Biology: Evolution

Theory of Evolution → Baron Cuvier

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.

Microevolution → Sources of Genetic Variation → Mutation

This is the most straightforward way to have a new allele, through genetic mutation. Note here that these mutations cannot be fatal

Evidence of Evolution → Comparative Anatomy → Analogous structures

are structures that have the same functions but are not derived from a common ancestor. Both birds and bats evolved to have wings, but they originated from different lineages. · example: A cat leg vs. a praying mantis leg

Evidence of Evolution → Comparative Anatomy → Homologous structures

are structures that may or may not perform the same function, but are derived from a common ancestor · example: Forearm within the wings of a bird and the forearm of a human arm have different functions, but both have the same ancestral origin.

Natural selection → Type: Artificial Selection

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 is macroevolution?

· In short, macroevolution looks at changes that occur at a level that is at or higher than 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.

Gene Equilibrium → To determine whether a population is in Hardy Weinberg equilibrium, we need to see if the Hardy Weinberg conditions are met:

"Large Random No MNM." Large populations: to minimize the effects of genetic drift (causes change in allele frequencies by chance) Random mating: Individuals do not seek a particular type of individual to mate with, for example they do not mate only with nearby individuals or express sexual selection. Random mating decreases the chances of a specific allele changing in frequency. No Mutation: There cannot be any mutations to introduce new alleles in the population No Natural Selection: The environment is not impacting the allele frequencies, and all traits are neutral. No Migration: This can also be written as no gene flow. To ensure that there is no gene flow, the population must be isolated. No amount of gene flow into or out of the population can occur Main Idea: these conditions are rarely (if ever) met in the real world → allele frequencies do change from generation to generation, and 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.

Gene Equilibrium

(No Evolution) · Gene equilibrium = state of no change. In this state of equilibrium → no change in gene frequencies → no evolution · When there is genetic equilibrium, calculate gene frequency by using the famous Hardy-Weinberg formula.

What are the five types of evidence of evolution?

1. Fossils 2. Biogeography 3. Embryology 4. Comparative Anatomy 5. Biochemical

Origins of Life → Timeline

1. Once upon a time, the Earth had a primordial atmosphere that was made of many different inorganic compounds, except for oxygen. It mostly consisted of: methane (CH₄), ammonia (NH₃), carbon monoxide (CO), carbon dioxide (CO₂), hydrogen gas (H₂), nitrogen gas (N₂), water (H₂O), hydrogen sulfide (HS). The fact that oxygen was not part of the primordial atmosphere is very important, because the primordial atmosphere was a reducing environment without oxygen. We will talk about this concept later down the timeline. 2. Eventually, as the Earth cooled down significantly, some of the gases in the primordial atmosphere condensed and formed the primordial sea. The primordial sea composed of mostly water and some minerals found in the Earth's crust. 3. Gradually, the simple compounds became complex compounds and then became organic compounds. The first organic compounds were: acetic acid, amino acids, formaldehydes. Oparin and Haldane, proposed the Organic "Soup" Theory which was supported by the Miller-Urey experiment 4. Simple organic monomers gradually became polymers, forming proteinoids *Humanoid = someone who looks and behaves like a human. *Proteinoid = something that looks and behaves like a protein - what we can do is to simply heat and dry amino acids through brute force in the lab and we can get proteinoids. 5. Protobionts arose These are actually precursors to cells which have microsomes (membrane-like substance) and have proteinoidsincorporated in them. 6. Heterotrophic prokaryotes form Fast-forwarding a couple of steps (more like millions of years), we have the simplest lifeform, heterotrophic prokaryotes! They obtain energy by consuming surrounding organic materials. 7. Autotrophic prokaryotes form As heterotrophic prokaryotes advance and evolve, they became capable of making their own food, hence autotrophs. A good example would be cyanobacteria, which are capable of photosynthesis. This is a very important milestone because photosynthesis = oxygen. With oxygen accumulating in the atmosphere, we will see some dramatic changes. 8. Oxygen accumulates and terminates abiotic chemical evolution "what ended the abiotic chemical evolution?" and "which important molecule was introduced by autotrophs?". With the introduction of oxygen, the Earth transformed from a reducing environment to an oxidizing environment. As oxygen accumulated in the Earth's atmosphere, it reacted with the incoming UV rays and formed a thick ozone layer. The ozone layer blocks a great amount of UV entering the Earth. As we have seen before, UV is perhaps the biggest source of energy propelling the abiotic formation of organic compounds. Now that the supply of UV is cut short, abiotic chemical evolution is forced to terminate. 9. Primitive eukaryotes form Again, fast-forwarding a few steps, we get the formation of primitive eukaryotes! A theory that explains how eukaryotic cells form is the endosymbiotic theory. Endo means within, and symbiotic is a harmonious relationship where both the "host" and the "invader" provide mutual benefits for each other. The endosymbiotic theory suggests that some membrane-bound organelles, such as mitochondria and chloroplasts, were actually once free-living prokaryotes and through means of phagocytosis, these free-living prokaryotes become engulfed in other prokaryotes. Afterwards, they actually lived in symbiosis and eventually became modern eukaryotes. There are several evidences that support this theory: Mitochondria and chloroplasts have their own DNA that is unbound (just like in prokaryotes). Thylakoid membranes of chloroplasts resemble the outer cell membrane of cyanobacteria (autotrophs). 10. More complex eukaryotes and multicellular organisms came about

