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Anaximander

about 2,500 years ago, the Greek philosopher promoted the idea that life arose in water and that simpler forms of life preceded more complex ones.

Aristotle

whose views had an enormous impact on Western culture, generally held that species are fixed, or permanent, and do evolve.

Plato

supported the view that variations noted among members of the same species were due to imperfection. Therefore, only one representation represented the perfect model of a particular species.

George Cuvier

a French naturalist known as the Father of Paleontology (the study of fossils). His views supported catastrophism.

Catastrophism

points to gaps in the fossil record being the result of catastrophic events that would cause the extinction of specie(s). In turn, God would create a new species that was similar to the original. (Cuvier)

Count Buffon

suggested that Earth might be much older than 6,000 years. He also observed some telling similarities between specific fossils and certain living animals. In 1766, Buffon proposed the possibility that a species represented by a particular fossil form could be an ancient version of a group of similar living species.

Lamarck

Inheritance of Acquired Characteristics; In the early 1800s, French naturalist Jean-Baptiste Lamarck suggested that the best explanation for this relationship of fossils to current organisms is that life evolves. Lamarck explained evolution as a process of adaptation, the refinement of characteristics that equip organisms to perform successfully in their environments. Unfairly, we remember Lamarck today mainly for his erroneous view of how adaptations evolve. He proposed that by using or not using its body parts, an individual develops certain characteristics, which it passes on to its offspring. However, you should remember from your introductory biology course that at the time of conception a child receives all of its genetic composition. Any physical changes that occur after birth are not passed on to the nest generation.

Inheritance of Acquired Characteristics example

if the Roc (at the time he was wrestling) conceived a child with China (female wrestler) the child would not automatically have the physical attributes of its parents. Students often misunderstand the basic process of evolution and reflect, instead, a Lamarckian point of view. Organisms do not evolve structures because of want or need. Evolution is a passive process in which the environment favors diversity that exists within a population. Adaptations evolve in populations of organisms. Organisms do not evolve adaptations

On November 24, 1859

Charles Darwin published The Origin of Species.

The Origin of Species

Darwin's book drew a cohesive picture of life. The Origin of Species focused biologists' attention on the great diversity of organisms—their origins and relationships, their similarities and differences, their geographic distribution, and their adaptations to surrounding environments.

The voyage of the HMS Beagle (1831-1836)

As a boy, Darwin was interested in nature. The Beagles was a tour that would have a profound effect on Darwin's thinking and eventually on the thinking of the entire world. Darwin was 22 years old when he sailed from Great Britain with the Beagle in December 1831. The main mission of the voyage was to chart poorly known stretches of the South American coastline. While the crew of the ship surveyed the coast, Darwin spent most of his time on shore, observing and collecting thousands of specimens of the native plants and animals of South America. As the ship worked its way around the continent, Darwin observed the various adaptations of organisms that inhabited such diverse environments as the Brazilian jungles, the grasslands of the Argentine pampas, the desolate and frigid lands of Tierra del Fuego near Antarctica, and the towering heights of the Andes. Darwin noticed that: (a) the plants and animals living in temperate regions of South America seemed more closely related to species living in tropical regions of that continent than to species living in temperate regions of Europe, and (b) the South American fossils Darwin found were distinctly South American in their resemblance to the living plants and animals of that continent.

Galápagos Islands

named after the giant tortoises found there. These are relatively young volcanic islands about 900 kilometers (540 miles) off the Pacific coast of South America. Most of the animals of the Galápagos live nowhere else in the world but resemble species living on the South American mainland. It is as though plants and animals that strayed from the mainland and then diversified as they adapted to environments on the different islands had colonized the islands. Among the birds Darwin collected on the Galápagos were several types of finches. Some were unique to individual islands, while others were distributed on two or more islands that were close together. Darwin did not appreciate the full significance of the finches he collected until years after returning to Britain. Since then, biologists have applied modern methods of comparing species to reconstruct the evolutionary history of Darwin's finches.

