Evolution by Natural Selection

Scientific Law

- A statement of relationship that expresses a fundamental principle of science. - Always applies under the same conditions - May be limited to very specific conditions - It implies a causal relationship - It does not provide a mechanism or explanation for a phenomenon Examples: -Law of gravity

Scientific Hypothesis

- A tentative explanation for an observation/phenomenon - Must be testable - Can be supported or refuted through experimentation or observation - Must be falsifiable - We make predictions based on testable hypotheses

Scientific Fact

- Repeatedly tested and confirmed - Overwhelmingly supported by evidence Examples: - Colds and flu are caused by viruses - Objects fall to the ground - Cellular membranes are made of lipids - Populations change over time

Examples of populations that have evolved over time

- bacteria have evolved resistance to drugs - insects have evolved resistance to herbicides - the timing of bird migrations, the emergence of insects, and the blooming of flowering plants have evolved in response to climate change

3 ways homology is a key concept in contemporary biology

- chemicals that cause cancer in humans can often be identified by testing their effects on mutation rates in bacteria, yeast, zebrafish, mice and other model organisms bakes the molecular machinery responsible for copying and repairing DNA is homologous in all organisms - Drugs intended for human use can be tested on mice or rabbits if the molecules targeted by the drugs are homologous -Unknown sequences in the human, rice, or other genomes can be identified if they are homologous to known sequences in yeast, fruit flies, or other well-studied model organisms.

Given a population that contains genetic variation, what is the correct sequence of the following events under the influence of natural selection? 1. Well-adapted individuals leave more offspring than do poorly adapted individuals. 2. A change occurs in the environment. 3. Genetic frequencies within the population change. 4. Poorly adapted individuals have decreased survivorship.

2 → 4 → 1 → 3

Evolution

A change in characteristics of a population over time. Species are not independent and unchanging entities, but are related to one another and can change through time

Malthus

All populations have the innate ability to grow exponentially, unless resources also increase exponentially, death rates must increase.

Darwin Four Postulates

Darwin broke the process of evolution by natural selection into four simple postulates (criteria) to form a logical sequences 1. Variation in Population. The individual organisms that make up a population vary in the traits they possess, such as their shape and size 2. Heritable Traits. Some trait differences are heritable, meaning that they are passed on to offspring. For example, tall parents tend to have tall offspring 3. Selection. In each generation, many more offspring are produced that can possible survive. Thus, only some individuals in the population survive long enough to produce offspring, and among the individuals that produce offspring, some will produce more than others 4. Differential Survival or Reproduction. The subset of individuals that survive best and produces the most offspring is not a random sample of the population. Instead, individuals with certain heritable traits are more likely to survive and reproduce. Natural selection occurs when individuals with certain characteristics produce more offspring than do individuals without those characteristics. The individuals are selected naturally - meaning, by the environment. Because the selected traits are passed on to offspring, the frequency of this selected traits increase from one generation to the next. The outcome of evolution by natural selection is a change in allele frequencies in a population overtime

Compare and contrast how the theory of evolution by natural selection, special creation, and evolution by inheritance of acquired characters might explain this observation: Scientists have observed white deer mice living on coastal beaches in Florida and brown deer mice living in nearby forests.

Evolution by natural selection: predicts that white and brown deer mice are descendants of an ancestral population that varied in color. the white mice had higher fitness in the beach environment; the brown mice had higher fitness in the shady forest environment; overtime, the average color of each population changed Special creation: claims that the two colors of mice do not change. claims that the two colors of mice were created by divine intervention Evolution by inheritance of acquired traits: predicts that the mice passed acquired characters onto their offspring. predicts that the mice in the different environments needed to change color, so they did so.