Natural selection → what are the four requirements for natural selection to occur?

1. There is more demand than supply infinite supply of resources means organisms reproduce/grow in exponential numbers wo struggle to survive → no natural selection always need insufficient supply to growing demand → organisms constantly competing for survival → only members of most 'fit' population survive and pass on their genes. Without this, there's no mechanism to be selected for or against. 2. There is a difference in the level of fitness all individuals equally fit means no way to select most "fit" → organisms must have variation in traits → variation among population members differentiates their ability to compete to survive ex: industrial revolution → white tree barks covered in soot turned black → frequency of black moths increases bc camouflage → after pollution cleared white moths favored by natural selection → different variations favored under different environments 3. Traits must be heritable If traits are not heritable, even if they prompt an individual's survival, they cannot be passed down to the offspring → differences in traits must be genetically-influenced. 4. The variation of traits must be significant to reproduction and/or survival differences in traits that do not impact reproductive success + mortality → would not participate in the process of natural selection. Genes that improve reproductive success + survival → will be favored and increase in frequency as generations go by. Genes that decrease reproductive success + survival will be filtered out and decrease in frequency as generations go by.

Gene Equilibrium → Hardy-Weinberg Equilibrium Example: We suppose that the green color is dominant and the yellow color is recessive. Therefore, GG = green, Gg = green, gg = yellow Say we're told that there is a population of peas that is 84% green and 16% yellow. And the question asks us what is the heterozygous frequency?

Approach: 1. We know that both homozygous dominant (GG) or heterozygous (Gg) peas will appear green. However, yellow is the recessive color, so they have to be homozygous recessive (gg). 2. We know that q² = frequency of gg 3. Therefore, knowing that 16% of the population is yellow: q² = 16% = 0.16 √0.16 = 0.4 q = 0.4 = frequency of q (recessive allele) in the population 4. Since q = 0.4: p + q = 1 p + 0.4 = 1 p = 0.6 5. Now let's calculate our heterozygous frequency, 2pq. Plug this into our heterozygous frequency component of the formula 2pq. Substitute in the values we've determined, p = 0.6 and q = 0.4 2pq = 2(0.4)(0.6) = 0.48 2pq = 48%

Macroevolution → Reproductive Isolation → prezygotic isolating mechanisms

As its name suggests, this mechanism prevents fertilization even if mating is attempted, hence preventing the formation of a zygote. Habitat Isolation Even if two species reside in the same geographical area, if they occupy different habitats, it will hinder mating. ex: many different species are restricted to only one layer of the canopy in tropical rainforests. Temporal Isolation Species breed and reproduce at different times or seasons. "Well, if you are only active past midnight whereas I am an early bird, I don't think we are right for each other." Behavioral Isolation 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. Mechanical Isolation Male and female genitalia are not compatible between different species. Gamete Isolation This is when gametes cannot recognize and fertilize each other. 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.