Principles of Geology

by Scottish geologist Charles Lyell. (one of two books that played a pivotal role in Darwin's thought process) The book presented the case for an ancient Earth sculpted by gradual geological processes that continue today.

new geology

First, Earth must be very old if it has been shaped by such slow processes as mountain building and erosion. Second, the new geology explained how slow and subtle processes occurring over vast tracts of time could cause enormous change. Darwin would eventually apply this principle of gradualism to the evolution of Earth's life.

Thomas Malthus

wrote an Essay on the Principles of Population. In this work he argues that death due to calamity, disease or predation is a necessary evil as means of population control. He proposed that death and famine were inevitable because the human population tends to increase faster than the supply of food.

Alfred Wallace

(considered the cofounder of the theory of natural selection), a British naturalist doing fieldwork in Indonesia, developed a concept of natural selection identical to Darwin's.

With the publication in 1859 of The Origin of Species, Darwin presented the world with

an avalanche of evidence and a strong, logical argument for evolution and natural selection as the mechanism of descent with modification. Two main points- First, he argued from evidence that the species of organisms inhabiting Earth today descended from ancestral species. Second, his argument for natural selection as the mechanism for descent with modification.

natural selection

is that a population of organisms can change over the generations if individuals having certain heritable traits leave more offspring than other individuals and that those offspring survive long enough to also reproduce. The result of natural selection is evolutionary adaptation, a population's increase in the frequency of traits that are suited to the environment. In modern terms, we would say that the genetic composition of the population had changed over time, and that is one way of defining evolution. We can also use the term evolution on a much grander scale to mean all of biological history, from the earliest microbes to the enormous diversity of modern organisms.

Fossils

are the preserved remnants or impressions left by organisms that lived in the past. Most fossils are found in sedimentary rocks.

fossil record

is this ordered array in which fossils appear in the rock layers that mark the passing of geological time.

The oldest known fossils

date from about 3.5 billion years ago and are prokaryotes (bacteria and archaea). Fossils in younger layers of rock chronicle the evolution of various groups of eukaryotic organisms. Fishlike fossils are the oldest vertebrates in the fossil record. Amphibians are next, followed by reptiles, then mammals, and birds.

Paleontologists

study fossils and have discovered many transitional forms that link past and present. For example- a series of fossils documents the changes in skull shape and size that occurred as mammals evolved from reptiles. Another example is a series of fossilized whales that connect these aquatic mammals to their land-dwelling predecessors.

Comparative Anatomy

The comparison of body structures between different species is called comparative anatomy. Certain anatomical similarities among species bear witness to evolutionary history. For example, the same skeletal elements make up the forelimbs of humans, cats, whales, and bats, all of which are mammals. The functions of these forelimbs differ. If these limbs had been uniquely engineered, we would expect that their basic designs would be very different. However, structural similarity would not be surprising if all mammals descended from a common ancestor with the prototype forelimb.

descent with modification

Ancestral structures that originally functioned in one capacity become modified as they take on new functions.

Comparative Embryology

The comparison of structures that appear during the development of different organisms is called comparative embryology.

Molecular Biology

Evolutionary relationships among species leave signs in DNA and proteins—in genes and gene products. If two species have libraries of genes and proteins with sequences of monomers that match closely, the sequences must have been copied from a common ancestor. Darwin's boldest hypothesis was that all forms of life are related to some extent to the earliest organisms through branching evolution. The molecular signs include a common genetic code shared by all species.

Darwin's Theory of Natural Selection

Darwin synthesized his theory of natural selection from two key observations. First, that all species tend to produce excessive numbers of offspring. (1) Natural resources are limited. (2) The production of more individuals than the environment can support leads to a struggle for existence among the individuals of a population. (3) In most cases, only a small percentage of offspring will survive in each generation. Second, individual variation abounds in almost all species and much of this variation is heritable.

