Biol 120: Evolution

Define Disruptive Selection 327

3rd kind of Natural Selection in which individuals with extreme phenotypes experience the highest fitness, and those with intermediate phenotypes have the lowest.

The fossil record 331

Physical evidence of organisms that lived in the past

Convergent Evolution 336

Analogous structures all developed from different original structures.

In regards to question number 96, why do these features exist during an embryo's development? 336

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Q>Why are Amish people more likely than other people to have extra fingers and toes? 314

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The Hardy

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Trait Frequency 320

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3 important elements to an organism's fitness 322

1. An individual's fitness is measured relative to other genotypes or phenotypes in the population. 2. Fitness depends on the specific environment in which the organism lives. 3. Fitness depends on an organism's reproductive success compared with other organisms in the population.

Four ways in which evolution can occur. 310

1. Mutation 2. Genetic Drift 3. Migration 4. Natural Selection

Lecture: 3 Condition Differential reproductive success

1. There are more organisms born than can survive

According to Charles Darwin, what are the 3 conditions that are necessary for natural selection to occur?

1. There must be variation for the trait within a population 2. That variation must be heritable (that is, capable of being passed from parents to offspring). 3. Individuals with one version of the trait must produce more offspring than those with a different version of the trait.

What did Darwin noticed 2 important and unexpected patterns on his voyage? 306

1. Traits exhibited by species 2. Throughout his voyage, at every location there was a striking similarity between the fossils of extinct species and the living species in that same area.

Define Migration 310

A change in allele frequencies cause by individuals moving into or out of a population.

Define Natural Selection 310

A change in allele frequencies that occurs when individuals with one version of a heritable trait have greater reproductive success than individuals with a different version of the trait.

Define Evolution 302

A genetic change in the population of an organism.

What is the term "population" in biology? 300

A group of organisms of the same species living in a particular geographic region.

What is Marsupial? 334

A mammal of an order whose members are born incompletely developed and are typically carried and suckled in a pouch on the mother's belly.

Natural Selection 324

A process by which, in each generation, the alleles that cause organisms to have the traits that make them most fit in that environment tend to increase in frequency. If the environment changes, the alleles that are most favored may change too.

Define Genetic Drift 313

A random change in allele frequencies in a population. Unrelated to the alleles influence on reproductive success A significant cause of evolutionary change Primarily in small population

Define Genetic Drift 310

A random change in allele frequencies, unrelated to any allele's influence on reproductive success.

Define Bottleneck 314

A rapid environmental change causes the deaths of a large proportion of individuals in a population.

Take Home Message 328

Acting on multi-gene traits for which populations show a large range of phenotypes, natural selection can change populations in several ways. These include directional selection, in which the average value for the trait increases or decreases; stabilizing selection, in which the average value of a trait remains the same while extreme versions are selected against; and disruptive selection in which individuals with extreme phenotypes have highest fitness.

Take Home Message 324

Adaption, which refers to the process by which organisms become better matched to their environment and to the specific traits that make an organisms more fit, occurs as a result of natural selection.

Take Home Message 305

After initially training in medicine and theology, Charles Darwin was able to focus on studying the natural world when, in 1831, he got a job on a ship conducting a five year round the world survey.

Take Home Message 308

After putting off publishing his thughts on natural selection for more than 15 years, Darwin did so only after alfred Russel Wallace independently came up with the same idea. The two men published a joint presentation on their ideas in 1858, and Darwin published a much more detailed treatment in The Origin of Species in 1859, sparking wide debate and discussion of natural selection.

Take Home Message 338

All living organisms share the same genetic code. The degree of similarity in the DNA of different species can reveal how closely related they are and the amount of time that has passed since they last shared a common ancestor.

Define Mutation 310

An alteration of the base-pair sequence in the DNA of an individual's gamete-producing cells that changes an allele's frequency. Note: Mutations almost always cause early death or lower the reproductive success of an organism.

What is the evidence that natural selection can cause evolution of complex traits and behaviors? 329

An experiment in 1954, in which rats was put in maze. The experimenter bred the fastest mouse to escape with another fastest mouse. And the slowest mouse with the slowest. As a result, after generations, the experimenter found that the mouse that was bred from faster parents are more likely to finish the maze easily than the other.