Evidence of Evolution → Comparative Anatomy → what is it?

Compares different body parts from different animals to see possible connections between them. Here, we will talk about three types of structures that are commonly tested: 1. Homologous structures 2. Analogous structures 3. Vestigial structures

Evidence of Evolution → Embryology → what is it? give an example.

Embryological similarities are observed during the development stage in related organisms. ex: phylum chordata comprises of all organisms with a notochord, but 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 embryology 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, notice how similar all of these different chordates are in their early embryo appearance

What is evolution?

Evolution is the gradual development and change of heritable traits in populations of species over successive generations. more specifically it refers to the changes in allele frequencies in populations over time ex: the allele that codes for white fur coat will become more common as a population of foxes begins to live in the arctic It is a long process that brings about biodiversity - from a single bacterium to a spectrum of plants and animals

Theory of Evolution → Charles Darwin

Finally, the third and perhaps most well-known scientist in evolutionary biology, Charles Darwin. He proposed the theory of natural selection Darwin → natural selection

Origins of Life → Miller-Urey Experiment

In short, the Miller-Urey experiment tried to mimic the primordial environments on Earth to test out the Organic "Soup" Theory proposed by Oparin and Haldane. It provided the first evidence to support that organic molecules needed for life could be formed from inorganic components. To mimic the reducing environment as proposed in the theory, Miller and Urey set up a flask with methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water (H₂O) in a closed system connecting to another flask that contains electrodes. they heated up the flask containing various gases to imitate the high temperature on Earth back in the day and the electrodes produced sparks that imitated lightning (energy source). After a week, they observed several organic compounds that formed: amino acids and other organic acids. However, they did not find any complete nucleic acid. This result echoed with the proposed abiotic chemical evolution requirements, and further confirmed Oparin and Haldane's theory.

Microevolution → Sources of Genetic Variation → Polyploidy

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. 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! Some plants are 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!

Origins of Life → Main components of modern Earth's atmosphere:

Nitrogen gas (78%) · Most commoNNNNNN\NN (N is for Nitrogen!) Oxygen gas (21%) · Though this is what we rely on to survive, it is only the second most abundant. Argon gas (0.9%) · Noble gas here The rest is small traces of carbon dioxide, methane, and ozone

Origins of Life → Timeline Facts → _____ years after Earth was born, we got the simplest life forms.

One billion years after Earth was born, we got the simplest life forms.

Origins of Life → Main components of modern Earth's crust (ranked by % by weight):

Oxygen atom (47%) · Careful here, in the Earth's crust oxygen is the most abundant atom. Whereas in the atmosphere, it is ranked second. Silicon atom (28%) · Think of all the sand we can find on the beach, plenty of silicon! Aluminum (8%)

Evidence of Evolution → Fossils → what is paleontology? what are the two types of fossils? what is petrification?

Paleontology - The study of fossils Fossils reveal information about prehistoric living organisms (anatomy, lineage, behavior, habitat) Two types of fossils — fossils of the actual remains of the animal fossils of their traces (ichnofossils), which records down details like footprints and nests Petrification - process of fleshy living organisms turn into solid rocks 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 - the deepest layer is the oldest fossil, and the shallowest layer is the youngest fossil. The anatomical change and timeline recorded through fossils is a solid piece of evidence to support the theory of evolution.

