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UNIT 1: Diversity of Living Things Chapter 1: Classifying Life’s Diversity Chapter 2: Diversity: From Simple to Complex What are the characteristics of bacteria, archaea, and protists? Chapter 3: Multicellular Diversity UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.1 2: Diversity: From Simple to Complex This mound, a microbialite found in a lake in British Columbia, is covered with different types of bacteria and other micro-organisms that trap minerals from the water to form the solid structures beneath them. Since microbialites were common millions of years ago, scientists hope to gain insight into the history of Earth and its life forms by studying them. What does this suggest about the evolutionary history of bacterial cells? UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.1 2.1 A Microscopic Look at Life’s Organization All species of living organisms, whether unicellular or multicellular, are comprised of cells and can be studied using a microscope. Scientists also investigate and classify viruses, although they are not considered alive since they cannot live outside of cells. Viruses differ from prokaryotic and eukaryotic cells in that: • they are dependent on the internal physiology of cells • they are not cellular and thus lack cytoplasm, organelles, and cell membranes UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.1 Classifying Viruses Scientists classify viruses by using each one’s unique characteristics, including: • size and shape of the capsid (protein coat surrounding genetic material) • shape and structure of the virus • type(s) of diseases the virus causes • genome (set of genes) and type of genetic material (RNA or DNA) • method of reproduction UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.1 Reproduction in Viruses Viruses undergo replication inside a host cell. Some viruses replicate by means of a lytic cycle, where they quickly attach, enter, replicate, assemble, and release from a cell, killing the cell in the process. Other viruses replicate by means of a lysogenic cycle, where they enter and then attach their DNA to the host’s chromosomes. Now referred to as a provirus, it can lie dormant within the host chromosome until it re-activates and continues with the lytic cycle. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Reproduction in Viruses Section 2.1 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.1 Viruses and Disease In multicellular species, lytic viruses burst from host cells and infect neighbouring cells. Host organisms that are already damaged are affected more rapidly. Lysogenic viruses may not cause any immediate effects on the host organism. HIV (human immunodeficiency virus) is an example of both a lysogenic virus and a retrovirus. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Viruses and Disease Retroviruses carry RNA and an enzyme called reverse transcriptase that causes the host cell to copy the viral RNA into DNA. Then it embeds into the host’s chromosomes and becomes a provirus. Every descendent cell then has HIV DNA copied within its genome. Section 2.1 UNIT 1 Chapter 2: Diversity: From Simple to Complex Prions: Non-viral Disease-causing Agents Prions, discovered in the1980s, are proteins and thus are the only known non-genetic disease agent. They become harmful when they change molecular shape. They remain infectious even after exposure to radiation. Examples include Creutzfeldt-Jacob disease (CJD) and Variant CreutzfeldtJacob disease (vCJD). Section 2.1 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.1 Review Section 2.1 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 2.2 Comparing Bacteria and Archaea Comparisons of cell type, morphology (shape), aggregation, nutrition, habitat, and reproduction show similarities and differences between the two domains. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Comparing Bacteria and Archaea Similarities • prokaryotic • similar shapes of cocci (spheres), bacilli (rods), and spiral cells • some species form aggregations • for energy, species either consume other organisms or use inorganic compounds • species live in aerobic or anaerobic habitats • both found in extreme environments; more archaea live in extreme habitats (extremophiles), while more bacteria live in moderate habitats (mesophiles) • reproduce by binary fission and can exchange genetic content by conjugation Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Comparing Bacteria and Archaea Differences • Some bacteria are shaped like pyramids, cubes, or rods with star cross-sections, while some archaea are shaped like plates or rectangular rods. • Some bacteria are photosynthetic, while some archaea are methanogenetic (produce methane gas as an anaerobic byproduct). • Bacteria live anaerobically in human guts; archaea live anaerobically in cattle guts. Cyanobacteria, such as Spirulina platensis, contain chlorophyll and carry out photosynthesis. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Three Types of Extremophiles • Thermophiles live in hot springs and deep sea vents, enduring temperatures over 100ºC. Example: Archaea Methanopyrus • Acidophiles live in volcanic craters and mine drainage lakes, enduring pH levels lower than 3. Example: Archaea Picrophilus • Halophiles live in salt lakes and inland seas, enduring salt concentrations above 20%. Example: Archaea Halococcus UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Reproduction of Bacteria and Archaea Reproducing Asexually Since both domains are prokaryotic and lack a nucleus, both reproduce asexually by binary fission. As a cell grows, it makes a copy of its single chromosome. After elongating and separating the two copies, the cell builds a septum between and splits into two identical cells. