Evolution

Biogeography is the second evidence of ecology....

Biogeography evidence explains the spread of different species throughout the world. As the supercontinent Pangea separated into 7 different continents, living organisms were also separated. As the organism's environment changed, evolution took place so that the organisms could better adapt to their new habitats. For example, both penguins and polar bears thrive in bitter cold environments. But why are polar bears only found in the North Pole whereas penguins are in the South Pole? This is because geographical barrier made it impossible to go to the other pole, so they each adapted to their respective surroundings.

Fossils is the first evidence of evolution.....

The study of fossils is also called paleontology. Fossils reveal a lot of information about prehistoric living organisms, including anatomy, lineage, behavior, habitat, etc. As we compare different fossils found in different layers of sedimentations, we can see the transition in time from the deepest (oldest) to the shallowest (youngest). The anatomical change and timeline recorded through fossils is a solid piece of evidence to support the theory of evolution.

A species is...

Species are individuals that can interbreed. Therefore, two different species are reproductively separated, which means that their respective gene pool is also isolated, denying gene flow between species. A species represents a population of organisms that may display a range of genotypic and phenotypic variation, and members have the potential to interbreed and produce viable and fertile offspring. Species exist as a discrete unit in nature

Hybridization causes sympatric speciation by.....

This is a similar idea as polyploidy in plants, but hybridization also occurs in animals. Some hybrids are infertile (mules), and are not defined as a new species. However, some hybrids could be more fit than the purebred species, and eventually form its own line of species.

There are two types of fossils...

one is fossils of the actual remains of the animal, another one is fossils of their traces (ichnofossils), which records down details like footprints and nests.

There are two modes of speciation is....

There are two modes of speciation: allopatric and sympatric speciation.

There are main theories of macroevolution....

There are two theories of macroevolution: 1. Phyletic Gradualism 2. Punctuated equilibrium

What is continental drift?

There was a theory that the continents had originally began as a giant landmass or "supercontinent" before breaking apart and drifting to locations where they now reside. This supercontinent was named Pangaea and was thought to originate about 250 million years ago. This theory helps to explain such things as how fossils in West Africa were the same as those found in South America. The Appalachian Mountains in the United States fit together with the Caledonian Mountains of Scotland.

Neutral variations is...

-These are variations that are passed down which do not cause any benefit or harm to the organism. One day they may come in handy if the environment changes. -Alleles that have a neutral impact on the fitness of an organism tend to accumulate in a population. These alles are not removed by natural selection. These alleles may increase or decrease as a result of genetic drift. -Eye color is a fine example, as are variations in human fingerprints. -Hopefully you can see that neutral mutation for example, are neither beneficial nor harmful to survival of an organism or its reproductive status.

Minority advantage is...

-This is when a rare phenotype offers higher fitness than common phenotypes, just as we saw in disruptive selection! -However, as the rare allele increases in frequency, it then becomes common again, and will be selected against, leading to a decrease in frequency. Hence, rare phenotypes cycle between low and high frequency -Example: hunters usually develop a "search image" for their prey according to the most common appearance, and they hunt accordingly. Preys that have the rare phenotype escape the predator, and are therefore more 'fit.'

Frequency-Dependent Selection is...

-here we see the survival and reproduction morph decline if that phenotype becomes too common in a population. -If for example, a butterfly with a certain color pattern is being killed off by birds, the frequency of other color patterns would increase.

The concept of "survival of the fittest" explains...

"survival of the fittest." The term "fitness" doesn't measure the strength or athleticism of an organism Fitness measures the ability to survive and produce viable and fertile offsprings. Viable and Fertile Offsprings are the two key conditions for natural selection favorability. This also is frequently tested on the DAT, a typical question would be asking you to choose the "fittest" organism, be sure to choose the one with the most viable and fertile offspring! Which organisms is more evoutionary successful...? A) Lays 10 eggs, 8 hatch, 2 reproduce B) Lays 6 eggs, 4 hatch, 3 reproduce I hope you said B!! We want offspring if we are to have "fitness" and be evolutionarily successful.

Polyploidy is....

-polyploids, meaning that they actually have multiple alleles for a gene. This introduces more variety and preservation of different alleles in the genome. You never know, one day an allele may come in handy when the environment changes! -Many animals are diploids, meaning that they have two copies of each chromosome, and therefore two alleles for each gene. -Diploidy is beneficial because the dominant allele can mask the effect of the recessive allele, which is very helpful in cases where the recessive allele is harmful, such as sickle cell anemia. -Most eukaryotes are diploid and much genetic variation lies hidden in the recessive allele. The recessive allele, that is harmful, for example, can remain hidden in the heterozygote individuals. -This heterozygote form actually "protects" the recessive alleles which could eventually bring new benefits if circumstances in the environment were to change. -Imagine if we only had one gene for hemoglobin, people who happen to have one copy of the sickle cell allele would suffer from that disease. But since we are diploids, we would need two copies of the sickle cell gene to have the disease — greatly reducing the number of sickle cell patients!

Heterozygote advantage is.....

-the hybrid is selected for because it has a higher reproductive rate. For example in areas where there is malaria, the heterozygote is favored by natural selection and hence resistant to malaria. -When a heterozygote form is more fitted to the environment than either homozygote forms. -An example would be sickle cell anemia genes thriving in Africa. AA genotypes give normal hemoglobin, SS genotypes give sickle cell anemia (likely to die before puberty), whereas AS genotypes are beneficial because they offer resistance against malaria - a common killer in Africa - without causing sickle cell anemia.

Charle's Darwin's most important points are....