Theories of Macroevolution

Phyletic gradualism: This theory says that evolution happened gradually with the accumulation of many small intermediate changes. But when we look at fossils, we cannot see those intermediary stages, hence this theory is not likely to be true. Punctuated equilibrium: This theory says that there are short spurts of evolutionary changes during long periods of stasis (no evolution). This theory is more supported by the fossil evidence.

Microevolution → Sources of Genetic Variation → Balanced polymorphism

Poly = many + morphism = forms → polymorphism = many different forms. A balanced polymorphism means that different phenotypes within the members of a population can be maintained, through these advantages: Heterozygote advantage: 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. Minority advantage: when a rare phenotype offers higher fitness than common phenotypes (disruptive selection) However, as the rare allele increases in frequency → becomes common again → will be selected against → leading to a decrease in frequency → rare phenotypes cycle between low and high frequency ex: hunters usually develop a "search image" for their preys according to the most common appearance, and they hunt accordingly. Preys that have the rare phenotype escape the predator, and are therefore more 'fit.' Hybrid advantage: hybrid = result of breeding between two different strains of organisms. More breeding options = more variety! offspring = 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. Neutral variations: 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.

Natural selection → Type: Sexual Selection

Sexual selection occurs in nature when there is differential, non-random mating between a male and a female. females need to carefully pick/choose the superior males to boost the quality of her offspring bc they have a limited capacity to reproduce due to the relatively long labor period. males fight for the chance to mate → preferentially selects stronger males to pass on their genes for most males cost of fathering an offspring is very low → increase their fitness by boosting the quantity of offspring (trying to impregnate as many females as possible) Note: The traits selected for may be favorable for reproduction but not for survival. 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). ex: the vibrant colors of a male peacock's feathers is great for attracting mates, but makes them more easily spotted by predators.

Microevolution → Factors that Cause Microevolution

Small Selective MNM Small populations: to maximize the effects of genetic drift (causes change in allele frequencies by chance) Selective (Non-Random) mating: Individuals seek a particular type of individual to mate with, for example they mate only with nearby individuals or express sexual selection. Selective (non-random) mating increases the chances of a specific allele changing in frequency bc certain traits are favored over others and get passed onto offspring and become more represented within the allele frequencies of future generations. Outbreeding: breeding with individuals with no distinct family ties. Inbreeding: breeding with relatives. 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: 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 Migration (gene flow): Gene flow is the process of moving alleles between populations through individuals' migration (like breeding amongst different ethnicities causing alleles to mix and make variations between populations smaller). To ensure that there is gene flow, the population must not be isolated - any amount of gene flow into or out of the population can occur Main Idea: these conditions are common in the real world → allele frequencies do change from generation to generation, and evolution will naturally occur.

Origins of Life → Timeline Facts → The Earth came _____ years ago.

The Earth came ~4.5 billion years ago.

Origins of Life → Oparin-Haldane hypothesis

The Oparin-Haldane hypothesis suggests that life arose gradually from inorganic molecules, with "building blocks" like amino acids forming first and then combining to make complex polymers. They said that since oxygen is very reactive, no organic chemical would have been formed if there were oxygen in the primordial atmosphere. They also said that the reactions to form complex molecules are driven by strong energy emitting naturally on the Earth e.g. lightning, volcanic heat, and most importantly, UV radiation from the Sun.

Origins of Life → Miller-Urey Experiment → Quiz question, which gas is missing?

The answer is oxygen.

Origins of Life → Timeline Facts → The first eukaryotes came ____ years ago - _____ years after prokaryotes!

The first eukaryotes came ~2 billion years ago - 1.5 billion years after prokaryotes!

Origins of Life → Timeline Facts → The first prokaryotes came _____ years ago.

The first prokaryotes came ~3.5 billion years ago.

