Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Learning goals: Lecture 2, Biological Diversity (Basic ideas; Prokaryotes, Protists) Readings: Chapters 1 (review), 26, 27, and 28 (read all of these, but the parts covered in lecture are by far the most likely to be on a test ). Biological Diversity What we mean by the term; diverse organisms solve problems differently; why solving problems differently is important to you; review some ideas from Chapter 1. The tree of life (Ch. 26) The tree of life. Prokaryotes (Ch. 27) Shapes; genome organization; reproduction; metabolism; representative groups; importance Protists (Ch. 28) Characteristics; endosymbiosis, colonial organisms; sexual reproduction, representative groups Biological Diversity What we mean by the term Diverse organisms solve problems differently Why solving problems differently is important Ideas from Chapter 1 Biodiversity is simply a term to describe the incredible variety of forms of life. One might think that only a few types of beetles would be “enough” to make the world work, but there are actually about a quarter of a million species. Cornell University Biological Diversity What we mean by the term Diverse organisms solve problems differently Why solving problems differently is important Ideas from Chapter 1 But an extremely important biological truth is that each species of life solves the problems of survival and reproduction differently. www.lrc.rpi.edu www.augsburg.edu/home/biology/ www.entomology.umn.edu Biological Diversity What we mean by the term Diverse organisms solve problems differently Why solving problems differently is important Ideas from Chapter 1 retina light lens mirror Ostracod picture 1 Ostracod picture 2 retina Biological Diversity What we mean by the term Diverse organisms solve problems differently Why solving problems differently is important Ideas from Chapter 1 An example of how differences are important: molecules of the antibiotic penicillin prevent the formation of the cell wall* in bacteria, which prevents their growth. Animal cells do not have a cell wall, just a membrane. Thus, we can take penicillin to kill bacteria living inside us, but without killing ourselves. This would not be possible if bacteria and animals didn’t solve the problem of how to contain the cell contents in different ways. * This is a simplification Some important concepts from Chapter 1 that you should review from your high school biology course 1. Fig. 1.2 properties of life 2. Fig. 1.3 - levels of biological organization 3. A closer look at cells - eukaryotic and prokaryotic (Fig. 1.8). Prokaryotes often also have a cell wall around the membrane. Some important concepts from Chapter 1 that you should review from your high school biology course 4. Fig. 1.14 natural groupings of life Canis familiaris - genus capitalized, species name not, italics. Family (e.g. Canidae) not italicized Some important concepts from Chapter 1 that you should review from your high school biology course 5. Fig. 1.23 - tree like graphs show relation ships Some important concepts from Chapter 1 that you should review from your high school biology course robin Phylogenetic trees are graphs that display genetic relationships of species. They are calculated from molecular data, or from data on visible features dove Unique feature evolved in only this branch (=clade): feathers dog bat Unique feature evolved in only this branch (clade): hair Unique (or derived) features are the clues for determining relationships time The tree of life (Ch. 26) The tree of life (also some Figures discussed with later chapters) The tree of life (Ch. 26) Geological time and Fossils The tree of life Fig. 26.22. The Tree of Life is really a better description of how life forms are related than a set of names, although we must still use names too. Don’t try to memorize all of this! We will learn important aspects as we discuss the various groups. Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance Fig. 27.3 The Gram stain divides bacteria into Grampositive and Gram-negative bacteria (which often are the more pathogenic ones). Fig. 27.2 Shape helps in classifying prokaryotes Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance All the strands are part of the one chromosome, making a loop. Fig. 27.8. The single chromosome (DNA + proteins) of a prokaryote contains all the directions for making a living cell. The chromosome of a prokaryopte is not organized into a nucleus, although it is generally located in one part of the cell). Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance Reproduction in prokaryotes occurs primarily by cell division - each cell divides into two daughter cells. However, bits of DNA can be exchanged between cells under certain circumstances, resulting in a form of sexual reproduction (making new combinations of genes). Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance Fig. 27.10 photosynthetic bacteria Metabolism (the chemical reactions of life) is extremely diverse in prokaryotes. Prokaryotes are structurally simple, but far more diverse metabolically than eukaryotes. One way to divide types of prokaryotic metabolisms is into autotrophic (can make the complex chemicals of life starting only with carbon dioxide and an energy source) and heterotrophic (requires chemicals more complicated than CO2) Another way to divide is into phototrophic (energy derived from light) and chemotrophic (energy derived from inorganic molecules like amonia) All four combinations occur in prokaryotes. Different forms of life solve the problem of obtaining energy in very different ways. Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance Fig. 26.22 Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance Fig. 27.13 Learn about: Chlamydias Spirochetes Cyanobacteria Read about and know characteristics Prokaryotes (Ch. 27) characteristics genome organization reproduction metabolism representative groups importance Fig. 27.16 Lyme disease. Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Fig. 27.1 Protists in pond water, light microscope Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups It is difficult to describe the exact characteristics of protists because we don’t know how to organize them into natural groupings yet. Look at the enormous diversity of protists at the left. They do have some common features eukaryotic single-celled, or, if multicellular, only a few differentiated cell types. sexual reproduction Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups The protist cell ( and in fact all eukaryotic cells) has some unusual features that are best explained as the results of endosymbionts. (symbiosis means living with another organisms, endosymbiosis means living inside another organism) evolving into a part of the host cell. If two organisms benefit each other, they are said to be engaging in mutualism. (Fig. 26.13). The first evidence of eukaryotes appears in the fossil record about 2 billion years ago. Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Multicellular eukaryotes first appear in the fossil record some 1.5 billion years ago. It is likely that a first step towards multicellular organisms was the appearance of colonial organisms - groups of cells functioning as a unit, like this flat algal species (Fig. 26.16). If some cells develop different features, they are said to be differentiated or show differentiation. Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Sexual reproduction to a biologist means making new combinations of genes. Protists (and all eukaryotes) have, at least at some point in their life cycle, two sets of the genes needed for life. A complete set of necessary genes is called a genome. Two genome states - Meiosis and syngamy have opposite effects on the number of genomes 2N Haploid - one genome - 1N Diploid - two genomes - 2N 1N Syngamy meiosis 1N 2N Both haploid and diploid cells can undergo cell division asexual reproduction. Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Fig. 28.31 In the single-celled Chlamydomonas, the gametes (sex cells, having the function of eggs and sperm) are unlike sperm and eggs in that they look the same. This is called isogamy. When cells join, it is called syngamy. A diploid cell formed by syngamy is called a zygote. Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Fig. 26.22 Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Diatoms Single-celled protists that make unique cell walls of, essentially, glass. Fig. 28.16 These have an extensive fossil record. Fig. 28.15 diatom Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Brown algae Many brown algae are quite complex and large, and many are harvested to be used in food (nori in sushi, also in making various gels that are used to thicken food). Fig. 28.18 Fig. 28.20 edible seaweed Protists (Ch. 28) characteristics endosymbiosis colonialism sexual reproduction representative groups Fig. 28.7 Cellular slime “molds” The life cycle includes a single-celled amobae, and a multicellular “slug”. What is an organism? Some thoughts on how bacteria and protists solve the same problem in different ways: Problem: osmoregulation (water regulation). When cells are placed in a hypotonic solution (one with less solute than in a cell), water tends to rush into the cell (osmosis). If you put human blood cells in distilled water, they swell up and burst (lyse). Both fresh-water bacteria and protists live in a hypotonic solution. Protist solution to problem (for some protists): Contractile vacuole - pumps out water Bacterial solution to problem (in part): Rigid cell wall prevents lysis. Learning goals: Lecture 2, Biological Diversity (Basic ideas; Prokaryotes, Protists) Readings: Chapters 1 (review), 26, 27, and 28 (read all of these, but the parts covered in lecture are by far the most likely to be on a test ). Biological Diversity What we mean by the term; diverse organisms solve problems differently; why solving problems differently is important to you; review some ideas from Chapter 1. The tree of life (Ch. 26) The tree of life. Prokaryotes (Ch. 27) Shapes; genome organization; reproduction; metabolism; representative groups; importance Protists (Ch. 28) Characteristics; endosymbiosis, colonial organisms; sexual reproduction, representative groups