1) The best adapted individuals tend to leave more offspring. (an adaption is a characteristic of an organism that will increase their chances at survival) 2) Competition occurs because so many individuals are introduced into an environment of limited resources (the stronger animal prospers!) 3) Food resources in the environment are limited, thus there will be a struggle for survival (the better hunter more likely will live). 4) The number of offspring emerging in an environemnt tends to be greater than the environment can support (the less efficient organisms tend not to survive). In his publications, Darwin wrote mainly about adaptations. Natural selection is ongoing, and can be seen when looking at certain pathogens such as bacteria or viruses. Some bacterials and viral particles can become resistant to a drug, and multiply rapidly.

Founder effect is.....

- When there are a couple of individuals that migrated to and settled in a new location, these individuals would have a much smaller gene pool than their original population. The successive generations will descend from the founders, and their unique genetic makeup. - So in the founder effect, a few members of a parent population may migrate to a new area. Once in the new area, this small population can establish a small, interbreeding population. - Consider a newly formed volcanic island. Seabirds can bring seeds from the mainland. These seeds can now dictate the phenotypic range. When a small population distances itself from a larger one and colonizes the area, it is likely not representive of the original larger population. - In a certain area of Venezuela, there is a high incidence of Huntington's disease. A single woman is believed to have been the "founder" of this population now affected with this pathology. In the image: This shows a small group of marbles that "migrated" out from its original population. Since the group is small, it is prone to genetic drift. After a few more generations, all of the original red marbles (alleles) are lost.

Hybrid advantage is...

-A hybrid is a result of breeding between two different strains of organisms. More breeding options = more variety! -The offspring is usually more superior due to the combination of different genes — avoiding deleterious homozygous diseases and maximizing heterozygous advantage. -*Interesting side note: humans are very good at producing hybrid veggies and fruits through selecting the best traits of each parent.

Any deviation from the five hardy- Weinberg conditions listed can cause evolution.....

1- Large Population: gene frequency doesn't change as a result of chance alone 2-Random Mating: inbreeding causes little mixing of genes 3-No Mutations: a mutation modifies our gene pool 4-No Natural Selection: survival differences can alter gene frequencies 5-No Gene Flow: no immigration, no emigration, no pollen transfers For example: (If a strong wind blows, pollen can move from Point A to Point B. We don't want this!! Another example of gene flow would be if a population has an influx of new members). Obviously, no natural population meets all of these criteria. Departure of any of these give conditions usually results in an evolutionary change. Any deviation from the five conditions listed can cause evolution. Factors like mutations, nonrandom mating, and inbreeding can all affect frequencies of homozygous and heterozygous genotypes, but usally has little effect on allele frequencies in the gene pool. The main idea is that these conditions are actually rarely (if ever) met in the real world. This means that allele frequencies do change from generation to generation, and that evolution will naturally occur. If we think reversely, the conditions that are listed above are actually the factors that propels evolution, because they introduce change into a population.

There are three ways to achieve sympatric speciation...

1. Balanced polymorphism 2. Polyploidy 3. Hybridization

Postzygotic Isolation includes...

1. Differences in chromosome number due to incorrect pairing during mitosis and meiosis 2. Hybrid mortality/viability 3. Hybrid sterility 4. Hybrid F2 breakdown

A mutation is a source of genetic variation in which...

1. Mutation This is the most straightforward way to have a new allele, through genetic mutation. Note here that these mutations cannot be fatal! Sexual reproduction and mutations (change in the nucleotide sequence of an organism's DNA) produce the genetic variation that makes evolution possible. Most genetic variations are not due to mutations but due to sexual recombination of alleles that are already in the population.

Evolution is indeed supported by much scientific evidence. This evidence can come from several sources....

1. Taxonomy 2. Molecular biology 3. Paleontology 4. Biogeography 5. Genetics 6. Comparative anatomy

Natural selection chooses the fittest being. But in order for natural selection to occur, there are 4 requirements.....

1. There is more demand than supply 2. There is a difference in the level of fitness 3. Traits must be heritable 4. The variation of traits must be significant to reproduction and/or survival

"There is more demand than supply" explains...

1. There is more demand than supply If the world has an infinite supply of resources, then organisms would reproduce and grow in exponential numbers, without needing to struggle to survive. In this case, there would be no natural selection. Natural selection occurs on the basis that there is always an insufficient supply to the growing demand. Therefore, organisms are constantly competing for survival. Only members of the population who are most "fit" can survive and pass on their genes. Without the competition for survival, there is no mechanism for variations to be selected for or against.

The process of speciation is....

A species represents a population of organisms that may display a range of genotypic and phenotypic variation, and members have the potential to interbreed and produce viable and fertile offspring. Species exist as a discrete unit in nature! It is possible for two species of a population to evolve in different ways. As time goes on, they become more and more different until they can no longer interbreed. This is speciation. The defining characteristic seperating one species from another is that they are reproductively isolated. The first and most important step of speciation is always reproductive isolation, which leads to the interruption of gene flow between populations of the same species. Alleles cannot cross between the populations, there must be a separation. As the separation continues, the two populations gradually develop into two different species.

Allele frequencies means...

Allele frequencies basically means how often you can find a yellow allele vs. a green allele (gene variant) in a pea population.

Allele frequency =

Allele frequency = gene frequency (could be used interchangeably).

Alleles refer to...

Alleles refer to different forms of a gene (yellow vs. green pea genes).

Allopatric speciation is....

