Diversity of Living Things

1. Diversity of Living Things

2. Taxonomy • The biosphere is the part of Earth that is inhabited by living organisms • Biologists estimate about 30-100 million different kinds of living organisms, but we have only described 1.75 million of them. • In order to understand the diversity of life, we need a system of classification that names organisms and puts them in categories • A species is used to describe a kind of organism that is similar in structure and shape, and they reproduced with one another.

3. Today we use the system called binomial nomenclature that was developed by Carolus Linnaeus, where all organisms are given the same naming structure: in Latin • The first part of the name referred to the genus (pl. genera), which is a relatively small group of related species and the second part of the name refers to the species and usually refers to an important characteristic of that organism. • eg dog Canis familiaris cat Felis sylvestris

4. Groups that Linnaeus assigned organisms to are called taxa and the science of naming organisms and assigning them to certain groups is called taxonomy • The taxon species is the smallest group, thengenus • Similar genera are grouped into a family (the names of animals end in –idae and the names of plant families end in –aceae) • Similar families are grouped into an order, and similar orders are grouped into a class, similar classes are grouped into phyla (sing. Phylum), which are grouped into a kingdom.

5. Kingdom Archaebacteria • Ancient bacteria that live in harsh habitats of high saltiness, low oxygen, high temperature, extreme acidity. • Prokaryotes (do not have nuclei or other organelles)

6. Kingdom Eubacteria • Found everywhere in the world. • Prokaryotes • Diverse genetic makeup and metabolism

7. Kingdom Protista • Single celled eukaryotes • Some have chloroplasts

8. Kingdom Fungi • Fungi are eukaryotes and build cell walls similar to plants but are not made of cellulose • Cannot carry out photosynthesis • Moulds, yeast, mushrooms

9. Kingdom Plantae • Multicellular • Cell walls with cellulose • Chloroplasts • Mosses, ferns, seed plants

10. Kingdom Animalia • Multicellular • Cell membranes, but no cell walls. • Often organized into tissues, organs, and organ systems • Divided into invertebrates and vertebrates

11. Dichotomous Key • Used to help place organisms into the appropriate classification group • Keys have 2 choices for each characteristic

13. Phylogeny, Taxonomy, Evolution

14. Principles of Phylogeny • Phylogeny: the evolutionary history of a species. It looks at the relationships between organisms and looks for similarities with developmental, structural, and molecular traits. • Embryonic development similarities might show common ancestry • Example: all vertebrate embryos go through a stage where they have gills like fish

15. Organisms that have similar anatomical structures called homologous, are likely to have a common ancestry. Example: wing of a bat, whale’s flipper, and a cat’s arm all have the same bones, but different shapes and sizes. • If animals are genetically similar, they may have the same ancestry. • Groups of organisms based on phylogeny can be shown on a phylogenetic tree

16. Clades • In a phylogenetic tree, species are grouped into clades • A clade is a taxonomic group that includes a single ancestor species and all its descendants. • We use cladograms to demonstrate the relationships between organisms.

17. Biodiversity and Natural Selection • Why do some species die off and new species appear? • Charles Darwin was a scientist who studied the origins of species • He knew that people selected animals that had certain characteristics and bred those to create ideal offspring. He called this process artificial selection. • Darwin also observed finches, turtles, and other reptiles while living on the Galapagos islands where he came up with a second theory of natural selection.

18. Natural selection theory refers to the fact that the environment selects the organisms that will reproduce. Individuals with characteristics unsuited to the environment would die or be unsuccessful finding mates to reproduce. • Individual organisms adapt to different environmental conditions, resulting in the evolution of the species over time.

19. Kingdoms and Domains

20. Eukaryote vs Prokaryote • Prokaryote: a single-celled organism that does not contain membrane-bound organelles • Eukaryote: any organism whose cells contain organelles; some eukaryotic organisms are single-celled, some are multicellular.

21. Eubacteria Kingdom • Oldest organisms living on Earth • Most abundant and very diverse • Similar characteristics: single-celled, prokaryotes, DNA is a single chromosome, reproduce asexually by binary fission. • Structure: small, 10 times smaller than a typical eukaryotic cell, a cell wall, cell membrane, ribosomes, DNA in a single strand that forms a ring, some have flagella. • Usually classified by shape, reaction to being stained, nutrition, respiration.

22. Capsule Cell membrane Cytoplasm Nuclear material Cilia ribosome Cell wall flagellum

23. Bacterial Shapes • Coccus is a spherical shaped bacterial cell • Bacillus is rod shaped • Spirillum is spiral shaped • Cocci that live on their own are called monococci, in pairs: diplococci, in linear chains: streptococci, in grape-like structures: staphylococci • Bacilli can be single, paired or chained (monobacilli, diplobacilli, streptobacilli) • Spiral can only exist as single cells.

