Diversity of Living Things

Taxonomy

The biosphere is the part of Earth that is inhabited by living organismsBiologists 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 categoriesA species is used to describe a kind of organism that is similar in structure and shape, and they reproduced with one another.

Today we use the system called binomial nomenclature that was developed by Carolus Linnaeus, where all organisms are given the same naming structure: in LatinThe 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

Groups that Linnaeus assigned organisms to are called taxa and the science of naming organisms and assigning them to certain groups is called taxonomyThe taxon species is the smallest group, then genusSimilar 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.

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)

Kingdom Eubacteria

Found everywhere in the world.

Prokaryotes

Diverse genetic makeup and metabolism

Kingdom Protista

Single celled eukaryotes

Some have chloroplasts

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

Kingdom Plantae

Multicellular

Cell walls with cellulose

Chloroplasts

Mosses, ferns, seed plants

Kingdom Animalia

Multicellular

Cell membranes, but no cell walls.

Often organized into tissues, organs, and organ systems

Divided into invertebrates and vertebrates

Dichotomous KeyUsed to help place organisms into the appropriate classification group

Keys have 2 choices for each characteristic

Phylogeny, Taxonomy, Evolution

Principles of PhylogenyPhylogeny: 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 ancestryExample: all vertebrate embryos go through a stage where they have gills like fish

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

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.

Biodiversity and Natural SelectionWhy do some species die off and new species appear?Charles Darwin was a scientist who studied the origins of speciesHe 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.

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.

Kingdoms and Domains

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.

Eubacteria KingdomOldest organisms living on EarthMost abundant and very diverseSimilar 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.

Capsule

Cilia

Cell membraneCytoplasm

ribosome

Cell wallflagellum

Nuclear material

Bacterial ShapesCoccus is a spherical shaped bacterial cellBacillus is rod shapedSpirillum is spiral shapedCocci that live on their own are called monococci, in pairs: diplococci, in linear chains: streptococci, in grape-like structures: staphylococciBacilli can be single, paired or chained (monobacilli, diplobacilli, streptobacilli)Spiral can only exist as single cells.

Reaction to StainBacteria 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.

NutritionMost 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).

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.

Respiration

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

Reproduction

All reproduce asexually by binary fissionCan 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.

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.

Eubacteria

Make up most of the prokaryotes on EarthSeparate them into 6 phylogenetic groups:

SpirochaetesChlamydiasGram-positive bacteriaGreen bacteriaCyanobacteriaproteobacteria

Each group has a wide variety of species with different nutritional patterns, gas exchange methods, and reactions to gram stain.

Bacteria and DiseasePathogenic bacteria produce toxins in the human body that cause disease symptoms.Example: Streptococcus pneumoniae may result in symptoms of pneumoniaSome 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.)

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

ArchaebacteriaOldest group of organisms on EarthAll life kingdoms are descended from the ancestors of archaebacteria, we think.Resemble primitive clusters of moleculesHas a cell wall, cell membrane that offer protection but are made of different chemicals than eubacteria.More than half their genes are different from eubacteriaGrouped 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 SeaThermophiles inhabit hot, acidic environments such as hot springs.Psychrophiles are cold-loving found in the Antarctic and Arctic and cold ocean depths

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.