Natural Selection

Explains how evolution occurs. - Darwin and Wallace proposed this Natural Selection occurs when two conditions are met: 1. Individuals within a population vary in characteristics that are heritable -- meaning, traits that can be passed on to offspring. A population is defined as a group of individuals of the same species living in the same area at the same time. 2. In a particular environment, certain version of these heritable traits help individuals survive better or reproduce more than do other versions. If certain heritable traits lead to increased success in producing offspring, then those traits become more common in the population over time. The populations characteristics change as a result of natural selection acting on individuals.

Darwin studied

Galapagos finches and mockingbirds - mainly studied the beak size and shape of different types on the different islands

Evolution by natural selection

If traits vary among individuals within a population and traits are heritable (genetic basis), then only those offspring that survive and reproduce (or reproduce more) can contribute their traits to the future generations and populations will change overtime and contribute to increasing fitness (based on individuals who posses the favorable traits).

The fossil record resembles the living species in the same geographic area. How does this pattern support the theory of evolution by natural selection?

It is evidence that species can change over time.

Why does the presence of homology support the pattern component of the theory of evolution by natural selection?

It supports the hypothesis that species descended from a common ancestor.

The average height of humans in industrialized nations has increased steadily for the past 100 years. This trait has clearly changed over time. Most physicians and human geneticists hypothesize that the change is due to better nutrition and a reduced incidence of disease. Has human height evolved?

No, because changes in height due to nutrition and reduced incidence of disease are not heritable.

______ evolve, not _____

Populations; individuals.

Evidence of Evolution

Prediction 1: Species are not static, but change over time - Life on Earth is ancient. Most species have gone extinct - Fossil (extinct) species frequently resemble living species found in the same area - Transitional fetures document change in traits through time - Vestigial trait are common - The characteristics of populations vary within species and can be observed changing today Prediction 2: Species are related, not independent - Closely related species often live in the same geographical area - Homologous traits are common and are recognized at three levels - genetic (gene structure and the genetic code) - development (embryotic structures and processes) - structural (morphological traits in adults) - The formation of new species, from preexisting species, can be observed today.

Why do related species share homologous traits?

Related species inherited homologous traits from a common ancestor. traits do not arise randomly, but are the result of evolution, and that closely related species will share more homologous traits than distantly related species.

Evolution of Evolutionary Thought

Species are fixed; some species are higher/better than others - Aristotle Species change through time = evolve - Inheritance of acquired characteristics - acquired traits during life time and then pass on to offspring (Lamarck) - Differential survival and reproduction of individuals better suited to the environment (Darwin, Wallace: multiple discovery)

Why are human and chimpanzee DNA 96 percent similar?

The two species descended from a recent common ancestor.

biogeography

They study of how species and populations are distributed geographically

Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?

Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.

Scientific Theory

Unifying idea that explains scientific facts, laws and observations. - Well-supported by multiple independent lines of evidence. - Well-accepted but constantly refined as more evidence is gathered and analyzed Examples: -Germ theory: explains how microorganisms cause disease -Cell theory: explains how cells function as the basic unit of all life -Gravitational theory: explains how mass and movement affect each other

population thinking

Variation among individuals in a population was key to understanding the nature of species. Population thinking overturned the idea that species are static and unchanging; replaced the typological thinking with population thinking; was scientific - proposed a mechanism that could account for change through time and made predictions that could be tested through observation and experimentation

Why did Darwin document and describe vestigial traits?

Vestigial traits indicate that species change over time. This is an important pattern component of the theory of evolution and is inconsistent with the theory of special creation.

Can humans observe evolution?