24. Reaction to Stain • Bacteria can be classified by their reaction to a dye that is made of crystal violet iodine called gram stain. • Cells that keep the violet are gram-positive and have a different cell wall structure. They are generally more common and not as pathogenic. • Cells that appear light pink are gram-negative.

25. Nutrition • Most eubacteria are heterotrophs, so they get their energy by breaking down organic molecules in the environment. • Some eubacteria are autotrophs and can make their own organic compounds. There are two types: photoautotrophs (use sunlight as their energy source) and chemoautotrophsf (use energy from chemical reactions as their energy source) • Heterotrophic bacteria live everywhere. Most are chemoheterotrophs, some are parasites (absorb nutrients from other species), and others are saprobes (decompose dead organic matter).

26. An important group in the photoautotrophs is called the cyanobacteria (blue-green bacteria). • These bacteria are photosynthetic and can use sunlight to make their own food, but lack chloroplasts. • They are common in freshwater lakes and ponds. • Sometimes their populations increase dramatically: called a bloom, which can indicate that the water is polluted with nitrates and phosphates from agricultural runoff. • Can also be found in salt water, in soil in snow, in volcanoes and on rocks. • Some species live symbiotically with fungi forming mixed organisms called lichens.

27. Respiration • Cellular respiration occurs within the inner folds of the membrane of the bacteria • Bacteria differ in whether or not they require oxygen. If they do need oxygen they are called aerobes • If oxygen is absolutely necessary for survival, they are called obligate aerobes • Bacteria that can carry out cellular respiration without needing oxygen are called anaerobes. • If the presence of oxygen kills bacteria, they are called obligate anaerobes

28. Reproduction • All reproduce asexually by binary fission • Can divide every 15 to 20 minutes if there is enough food, warmth and space. • Mutation rate is affected by the fast reproduction rate. Mutations can evolve if successful. • In addition to the chromosome, a bacterium has another, smaller ring of DNA called a plasmid, which contains fewer genes and is not necessary for the survival of the bacterium.

29. Conjugation is a type of sexual reproduction that bacteria can do when conditions for survival are not ideal. Two bacteria connect by building a protein bridge and the plasmid of one is transferred to the other cell. This is done so that the bacterium receiving the plasmid can become more able to adapt to worsening environmental conditions. • When growth conditions become extremely unfavourable, many gram-positive bacteria form structures called spores. One type of spore, called an endospore, is made when the bacterium makes a thick wall surrounding its DNA and cytoplasm.

30. Eubacteria • Make up most of the prokaryotes on Earth • Separate them into 6 phylogenetic groups: • Spirochaetes • Chlamydias • Gram-positive bacteria • Green bacteria • Cyanobacteria • proteobacteria • Each group has a wide variety of species with different nutritional patterns, gas exchange methods, and reactions to gram stain.

31. Bacteria and Disease • Pathogenic bacteria produce toxins in the human body that cause disease symptoms. • Example: Streptococcus pneumoniae may result in symptoms of pneumonia • Some bacteria produce toxins that enter the bloodstream and attack the nervous system: tetanus, botulism (deadly form of food poisoning). These are anaerobic and survive as spores until they are introduced into a favourable environment such as a host. • The consequences of an infection depend on the invasiveness and toxicity of the pathogen. • Two types of toxins: endotoxins (released when certain gram-negative bacteria split and are seldom fatal. They normally cause fever, vomiting, and diarrhea: Salmonella and Echerichia) and exotoxins (released by living, multiplying bacteria that travel throughout the host’s body. They are highly toxic and often fatal.)

32. Antibiotics • Can be used to kill bacterial infections • But may not be effective in the future due to their overuse • Overuse causes bacteria to adapt and become resistant

33. Archaebacteria • Oldest group of organisms on Earth • All life kingdoms are descended from the ancestors of archaebacteria, we think. • Resemble primitive clusters of molecules • Has a cell wall, cell membrane that offer protection but are made of different chemicals than eubacteria. • More than half their genes are different from eubacteria • Grouped into several phyla based on their habitats. • methanogens live in oxygen-free places such as the gut of animals that produce methane gas, at the bottom of marshes and swamps, and on the ocean floor near the deep-sea vents. • Halophiles are salt-loving and inhabit salt lakes such as the Dead Sea • Thermophiles inhabit hot, acidic environments such as hot springs. • Psychrophiles are cold-loving found in the Antarctic and Arctic and cold ocean depths

34. Putting Bacteria to Work • Waste Management: use special bacteria that neutralize a variety of toxic compounds such as oil, battery acid, heavy metals, detergents, pesticides, old paint, plastics, radioactive materials, etc. • Sewage Treatment: bacteria decompose organic matter. A septic tank is an underground tank that contains billions of anaerobic bacteria, which degrade sewage slowly. • Dairy Foods: Bacterium lactis is used in the production of dairy foods. Lactic acid bacteria provide resistance to intestinal pathogens, stimulate the immune system, and help maintain a healthy balance of microorganisms in the digestive system.