Ch 14 and 15
Origin of Life and Evolution
Terms in this set (89)
The idea that life arises only from life is referred to as ____________________.
Breeding organisms with specific traits in order to produce offspring with identical traits.
A way that populations can change when organisms with favorable variations survive, reproduce and pass their variations to the next generation.
A structural adaptation that enables one species to resemble another species.
A structural adaptation that enables a species to blend in with their surroundings.
Structural features with a common evolutionary origin. Can be similar in arrangement, function, or both
structures that do not have a common evolutionary origin but are similar in function
remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species
An organism in the earliest stage of development
Summarize Darwin's theory of natural selection
Organisms produce many more offspring than can survive. Not all of these offspring are the same. There are genetic variations among them. Individuals with certain useful variations survive and produce more offspring with similar characteristics. Over many generations, the population is mostly made up of individuals with the useful variations.
Why are fossils important?
Fossil evidence formed the basis of early evolutionary concepts. They give us information about how, where and when organisms lived, as well as what they looked like.
Types of adaptations
Structural (chang in the body's appearance)
Physiological (Change in the body chemicals)
Examples of Structural adaptations
Examples of Physiological adaptations
antibiotic resistance in bacteria
pesticide resistance in insects
This is a map of Darwin's voyage on the HMS Beagle. Darwin studied and collected biological and fossil specimens at every port along the route. His studies provided the foundation for his theory of evolution by natural selection.
What does this picture represent? Why is it important?
What is the significance of the Galapagos Islands?
On the Galápagos Islands, Darwin studied many species of animals and plants that are unique to the islands but similar to species elsewhere. These observations led Darwin to consider the possibility that species can change over time.
English economist Thomas Malthus had proposed an idea that Darwin modified and used in his explanation. Malthus's idea was that the human population grows faster than Earth's food supply.
any variation that aids an organism's chances of survival in its environment
What is the evidence for evolution? (Direct and Indirect)
Physiological resistance in species of bacteria, insects, and plants is direct evidence of evolution. However, most of the evidence for evolution is indirect, coming from sources such as fossils and studies of anatomy, embryology, and biochemistry.
Why is the presence of pelvic bones in the baleen whale considered to be evidence of evolution?
Pelvic bones are evidence that whales once possessed hind limbs. Since whales now have no hind limbs, their loss must be the result of an evolutionary change.
How does a structure become a vestigial structure?
A structure becomes vestigial when the species no longer needs the feature for its original function, yet it is still inherited as part of the body plan for the species. Ex. Pelvic bone for a whale.
How does embryology give evidence of evolution?
The embryos of a fish, a reptile, a bird, and a mammal have a tail and pharyngeal pouches. It is the shared features in the young embryos that suggest evolution from a distant, common ancestor.
How does biochemistry give evidence of evolution?
Nearly all organisms share DNA, ATP, and many enzymes among their biochemical molecules. One enzyme, cytochrome c, occurs in organisms as diverse as bacteria and bison. Organisms that are biochemically similar have fewer differences in their amino acid sequences.
_______ is considered to be the fundamental concept of biology.
the modern theory of evolution
What is the difference between artificial selection and natural selection?
Artificial selection is the intentional breeding of organisms with specific traits in order to produce offspring with identical traits. Natural selection occurs when organisms with favorable variations of traits survive in nature, reproduce, and pass these favorable variations to offspring.
How does mimicry differ from camouflage?
Mimicry is an adaptation that allows one species to resemble another species. Camouflage is an adaptation that allows one species to resemble its surroundings.
The fur of an Arctic fox turns white in the winter. Is this an example of natural selection? Why or why not?
The answer is no. An individual cannot evolve a new phenotype (in this case, changing the color of its fur) within its lifetime in response to its environment.
Which type of natural selection does NOT favor the evolution of new species?
Stabilizing selection reduces variation in a population.
Which of the following rarely affects a population's genetic equilibrium?
Organisms with lethal mutations do not survive. Therefore, organisms with lethal mutations cannot produce enough offspring to affect a population's genetic equilibrium.
Why are the Galapagos Islands rich in unique species of organisms?
Geographic isolation has helped to keep the islands' species unique.
How does evolution occur? (Mechanisms for evolution)
Evolution can occur only when a population's genetic equilibrium changes. Mutation, genetic drift, and gene flow can change a population's genetic equilibrium, especially in a small, isolated population. Natural selection is usually a factor that causes change in established gene pools—both large and small. The separation of populations by physical barriers can lead to speciation.
How fast does evolution happen?
Gradualism is the hypothesis that species originate through a gradual change in adaptations. The alternative hypothesis, punctuated equilibrium, argues that speciation occurs in relatively rapid bursts, followed by long periods of genetic equilibrium. Evidence for both evolutionary rates can be found in the fossil record.
Why does disruptive selection favor speciation?
Disruptive selection favors extreme variations of a trait. Over time, it is less likely that species with extreme variations will mate, therefore giving rise to new species.
Are the physical similarities between a dolphin and a shark evidence of convergent or divergent evolution?