Allopatric speciation-Geographical Barrier In allopatric speciation interbreeding between populations is prevented because of a geographical barrier. Gene flow cannot occur. Geographical barriers can include: rivers, oceans, mountains, deserts, glaciers, canyons and ranges, & altitude or longitude. The geographical barrier will stop populations from breeding. As they continue to live in their respective environments, they are subject to the effects of natural selection and will gradually differ from the original group that they used to belong to. Eventually, they will go off to become a new species.

Analogous structures are....

Analogous structures: Formed by Convergent evolution-No common Ancestor Analogous structures must perform the same function and must not have the same ancestry. These are structures that have the same functions but are not derived from a common ancestor. These are structures with the same function but evolved separately...they also have a similar appearance. There is no common ancestor. Both birds and bats evolved to have wings, but they originated from different lineages. Analogous structures evolve due to what is called convergent evolution. In convergent evolution, we see organisms that are not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. The North American cactus and the African Euphorbia plant look alike. Both plants developed in harsh, aris desert climates, but both experienced convergent evolution since they have no common ancestor! Analogous structures include: -Wing of a bat and wing of a bird -Wing of an insect and the wing of a bird -Fish fins and whale flippers -Jointed legs of insects and vertebrates used for locomotion -The spine of a cactus and thorn of a rose

Comparative anatomy is the fourth piece of evidence for the theory of evolution.....

As the name suggests, comparative anatomy compares different body parts from different animals to see possible connections between them. There are three important structures in comparative anatomy....homologous structures, analogous structures, and vestigial structures.

Artificial selection is....

As the name suggests, this is not a type of natural selection. Artificial selection is usually carried out by humans when they selectively breed for favorable traits, such as breeding for certain traits in dogs. The artificial selection of dogs with certain characteristics to create a new, adorable dog breed for example. What does artifical selection mean? Artifical selection is when humans modify a species. In artificial selection, we give a population desirable traits. Artificial selection is seen in: Plants: superior crops of corn, soybean, and wheat have been produced. Flowers such as roses produce "hybrid" roses. Animals: the meats many people eat are the result of careful selective breeding of pigs, cows, chickens, turkeys, and sheep. Cats without fur can be produced for those that are allergic.

Balanced Polymorphism is a source of genetic variation in which...

Balanced polymorphism- maintains a variety of phenotypes within a population Poly = many and morphism = forms; hence, polymorphism = many different forms. A balanced polymorphism means that different phenotypes within the members of a population can be maintained, through these advantages: 1. Heterozygote advantage 2. Minority advantage 3. Hybrid advantage 4. Neutral advantage Two or more forms of a phenotypics characteristic in a population is called a morph. A population is said to be polymorphic for a characteristic if two or more morphs are found in noticeable numbers. Freckles is a good example. If two or more snakes differ in color from a single population, we are looking at polymorphism. ABO blood groups is another example. This balanced polymorphism can indeed allow for diversity or variation of a population's gene pool.

Baron Cuvier's theory of evolution was Catastrophism ....

Baron Cuvier — Catastrophism Cuvier proposed catastrophism. Through observing fossil patterns, he proposed that there must have been sudden catastrophes that happened spontaneously throughout history causing mass extinction of species in those areas (dinosaurs, for example). The different populations were shaped by what catastrophes had occurred, and what random organisms survived. After the catastrophe, the landscape is drastically changed and new life forms will eventually populate the area, giving off new fossil specimens.

Biochemical is the fifth piece of evidence for the theory of evolution.....

Biochemical - Conserved DNA regions + Common Conserved Pathways This is the newest type of evidence that supports the theory of evolution, as scientific analysis methods has gotten more and more advanced. When we compare DNA sequences in genomes, we see conserved DNA regions across species which are related. The higher the similarity, the stronger the relatedness. Chimpanzees have roughly 98% similarity with humans, showing a strong lineage connection. We also observe common conserved pathways in species that are related. For example, respiration (Kreb's cycle, ETC) can be seen in many eukaryotes like plants and animals, which provides evidence that both plant and animal eukaryotes evolved at one point from a common eukaryotic ancestor.

Biogeography is...

Biogeography is the study of past and present specie distribution

The bottleneck effect is....

Bottleneck effect - loss of alleles due to a disaster - smaller gene pool, some alleles may be lost easily through natural disasters. The gene pool is all the genes available for reproduction in a population. When there is a disaster that kills off most of the population. For example, a forest fire kills off all squirrels, and by chance two albino squirrels survive. The new population may be albino (if new squirrels don't migrate to this area). What's left is a handful of lucky individuals that survived and a much smaller gene pool. Some alleles may be lost from this (by chance). So in a bottleneck effect, something bad occurs such as a flood, tsunami, starvation, earthquake, or fire, that reduces the population size. By chance alone, some alleles may be underrepresented, others may be overrepresented, or lost all together. A loss of genetic variation occurs giving rise to a new population that is not representative of the original. Let's do some examples... 1. Northern elephant seals were hunted and reduced to about 20 at the end of the 19th century. Today, over 30,000 exist. However, much less variation is seen then with a population of Southern elephant seals that were not hunted. 2. European bison faced becoming extinct in the 20th century. The animals living today have very little genetic variation. They are descendants of 12 individual bison. 3. And a final example....A volvano wipes out most of an island. Only a small fraction survives. New populations are not built from just these small number of survivors. In this picture, we can assume that the colors of the marbles refer to the different alleles in a population. Inside the bottle, there were many green and red marbles. However, after passing through the bottleneck, we have lost all red marbles and only a few green ones remain. This shows the loss of alleles during a disaster.

Comparative anatomy is....

Comparative anatomy is the study of different structures

Directional selection explains...