From these two observations, Darwin arrived at the conclusion that defines natural selection

Individuals whose inherited traits are best suited to the local environment are more likely to survive and reproduce than less fit individuals. In other words, the individuals that function best in the local environment tend to leave the most offspring. The environment screens a population's inherent variability. Differential success in reproduction causes the favored traits to accumulate in the population over the generations.

Environment and Natural Selection

You must understand that the environment does the selecting in natural selection. Species don't evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate, it is reactive. For example: ―Birds evolved wings seems as if birds did something deliberately. ―Wings evolved in birds is more accurate, in that something was done to birds in the process.

Population

is a group of individuals of the same species living in the same area at the same time. One population may be isolated from others of the same species. One population center may blur into another in a region of overlap where members of both populations are present but less numerous. Individuals are more concentrated in the population centers, and they are likely to breed with other locals. A population is the smallest biological unit that can evolve. A common misconception is that individual organisms evolve, in the Darwinian sense, during their lifetimes. The evolutionary impact of natural selection is only apparent in tracking how a population changes over time.

population genetics

emphasizes the extensive genetic variation within populations and (2) tracks the genetic makeup of populations over time.

Genetic Variation in Populations

Individual variation abounds in populations of all species that reproduce sexually. Most populations have a great deal of variation that can be detected only by biochemical means, such as ABO blood groups in humans.

Not all variation in a population is heritable

Phenotype results from a combination of the genotype, which is inherited, and the many environmental influences. Only the genetic component of variation is relevant to natural selection.

morphs

When a population includes two or more forms of a phenotypic characteristic

Polymorphic population

two or more morphs are present in readily noticeable numbers—that is, if neither morph is extremely rare.

Sources of Genetic Variation

Mutations and sexual recombination, which are both random processes, produce genetic variation

Mutations

random changes in the genetic material, can actually create new alleles.

The gene pool

consists of all alleles (alternative forms of genes) in all the individuals making up a population.

Phenylketonuria (PKU)

which is an inherited inability to break down the amino acid phenylalanine. If untreated, the disorder causes severe mental retardation. PKU is due to a recessive allele.

Microevolution

as Change in a Gene Pool

Hardy- Weinberg equilibrium

A nonevolving population is in genetic equilibrium. The population's gene pool remains constant over time. (1) The frequencies of alleles and genotypes are unchanged. (2) Sexual shuffling of genes cannot by itself change a gene pool.

Microevolution

is a generation-to-generation change in a population's frequencies of alleles.

causes of microevolution are

genetic drift, (Founder Effect and Bottleneck Effect), gene flow, mutation, and natural selection.

Genetic Drift

This evolutionary mechanism, a change in the gene pool of a small population due to chance

The Bottleneck Effect

Disasters such as earthquakes, floods, droughts, and fires may reduce the size of a population drastically. The small surviving population may not be representative of the original population's gene pool. Certain alleles will be overrepresented, some underrepresented, and some eliminated. Bottlenecking usually reduces the overall genetic variability in a population because at least some alleles are likely to be lost from the gene pool. An important application of this concept is the potential loss of individual variation, and hence adaptability, in bottlenecked populations of endangered species. The loss of genetic diversity in a population because of the bottleneck effect is a significant problem in conservation. When a species is reduced to relatively few individuals and then is brought back to abundance by extraordinary efforts, the species is not fully recovered. The lost genetic diversity may be a prerequisite for the long-term survival of the species.

Chance

may continue to change the gene pool for many generations until it grows large enough for sampling errors to be insignificant.

The Founder Effect

Genetic drift is also likely when a few individuals colonize an island, lake, or some other isolated habitat. The smaller the colony, the less its genetic makeup will represent the gene pool of the larger population from which the colonists emigrated. It undoubtedly contributed to the evolution of organisms that arrived on the Galápagos Islands. Consider that you and all the students present in today's class are the only survivors of some global catastrophe. Would your class adequately represent the biological diversity of the current human population?