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Reproduction of Bacteria and Archaea In less favourable conditions, DNA can be exchanged instead of reproducing by binary fission. In conjugation, one cell links to another by a pilus (tube) and transfers a copy of some or all of the chromosomes. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Reproduction of Bacteria and Archaea In addition, bacteria and achaea house small DNA loops called plasmids that contain genes different from those of the chromosome. Plasmids can also be transferred through conjugation. This results in new genetic combinations and is an agent for increasing biodiversity. In some circumstances, bacteria form hard-walled structures called endospores to protect and store the genetic material. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Classifying and Identifying Bacteria/Archaea The following characteristics are used to classify and identify these two prokaryotic domains: • • • • • size and shape nutrition movement genetic components Gram staining Continued… The Gram stain divides most bacteria into two groups: Grampositive (A) and Gram-negative (B). The Gram-negative group of bacteria are larger in number and have more diverse species than the Gram-positive group. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Classifying and Identifying Bacteria/Archaea Gram staining works to separate bacteria into two groups; those species that will stain because they contain a thick protein layer on their cell wall are Gram-positive (become purple), and those species that will not stain because they have a thin protein layer are Gram-negative (become pink). UNIT 1 Chapter 2: Diversity: From Simple to Complex Bacteria, Human Health, and the Environment Some bacteria can harm human health. Examples include: • Clostridium botulinum causes food poisoning • Streptococcus pyogenes causes strep throat • Streptococcus mutans causes tooth decay Section 2.2 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Bacteria, Human Health, and the Environment Bacteria are decomposers. They break down organic molecules and release carbon, hydrogen, nitrogen, and sulfur, thereby supporting those nutrient cycles. Through the process of photosynthesis, cyanobacteria are major producers of oxygen gas on Earth. Some species in Archaea have enzymes that are of special use to humans because they can withstand extreme temperatures, salinity, and acidity. Biotechnologists have been able to use some of these enzymes for various procedures in DNA research. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.2 Review Section 2.2 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.3 2.3 Eukaryotic Evolution and Diversity About 2 billion years ago, eukaryotes evolved and this led to an increase in the diversity of life on Earth. These organisms are more complex than prokaryotes. They include more genes, allowing for greater cellular diversity in terms of size, shape, mobility, and specialized functions. Scientists examined the important question of how eukaryotic cells evolved and have come up with some theories supported by observations and evidence. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.3 Endosymbiosis The theory of endosymbiosis suggests that eukaryotic cells evolved from symbiotic relationships between two or more prokaryotic cells. Although one prokaryotic cell engulfed a different, simpler prokaryotic cell, the engulfed cell survived and became part of the host cell. UNIT 1 Chapter 2: Diversity: From Simple to Complex Chloroplasts and Mitochondria Chloroplasts and mitochondria may have been free-living prokaryotes engulfed by larger prokaryotes. They continued to perform their cellular activities while surviving and serving the host cell. A comparison of chloroplasts, mitochondria, and prokaryotes shows: • • • • • similar types of membranes similar types of ribosomes each reproduces by binary fission each contains circular chromosomes gene sequences match Section 2.3 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.3 Multicellularity Based on fossil evidence, scientists think that large, complex eukaryotes first developed about 550 million years ago. They have also found fossils of simple red algae in the Arctic that date multicellular eukaryotes as far back as between 1.2 and 1.5 billion years ago. Scientists hypothesize that the first multicellular organisms arose from colonies created by individual cells that divided. Genes within these cells contained instructions for some cells to become specialized. With the passage of time, groups of cells developed different functions. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.3 Life Cycles and Reproduction Eukaryotes reproduce by a number of methods: • simple asexual reproduction (shown below) • multiple fission asexual reproduction – where multiple copies of a cell are made at one time • sexual reproduction performed by a diploid organism • sexual reproduction performed by a haploid organism • sexual reproduction performed by an organism with both a haploid and diploid stage of life Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.3 Life Cycles and Reproduction In the case of sexual reproduction, the timing of the production of gametes (egg and sperm) differs as the organism may be haploid (contain one set of chromosomes per cell) or diploid (contain two sets of chromosomes per cell). UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.3 Review Section 2.3 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 2.4 Protists: The Unicellular Eukaryotes Most protests are unicellular. They are