Directional Selection: This is the type of selection where one extreme is favored (as evolution occurs, the population evolves to traits in one direction). For example, black color is more favorable than white color during the Industrial Revolution (where there is lots of black soot around) for moths, so moths eventually develop darker colors that blend in. In directional selection, allele frequencies shift due to changing conditions in the environment. Examples: 1- The classic example is the Peppered moth in England. At one time, it was light-gray in color, and very uncommon to see a dark-gray moth. As industrialization grew, and the environment became pollutioned, the moths became dark!! They were now camouflaged and had a selective advantage. These dark moths survived and reproduced more, thus the allele frequencies of the population changed. 2-Another example is insecticide resistance. Most...let's say 99% of insects are killed off by the spraying of insecticide. 1% are able to survive. Perhaps some aspect of their genetic make-up or anatomy allows them to survive the deadly chemical. What do you expect to happen? When the next generation appears, there will be a significantly larger percentage that displays insecticide resistance. 3- Another example would be bacteria resistant to a certain type of antibiotics. As we take penicillin for an infection, there might be a bacterium that is genetically resistant to penicillin. After taking the drug, mainly drug resistant bacteria survive and is directionally selected to reproduce and pass on its resistance genes. This is a diagram that shows directional selection that giraffes evolve to be taller (which enables them to reach leaves of taller trees and which contributes to fitness). Note one extreme is favored by directional selection (red = before, blue = after).

There are four important sources of genetic variation....

Each organism is unique, all thanks to the massive genetic diversity! 1. Mutation 2. Sexual Reproduction 3. Balanced polymorphism- maintains a variety of phenotypes within a population. 4. Polyploidy

Geographic Variation-Ecoline:

Ecolines consist of forms of species that show gradual phenotypic and/or genetic differences over a geographical area. -For example 2 different varients of mice exist in two different areas of the United States seperated by mountainous terrain. -Rabbits in the North might have white fur, while rabbits in the South have brown fur...such a gradual difference in appearance is a good example of a directional cline. (Plant size decreases as you climb up mountains is an example of a cline too).

Embryology is the third piece of evidence for the theory of evolution....

Embryological similarities are observed during the development stage in related organisms. For example, if we look at phylum chordata, it comprises of all organisms with a notochord. It includes a variety of animals ranging from small fishes to humans. From the outside, there is a huge physical difference between a human and a fish. But on the embryological level, we can see a lineage because all chordates (e.g. human and fish embryos) have a gill slit at some point of their development. In the image below, notice how similar all of these different chordates are in their early embryo appearance.

Habitat Isolation is.....

Even if two species reside in the same geographical area, if they occupy different habitats, it will hinder mating. So in habitat isolation, two species living in the same area, but one prefers water, while the other prefers land. They simply DO NOT encounter each other. For example, many different species are restricted to only one layer of the canopy in tropical rainforests.

Evidence of continent movement comes from.....

Evidence for continent movement on what is called tectonic plates, are now extensive. These plates consist of churning currents of molten lava, and can now move apart, move sideways, etc. When plates collide, the crust crumpls and buckles into mountain ranges. California has tectonic plates that move relatively fast, thus the area is prone to many earthquakes.

Charles Darwin's proposed the theory of natural selection to explain evolution....

Evolution can occur by a mechanism called natural selection. This idea was championed by Charles Darwin in his book, "On the Origin of Species". Evolution can occur by a mechanism called natural selection. This idea was championed by Charles Darwin in his book, "On the Origin of Species". Randomy evolutionary changes are selected for by nature in an orderly and consistent fashion. There are limited resources in nature, thus, those organisms that have traits that favor survival and reproduction will leave more offspring allowing the traits to be passed down through generations. Thus, natural selection can lead to increased fitness.

Evolution is....

Evolution is the gradual development and change of heritable traits in populations over successive generations. It is a long process that brings about biodiversity - from a single bacterium to a spectrum of plants and animals, all thanks to evolution!

Evolution refers to the...

Evolution refers to the heritable changes in populations of species over generations. More specifically, evolution refers to the changes in allele frequencies in populations over time. For example, the allele that codes for white fur coat will become more common as a population of foxes begins to live in the arctic.

Hybrid F2 breakdown is...

F2 refers to the next generation of hybrids. In this case, even if hybrids can reproduce, their offspring would suffer from decreased fitness.

Factors that cause microevolution....Opposite of "Large Random M&M"

Factors that Cause Microevolution: Opposite of 'Large Random M&M' for the conditions for Hardy-Weinberg equilibrium will cause microevolution.

Gene flow causes microevolution by....

Gene Flow Gene flow is the process of moving alleles between populations through individuals' migration. You can think of gene flow like how we are living in a global village nowadays — people emigrate and immigrate around the world and breed amongst different ethnicities. This causes alleles to mix and eventually make variations between populations smaller.

Genetic Drift causes microevolution by....

Genetic drift is a change in allele frequencies in a gene pool by chance. The fact that luck is involved differentiates genetic drift from natural selection, where allele frequencies are selected by the environment to increase or decrease. This is why genetic drift has a much bigger impact on small populations than big populations. Genetic Drift are random fluctuations in the relative allele frequencies of a small breeding population. Let us consider a population on a small island of only 50 people If an allele y is carried by a certain individual who either failed to mate or gotten killed, allele y would be completely lost. This is a genetic drift. This is clearly a microevolutionary process. Thus, the change in allele frequencies in a gene pool of a small population arising from chance events is called genetic drift. In a large population, chance events do not do very much with regard to the gene pool, but can do much if the population is small.