Macroevolution → Reproductive Isolation → postzygotic isolating mechanisms

There always needs to be a plan B for things if plan A fails. Postzygotic isolation is the backup in case a hybrid zygote actually forms. Hybrid mortality 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. Hybrid sterility 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) Hybrid F2 breakdown F2 refers to the next generation of hybrids. In this case, even if hybrids can reproduce, their offspring would suffer from decreased fitness.

Natural selection → Type: Disruptive Selection

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. ex: 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.

Natural selection → Type: Stabilizing Selection

This is the type of selection where mainstream is favored, oddballs are selected against. ex: 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.

Natural selection → Type: Directional Selection

This is the type of selection where one extreme is favored (as evolution occurs, the population evolves to traits in one direction). ex: Industrial Revolution → black color moth more favorable than white color moth bc of soot ex: bacteria resistant to a certain type of antibiotics survive and are directionally selected to reproduce and pass on its resistance genes.

Macroevolution → Speciation → Allopatric speciation

This is when speciation occurs due to the presence of a geographical barrier. 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. Adaptive radiation One type of allopatric speciation is adaptive radiation. In this case, many new species arise from a single ancestor as they adapt to their respective environments differently. ex: 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.

Microevolution → Sources of Genetic Variation → Sexual Reproduction

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

Origins of Life → Timeline Facts → We can think of the Earth as ____ as old as the Universe!

We can think of the Earth as ⅓ as old as the Universe!

Macroevolution → Patterns of Evolution → Divergent evolution

When species diverge from a common ancestor through speciation.

Macroevolution → Patterns of Evolution → Convergent evolution

When two completely unrelated species grow more and more alike (development of analogous) due to adaptations in similar environments.

Macroevolution → Patterns of Evolution → Parallel evolution

When two related species diverge off from a common ancestor but they both went through similar changes.

Macroevolution → Patterns of Evolution → Coevolution

When two species impart selective pressures on each other, resulting in the evolution of both species. 3 types: 1. Camouflage (cryptic coloration) allows animals to avoid visual detection through matching of their appearance to the environment. An insect appearing stick-like is an example of this. 2. Aposematic coloration (warning coloration) is a vibrant, bright coloration of poisonous animals, which warns predators that they are poisonous. An example of aposematic coloration is the bright coloring of poison dart frogs. 3. Mimicry refers to when one species evolves to resemble another species. · Batesian mimicry: A non-harmful animal mimics the coloring of a harmful animal. An example is a harmless fly that mimics the coloring of a stinging bee. · Mullerian mimicry: when different poisonous species that share a common predator evolve to resemble each other. This way, it is easier for the predator to learn to avoid these species. An example is of a stinging bee and a stinging wasp, which have evolved to share similar coloring and body size.

Macroevolution → Phylogenetic Trees

a branch diagram that shows the inferred evolutionary relationship between different taxa. Here, the word inferred is very important, because we are tracing back history, biologists can only infer the relationship between species using bits and pieces of the biological evidences of evolution we mentioned earlier (fossils, anatomical structures). clade - every cluster you see on a phylogenetic tree is; includes an ancestor and all descendants from that ancestor. Therefore, a clade could be as big as the entire tree, or just a small branch at the tip of the tree. the tree with the least amount of assumptions is preferred because it minimizes homoplasy. 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. The idea of parsimony is very important in evolutionary biology. Parsimony refers to the idea: 'the simpler, the better'. The tree with the least number of evolutionary reversals, convergent evolution, and parallel evolution is the most parsimonious - or the simplest. This is often how biologists formulate phylogenetic trees.

Evidence of Evolution → Comparative Anatomy → Vestigial structures

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. examples: · Wings of ostrich (homologous to wings of eagles) · Appendix of humans (homologous to cecum of cows)

Evidence of Evolution → Biogeography → what is it? give an example.

explains the spread of different species throughout the world as 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. ex: 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.