Gene Flow

a population may gain or lose alleles by gene flow, the genetic exchange with another population. Gene flow occurs when fertile individuals or gametes migrate between populations. Gene flow tends to reduce genetic differences between populations. Extensive gene flow can amalgamate neighboring populations into a single population with a common gene pool. As humans began to move about the world more freely, gene flow became an important agent of microevolution in populations that were previously isolated.

Darwinian Fitness

Reproductive success is generally subtle and passive. Darwinian fitness is the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals. Production of fertile offspring that then reproduce is the only score that counts in natural selection.

Directional selection

shifts the phenotypic ―curve of a population by selecting in favor of some extreme phenotype. For example, directional selection might favor the darkest mice or pesticide resistance in insects.

Stabilizing selection

maintains variation for a particular trait within a narrow range, works by selecting against the more extreme phenotypes, and typically occurs in relatively stable environments.

Iridium

the rock deposited at the time of the dinosaurs contains a thin layer of clay rich in, an element very rare on Earth but common in meteorites. Many paleontologists conclude that the iridium layer is the result of fallout from a huge cloud of dust formed when a large meteorite or asteroid hit Earth. The cloud would have blocked light and disturbed climate severely for months, perhaps killing off many plant species.

The impact hypothesis

predicts that we should find a huge impact crater of the right age. In 1981, two petroleum geologists discovered the Chicxulub crater near the Yucatán Peninsula in the Caribbean Sea. This 150-300 kilometers wide impact site dates to the predicted time, was created when a meteorite or asteroid the size of San Francisco slammed into the Earth, and would have released thousands of times more energy than the world's combined stockpile of nuclear weapons.

Macroevolution includes 4 major things

the multiplication of species; the origin of evolutionary novelty, such as the wings and feathers of birds and big brains in humans; the explosive diversification that follows some evolutionary breakthrough—such as the origin of thousands of plant species after the flower evolved; and mass extinctions.

speciation

The origin of new species is the focal point of our study of macroevolution.

Nonbranching evolution

occurs when a population may change so much through adaptation to a changing environment that we call it a new species.

Species

is a Latin wording meaning "kind" or "appearance." A population or group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring, but who cannot successfully interbreed with members of other species.

Ernst Mayr

1927, led an expedition to New Guinea and identified 138 species of birds on the basis of differences in their appearance. The local tribe of Papuan natives had given names of their own to 137 bird species. Mayr defines species based upon the biological species concept.

The biological species concept

species as "groups of interbreeding natural populations that are reproductively isolated from other such groups" (in Mayr's words). The biological species concept does not account for organism that reproduce asexually.

Reproductive isolation

blocks exchange of genes between species and keeps their gene pools separate.

Pre-zygotic barriers

impede mating between species or hinder fertilization of eggs if members of different species should attempt to mate. Such barriers may involve one or more of the following mechanisms of isolation

Temporal

species have different breeding periods;

Habitat

species are spatially segregated;

Behavioral

species evolved significant differences in courtship rituals;

Mechanical

species possess anatomically incompatible sex organs; and

Gametic

gametes of the two species are incompatible and fertilization does not occur.

Post-zygotic barriers

are back-up mechanisms that operate should interspecies mating actually occur and form hybrid zygotes.

hybrid inviability

hybrids die before reaching reproductive maturity; or

hybrid sterility

offspring are infertile. A mule is the hybrid offspring of a female horse and a male donkey. Mules are sterile. Mules are one exception to the hybrids that are often produced this way because they are strong. Often these hybrids may be weak and have many genetic abnormalities

allopatric speciation

the initial block to gene flow is a geographical barrier that physically isolates the splinter population. Allopatric speciation is more likely when a population is small and isolated. Speciation occurs only with the evolution of reproductive barriers between the isolated population and its parent population. ie. creeping glacier, land bridge.

sympatric speciation

is the origin of a new species, without geographic isolation, in the midst of the parent population. A genetic change can produce a reproductive barrier between mutants and the parent population. Sympatric speciation is not widespread among animals but may account for over 25% of all plant species.