Gene flow vs Genetic Drift

Genetic drift is the result of a random change in allele frequency. Gene flow is the process of moving alleles between populations through individuals' migration. You can think of gene flow like how we are living in a global village nowadays — people emigrate and immigrate around the world and breed amongst different ethnicities. This causes alleles to mix and eventually make variations between populations smaller.

Genetics is....

Genetics is the study of genes and diseases

Prezygotic isolation includes....

Habitat Isolation, Temporal Isolation, Behavioral Isolation, Mechanical Isolation, Gamete Isolation

Homologous structures are....

Homologous structures: Formed by Divergent Evolution-Common Ancestor Homologous structures may or may not perform the same function, and must have the same ancestry. Homologous structures: these structures or organs that are similar in morphology (shape), anatomy, genetics, and embryology, but have different functions. They may even look different! They have a common ancestor. The relationship between homologous structures is termed homology. Homologous stuctures are formed due to divergent evolution. In divergent evolution we see an ancestral species form into a number of different species with both similar and different traits. Darwin's finch birds on the Galapagos Archipelago are a great example. Some signature examples that you may want to remember: -Forearm of a bird and the forearm of a human -Forearms within wings and human arms have different functions, but both have the same ancestral origin. -Flipper of a whale -Wing of a bat -Leg of a cat -Arm of a human

Homoplasy is....

Homoplasy, also known as convergent evolution, is a phenomenon that describes when two distinct clades develop strikingly similar characteristics (analogous structures) despite the fact that there is no common ancestor with the trait

"There is a difference in the level of fitness" explains....

If every individual is equally fit, then there would be no way to select the "fittest" one. Therefore, organisms must have variation in traits. Variation among members of the population differentiates their ability to compete to survive. For example, during the Industrial Revolution, white tree barks were covered by soot and turned black. At that time, the frequency of black peppered moths increased because of its camouflage color. After the Industrial Revolution was over, pollution was cleared and the white peppered moths became favored by natural selection. This shows how different variations are favored under different environments.

"Traits must be heritable" explains...

If traits are not heritable, even if they prompt an individual's survival, they cannot be passed down to the offspring. Therefore, the differences in traits must be genetically-influenced.

Adaptive radiation is....

In adaptive radiation many new species arise from a single ancestor as they adapt to their respective environments differently Adaptive radiation is a "burst of speciation" in which numerous species are produced from a common ancestory. Adaptive radiations are common during the first few million years following a mass extinction. For example the development of mammals occurred after dinosaur extinction, or the many finches seen today in the Galapagos Islands that originated from a single ancestor, and the marsupials of Austrialia illustrate the adaptive radiation concept nicely. An example of this would be Darwin's finches on Galapagos Island, which originated from the same ancestor from the mainland. As the finches flew to each small islands, they grew apart from their ancestors and became different species that "radiated" away from the main branch. Adaptive radiations is a type of divergent evolution. Adpative radiations are not limited to only animals but plants also have shown adaptive radiations. For example, in the Hawaii islands, 28 species of a certain plant are known, but the entire family is traceable to a single ancestor. This is another example of adaptive radiation. Adaptive radiations, especially on islands that are remote from continents, have allowed, the successful "pioneers" to diversify into new niches without much competition, often becoming new species.

Sympatric speciation is...

In sympatric speciation, different species are produced from populations that occupy the SAME geographical area. There are no geographical barriers!! This is less commonly seen than allopatric speciation. Realistically, being physically separated is probably the most straightforward way to stop species from mating. However, there are still other ways that will prevent mating and induce speciation without necessarily being isolated. In the case of sympatric speciation, speciation occurs WITHOUT the presence of a geographical barrier.

Speciation is....

It is possible for two species of a population to evolve in different ways. As time goes on, they become more and more different until they can no longer interbreed. This is speciation.

Macroevolution is...

Macroevolution is long-term and occurs at a level at or higher than species. In macroevolution species are reproductively isolated (via prezygotic and postzygotic isolating mechanisms) resulting in a lack of gene flow between species. In short, macroevolution looks at changes that occur at a level that is at or higher than species. Recall the 7 levels of taxonomy (Kingdom, Phylum, Class, Order, Family, Genus, Species). Since we are at least at the level of species, evolution will take time. We need to look from a long-term perspective to see evolutionary patterns. This is unlike microevolution, where genes can change within one generation.

Mechanical Isolation is...

Male and female genitalia are not compatible between different species. For example, two animals differ greatly in size...incompatibility of genitalia or two flowers which have different floral anatomy.

sexual dimorphism is....

Males and females are reconizibly different in the way they look!! They could differ in: a) Size B) Color C) Behavior D) Outward appearance For example, consider the Mandarin duck. The male has a red bill and colorful feathers, the female does not. Male pheasants are large in size, have larger rails, and are colorful. The female has much less color, and smaller in size with a shorter tail. Thus, this is a case of sexual selection.

Behavioral Isolation is...

Many species perform courtship rituals to signal to his/her partner, such as singing songs in birds or pheromones in ants. Different species would not perform the right type of rituals, hence preventing mating. Behavior isolation is another prezygotic barrier. Perhaps a species dances a certain dance, sings a certain song, or gives off a certain pheromone which is only unique to that particular species.

Mutations happen randomly... Mutations that lead to successful organisms for that environment allow that specific genetic variant to...

Mutation happens randomly. Mutations that lead to successful organisms for that environment allow that specific genetic variant to thrive. This increases the number of organisms in that population that have the favorable genetics over successive generations.

Mutations cause microevolution by...

Mutations Mutations (a heritable change in DNA) happen with varying damage, to all organisms. Some mutations can happen and go into a 'dormant' phase until there is sudden environmental changes and the mutated traits suddenly become favorable and flourish.