Theory of Evolution → Jean-Baptiste Lamarck

first biologist who believed in evolution, instead of special creation of life forms. He proposed two interesting hypotheses of evolution: 1. Use and disuse · The more used the body part is, the more it will develop i.e. a giraffe's neck grows longer when it tries to feed from higher trees. · The less used the body part is, the more weakened it will be i.e. certain species of monkeys didn't use their tails much, so through disuse that species evolved to not have tails 2. Inheritance of acquired traits · characteristics the organism acquires throughout its life (through use and disuse) will be passed onto its offspring · ex: if a giraffe stretches its neck continually, it will develop a longer neck, and will pass on the long neck to its offspring. · 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 the use/disuse doesn't change the genetic code, i.e. the DNA. · exceptions to this is epigenetic changes (changes that do not actually change the nucleotide sequence of DNA) are heritable.

Macroevolution → What is speciation? what's the first and most important step of speciation? what are the two modes of speciation?

how species actually form 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. There are two modes of speciation: allopatric and sympatric speciation.

Evidence of Evolution → Biochemical

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.

Gene Equilibrium → define Hardy-Weinberg Equilibrium:

phenotype frequency: p = frequency of the dominant allele (G) q = frequency of the recessive allele (g) genotype frequency: p² = frequency of the homozygous dominant (GG) 2pq = frequency of the heterozygous (Gg) q² = frequency of the homozygous recessive (gg) p + q = 1 Implies that all alleles of the same gene should add up to 100% (all the dominant alleles + all the recessive alleles = 100% of the alleles in the population) p² + 2pq + q² = 1 means that all individuals should add up to 100%. This variant of the formula looks at the different allele variations that any given individual could be, and in total all the variations add up to 100%. If both equations hold true, then the population would be under Hardy Weinberg equilibrium. However, if any of the two is not met, then the population is not under Hardy Weinberg equilibrium. These two formulas are only valid if the population is in Hardy Weinberg equilibrium.

Macroevolution → what is reproductive isolation? what are the two ways that it's secured?

reproductive isolation → Remember, 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. · prezygotic isolating mechanisms · postzygotic isolating mechanisms

Macroevolution → Speciation → Sympatric speciation

speciation occurs without the presence of a geographical barrier. There are three main ways to achieve this: 1. Balanced polymorphism: 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. 2. Polyploidy: Polyploidy is a common phenomenon that occurs in plants, often resulting from nondisjunction when chromosomes separate during cell division, specifically meiosis. ex: Imagine plant A normally contains 2n chromosomes and nondisjunction occurs during meiosis → ²/₄ gametes have 0n chromosomes and the other ²/₄ will have 2n chromosomes, whereas under normal conditions all four gametes should each n chromosomes If one of the 2n gametes fuses with another normal n gamete, there will be a 3n chromosome zygote, that's 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. 3. Hybridization: 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.

What is microevolution?

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.

Gene Equilibrium → what is Genetic drift? what are the two types?

· Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). · Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations. · Genetic drift may result in the loss of some alleles (including beneficial ones) and the fixation, or rise to 100% frequency, of other alleles. · Genetic drift can have major effects when a population is sharply reduced in size by a natural disaster (bottleneck effect) or when a small group splits off from the main population to found a colony (founder effect).

Origins of Life → Timeline Facts → The Big Bang gave rise to the Universe _____ years ago

· The first eukaryotes came ~2 billion years ago. o 1.5 billion years after prokaryotes!

Natural selection → what are the two key conditions for natural selection favorability?

· This brings us to the concept of "survival of the fittest" · Fitness measures the ability to survive and produce viable and fertile offspring. · these are the two key conditions for natural selection favorability

Microevolution → allele and allele frequency

· a micro perspective revolves around the concept of allele frequencies. Allele frequency = gene frequency (could be used interchangeably) · alleles refer to different forms of a gene (yellow vs. green pea genes) · allele frequencies is how often you can find that allele in a population (finding a yellow allele vs. a green allele (gene variant) in a pea population)

What is natural selection?

· 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. Note in the image: 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.