Polyploids

Many plant species have originated from accidents during cell division that resulted in extra sets of chromosomes producing polyploids. Tetraploid species may evolve in a single generation without geographic isolation. Most polyploid species arise from the hybridization of two parent species.

Graudalistic model

Under the microevolution theory, traditional evolutionary trees sprout branches that diverge gradually. New species are an accumulation of many smaller changes occurring over vast spans of time. Darwin- "Although each species must have passed through numerous transitional stages, it is probable that the periods during which each underwent modification, though many and long as measured by years, have been short in comparison with the periods during which each remained in an unchanged condition."

The punctuated equilibrium model

suggests that species diverge in spurts of relatively rapid change, instead of slowly and gradually. The term punctuated equilibrium is derived from the idea of long periods of stasis (equilibrium) punctuated by episodes of speciation.

Paedomorphosis

is the retention of juvenile body features in the adult (from the Greek paedos, "child," and morphosis, "shaping"). Paedomorphosis is an example of such a dramatic shift in development. A salamander called an axolotl grows to full size and reproduces without losing its external gills, a juvenile feature in most species of salamanders. This albino axolotl salamander illustrates paedomorphosis. Paedomorphosis has also been important in human evolution. Humans and chimpanzees are much more alike as fetuses than they are as adults. As fetuses, they share certain features: rounded skulls, small jaws, and a flat and rounded face. The adult human skull retains fetal features even after we are mature. The human brain is proportionately larger than the chimpanzee brain because growth of the organ is switched off much later in human development.

geological periods

(1) the Precambrian,= the longest era (2) Paleozoic, (3) Mesozoic, and (4) Cenozoic eras. The boundaries are marked in the fossil record by explosive diversification of many new forms of life and mass extinctions.

radiometric dating

The most common method to determine the ages of fossils in years. This method is based on the decay of radioactive isotopes.

North America and Europe are presently drifting apart at a rate of

about 2 cm per year.

Pangaea

About 250 million years ago, near the end of the Paleozoic era, plate movements brought all the landmasses together into the supercontinent named Pangaea, meaning "all land." Many habitats were dramatically changed, and biological diversity was reshaped. Species that had been evolving in isolation came together and competed. The total amount of shoreline was reduced. Ocean basins increased in depth, which lowered the sea level and drained the shallow coastal seas. Ocean currents changed. About 180 million years ago (during the Mesozoic era), Pangaea began to break up, causing geographical isolation of colossal proportions.

The Permian extinctions

at about the time Pangaea formed, claimed over 90% of the species of marine animals and took a tremendous toll on terrestrial life. (largest extinction). Each massive dip in species diversity has been followed by explosive diversification of certain survivors.

Mammals existed for at least 75 million years before

undergoing an explosive increase in diversity just after the Cretaceous.

Systematics

is the study of biological diversity, past and present.

Taxonomy

is the identification, naming, and classification of species.

Carolus Linnaeus

(1707-1778), a Swedish physician and botanist (plant specialist), started the taxonomic system with binomial names and a hierarchical classification.

Binomial

(1) The first, the genus, is capitalized. (2) The second refers to one species within the genus, in lowercase.

Homologous structures

may look and function very differently in separate species, but they evolved from the same structure and a common ancestor. Examples include a whale limb and a bat wing. The greater the number of homologous structures between two species, the more closely the species are related. Not all likeness is inherited from a common ancestor: Similar evolutionary pressures acting on unrelated species may produce similar, or analogous, structures. Homologous structures are used to develop phylogenetic trees and classify organisms according to evolutionary history.

convergent evolution

Species from different evolutionary branches may have analogous but not homologous structures. Similarity due to convergence is termed analogy, not homology. Wings of an insect and wings of a bird are analogous but not homologous.