Natural Selection causes microevolution by...

Natural Selection As we've discussed, natural selection is the increase or decrease in allele frequency due to adaptations to the environment. No luck is involved, traits are selected for based on how they confer fitness within an ecosystem.

Natural selection is the....

Natural selection is the gradual, non-random process where alleles become more or less common as a result of the individual's interactions with the environment The genetic variations that lead to different traits in organisms are random, but natural selection itself is a non-random process Those organisms better adapted to survive and reproduce are more successful in passing on their genes, resulting in the evolution of populations over time. Individuals do not evolve, populations evolve over generations.

non-random mating such as sexual selection, outbreeding, and inbreeding causes microevolution by....

Non-random mating- sexual selection, outbreeding, inbreeding This is when individuals choose who they want to mate with. This is a consequence of sexual selection, which we've covered beforehand. When certain traits are favored over others, they get passed onto offsprings and become more represented within the allele frequencies of future generations. Outbreeding: breeding with individuals with no distinct family ties. Inbreeding: breeding with relatives.

A type of allopatric speciation is....

One type of allopatric speciation is adaptive radiation....

Paleontology is...

Paleontology is the study of fossils

Polyploidy can occur when a mistake during cell division results in an extra chromosomal set. For example.....

Polyploidy can occur when a mistake during cell division results in an extra chromosomal set. Thus, a plant for example, has a 4N chromosome number, instead of 2N. These 4N cells cannot breed with 2N cells, but the 4N cells can produce fertile offspring by self-pollinating or mating with other 4N cells

polyploidy causes sympatric speciation by.....

Polyploidy is a common phenomenon that occurs in plants, often resulting from nondisjunction when chromosomes separate during cell division, specifically meiosis. Polyploidy can occur when a mistake during cell division results in an extra chromosomal set. Thus, a plant for example, has a 4N chromosome number, instead of 2N. These 4N cells cannot breed with 2N cells, but the 4N cells can produce fertile offspring by self-pollinating or mating with other 4N cells. Let's imagine plant A, which normally contains 10 chromosomes (2n = 10). During meiosis, if nondisjunction occurs and two of the four gametes have 0 chromosomes, the other two will have 10 chromosomes (2n). Whereas under normal conditions all four gametes should each have 5 chromosomes (n). So what happens next? If one of the 2n gametes fuses with another normal n gamete, there will be a 15 chromosome (3n) zygote. This 3n zygote will be sterile, unless it encounters another polyploidy 3n gamete. This will result in reproductive isolation and could eventually result in polyploidy speciation, if two 3n organisms meet and are reproductively compatible.'There are two forms of polyploidy: a) Autopolyploidy: organism has more than 2 sets of chromosomes all derived from a single species. Ex: AAAA b) Allopolyploidy: organism has more than 2 sets of chromosomes, derived from different species. Ex: AABB is the chromosomal composition I hope you can see this. The organism has another set of chromosomes from another species.

Prezygotic Isolation is...

Prezygotic Isolation: this mechanism prevents fertilization even if mating is attempted, hence preventing the formation of a zygote. Prezygotic barriers are barriers that prevent members of different species from mating.

Alleles refer to...

Remeber that alleles refer to different forms of a gene (yellow vs. green pea genes). Hence, allele frequencies basically means how often you can find a yellow allele vs. a green allele (gene variant) in a pea population.

"The variation of traits must be significant to reproduction and/or survival" explains....

Remember the two key conditions for evaluating fitness? If the differences in traits do not impact reproductive success nor mortality, they would not participate in the process of natural selection. Genes that improve survival and/or reproductive success will be favored and increase in frequency as generations go by. Genes that decrease survival and/or reproductive success will be filtered out and decrease in frequency as generations go by.

Examples of sympatric speciation...

Reproducive isolations occur due to natural selection. For example, a mutation causes a "shift" in the timing of reproduction or even a "shift" in food preference. Individuals are in a situation which may cause breedings among themselves only. This can also occur if herbivorous insects try out a new plant host. By exploiting a new niche, such as this could trigger sympatiric speciation. Consider a bacteria population. If some bacteiral members are specialized for living in a certain environment, this population may go on to occupy a different environmental niche and could indeed evolve into a new species over time. A recent example I found for you of sympatric speciation occurred with apple maggot flies. These flies lay eggs on Hawthorn trees, but less than 200 years ago, they began to lay eggs on apples. Guess what? Yes, indeed!! Two groups of apple maggot flies have emerged. One group lays eggs on Hawthorn trees, the other group layers eggs on apples. The groups were studied by scientists and have shown to have genetic differences. It is very possible that in the future, we woulc see seperate species!! The bottom line is that speciation can occur even when different populations of the same species are in the same geographic boundary. Back to earlier, three main ways to achieve sympatric speciation is through balances polymorphism, polyploidy, and hybridization.

______ is a major working criterion for the species definition....

Reproductive isolation is a major working criterion for species definition, but it is not perfect. For example, sometimes, occasional mating does occur between members of two different species. However, most of the offspring are sterile and have no evolutionary future. The reproductive isolation criterion is for organisms that do sexual reproduction, thus a shortcoming is that is cannot be applied to organisms that reproduce asexually. Nevertheless, it remains as the major criterion for species definition.

sexual selection is....

Sexual selection is a "special case" of natural selection sexual selection is often powerful enough that can lead to the death of the individual. Color, for example, can indeed attract predators in addition to members of the opposite sex. However, the colorful animal often has a better time finding a mate. The bottom line is that sexual selection often helps you find a mate to reproduce with, but does not provide any survival benefits!

sexual selection is different from natural selection because...