The answer is convergent evolution. Dolphins and sharks are unrelated organisms that have evolved similar traits because they share similar environmental pressures.
Why do some insects and bacteria evolve adaptations more rapidly than other species?
Insects and bacteria are examples of species that reproduce in large numbers and many times in a relatively short span of time, allowing adaptations to be more easily observed.
Why is most of the evidence for evolution indirect rather than direct evidence?
Evolutionary processes are difficult for humans to observe directly. The short scale of human life spans makes it difficult to comprehend evolutionary processes that occur over millions of years.
Are the fangs of a rattlesnake and the fangs of a spider homologous structures or analogous structures, and why?
The fangs of these organisms are analogous structures. They share the same function in each organism, to deliver venom, but the organisms do not share a common evolutionary origin.
How do bird bones show an adaptation to flying that the bones of the flightless organisms, though homologous, do not?
Bird bones have evolved to be delicate, lightweight, and elongated.
How do analogous structures provide evidence of evolution?
Analogous structures show the way dissimilar organisms adapted independently to similar ways of life by developing functionally similar structures.
A pattern of evolution in which distantly related organisms evolve similar traits. Convergent evolution occurs when unrelated species occupy similar environments in different parts of the world.
Do Individuals Evolve?
Genes determine most of an individual's features, such as tooth shape or flower color. If an organism has a feature that is poorly adapted to its environment, the organism may be unable to survive and reproduce. However, within its lifetime, it cannot evolve a new phenotype by natural selection in response to its environment. Natural selection acts on the range of phenotypes in a population. Each member has the genes that characterize the traits of the species, and these genes exist as pairs of alleles. Evolution occurs as a population's genes and their frequencies change over time.
How can a population's genes change over time?
Picture all of the alleles of the population's genes as being together in a large pool called a gene pool. The percentage of any specific allele in the gene pool is called the allelic frequency. They refer to a population in which the frequency of alleles remains the same over generations as being in genetic equilibrium. Any factor that affects the genes in the gene pool can change allelic frequencies, disrupting a population's genetic equilibrium, which results in the process of evolution.
the combined genetic information of all members of a particular population
percentage of any specific allele in a population's gene pool
condition in which the frequency of alleles in a population remains the same over generations
A population that is in genetic equilibrium is not evolving.
How can genetic equilibrium be disrupted?
the movement of individuals in and out of a population
Environmental factors, such as radiation or chemicals, cause many mutations, but other mutations occur by chance. Many are lethal. However, occasionally, a mutation results in a useful variation, and the new gene becomes part of the population's gene pool by the process of natural selection.
the alteration of allelic frequencies by chance events.
Genetic drift can greatly affect small populations that include the descendants of a small number of organisms.
The transport of genes by migrating individuals. When an individual leaves a population, its genes are lost from the gene pool. When individuals enter a population, their genes are added to the pool.
What are the three different types of natural selection that act on variation?
stabilizing, directional, and disruptive.
natural selection that favors average individuals in a population
natural selection that favors one of the extreme variations of a trait
individuals with either extreme of a trait's variation are selected for
What was early earth like?
Some scientists suggest that it was probably very hot. The energy from colliding meteorites could have heated its surface, while both the compression of minerals and the decay of radioactive materials heated its interior.
Volcanoes might have frequently spewed lava and gases, relieving some of the pressure in Earth's hot interior. These gases helped form Earth's early atmosphere.
About 4.4 billion years ago, Earth might have cooled enough for the water in its atmosphere to condense. This might have led to millions of years of rainstorms with lightning—enough rain to fill depressions that became Earth's oceans.
How old is the earth?
There is no direct evidence of the earliest years of Earth's history. The oldest rocks that have been found on Earth formed about 3.9 billion years ago.
Types of fossils
A fossil is evidence of an organism that lived long ago that is preserved in Earth's rocks.
scientists who study ancient life, are like detectives who use fossils to understand events that happened long ago.
They use fossils to determine the kinds of organisms that lived during the past and sometimes to learn about their behavior.
How do fossils form?
For fossils to form, organisms usually have to be buried in mud, sand, or clay soon after they die.
Most fossils are found in sedimentary rocks. These rocks form at relatively low temperatures and pressures that may prevent damage to the organism.
If the rock layers have not been disturbed, the layers at the surface must be younger than the deeper layers.
The fossils in the top layer must also be younger than those in deeper layers. Using this principle, scientists can determine relative age and the order of appearance of the species that are preserved as fossils in the layers.
To find the specific ages of rocks, scientists use radiometric dating techniques utilizing the radioactive isotopes in rocks. Because every radioactive isotope has a characteristic decay rate, scientists use the rate of decay as a type of clock. Scientists try to determine the approximate ages of rocks by comparing the amount of a radioactive isotope and the new isotope into which it decays.
The decay rate of a radioactive isotope is called its half-life.
Geological Time Scale
The divisions in the geologic time scale are distinguished by the organisms that lived during that time interval.The fossil record indicates that there were several episodes of mass extinction that fall between time divisions.