diverse and are essentially grouped into one kingdom because they do not fit well into other kingdoms. There is still debate about whether multicellular algal species fit into this kingdom or belong in the plant kingdom. The rest of the kingdom can be grouped as follows: • animal-like protists • fungus-like protists • plant-like protists Can you identify the type of protist shown in the photo? UNIT 1 Chapter 2: Diversity: From Simple to Complex Animal-like Protists The protozoans (animal-like) are heterotrophic and consume prokaryotes, other protists, or organic wastes. Some are parasitic and consume nutrients from the organism they live in. Four phyla will be highlighted: • • • • Cercozoa Ciliophora Zoomastigina Sporozoa Continued… Section 2.4 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Animal-like Protists Phylum Cercozoa includes the amoebas. Using pseudopods (“false feet”) they change shape to move and engulf food. They inhabit various environments, including freshwater, saltwater, and humans (as parasites). When amoebas detect food, they form pseudopods from the cell membrane and engulf their target. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Animal-like Protists Phylum Ciliophora includes the ciliates such as paramecia. The surface of the cell has hair-like projections called cilia that are used for locomotion and food sweeping. These protists inhabit various environments, and some are parasites. They are large and complex organisms. Paramecia use cilia to move through the water and to move food into the gullet. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Animal-like Protists Phylum Zoomastigina contains species with hard protective coverings over their outer membrane. These protists are called flagellates because they have one or more whip-like flagella, used for locomotion. They live in a variety of environments and conditions, including mutualistic relationships where both organisms benefit. Phylum Sporozoa includes parasitic protists. They are unique in that they alternate between asexual and sexual reproduction that often occurs in different hosts. One sporozoan species causes malaria in humans. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Animal-like Protists Section 2.4 UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Fungus-like Protists These protists absorb nutrients from living organisms, dead organisms, and wastes and are thus considered heterotrophic. They are similar to fungi in that they produce spores. However, the structure of their cell wall is different from those of fungi. They are classified generally into two categories: slime moulds and water moulds. Three phyla will be highlighted: • Myxomycota • Acrasiomycota • Oomycota Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Fungus-like Protists Organisms in phylum Myxomycota are also known as the plasmodial slime moulds. Visible to the unaided eye as tiny slug-like organisms, they creep and stream over decaying plant matter in forests and engulf small particles. A plasmodium contains many nuclei. Hemitrichia clavata can be found on rotting logs. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Fungus-like Protists Organisms in phylum Acrasiomycota are also known as the cellular slime moulds. They differ from Myxomycota in many ways; for example, their cells contain only one nucleus. They live as separate cells and behave like amoebas until food is scarce, when they join together as a slime mould. Continued… This slime mould is likely a member of the genus Fuligo. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Fungus-like Protists Organisms in phylum Oomycota (oh-oh-my-cota) are filamentous water moulds that consume dead organic matter. However, some species are parasitic and draw nutrients out of their hosts by extending fungus-like threads into their tissues and releasing digestive enzymes. This species of saprolegnia is digesting a goldfish. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Plant-like Protists Unicellular, plant-like protists include diatoms, dinoflagellates, and euglenoids. They all contain photosynthetic pigments in their chloroplasts, many of which contain chlorophyll. Three phyla will be highlighted: • • • Chrysophyta Pyrrophyta Euglenophyta Continued… The many species of diatoms have different shapes and sizes based on differences in their silica walls. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Plant-like Protists Organisms in phylum Chrysophyta are also called phytoplankton. They are a diverse group of free-living aquatic diatoms that are an important source of food for many marine organisms. They all contain a rigid cell wall with an outer layer of silica. They can reproduce asexually and sexually (when conditions become less favourable). Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Plant-like Protists Organisms in phylum Pyrrophyta are also called dinoflagellates. Two flagella, extending at right angles on the organism, produce a spinning movement during locomotion. When food is plentiful, these organisms reproduce quickly and cause great algal blooms. While dinoflagellates are photosynthetic, some live in mutualistic relationships with coral. Dinoflagellates, such as Gonyaulax catenella, can cause red tides, during which many marine organisms can die and shellfish can become toxic. Continued… UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Plant-like Protists Organisms in phylum Euglenophyta are mostly freshwater species. They tend to be autotrophs in sunlight and heterotrophs in the dark. They have chloroplasts for making food by day and can absorb nutrients at night. UNIT 1 Chapter 2: Diversity: From Simple to Complex Section 2.4 Review Section 2.4