Robert H. Whittaker

In 1969, American ecologist argued effectively for a five-kingdom system.

Kingdom Monera

included all the prokaryotes.

Kingdoms Plantae, Fungi, and Animalia

consist of multicellular eukaryotes that differ in structure, development, and modes of nutrition.

Protista

contains: all eukaryotes that do not fit the definitions of plants, fungi, or animals and certain large, multicellular organisms that are believed to be direct descendants of unicellular protists.

three-domain system

as one alternative to the five- kingdom system. The three domains include (1) two domains of prokaryotes, the Bacteria and Archaea

Eukarya

one domain of eukaryotes

The most frequently employed biowarfare agents

bacteria.

Bio-warfare

the deliberate use of viruses, bacteria, fungi, or toxins to cause harm or death to a population.

Bio-crime

using biological agent introduced through the air, water supply or food in order to cause harm.

Bio-terrorism

intentional threatening use of biological agents to cause death in large numbers for political reasons.

Agro-terrorism

the threat to agriculture by means of bio-terrorism.

The Earth formed

about 4.5 billion years ago. Its crust solidified about 4.0 billion years ago.

The first life appeared

about 3.5 billion years ago. Within the next billion years, two distinct groups of prokaryotes diverged: bacteria and archaea. An oxygen revolution began about 2.5 billion years ago when photosynthetic prokaryotes split water molecules, releasing oxygen gas into Earth's atmosphere. The oldest eukaryotic fossils are about 1.7 billion years old.

Eukaryotic cells possess

nuclei and many other organelles lacking in prokaryotic cells

Eukaryotic cells evolved from

a prokaryotic community, a host cell containing even smaller prokaryotes.

Mitochondria and chloroplasts are descendants of

smaller prokaryotes.

Protists

are mostly microscopic and unicellular. Protists include protozoans and algae, including diatoms.

The first multicellular eukaryotes evolved

about a billion years ago as colonies of single-celled ancestors. Their modern descendants include- multicellular protists, such as seaweeds, animals, plants, and fungi.

Cambrian explosion

The greatest diversification of animals was the so-called. All the major body plans (phyla) of animals had evolved by the end of that evolutionary eruption.

Plants, in the company of fungi, first colonized land

about 475 million years ago.

Plants transformed the landscape

Opportunities arose for herbivorous animals and their predators.

spontaneous generation

Until well into the nineteenth century, it was common knowledge that life could arise from nonliving matter

Louis Pasteur

1862 famous experiments confirmed what many others had suspected: All life today, including microbes, arises only by the reproduction of preexisting life.

Biogenesis

This life-from-life principle

first organisms

Although there is no evidence that spontaneous generation occurs today, conditions on the early Earth were very different. Earth's earliest atmosphere was void of oxygen to tear apart complex molecules. Energy sources such as lightning, volcanic activity, and ultraviolet sunlight were more intense than what we experience today. Most biologists now think that it is at least a credible hypothesis that chemical and physical processes in Earth's primordial environment could eventually have produced very simple cells through a sequence of stages. Debate abounds about the nature of those steps.

Stanley Miller

In 1953, built a contraption that simulated key conditions on early earth. His apparatus produced a variety of small organic molecules that are essential for life, including amino acids, the monomers and proteins. In the half-century since Miller's seminal experiments, many scientists have repeated and extended the research by varying such conditions as the composition of the ancient―atmosphere and ―sea

Miller's experiments have collectively produced

(a) all 20 amino acids, (b) several sugars, (c) lipids, (d) nucleotides that are monomers of DNA and RNA, and (e) ATP.

If the abiotic synthesis of life is correct

it should be possible to link organic monomers to form polymers (proteins, nucleic acids) without enzymes and other cellular equipment.