The geologic time scale begins with the formation of Earth about 4.6 billion years ago.
A mass extinction is an event that occurs when many organisms disappear from the fossil record almost at once.
Fossilized remains of domeshaped mats of shallow-water communities, cyanobacterial species especially, that were infiltrated with dissolved minerals and fine sediments. Some are 3 billion years old. Stromatolites still form today in Australia from mats of cyanobacteria. Thus, the stromatolites are evidence of the existence of photosynthetic organisms on Earth during the Precambrian.
name for the time in earths early history that accounts for ninety percent of earth's time, but only cellular organisms lived.
By the end of the Precambrian, about 543 million years ago, multicellular eukaryotes, such as sponges and jelly-fishes, diversified and filled the oceans.
lasted until 248 million years ago, many more types of animals and plants were present on Earth, and some were preserved in the fossil record.
The first period in the Paleozoic Era. During the Cambrian Period, the oceans teemed with many types of animals, including worms, sea stars, and unusual arthropods.
The Mesozoic Era began about 248 million years ago. Fossils from the Triassic Period, the oldest period, show that mammals appeared on Earth at this time. These fossils of mammals indicate that early mammals were small and mouse-like. Recent fossil discoveries support the idea that modern birds evolved from one of the groups of dinosaurs toward the end of this period.
The theory of continental drift, suggests that Earth's continents have moved during Earth's history and are still moving today at a rate of about six centimeters per year.
The Cenozoic began about 65 million years ago.
It is the era in which you now live. Mammals began to flourish during the early part of this era.
Primates first appeared approximately 75 million years ago and have diversified greatly.
The modern human species appeared perhaps as recently as 200,000 years ago.
What determines the divisions in the geologic time scale?
A. the types of rock formed during the different divisions
B. dates based upon radioactive isotope decay
C. periodic episodes of mass extinction
D. the organisms that lived during that time interval
The answer is D, the organisms that lived during that time interval.
How can scientists determine when a mass extinction occurred in Earth's history?
The fossils from a large percentage of species disappear from the fossil record almost at once.
What organisms have occupied Earth for the longest period of time?
Single-celled organisms have been present on the Earth since the Precambrian period and are still present today.
Given that volcanoes have erupted since Earth's early history, why does volcanic rock not contain many fossils?
Lava is subject to high heat and strong pressure changes that prevent fossils from forming in it.
If scientists discover an early human fossil lying next to a dinosaur fossil, might they infer that some early humans actually lived at the time of dinosaurs?
The answer is no. The two fossils may have come to lie next to one another because of the effects of erosion, earth movements, the movement of water, or other artificial means.
the idea that living things come from nonliving things.
In the past, the ideas that decaying meat produced maggots, mud produced fishes, and grain produced mice were reasonable explanations for what people observed occurring in their environment.
In 1668, an Italian physician, Francesco Redi, disproved a commonly held belief at the time—the idea that decaying meat produced maggots, which are immature flies. Redi's well-designed, controlled experiment successfully convinced many scientists that maggots, and probably most large organisms, did not arise by spontaneous generation.
Did Redi completely disprove the idea of spontaneous generation?
No. Although Redi had disproved the spontaneous generation of large organisms, many scientists thought that microorganisms were so numerous and widespread that they must arise spontaneously-probably from a vital force in the air.
In the mid-1800s, Louis Pasteur designed an experiment that disproved the spontaneous generation of microorganisms.
Pasteur set up an experiment in which air, but no microorganisms, was allowed to contact a broth that contained nutrients.
Pasteur's experiment showed that microorganisms do not simply arise in broth, even in the presence of air.
When and how did life begin on Earth?
Scientists hypothesize that two developments must have preceded the appearance of life on Earth. First, simple organic molecules, or molecules that contain carbon, must have formed.
Then these molecules must have become organized into complex organic molecules such as proteins, carbohydrates, and nucleic acids that are essential to life.The next step in the origin of life, as proposed by some scientists, was the formation of complex organic compounds.
In the 1930s, a Russian scientist, Alexander Oparin, hypothesized that life began in the oceans that formed on early Earth. He suggested that energy from the sun, lightning, and Earth's heat triggered chemical reactions to produce small organic molecules from the substances present in the atmosphere. Then, rain probably washed the molecules into the oceans to form what is often called a primordial soup.
Stanley Miller and Harold Urey
In 1953, two American scientists, Stanley Miller and Harold Urey, tested Oparin's hypothesis by simulating the conditions of early Earth in the laboratory.
the hypothetical evolutionary precursor of living cells, consisting of a mixture of organic molecules within a membrane, a large, ordered structure, enclosed by a membrane, that carries out some life activities, such as growth and division
the theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism.
First forms of life
similar to present day archaebacteria
are prokaryotic and live in harsh environments, such as deep-sea vents and hot springs.
The earliest autotrophs probably made glucose by chemosynthesis rather than by photosynthesis.
autotrophs release the energy of inorganic compounds, such as sulfur compounds, in their environment to make their food.
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