Heterozygous 320

An individual having two different alleles of a particular gene or genes, and so giving rise to varying offspring.

Take Home Message 326

Animal breeders and farmers are making use of natural selection when they modify their animals and crops, because the 3 conditions for natural selection are satisfied. Since the differential reproductive success is determined by humans rather than by nature, this type of natural selection is also called artificial selection.

Why do trait does not decrease in frequency? 320

Because it is inactive.

Why is the fossil record a very incomplete record? 331

Because parts of an organism tend to decay rapidly and completely after death, but bones teeth and shells can be preserved for thousands or even millions of years.

Why does history matter in terms of species distribution? 334

Because species were not designed from scratch to fill a particular niche. Rather, whatever arrived in a geographic region first-usually a nearby species- took up numerous different lifestyles in numerous different habitats, and the populations ultimately adapted to and evolved in each environment.

Q> Why is "Survival of the fittest" is a misnomer? 323

Because survival of the fittest means the organisms reproductive success, rather than the definition of who has the greater physical strength or the ability to survive. If an organism was given a trait that can live 200 years for example, but sterile, its fitness is 0 because it can not pass that trait to another. On the other hand, if an organism has a trait that causes it to die half the age of everyone else, but can reproduce twice as many offspring, it has a much greater fitness.

Why is Artificial Selection is considered a special case of natural selection? 326

Because the differential reproductive success is being determined by humans rather than by nature. Example: Apple growers, use artificial selection to produce the wide variety available. What is important is that it is still differential reproductive success, and the results are no different.

Q> Why do vampire bats grow teeth specialized for grinding solid food, when the bats have a completely liquid diet? 336

Because they had value Ancestrally. Example: The appendix of humans. It is greatly enlarged in our relatives the great apes, acting as host to cellulose-digesting bacteria that aid in breaking down the plants in the ape diet, but in humans it seem to serve no purpose.

Q> Most agricultural pests evolve resistance to pesticides. How does this happen? 319

Because those pests that gain resistant gene tend to survive more, thus, it eliminates the weaker generation and reproduce a stronger generation.

Why is it that each hour without food is more dangerous when you're tiny? 300

Because tiny bodies don't hold very large caloric reserves. Hence, they ran out faster than regular sizes. (Research Selection) not (Natural Selection)

What do you call the study of the distribution patterns of living organisms around the world? 334

Biogeography

How can you measure the DNA similarity between 2 species? 338

By comparing their DNA sequences for individual genes. Example: Hemoglobin. In vertebrate animals, hemoglobin is found inside the red blood cells. It is made up of 2 types of chains of amino acids, the alpha chain and the beta chain. In humans, the beta chain has 146 amino acids. In rhesus monkeys, this beta chain is nearly identical : of the 146 amino acids, 138 are the same as those found in human Hemoglobin, and only 8 are different. In dogs, the sequence is still somewhat similar, with 114 amino acids, 101 are similar with humans.

Natural Selection. 316

Certain individual organisms in a population born with characteristics (due to genes)

What is important to remember regarding evolution by natural selection? 329

Changing the allele frequencies for traits, whenever: 1. There is a variation for the trait 2. That variation is heritable 3. There is differential reproductive success based on that trait.

What can comparative anatomy and embryology reveal? (Third Line of Evidence) 335

Common evolutionary origins.

What is Variation of Trait? 316

Differences between an organism not just physically, but also physiologically. For example, Different people have different faces, that's a fact, but also, they vary in biochemical ways too. Some people may digest alcohol quickly, some may not. Some people may feel violently ill after drinking a glass of wine, some may not.

Take Home Message 307

Darwin noted unexpected patterns among fossils he discovered and living organisms he observed while on the voyage of the Beagle. Fossils resembled but were not identical to the living organisms in the same area where they were found. And finch species on each of the Galapagos islands differed from each other in small but significant ways. These observation helped Darwin develop his theory of how species might change over time.

What cause mutations?

Environmental phenomena Mutagens

Take Home Message 310

Evolution is a change in allele frequencies within a population. It can occur by four different mechanisms: mutation, genetic drift, migration, and natural selection.