Sexual selection is different from natural selection because the evolutionary changes each gender makes could lead to less survival (despite making them more competitive for sex). For example, consider the vibrant colors of a male peacock's feathers - it's great for attracting mates, but makes them more easily spotted by predators.

Sexual selection occurs in nature when....

Sexual selection occurs in nature when there is differential, non-random mating between a male and a female. In nature, and perhaps in our daily lives as well, females can be very picky and they are the ones who choose which male to mate with. This is because compared to males, females have a limited capacity to reproduce due to the relatively long labor period. Hence, females need to carefully pick the superior males to boost the quality of her offsprings. In some species, males even fight for the chance to mate. This preferentially selects males with bigger muscles, stronger horns, and larger stature to pass on their genes. Since the cost of fathering an offspring is very low for most male animals, males increase their fitness by boosting the quantity of his offsprings (trying to impregnate as many females as possible). Note: The traits selected for may be favorable for reproduction but not for survival.

Temporal Isolation is...

Species breed and reproduce at different times/seasons. Temporal isolation is yet another prezygotic barrier. Here we see breeding at different time so the day or night, or different seasons. For example, a species of skunk mates in the winter, another mates in the summer. "Well, if you are only active past midnight whereas I am an early bird, I don't think we are right for each other."

There are 5 types of natural selection.....

Stabalizing Selection Directional Selection Disruptive Selection Sexual Selection Artifical Selection

Taxonomy is....

Taxonomy is naming and classifying organisms

Reproductive Isolation is....

The defining characteristic seperating one species from another is that they are reproductively isolated. Reproductive Isolation is a major working criterion for species definition, but it is not perfect! For example, sometimes, occasional mating does occur between members of two different species. However, most of the offspring are sterile and have no evoutionary future. For example, sometimes, occasional mating does occur between members of two different species. However, most of the offspring are sterile and have no evoutionary future.

The gene pool of a population that is not evolving can be described by the.........

The gene pool of a population that is not evolving can be described by the Hardy-Weinberg Principle This principle examines gene pools of a population and is not concerned with genotypes or phenotypes of specific individuals within the population. According to the Hardy-Weinberg Principle, the genotypes and allele frequency in a given population will remain constant from one generation to the next, providing that only Mendelian segregation and recombination of alleles operate.

Postzygotic Isolation is....

There always needs be a plan B for things if plan A fails. Postzygotic isolation is the backup in case a hybrid zygote actually forms. In postzygotic barriers, once mating has occured, a post zygotic barrier prevents the production of fertile offspring.

There are two signature extreme cases that result in genetic drift....

There are two signature extreme cases that result in genetic drift: Bottleneck Effect and Founder Effect ◙ Founder effects and population bottlenecks have similar effects: genetic diversity is reduced. ◙ Some genes are thrown out, some genes that were once rare, now become common. They are both random. ◙ In natural selection, the genes with the best chance of survival are the ones that are passed down to the next generation. In the founder effect or population bottleneck, this might not be the case. The genes that passed down are not necessarily the "good ones". I hope I have illustrated this clearly to you.

Disruptive selection explains...

This is the type of selection that is the exact opposite of stabilizing selection. In this case, oddballs (rare traits) are favored, while mainstreams (common traits) are not. Disruptive selection illustrates a very interesting phenomenon. Intermediate forms of a phenotype are selected against. Let us consider a small population of finches on the Galapagos Islands. The finches differ in beak size and shape. Longer beaks can open fruits and get to their seeds. Wider, but shorter beaks can simply crack the fruit on the ground and get to the seeds. The finches were studied during a drought. Survival was higher for those with long beaks and shorter but wider beaks than finches with intermediate beaks! As you can see, individuals with either extreme variation of a trait have greater fitness than those that are average!! Examples: 1- In an environment of black and white rocks and colored rabbits: White rabbits...live...can hide against the white rocks Black rabits.....live....can hide against the black rocks Grey rabbits...die.... 2- Another example is that there is a breed of snails that live both in low-vegetation areas (grassfields, meadow) and high-vegetation areas (forests). In low-vegetation areas, predators can detect snails with black shells, so snails with white shells will thrive. In high-vegetation areas, predators feed on snails with white shells, so the ones with black shells will flourish. Clearly you see that as the number of favorable traits increase in individuals, the match between the specie and the environment improves. Adaptive evolution occurs. Here, we can see that the middle shellfish is selected against in disruptive selection (red = before, blue = after).

stabilizing selection explains...

This is the type of selection where mainstream is favored, oddballs are selected against. For example, an average newborn weighs around 3.5kg, babies who are born too small are fragile and risk losing too much body heat, whereas babies who are born too big may face complications during the birth process. In a stabalizing selection, the alleles that produced uncommon phenotypes are eliminated over time. Thus, stabalizing selection tends to undo the effects of gene flow, mutation, or genetic drift. For example, babies smaller or larger than the range of 6.5-9 pounds often die. In the world of birds, robins usually lay 4 eggs each season. More eggs would be bad, parents couldn't provide food for all of them. Fewer eggs might not bring forth enough healthy birds. This diagram shows the signature bell curve of stabilizing selection in regards to tail length of geckos. Here, red = before selection and blue = after selection. Note that through the evolutionary process, more geckos have medium length tails and less have short/long tails.

Hybrid sterility is...

This is when a hybrid zygote is sterile and cannot reproduce. The most well-known example would be the mule (hybrid of a horse and a donkey). It's viable (doesn't die) but is infertile (can't produce new offspring)

Gamete Isolation is...

