution: more proof endosymbiosis occurred Two lineages: red algae and green algae 3 membranes o Cyanobacteria inner membrane (has two because it is gram negative) o Cyanobacteria outer membrane o Host’s membrane Reduces to 2 membranes Secondary endosymbiosis o Eukaryote engulfs eukaryote o 4 membranes around these plastids Nucleomorph in plastid is remnant Stramenopiles plastid – 4 membranes Chlorophite plastid - 2 membranes 25.2 multicellularity has originated several times in eukaryotes Colonies – the simplest form of multicellularity Seen early in evolution, still happens today Eukaryotes with cell walls share cell walls Eukaryotes without cell walls proteins stick together Stepping stone to more complexity Multicellularity Originated independently in many lineages One example, Chamydomonas-Volvox clade of Chlorophytes o Series of increasingly complex ancestors o Only a few genes involved Origin of animals? How many novel genes? We can get an idea from the Choanoflagellates, which are single celled most closely related group to animals o Most genes already existed in common ancestor o CCD domain: novel in animal clade Cadherin proteins – proteins that aid in cell attachment 26.1 – Fossils show that plants colonized land more than 470 million years Ago Fungus is more closely related to animals than it is to plants. Charophytes are most closely related to land plants Shared derived traits of charophytes and land plants: 1. Cell walls made by proteins in rings 2. Similar flagellated sperm structure 3. Genetic and molecular similarities 4. Sporopollenin – prevents them from drying out Shared derived traits of land plants: 1. Alternation of generations Zygotes (single cell diploid) develop as embryos (multicellular) protected by maternal gametophyte tissue Multicellular stages as haploid (gametophyte – produce gametes via meiosis) and diploid (sporophyte – produce spores) 2. Walled spores produced in sporangia Spores (n) are produced by sporophyte (2n) Spores: haploid, enable movement and protection, germinate to produce multicellular organism Sporopollenin – protects the spores, allowed them to survive on land (charophytes also have them) 3. Apical meristems Cell division (mitosis) at root and shoot tips 4. Most: cuticle (protects plant from drying) and stomata (allows gas and water exchange) Fossil Evidence for Plants: 470 million years ago: spores o Preserve well because of sporopollenin 425 million years ago: fossilized spore producing structures 400 million years ago: o Water transport o Stomata o Branched sporophytes 26.2 Fungi played an essential role in the colonization of land Closest ancestor: Nucleariids Fungi nutrition Heterotrophs that absorb o Animals are heterotrophs that ingest o Secrete digested enzymes o Digests living or dead material Chitin in cell walls o Keeps cells from bursting Increase surface area o Hyphae (multicellular) form mycelium o Yeast (single cells) Generic fungus 1. Spore stage – can be asexual 2. Sexual part of life cycle – mycelium from 2 individuals can merge Plasmogamy - merged cytoplasm, look like once cell, but the nuclei never merge Heterokaryotic – 2 nuclei, can sit in this stage for a long time Karyogamy – nuclei can merge, becomes a true diploid cell Mycorrhizal Mycorrhizae: mutualism between fungus and plants Haustoria: hyphae pushing against plants plasma membrane Types: o Ectomycorrhizal fungi: outside root and extracellular spaces o Arbuscular Mycorrhizal fungi: outside root and inside cell wall pushing against plasma membrane Increase growth rate of plants The first fungi? Animal fungi split 1.5 billion years ago Oldest accepted fossil – 460 million years ago Fungus to land Probably moved with early land plants Soon after (405 million years ago): mycorrhizal o Fossil evidence looks like arbuscular mycorrhizal Plant genes for symbiosis found (at least inactive) across land plants clade o This suggests ancient mycorrhizal mutualism 26.3 - Land Plants Define function and evolutionary history of vascular tissue, roots, leaves, xylem, and phloem Monophyletic plants: Vascular plants Embryophytes Seed plants Archaeplastida Gymnosperm Angiosperm Eudicots – 2 parts to seed Monocots In which of the following taxa does the mature sporophyte depend completely on the gametophyte for nutrition? Hornworts 27.1 Animals Originated more than 700 million years ago Split between chaonoflagellates and animals, which are sister taxa 710 million year old: steroid fossils (sponge-like) 560 million years ago – Ediacaran Biota – actually look and know animals are in the fossil record - things that look like sponges, cnidarians, and molluscs Porifera/Sponges: First to separate from rest of animal groups Metezoa = general animals Most marine, some freshwater Filter feeders Different cell types o Choanocytes (collar cells) Consume via phagocytosis – brought into cell through vacuoles o Amoebocytes Pseudopodia Digest food and transport nutrients Lack tissues, which are group of cells acting as unit Radical symmetry – no front, back, left, right – symmetric around a central axis Cnidarians (jellies, sea anemones): Eumetazoans = true animal o They are considered this because they have tissues Sessile and mobile Gastrovacular cavity: mouth = anus o Digestion external to cells, digestive enzymes can be desecrated o This is what separates them Non-centralized nervous system o No brain o Advantage: can respond to all directions 27.2 The diversity of large animals increased dramatically during the “Cambrian explosion” Cambria Explosion First fossils of 50% of animal phyla o Look very different from todays animals Lots of bilaterians o Complete digestive tract o Two sides (bilateral) Predators Prey defense (spiked spine) What is the transition from ediacaran Cambrian like, what caused the explosion? More predators – predator prey feedback o Decline in soft-bodied animals from ediacaran More oxygen – change in atmosphere composition o Higher metabolism Larger animals Predators and prey that move a lot Evolution of HOX genes – genes that control basic body plans o New types of body plans Molecular clock suggests bilaterians evolved 670 million years ago, before ediacaran Prey defenses suggest predators in ediacaran – defensive features, larger animals, but don’t have fossils of these predators Order of evolutionary periods: Ediacaran cambrian carboniferous modern Animal Phyla and their distinguishing features: Arthrapoda – invertebrate animal with exoskeleton and segmented body and jointed apendages (insects, spiders, crustaceans) Cnidaria Mollusca Porifera Chordata – Echniodermata – sea stars Brachiopoda – not molluscs, in shell marine animals, Annelida 27.3 Diverse animal groups radiated in aquatic environments Body Plans: Radial symmetry – multiple lines of symmetry, cnidarians o Sessile or planktonic animals This is because they can respond equally to environment in all directions Bilateral symmetry – one axis that divides animal o Generally these animals have a central nervous system o Can perform coordinated movements o Anterior – front o Dorsal – back o Ventral – bottom Tissues: Cnidarians o Ectoderm: outer covering; Endoderm: inner covering Bilateria o Ectoderm: outer covering & nervous system o Mesoderm: lines body cavity o Endoderm: digestive tract & organs Animal Diversity: 36 phyla Phylogeny determined by: o Ribosomal RNA o Hox genes o Nuclear genes o Mitochondrial genes o Morphology Animal Summary: 1. All animals share a common ancestor Monophyletic: metazoa 2. Sponges are basal animals Porifera: first lineage to diverge (not eumetazoa) 3. Eumetazoa is a clade of animals with true tissues Cnidarians have two layers (no mesoderm) 4. Most animal phyla belong to the clade bilateria Three layers Bilateral symmetry Diversified in cambrian period 5. Most animals are invertibrates chordata: includes vertibrates Bilateria Dueterostomia o Hemichordate – marine worms o Echinodermata – sea stars, sea urchins o Chordate: includes vertibrates Seen in fossils 530 million years ago Characteristics: Notochord: flexible support rod Dorsal, hallow nerve chord Pharyngeal slits Muscular post-anal tail Clades: Lancelet & Tunicate Vertebrates o Characters: elaborate skeleton and nervous system that allows them to capture food and escape predators o Extinct lineages: chonodonts (no jaw, barbed mouth) o Gnathostomes Jaw, paired fins and tale Chondrichthyans: cartalige fish Osteichthyans: includes humans Hardened skeleton Lungs or gills Lophotrochozoa – o SUPER DIVERSE Ecdysozoa o Nematode o Arthropoda: “Jointed feet” Diverse & numerous 2/3 of all described species among first to colonize land present in the cambrian period Segmented body plan Eventually fused and specialized Facilitated by rearranged Hox genes 27.4 Land Animals Repeated Animal marine/land transition: 1. Arthropods o One of the first animals to colonize land: 450 million years ago o Colonization happened multiple times o The latest was crabs in Jamaica 4 million years ago 2. Molluscs o Snails, happened multiple times 3. Vertibrates These generally needed less adaptations compared to plants Arthropods: Specialized limbs Cuticle exoskeleton o Protection o Movement o For land transition: protects them from drying out Gas exchange **Key for them moving to land** o Aquatic: gills o Land: tracheal system (network of tubes in body) Insects – most successful arthropods o Are in most habitats – land and water o Their diversity increased when they started flying o Have wings AND limbs o Angiosperm – insect interaction – increased diversity of both insects and plants Terrestrial Vertibrates: Aquatic lobe fins o Spending time near shore o Developing lungs Lobe fins modified into limbs with digits Tetrapods: Amphibians o Characteristics Live normally in moist environments Usually hop or bend to move o Clades Salamanders Frogs Caecilians (legless and blind) Amniotes – more successful than amphibians o Characteristics Amniotic egg Enables use of dry land Amnion: fluid filled cavity that physically protects Yolk sac: provides nutrients Shell: prevents drying o Mammals lost shell and use mother instead o Clades Reptiles Synapsids Mammals come out of this Mammals: Characteristics: o Mammary glands: milk for offspring o Hair o Fat under skin for heat retention o High metabolism o Variety of tooth type: lots of food Clades: o Monotremes: egg laying o Marsupials: pouch o Euthrians: placental Apes humans
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