Yes, evolution never stops

phylogenetic tree

a branching diagram that describes the ancestor-decendant relationships among species or other tax

In biology, an adaptation is defined as _____.

a heritable trait that increases the fitness of an individual in a particular environment

speciation

a process that results in one species splitting into two or more descendent species

vestigial trait

a reduced or incompletely developed structure that has no function or reduced function, but is clearly similar to functioning organs or structures in closely related species. ex: -some whales and snakes have tinny hip and leg bones that do not help them swim or slither - ostriches and kiwis have reduced wings and cannot fly - eyeless, blind cave-dwelling fish have eye sockets

Geological time scale

a sequence of named intervals called eons, eras, and periods that represented the major events in Earth's history.

extinct species

a species that no longer exists

transitional feature

a trait in a fossil species that is intermediate between those of ancestral (older) and derived (younger) species. for example - intensive work over the past several decades has yielded fossils document gradual change overtime from aquatic animals that had fins to terrestrial animals that had limbs. over a period of about 25 million years, the fins of the species similar to today's lungfish changes into limbs similar to those found in todays amphibians, reptiles, and mammals - a group called tetrapods (four-footed)

adaption

a trait that increases the fitness of an individual in a particular environment

Which statement about adaptation is correct? a. Adaptations arise because they are needed in particular environments. b. The adaptive value of a trait varies as the environment changes. c. Higher organisms are better adapted than lower organisms. d. Better-adapted organisms are more complex than are poorly adapted organisms.

a. Adaptations arise because they are needed in particular environments.

Which of the following statements is an accurate combination of postulates 3 and 4 of natural selection? a. Individuals experience differential success in their ability to survive or reproduce. b. Individuals experience unlimited success in their ability to survive or reproduce. c. Individuals experience no success in their ability to survive or reproduce. d. Individuals experience uniform success in their ability to survive or reproduce.

a. Individuals experience differential success in their ability to survive or reproduce.

According to data presented in this chapter, which of the following statements is correct? a. Species descended from a common ancestor and change over time. b. When individuals change in response to challenges from the environment, their altered traits are passed on to offspring. c. Individuals - not populations - change when natural selection occurs. d. The traits of populations become more perfect over time.

a. Species descended from a common ancestor and change over time.

If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more antibiotic-resistance genes, what would happen in environments that lack antibiotics? a. These bacteria would be outcompeted and replaced by bacteria that have lost these genes. b. The number of genes conveying antibiotic resistance would increase in these bacteria. c. These genes would be maintained in case the antibiotics appear. d. These bacteria would try to make the cost worthwhile by locating and migrating to microenvironments where traces of antibiotics are present.

a. These bacteria would be outcompeted and replaced by bacteria that have lost these genes.

Which of the following is a fitness trade-off (compromise)? a. Turtle shells provide protection but are heavy and burdensome when moving. b. In some hornbill species, the male helps seal the female in a tree with her nest until the young are ready to fledge. c. The strong, thick beak of a woodpecker helps it find insects in trees. d. Hummingbirds are the best pollinators of certain flowers, but bees are the best pollinators for orchids.

a. Turtle shells provide protection but are heavy and burdensome when moving.

fitness

ability of an individual to produce viable offspring. Individuals with high fitness produce many surviving offspring measurable quantity

Not all traits are ______

adaptive even adaptive traits are constrained by genetic and historical factors.

fossil

any trace of an organism that lived in the past

Which of the following statements is an accurate combination of postulates 1 and 2 of natural selection? a. Drug resistance exists among all individuals in a population. b. Heritable variation exists for traits among individuals in a population. c. Heritable variation does not exist among individuals in a population. d. Environmental variation exists for traits among individuals in a population.

b. Heritable variation exists for traits among individuals in a population.

DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Instead, DDT is largely useless against many insects. Which of these would have prevented this evolution of DDT resistance in insect pests? a. All habitats should have received applications of DDT at about the same time. b. None of the insect pests would have genetic variations that resulted in DDT resistance. c. DDT application should have been continual. d. The frequency of DDT application should have been higher. e. Larger doses of DDT should have been applied from the air, into water, and within the soil.

b. None of the insect pests would have genetic variations that resulted in DDT resistance.