This is when gametes cannot recognize and fertilize each other In gamete isolation, the sperm and ova of the two species are chemically and genetically incompatible and no zygote forms. If not for gamete isolation, any sperm in the water could fuse with any egg, and we'd see hybrids of marine creatures abound!! If you recall from the reproduction chapter, mammalian oocytes have a structure called the zona pellucida that blocks the binding of sperm from alien species. This is an example of gametic isolation.

Hybrid mortality/viability is...

This is when the hybrid dies prematurely (mating between two frog genus results in offspring with incomplete development. This is when a hybrid zygote is not viable and dies before reaching reproductive age. Usually, different species have different # of chromosomes. When gametes with a different # of chromosome fuse, the maternal and paternal genetic information cannot match properly.

Sexual reproduction is a source of genetic variation in which...

This will create diversity in 3 ways, as we have seen in the cell division chapter. 1- Crossing over 2- Independent assortment 3- Random joining of gametes

Balanced polymorphism causes sympatric speciation by.....

Two ore more forms of a phenotypic characteristic in a population is called a morph. A population is said to be polymorphic for a characteristic if two or more morphs are found in noticeable numbers. Freckles is a good example. Let's imagine we have black and white butterflies of the same species due to polymorphism. They are living in an area with dark tree barks, and light tree leaves. The white butterflies will stick to the leaves where they're camouflaged, and the black moths to the dark bark. Where does this lead to? Reproductive isolation. If this continues for a long time (hundreds of thousands of years), the black and white butterflies can become an entirely different species. If two or more snakes differ in color from a single population, we are looking at polymorphism. ABO blood groups is another example. This balanced polymohphism can indeed allow for diversity or variation of a population's gene pool.

Jean-Baptiste Lamarck proposed two interesting theories of evolution.....

Use and Disuse (incorrect ) + Theory of Acquired Characteristics (incorrect)

Jean-Baptiste Lamarck Theory of Use and Disuse explained....

Use and disuse (LAMARCK INCORRECT THEORY) Lamarck believed that whatever characteristics an organism acquires throughout its life (through use and disuse) will be passed onto its offspring. His theory of evolution is also known as the theory of use and disuse. This theory is incorrect because environmentally acquired characteristics are actually not heritable. They are changes to the organism but don't represent a heritable change because their use/disuse doesn't change the genetic code, ie. the DNA.

Vestigial Structures are....

Vestigial structures: These are structures that exist, but do not serve a purpose in an organism. Note: they are often homologous to structures that are functional in other organisms. A vestigial structure has little or no importance to an organism. A vestigial structure (organ) has lost most of all functioing through evolution. They have important functions in ancestors, however. Some examples: -Wings of ostrich (homologous to wings of eagles) -Wisdom teeth in humans -Coccyx (tailbone) in humans Appendix of humans (homologous to cecum of cows) If you examined a cave-dwelling animal which organ do you think would most likely become vestigial? a) Ears b) Mouth c) Eyes d) Legs I hope you said eyes!! Caves are dark..eyes might not be needed!!

_________ is the only evolutionary mechanisms that will lead to adaptive evolution on a consistent basis

Yes, genetic drift, and gene flow can cause gene frequency to increase or decrease, but natural selection is the only evolutionary mechanism that will lead to adpative evolution on a consistent basis.

The process of petrification is....

You may also wonder, how do fleshy living organisms turn into solid rocks? This can be achieved through the process of petrification. As the body of the living organism becomes buried under layers of sediments, minerals slowly seep into its body and replaces organic materials, hardening the corpse.

There are 2 forms of polyploidy:

a) Autopolyploidy Organism has more than 2 sets of chromosomes all derived from a single species For example AAAA Additional chromosal set that is identical to parent species. For example, if Plant X has a 2N = 10, a new species Y, arises as an autodiploid from X has a 2N=20 b) Allopolyploidy: organism has more than 2 sets of chromosomes, derived from different species. For example AABB is the chromosomal composition The organism has another set of chromosomes from another species.

Convergent evolution VS. Divergent Evolution?

convergent evolution: -Different ancestor -converge to produce analogous structures -species appearance become more similar over time -species are unrelated (genetically different) Example: Wings in insects, birds, and bats Divergent Evolution: -Common ancestor -diverge to produce homologous structures -species appearance becomes more different over time -species are closely related (share genetic homology) Example: Pentadactyl limb structure (vertebrates)

There are many different types of evidences that support the theory of evolution. The 5 lines of evidence for evolution is...

fossils, biogeography, embryology, comparative anatomy, biochemical.

When there is no change in evolution, it is known as....

no change = gene equilibrium. In this state of equilibrium, there is no change in gene frequencies, hence there would be no evolution.

Nature secures reproductive isolation for each species through two ways....

prezygotic and postzygotic isolating mechanisms

Molecular biology is....

studies molecular structures

Microevolution is...

◙ refers to the process when gene frequencies change within a population from generation to generation ◙ Genes that translate into traits that best suit the environment will proliferate — they increase in frequency; whereas genes which become traits that suit the environment less optimally will die out — these unfavorable alleles decrease in frequency. ◙ Microevolution is the process when gene frequencies change within a population over generations (favorable genes increase, unfavorable decrease) ◙Microevolution happens on a small scale within a single population. The changes would not result in the new organism being considered as different species. ◙ Example: A species has a color or size change. Thus, genes in a gene pool of populations = microevolution. ◙ The smallest scale that we can define evolution is termed microevolution. Microevolution is change in allele frequencies of a population over generations.