Molecular biology 331

Examination of life at the level of individual molecules

Why is it that all organisms of populations will never be perfectly adapted to their environment? 324

Example, beak size of Galapagos finches. Over the course of a multi-decade study, biologists closely monitored the average size of the finches' beaks. During dry years when the finches had to eat large, hard seeds, bigger and stronger beaks become the norm. During the wet years, smaller-beaked birds were more successful, since there was a surplus of small soft seeds.

Take Home Message 323

Fitness is a measure of the relative amount of reproduction by an individual with a particular phenotype, compared with the reproductive output of individuals with alternative phenotypes. An individual's fitness can vary, depending on the environment in which it lives.

Define Founder effect 314

Founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. Lecture: Small number of individuals become the founding members of a new, isolated population. Founders may have different allele frequencies than original population. Particularly if they are a small sample

What does organism have in similarity in terms of genetic code? 337

Four simple bases, arranged in an almost unlimited variety of sequences. In short, all living organisms share the same genetic code.

What is another name for Migration? 315

Gene Flow

Take Home Message 315

Genetic drift is a random change in allele frequencies within a population, unrelated to the allele's influence reproductive success. Genetic drift is a significant agent of evolutionary change, primarily in small population.

Comparative anatomy and embryology 331

Growth, development, and body structures of major groups of organisms

In biology, what does "survival of the fittest" means? 322

Has everything to do with an organism's reproductive success, rather than being defined as the ability to survive, or its physical strength.

Define Radiometric Dating 332

Helps in painting a clearer picture of organisms' evolutionary history by telling us the age of the rock in which a fossil is found.

How can mutation occur? 311

It can be induced by a variety of environmental factors including: 1. Radiation 2. Chemical

Gene Flow or Migration in detail 316

If migrating individuals survive and reproduce in the new population, and if they carry a different proportion of alleles than the individuals in their new home, then the recipient population experience a change in allele frequencies and, consequently, experiences evolution. and because alleles are simultaneously lost from the population, too, will experience a change in its allele frequencies and, thus, will evolve.

Take Home Message 321

If we know the frequency of each allele in a population, we can predict the genotypes and phenotypes we should see in that population. If the phenotypic frequencies in a population are not those predicted from the allele frequencies, the population is not in Hardy-Weinberg equilibrium, because an assumption has been violated. Either non-random mating or evolution is occurring. But as long as the Hardy-Weinberg assumptions are not violated, recessive alleles and dominant alleles do not change their frequencies over time.

Laboratory and fields studies 331

Implementation of the scientific method to observe and study evolutionary mechanisms

What is Heritability? 317

In Darwin's studies, it is the act on a trait within a population, offspring must inherit the trait from their parents.

Define Directional Selection 326

In Directional Selection, individuals with one extreme of the range of variation in the population have higher fitness. Milk production in cows is an example. There is a lot of variation in milk production from cow to cow. As you might expect, farmers select for breeding those cow with the highest milk production and have done so for many decades. The result of such selection is not surprising: it increased the milk production by 50% between 1920s and 1945.

What can Fossils provide to us? 331

It can be used to reconstruct what organisms must have looked like long ago.

What can Laboratory and field experiments provide us? (Fifth Line of Evidence) 338

It enables us to watch evolution in progress.

Take Home Message 304

In the 18th and 19th Centuries, scientists began to overturn many commonly held beliefs in the Western world, including that the earth was only about 6000 years old and that all species had been created separately and were unchanging. These gradual changes in scientists; beliefs helped shape Charles Darwin's thinking.

What is Differential Reproductive Success? 319

Individuals with the version of a trait most suited to reproduction in their environment generally leave more offspring than individuals with other versions of the trait. Example: In the fruit fly experiment, we saw that the flies that inherit the ability to pack on fat when food is available end up leaving more offspring than those inheriting a poor ability to pad their little fruit fly frames with fat deposits. The portly fruit flies have greater reproductive success than other individuals in the population.

Define Fitness 322

Is a measure of the relative amount of reproduction of an individual with a particular phenotype, compared with the reproductive output of individuals of the same species with alternative phenotypes.