Parasitic species tend to have simple morphologies. Which of the following statements best explains this observation? a. Parasites are lower organisms, and this is why they have simple morphologies. b. Simple morphologies convey some advantage in most parasites. c. Parasites have not yet had time to progress, because they are young evolutionarily. d. Parasites do not live long enough to inherit acquired characteristics.

b. Simple morphologies convey some advantage in most parasites.

Which of these lists contains the four postulates of natural selection? a. Uniform population, heritable traits, selection, differential survival or reproduction b. Variation in population, heritable variation, selection, differential survival or reproduction c. Variation in population, environmental variation, selection, differential survival or reproduction d. Variation in population, heritable variation, selection, unlimited survival and reproduction

b. Variation in population, heritable variation, selection, differential survival or reproduction

Which of the following is the best modern definition of evolution? a. inheritance of acquired characters b. descent with modification c. change in the number of genes in a population over time d. survival of the fittest

b. descent with modification

relative dating

based on the positions of sedimentary rocks where fossils are found

In the United States today, about half of the corn crop is genetically engineered with a protein that is toxic to corn borers, an insect pest of corn. Which of the following conditions would be necessary for evolution of resistance to the toxic protein to occur in the corn borer? a. The corn borers must experience unlimited success in their ability to survive or reproduce. b. The corn borer must lack variation in resistance to the toxic protein. c. The corn borer must have or generate (by mutation) heritable variation in resistance to the toxic protein. The resistant corn borers must survive better or reproduce more than nonresistant corn borers. d. The corn borers must experience no success in their ability to survive or reproduce.

c. The corn borer must have or generate (by mutation) heritable variation in resistance to the toxic protein. The resistant corn borers must survive better or reproduce more than nonresistant corn borers.

In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. The sickle-cell allele is pleiotropic (that is, it affects more than one phenotypic trait). Specifically, this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria. Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria. Thus, pleiotropic genes/alleles reveal that _____. a. evolution is limited by historical constraints b. new advantageous alleles do not arise on demand c. adaptations are often compromises d. chance events can affect the evolutionary history of populations

c. adaptations are often compromises

artificial selection

changes in populations that occur when humans select certain individuals to produce the most offspring Darwin crossbred pigeons and observed how characteristics were passed on to offspring

fossil record

consists of all of the fossils that have been found on Earth and described in the scientific literature.

Which explanation of transitional features in the fossil record is most consistent with the idea of special creation? a. Transitional features represent a supernatural tendency for design. b. Features represent links between older and newer lineages of taxa. c. Transitional features represent reasons why species went extinct. d. Features represent the whims of a supernatural creator.

d. Features represent the whims of a supernatural creator. According to special creation, features in extant species are the same as when created and so, serving no obvious function, are presumed to be supernatural.

Which statement shows population thinking? a. Species do not change over time. b. All species can be organized into a sequence of increasing complexity. c. A single perfect specimen can represent a species. d. Variation among individuals in a species is real and important.

d. Variation among individuals in a species is real and important.

Of the following anatomical structures, which is homologous to the bones in the wing of a bird? a. bony rays in the tail fin of a flying fish b. chitinous struts in the wing of a butterfly c. cartilage in the dorsal fin of a shark d. bones in the flipper of a whale e. bones in the hind limb of a kangaroo

d. bones in the flipper of a whale

Which of the following evidence most strongly supports the common origin of all life on Earth? All organisms _____. a. require energy b. show heritable variation c. evolve d. use essentially the same genetic code e. reproduce

d. use essentially the same genetic code

Example of direct observation of evolutionary change

development of drug resistance in bacteria

Evolution occurs when heritable variation leads to ______ in reproduction

differential success

Examples of fossil record

discovery of shells of extinct species discovery f transitional forms of horses

d. Variation among individuals in a species is real and important.

dismissed the idea that species are constant and emphasized the importance of variation and change in populations

Species are _____, not _____

dynamic; static

microevolution

evolution of a short period of time so that you don't see the physical change

macroevolution

evolution over long period of time.