Graham-Cairnes & Smith

Researchers have observed such polymerization by dripping solutions of organic monomers onto hot sand, clay, or rock. The heat vaporizes the water in the solution and concentrates the monomers on the underlying substance. Some monomers then bind together.

Sidney Fox

conducted experiments that indicated that perhaps on early Earth, raindrops or waves may have splashed dilute solutions of organic monomers onto fresh lava or other hot rocks and then rinsed polypeptides and other polymers back into the sea.

What were the first genes like?

One hypothesis is that the first genes were short strands of RNA that replicated without the assistance of enzymes (proteins). In laboratory experiments, short RNA molecules can assemble spontaneously from nucleotide monomers without the presence of cells or enzymes. The result is a population of RNA molecules, each with some random sequences of monomers. Some molecules self-replicate, but they vary in their success at this reproduction. The results are a sort of molecular evolution in a test tube.

Ribozymes

RNA genes are also likely because cells have catalytic RNA. These enzymes were discovered by scientist Cech and Altman and they were awarded the Nobel Prize in 1989. Early ribozymes may have catalyzed their own replication. The molecular biology of today may have been preceded by an "RNA world."

Formation of Pre-cells

The creation of membranes. The properties of life emerge from an interaction of molecules organized into higher levels of order. But such molecular teams would be much more efficient if they were packaged within membranes that kept the molecules close together in a solution that could be different from the surrounding environment. keep the molecules close together and in a solution different from the surrounding environment. Certain types of pre-cells store energy in the form of a voltage across their membranes, even discharging voltage much like nerve cells do. If specific enzymes are included, some pre-cells: show rudimentary metabolism, absorb substrates from their surroundings, and release products

Prokaryotes

For the first 75% of life's history, Earth was populated only by organisms that were microscopic and unicellular. Prokaryotes are both harmful and beneficial to humans. prokaryotes can be found everywhere on earth and outnumber all eukaryotes combined. More prokaryotes inhabit a handful of fertile soil or the mouth or skin of a single human than the total number of people who have ever lived. Prokaryotes also thrive in habitats too cold, too hot, too salty, too acidic, or too alkaline for any eukaryote.

Prokaryotes and disease

During the fourteenth century, bubonic plague killed about 25% of the European human population. Prokaryotes cause tuberculosis, cholera, many STDs and some types of food poisoning. Some prokaryotes are benign or even beneficial. Bacteria in our intestines provide us with important vitamins and mouths prevent harmful fungi from growing there. Prokaryotes also decompose dead organisms and recycle carbon and other vital chemical elements back and forth between organic matter and the soil and atmosphere. If prokaryotic decomposers were to disappear, the chemical cycles that sustain life would come to a halt.

The Structure, Function, and Reproduction of Prokaryotes

Nearly all prokaryotes have cell walls exterior to their plasma membranes. These walls are chemically different from the cellulose walls of plant cells. Some antibiotics, including the penicillins, kill certain bacteria by incapacitating an enzyme the microbes use to make their walls.

Cocci

Spherical species are called (singular, coccus) from the Greek word for ―berries. Cocci that occur in clusters are called staphylococci (from the Greek staphyle, ―cluster of grapes), or staph for short (as in staph infections). Other cocci occur in chains called streptococci (from the Greek streptos, ―twisted) and include the bacteria that cause strep throat in humans.

Bacilli

Rod-shaped prokaryotes are called (singular, bacillus).

Spirochetes

A third group of prokaryotes is curved or spiral-shaped. The largest spiral-shaped prokaryotes are called spirochetes. The bacterium that causes syphilis, for example, is a spirochete. So is the culprit that causes Lyme disease.

Streptococci

Some species tend to aggregate transiently into groups of two or more cells. Others form true colonies, which are permanent aggregates of identical cells. Some exhibit a simple multicellular organization, with a division of labor between specialized types of cells. About half of all prokaryotic species are mobile using one or more flagella.

