Finishing Chapters 15 and 16. For Next Week

Transcription

1 Finishing Chapters 15 and 16 For Next Week Lab Invertebrate questions due at 8:40 AM Bring dissecting kit and gloves to lab Lecture Assignment: Collect 5 branches from trees, put in plastic bags For each, Identify if it is from a gymnosperm or an angiosperm Try to identify the tree common name and latin name Extra credit: 1-2 page earthworm paper with references 1

2 Outgroup Analysis Distinguishing derived from primitive similarity Parsimony Distinguishing derived from convergent similarity 2

3 Parsimony The cladogram requiring the fewest evolutionary changes is (usually) preferred 1 step to evolve wings but Parsimony The cladogram requiring the fewest evolutionary changes is (usually) preferred Many steps for bats and other mammals to evolve all the mammalian characters 3

4 Molecular systematics Molecular systematics compares nucleic acids or other molecules to infer relatedness Scientists have sequenced more than 100 billion bases of nucleotides from thousands of species The more recently two species have branched from a common ancestor, the more similar their DNA sequences should be The longer two species have been on separate evolutionary paths, the more their DNA should have diverged Procyonidae Lesser panda Raccoon Giant panda Ursidae Spectacled bear Sloth bear Sun bear American black bear Asian black bear Polar bear Brown bear Oligocene Miocene Millions of years ago Pleistocene Pliocene 4

5 Molecular Clocks Some regions of the genome appear to accumulate changes at constant rates Molecular clocks can be calibrated in real time by graphing the number of nucleotide differences against the dates of evolutionary branch points known from the fossil record Molecular clocks are used to estimate dates of divergences without a good fossil record Ch 16 5

6 The origin of life An evolutionary tree for living things has been developed, using rrna genes Life is divided into three domains: the prokaryotic domains Bacteria and Archaea and the eukaryote domain Eukarya (including the kingdoms Fungi, Plantae, and Animalia) Molecular and cellular evidence indicates that Bacteria and Archaea diverged very early in the evolutionary history of life The first major split was divergence of Bacteria from other two lineages, followed by the divergence of the Archaea and Eukarya Prokaryotes Prokaryotes lived alone on Earth for over 1 billion years The most numerous and widespread organisms on Earth The total biomass of prokaryotes is ten times that of eukaryotes Most prokaryotes are 1 5 µm in diameter (vs µm for eukaryotic cells) There are ten times as many prokaryotes living in and on your body as the number of cells in your body 6

7 Bacteria on a pin point. Prokaryotes Prokaryotes live in cold, hot, salty, acidic, and alkaline habitats Although some bacteria are pathogenic and cause disease, most bacteria on our bodies are benign or beneficial Several hundred species of bacteria live in and on our bodies, decomposing dead skin cells, supplying essential vitamins, and guarding against pathogenic organisms Prokaryotes in soil decompose dead organisms, sustaining chemical cycles 7

8 1 Most recent common ancestor of all living things 2 3 Gene transfer between mitochondrial ancestor and ancestor of eukaryotes Gene transfer between chloroplast ancestor and ancestor of green plants Bacteria Eukarya Archaea Billions of years ago 8

9 Structure of Prokaryotes Most common shapes: Bacillus, Coccus, Spiral Prokaryotic cell walls maintain cell shape, provide physical protection, and prevent the cell from bursting in a hypotonic environment In a hypertonic environment, most prokaryotes lose water and shrink away from their wall Structure of prokaryotes Cell walls can be distinguished with gram stains Gram-positive bacteria have simple walls with a thick layer of peptidoglycan Very common in soil Include solitary species Includes Staphylococcus and Streptococcus Gram-negative bacteria have complex walls with less peptidoglycan and an outer membrane of lipids bonded to carbohydrates Often toxic, membrane protects them against antibodies 9

10 Structure of prokaryotes Some can stick to the substrate or each other with hair-like appendages called pili Some have flagella to move in response to chemical and physical signals in their environment Some prokaryotic cells have specialized membranes that perform metabolic functions like cellular respiration or photosynthesis Structure of prokaryotes Some prokaryotes can withstand harsh conditions by forming endospores within an outer cell The endospore has a thick protective coat It can dehydrate and is tolerant of extreme heat or cold When conditions improve, the endospore absorbs water and resumes growth, sometimes after centuries 10

11 Structure of prokaryotes Prokaryotic DNA forms a circular chromosome Smaller rings of DNA called plasmids carry genes that may provide resistance to antibiotics or metabolize rare nutrients, among other metabolic activities Many prokaryotes can transfer genes, such as antibiotic resistance genes, within or between species Energy source Light Chemical CO 2 Photoautotrophs Chemoautotrophs Carbon source Organic compounds Photoheterotrophs Chemoheterotrophs 11