Recent analysis of the fossil record suggest that over 99 percent of all the species that have ever lived are now

extinct

Sedimentary rocks

form from sand or mud or other materials deposited at locations such as beaches or river mouths. are known to form layers - younger layers are deposited on top of older layers. Researchers used this information to place fossils in younger-to-older sequence, based on the fossils' relative position in layers of sedimentary rock.

phylogeny

genealogical relationships. The evolutionary history of a group of organisms

Evolution is not ___ directed

goal adaptions do not occur because organisms want or need them. they occur because the traits happened to be advantageous when the environments changed.

Organisms to don't act for the ___ of the species

good - individuals sacrifice themselves for the good of the entire species. Individuals with self-sacrificing alleles die and do not produce offspring, But individuals with selfish, cheater alleles survive and produce offspring. As a result, selfish alleles increase in frequency while self-sacrificing alleles decrease in frequency. Thus it is not possible for self-sacrificing alleles to evolve by natural selection.

Darwin discovered that mockingbird populations that colonized on different islands...

had changes through time and formed new species

There is no such thing as a ___ or ____ organism

higher; lower Lamarck and Aristotle's hypotheses are refer to "higher" and "lower" organisms Under evolution by natural selection, there is no such thing as higher or lower organisms. A human is no higher than its tapeworm parasite; each is well adapted t its environment.

The theory of evolution by natural selection predicts that _____ will occur

homologies If species were created independently of one another, as special creation claims, these types of similarities would not occur.

Traits that are derived from a common ancestor, like the bones of human arms and bird wings, are said to be _____.

homologous

As adaption progresses, fitness

increases. adaption increases the fitness of an individual in particular environment relative to individuals lacking the trait. adaptions increase fitness - the ability to produce viable, fertile offspring

Natural selection acts on ______, but evolutionary change occurs in _____

individuals; populations

Most powerful evidence for evolution

internal consistency - observation that data from independent sources agree in supporting predictions made by a theory. example: evolution of whales and dolphins from cetaceans - the fossil record contains a series of species that are clearly identified as cetaceans based on the unusual ear bones found only in this group. Some of the species have long legs and compact bodies typical of mammals that live primarily on land, some are limbless and have the streamlines bodies typical of aquatic mammals, some have intermediate features -a phylogeny of the fossils cetaceans, estimated on the basis of similarities and differences in morphological traits other than limbs and overall body shape, indicated that a gradual transition occurred between terrestrial forms and aquatic, whale like forms. -relative dating, based on the positions of sedimentary rocks where the fossils were found, agrees with the order of species indicated in the phylogeny - absolute dating, based on analysis of radioactive atoms in rocks in or near the layers where the fossils were found, also agrees with the order of species indicated in phylogeny -A phylogeny of living whales and dolphins, estimated from similarities and differences in DNA sequence, indicated that hippos, which spend most of their time in shallow water - are the closest living relative of the cetaceans and hippos share a common ancestor that was semiaquatic - Some whales have a vestigial hip and limb bones as adults, and some dolphin embryos have vestigial hindlimb buds - outgrowth where legs form in other mammals.

Vestigial traits and neutral changes in DNA sequences are good examples of _____.