Endospores

Unlike the arachae, most bacteria can not thrive in extreme environments. Instead, they survive by forming ―resting cells. Remain dormant for centuries and survive boiling water. Laboratories heat water to 121°C in special high-pressure autoclave machines. The food-canning industry uses similar methods to kill dangerous soil bacteria such as Clostridium botulinum, which produces the potentially fatal disease botulism.

binary fission

can copy their DNA and divide nearly continuously. Bacteria show exponential growth. Their populations may double every 20 minutes. Fortunately, few bacterial populations can sustain exponential growth for long. Populations grow quickly but are soon limited by: nutrients, space, and accumulations of metabolic wastes. Refrigeration retards (but doesn't stop) bacterial growth.

Nutrition

refers to how an organism obtains two resources for synthesizing organic compounds- energy and a source of carbon

Phototrophs

use light.

Chemotrophs

use energy from chemicals taken from the environment.

Carbon sources

Autotrophs need only the inorganic compound CO2 as a carbon source. Heterotrophs require at least one organic nutrient (for example, glucose) as a source of carbon for making other organic compounds.

Photoautotrophs are

photosynthetic organisms that harness light energy to drive the synthesis of organic compounds from CO2. Examples include: cyanobacteria and all plants and algae.

Chemoautotrophs

extract energy from certain inorganic substances, such as hydrogen sulfide (H2S) or ammonia (NH3), and need only CO2 as a carbon source. This mode of nutrition is unique to certain prokaryotes. For example, prokaryotic species living around hot-water vents deep in the seas are the main food producers in those bizarre ecosystems.

Photoheterotrophs

can use light to generate ATP but must obtain their carbon in organic form. This mode of nutrition is restricted to certain prokaryotes.

Chemoheterotrophs

must consume organic molecules for both energy and carbon. Examples are: many prokaryotes, certain protists, some plants, all fungi, and all animals.

Prokaryotic Evolution

Bacteria and Archaea. Prokaryotes lack a membrane-enclosed nucleus and other organelles found in eukaryotes. The traditional five-kingdom classification scheme emphasizes this fundamental difference in cellular organization. Both are prokaryotes, but they differ in many structural, biochemical, and physiological characteristics. There is also evidence that archaea are more closely related to eukaryotes than they are to bacteria. Most prokaryotes are bacteria.

Archaea

The name (from the Greek archaio, ―ancient) refers to the antiquity of the group's origin from the earliest cells. (1) Today, most species of archaea inhabit extreme environments such as hot springs and salt ponds.

Extremophiles

Some biologists refer to archaea as extremophiles, or ―lovers of the extreme. Extremophiles can survive harsh environments.

Halophiles

live in concentrated salt solutions such as Utah's Great Salt Lake and seawater-evaporating ponds used to produce salt.

Thermophiles

live in very hot water, such as deep-ocean vents exceeding 100°C.

Pathogens

Bacteria and other microorganisms that cause disease. Our body defenses check the growth of pathogens. Normal residents of the human body can make us sick when our defenses are weakened. Most pathogenic bacteria cause disease by producing one of two classes of poisons.

Exotoxins

are toxic proteins secreted by bacterial cells.

Endotoxins

are not cell secretions but are chemical components of the cell walls of certain bacteria. All endotoxins induce the same general symptoms: fever, aches, and sometimes a dangerous drop in blood pressure (shock). Different species of Salmonella produce endotoxins that cause food poisoning and typhoid fever.

the first oxygen on earth

was the result of by products from cyanobacteria

bioremediation

The use of organisms to remove pollutants from water, air, and soil is called.

Protists

the first eukaryotes to evolve from prokaryote ancestors and are much more complex than prokaryotes.

The primal eukaryotes were the predecessors of

modern protists and all other eukaryotes—plants, fungi, and animals. protists are often defined by what they are not, they do not have the defining characteristics of plants, fungi, and animals

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