Migration 315

Is the movement of some individuals of a species from one population to another.

What is Artificial Selection 326

Is the process by which humans breed other animals and plants for particular traits.

Some of the tigers are born white black stripes when it's supposed to be yellow black. How is this possible? 309

It is the result of a rare pair of alleles that suppresses the tiger's production of most fur pigment.

What is Fixation? and how does it occur? 313

It occurs when an allele's frequency in a population reaches 100% (and the frequency of all other alleles of that gene becomes 0%) If this occurs, there is no longer genetic variation for the gene.

How does tanning bed work? and could the stimulation be inherited? 311

It uses ultraviolet rays that induces tanning just as exposure to the sun does. By stimulating pigment-producing cells to produce more melanin. (A pigment that darkens skin color.) No, it can not be inherited because it only affects the somatic cells, not the reproductive cells.

What book Darwin brought with him on the Beagle? 306

Lyell's Principle of Geology.

Take Home Message 316

Migration, or Gene Flow, leads to a change in allele frequencies in a population as individuals move into or out of the population.

When considering mutation as an agent of evolution, what is important to remember regarding multicellular eukaryotic organism? 311

Multicellular eukaryotic organism can be divided into two types: 1. Somatic Cells 2. Reproductive Cells

Take Home Message 312

Mutation is an alteration of the base-pair sequence in an individual's DNA. If such an alteration changes an allele in an individual's gamete-producing cells, this constitutes evolution within the population. Mutations can be caused by high-energy radiation or chemicals in the environment, and also can appear spontaneously. Mutation is the only way that new alleles can be created within a population, and thus it generates the variation on which natural selection can act.

Take Home Message 330

Natural Selection can change allele frequencies for genes involved in complex physiological processes and behaviors. Sometimes a trait that has been selected for one function is later modified to serve a completely different function.

Take Home Message 325

Natural selection does not lead to organisms perfectly adapted to their environment, because (1) environments can change more quickly than natural selection can adapt organisms; (2) mutation does not produce all possible alleles; (3) there is not always a single, optimum adaptation for a given environment.

Take Home Message 319

Natural selection is a mechanism of evolution that occurs when there is heritable variation for a trait, and individuals with one version of the trait have greater reproductive success than do individuals with a different version of the trait. Natural selection can also be thoughts of as the elimination of alleles that reduce the reproductive rate of individuals carrying those alleles, relative to the reproductive rate of individuals who do not.

Can mobile phones potentially source of DNA-damaging energy? 311

No, because majority of experiments have not found any consistent casual relationship between mobile phone usage and any short-or-medium-term health hazards. In addition, Cell phones only emits very low electromagnetic Radiation, hence, it is generally unable to break chemical bonds and therefore cause mutations.

Take Home Message 335

Observing geographic patterns of species distributions-noting similarities and differences among species living close together but in very different habitats and among species living in similar habitats but located far from one another-helps us understand he evolutionary histories of populations.

Define Stabilizing Selection 327

Occurs when individuals with intermediate phenotypes are the most fit. Example: Death rate of babies is lowest between 7 and 8 pounds, increasing for both lighter and heavier babies. This outcome has kept the average weight if a baby constant over many generations; but at the same time, the variation in birth weight has decreased as stabilizing selection has reduced the frequencies of genes associated with high and low birth weights.

Example of "Survival of the Fittest" 322

One fly carries the genes for a version of a trait that allows it to survive a long time without food. The other has the genes for a different version of the trait that allows it to survive only a short while without food. if the environment is one in which there are long periods of time without food, the fly that can live a long time without food is likely to produce more offspring than the other fly, and so over the course of its life has greater fitness.

Biogeography 331

Patterns in the geographic distribution of living organisms

Take Home Message 333

Radiometric dating confirms that the earth is very old and allows scientists to determine the age of fossils. By analyzing fossil remains, biologists can reconstruct what organisms looked like long ago, learn how organisms were related to each other, and understand how groups of organisms evolved overtime.

Define Adaptation 323

Refers both to the process by which organisms become better matched to their environment and to the specific features that make an organism more fit. Example: Bats have an extremely accurate type of hearing for navigating and finding food, even in complete darkness Porcupine quills make porcupines almost impervious to predation. Mosquitoes produce strong chemicals that prevent blood from clotting, so that they can extract blood from other animals.