nonadaptive traits

Constraints on natural selection

nonadaptive traits - traits that do not increase fitness - vestigial traits - do not increase the fitness of individuals with those traits. are present because they were present in the ancestral population - silent mutations - dont change the phenotype and can't be acted on by natural selection and are not adaptive genetic constraints - selection is not able to optimize all aspects of a trait due to genetic correlation. genetic correlation occurs because of pleitrophy, in which a single allele affects multiple traits. alleles for one trait cause a correlated though suboptimal, increase in another trait. ex. In the drought of 1977, finches with deeper beaks survived better than finches with shallow beaks, and finches with narrow beaks survived better than finches with wider beaks. Although, narrow beaks did not evolve in the population. Parents with deep beaks tend to have offspring with deep and wide beaks (common pattern). Many alleles that affect the body size have an effect on all aspects of size - not just one structure or dimension. As a result, selection for increased back depth overrode selection for narrow beaks, even though deep and narrow beaks would have been more advantageous. - lack of genetic variation - species lack the type of genes to produce specific traits that are advantageous to other species. ex - salamanders have the ability to regrow severed limbs, but humans cannot. fitness trade-offs - a compromise between traits, in terms of how those traits perform in the environment. ex. medium ground finches with large bodies had an advantage because they were able to chase off smaller birds from few remaining sources of seeds, but individuals with large bodies require large amounts of food to maintain their mass; they also tend to be slower and less nimble than smaller individuals. When food is scares, large individuals are more prone to starvations. Even if larger size is advantageous in an environment, there is always counteracting selection that prevents individual from getting even bigger. Because selection acts on many traits at once, every adaption is a compromise historical constraints - All traits have evolved from previously existing traits. Natural selection acts on structures that originally had a very different function. example - the tiny incus, malleus, and stapes bones found in your middle ear evolved from bones that were part of the jaw and jaw support in the ancestors of mammals. These bones now function in transmitting and amplifying sound from your outer ear to your inner ear.

genetic homology

occurs in DNA nucleotide sequences, RNA nucleotide sequences, or amino acid sequences. example: the eyeless gene in fruit flies and the Aniridia gene in humans are so similar that their protein products are 90 % identical in amino acid sequence. Both genes act in determining where the eye develops - even though fruit flies have a compound eye with many lenses and humans have a camera eye with a single sense

Evolution is not _____

progressive organisms have not gotten "better" overtime

development homology

recognized in embryos. example: early chick, human, and cat embryos have tails and structures called gill pouches. Later, gill pouches are lost in al three species and tails are lost in humans. But in fish, the embryonic gill pouches stay intact and give rise to functioning gills in adults. To explain this observation, biological hypothesize that gill pouches and tails exist in chicks, human, and cats because they existed in the fishlike species that was the common ancestor of todays vertebrates. Embryonic gills pouches are vestigial traits in chicks, human, and cats; embryonic tails are vestigial traits in humans.

examples of homology

same genetic code in fireflies and tobacco plants similarities in mammalian forelimbs vestigial pelvis in right whales

structural homology

similarity in adult morphology, or form. example: common structural plan observes in the limbs of vertebrates

examples of biogeography

similarity of endemic island species to nearby mainland species the high concentration of marsupial species in Australia

homology

similarity that exists in species because they inherited that trait from a common ancestor. genetic homologies cause the development homologies observed in embryos, which then lead to structural homologies recognized in adults human hair and dog fur are homologous. 3 levels of homology - genetic; development; structural

the geological record indicated...

that the Earth was much, much older than the 6000 years claimed by proponents of special creation

radioactive decay

the steady rate at which unstable or "parent" atoms are converted into more stable "daughter" atoms

radioactive dating

used too assign absolute ages, in years, to the relative ages in the geological time scale Radiometric dating is based on: 1. Observed decay rates of parent to daughter atoms 2. The ratio of parent to daughter atoms present in nearby rocks - such as the amount of uranium atoms versus lead atoms when uranium-containing molten rock first cools 3. The ratio of parent to daughter atoms present in a particular rock sample

Populations have individuals that vary with _____

variable traits

Speciation

when natural selection causes populations of one species to diverge and form new species The evolution of two or more distinct species from a single ancestral species.

Evolution occurs when...

1) heritable traits lead to 2) differential reproductive success

special creation

1. All species are independent, in the sense of being unrelated to each other 2. life on Earth is the sense of being unrelated to each other 3. Species are immutable, or incapable of change.

The cell theory and the theory of evolution provided young science of biology with two central unifying ideas:

1. The cell is the fundamental structure unit in all organisms 2. All species are related by common ancestry and have changes over time in response to natural selection