12 Some bacteria cause disease Pathogenic bacteria cause disease by producing poisonous exotoxins or endotoxins Exotoxins are proteins secreted by bacterial cells Some of the most powerful toxins known are exotoxins, including the toxin that causes lockjaw Staphylococcus aureus produces several exotoxins, including one that causes deadly toxic shock syndrome Some bacteria cause disease Endotoxins are components of the outer membrane of gram-negative bacteria, released when the cell dies or is digested by a defensive cell Endotoxins produce septic shock, bacterial meningitis, and food poisoning The most widespread pest-carried disease in the United States is Lyme disease, caused by the spirochaete Borrelia burgdorferi 12

13 Spirochete that causes Lyme disease Tick that carries the Lyme disease bacterium Bull s-eye rash Some bacteria are helpful Prokaryotes are key participants in chemical cycles, making nitrogen available to plants and thus animals They also decompose organic wastes and dead organisms to inorganic chemicals Bioremediation is the use of organisms to remove pollutants from soil, air, or water Prokaryotes are decomposers in sewage treatment and can clean up oil spills and toxic mine wastes 13

14 1 Most recent common ancestor of all living things 2 Gene transfer between mitochondrial ancestor and ancestor of eukaryotes 3 Gene transfer between chloroplast ancestor and ancestor of green plants Bacteria Eukarya Archaea Billions of years ago Archaea Among the most abundant cells on Earth They are a major life-form in the oceans Live in extreme environments 14

15 1 Most recent common ancestor of all living things 2 3 Gene transfer between mitochondrial ancestor and ancestor of eukaryotes Gene transfer between chloroplast ancestor and ancestor of green plants Bacteria Eukarya Archaea Billions of years ago Eukaryotes Protists are eukaryotes, with Membrane-bound chromosomes Multiple chromosomes Flagella or cilia Some protists have a very high level of cellular complexity 15

16 Protists Protists obtain their nutrition in a variety of ways Algae are autotrophic protists Protozoans are heterotrophic protists, eating bacteria and other protists Fungus-like protists obtain organic molecules by absorption Some protists are endosymbionts Symbiosis is a close association between organisms of two or more species Endosymbiosis living within another Termite endosymbionts digest cellulose in the wood eaten by the host The protists have endosymbiotic prokaryotes that metabolize the cellulose 16

17 Diplomonads Parabasalids Euglenozoans Protists are diverse! Alveolates Stramenopiles Amoebozoans Green algae Dinoflagellates Apicomplexans Ciliates Diatoms Brown algae Water molds Forams Radiolarians Red algae Chlorophytes Charophytes Land plants Amoebas Slime molds Fungi Choanoflagellates Animals Euglenozoans Euglenozoans are a diverse clade of protists that include heterotrophs, photosynthetic autotrophs, and pathogenic parasites 17

18 Alveolates Alveolates have membrane-enclosed sacs or alveoli beneath the plasma membrane Dinoflagellates are important members of marine and freshwater phytoplankton Ciliates use cilia to move and feed. Apicomplexans are animal parasites such as Plasmodium, which causes malaria Stramenopiles Stramenopiles Water molds are fungus-like and decompose dead organisms in freshwater habitats Diatoms are unicellular, with silicate cell walls Brown algae are large, complex algae called seaweeds; all are multicellular and most are marine 18

19 Foraminiferans and radiolarians Foraminiferans and radiolarians move and feed by means of threadlike pseudopodia Amoebozoans Amoebas move and feed by means of pseudopodia Members of the clade amoebozoans include many free-living amoebas, some parasitic amoebas, and slime molds 19

20 Amoebozoans A plasmodial slime mold forms a multinucleate mass of cytoplasm The plasmodium extends pseudopodia through soil and dead logs, engulfing food by phagocytosis Under adverse conditions, the plasmodium forms reproductive structures that produce spores Amoebozoans Cellular slime molds are solitary amoeboids When food is scarce, the amoeboid cells swarm together in a slug-like aggregate, migrate to the soil surface, form a fruiting body and disperse as spores Reproductive structure of cellular slime mold Amoeboid cells 20

21 Algae Red algae are typically soft-bodied, but some have cell walls encrusted with hard, chalky deposits Green algae Include the closest living relatives of land plants The life cycles of most green algae involve the alternation of generations, in which a haploid (n) gametophyte alternates with a diploid (2n) sporophyte generation Algae 21

22 Alveolates Stramenopiles Amoebozoans Green algae Diplomonads Parabasalids Euglenozoans Dinoflagellates Apicomplexans Ciliates Diatoms Brown algae Water molds Forams Radiolarians Red algae Chlorophytes Charophytes Land plants Amoebas Slime molds Fungi Choanoflagellates Animals 22