Take home Message 339

Replicated, controlled laboratory selection experiments and long-term field studies of natural populations allow us to watch and measure evolution as it occurs.

Which kind of cell can be inherited considering mutation? 311

Reproductive cells.

What is Somatic Cells? and can it be passed from parent to offspring? 311

The cells forming the body of an organism. No, it can not. Only reproductive cells can.

Q> Why doesn't natural selection lead to perfect organism? 325

Several Factors: 1. Environment change quickly. Natural selection may be too slow to adapt the organisms in a population to such a constantly moving target. 2. Variation is needed as the raw material of selection - remember, it is the first necessary condition for natural selection to occur. If a mountain creating a new, "perfect" version of a gene never occurs, the individuals within a population will never be perfectly adapted. 3. There may be a different alleles for a trait, each causing individuals to have the same fitness. In this case, each allele represents an equally fit "solution" to the environmental challenges.

What is the important factor that distinguishes genetic drift from natural selection? 313

The change in allele frequencies is not related to the allele's influence on reproductive success. A cleft chin does not affect an individual's ability to reproduce.

Q> How can a wing evolve if 1% of a wing doesn't help an organism fly or glide at all? 330

That 1% of a wing does not actually need to function as a wing to increase an individual's fitness, rather, their structures are enhanced on by natural selection because they enhance fitness by serving some other purpose. Example: The fly with small wings allow much more efficient temperature control, so that an insect can gain heat from the environment when the insect is cold and dissipate heat when the insect is hot.

What did the people of victorian times believed about species? 303

That all species had been created at the same time and never changed and never died out.

What does molecular biology reveal in terms of evolution? (Fourth line of evidence) 336

That common genetic sequences link all life forms.

What did the fossil led to conclusion in Cuvier? 303

That extinction was a fact.

Take Home Message 302

The characteristics of individuals in a population can change over time. We can observe such change in nature and can even cause it to occur.

What was the first lines of evidence? 331

The fossil record.

In Darwin's time, researchers determine how old the rock is by how deep it is; today however, is different. How can researchers determine the age of rock? 332

They evaluate the amounts of certain radioactive isotopes present in the fossil-containing rocks.

What did the researchers find on the grass experiments regarding mortality and evolution? 338

They found out that the grass that they cut frequently tend to be short lived with rapid development to reproductive age and a very high seed output. The other grass however (that was not frequently cut), had slightly slower development and a reduced seed output, while those in the rough had the slowest development and the lowest seed output of all.

On the other hand, what happens to the cows that produce the smallest amount of milk? 326

They have reduced fitness because farmers do not allow them to reproduce, limiting the number of less milk alleles in the next generation.

Q> Turkeys on poultry farmers have such large breast muscles that they can't get close enough to each other to mate. How can such a trait evolve? 327

Turkey breeders choose the trait of the turkey of the biggest breast muscles for larger profit, but with this breast muscles, turkeys cannot get close to each other to mate. Turkeys with large breasts traits are reproduced through artificial insemination.

Sometimes, homologous structures come to have little or no function at all. What do you call this evolutionary leftovers? 336

Vestigial Structures.

In regards to question number 107, why is this possible? 338

When plants from each of the habitats were collected and grown in greenhouses under identical conditions, the dramatic differences in growth, development, and life span remained, confirming that the frequencies of the various alleles controlling the traits of life span and reproductive output in the 3 populations had changed.

Q> Tanning beds and mobile phones expose people to radiation. Can they damage DNA? 311

Yes it can. Because ultraviolet rays are a form of energy, and they can damage DNA just as the sun's ray can.

Can Natural Selection cause the evolution of complex traits and behaviors? 329

Yes, Natural Selection can cause the evolution of complex traits and behaviors.

Can Natural selection change the traits in a population? 326

Yes, Natural selection can change the traits in a population in several ways.

If you observe any vertebrate embryo, what will you find? 335

You will see that it passes through a stage in which it has a long bony tail. It also has gill pouches that disappear before birth in all.