1. THE PACE OF EVOLUTION
1.1. Gradualism: model that views evolutionary change as slow and steady. Big changes occur by accumulating many small changes. If it were drawn into a graph it would be a very steady linear graph.
1.2. Punctuated Equalibrium: model that views evoultionary history as long periods of stasis that are puncuated by periods of divergence. If correct, fossil records should consist of fossils from long periods of time where no change occur. If it were drawn into a graph it would spike up and down.
1.3. BOTH MODELS ARE CORRECT. Both are at work. Many species have evolved rapidly during periods of Earth's history. Fossil records also show very gradual change for some species over long periods of time.
2. SPECIATION
2.1. Species: a group of organisms composed of individuals that are similar to one another and can successfully breed (produce viable offspring)
2.1.1. 2 types of evolution
2.1.1.1. Micro evolution: evolution on small scale, repersents the changes in allele frequencies that occur over time within a population.
2.1.1.2. Macro evolution: evolution on a scale of seperated gene pools, focus is on the changes that occur at or above the species
2.2. Also known as macro evolution. FORMATION OF A NEW SPECIES from an existing species. In order for speciation to occur, there must me barriers between 2 or more groups (gene pools) within a species. Over time these groups develop their own unique characteristics and can no longer interbreed and produce viable offspring sucessfully.
2.2.1. 2 types of speciation: Allopatric and sympatric
2.2.1.1. Allopatric Speciation: Speciation in which a population is split in 2 or more isolated groups by a GEOGRAPHICAL BARRIER. Eventually the 2 groups cannot interbreed due to reproductive isolating mechanisms.
2.2.1.2. Sympatric Speciation: speciation in which populations within the SAME GEOGRAPHICAL AREA diverge and become reproductively isolated. More common in plants than animals. Factors such as chromosomal changes (polyploidy in plants) and non-random mating (in animals) alter gene flow.
2.3. REPRODUCTIVE ISOLATING MECHANISMS: barriers that prevent species from mating with each other
2.3.1. PRE-ZYGOTIC: a barrier that impedes mating between species or prevents fertilization.
2.3.1.1. Prevention of Mating
2.3.1.1.1. Behavioural Isolation: Any special signals or behavious (ex. mating rituals, food choices) that are species specfic prevent interbreeding with closely related species.
2.3.1.1.2. Temporal Isolation: Species are KEPT SEPERATE BY TIMING barriers. ex. 2 species occupy the same habitat but mate or flower at different times of the day or in different seasons.
2.3.1.1.3. Ecological/habitat Isolation: 2 species occupy the SAME AREA but in DIFFERENT HABITATS and rarely encounter each other.
2.3.1.2. Prevention of Fertilization
2.3.1.2.1. Mechanical Isolation: Closely related species try to mate but fail to achieve fertilization because they're ANATOMICALLY INCOMPATABLE.
2.3.1.2.2. Gamete Isolation: the gametes of 2 species meet but DO NOT FORM A VIABLE ZYGOTE. Could be due to how the eggs are fertilized within the female reproductive tract. In plants, the pollen of one species do not germinate on the stigma of another species.
2.3.2. POST ZYGOTIC: a barrier that prevents hybrid zygotes from developing into viable fertile individuals.
2.3.2.1. Prevention of Hybrids
2.3.2.1.1. Hybrid Inviability: Genetic incompatibility of the interbred species stops development of the hybrid zygote during its development. This prevents normal mitosis after the fusion of the gametes.
2.3.2.1.2. Hybrid Sterility: 2 species mate and produce offspring but the offspring CANNOT REPRODUCE. Meiosis in these individuals fails to produce normal gametes.
2.3.2.1.3. Hybrid Breakdown: The 1st generation of hybrids are viable and fertile, but when they mate with each other or an individual from the original species, they producec sterile or weak offspring.
2.4. ADAPTIVE RADIATION: The diversification of a common ansceteral species into a varity of species. Each of the species are adapted to fit a particular ecological niche.
2.4.1. Ex. Darwin's Finches
3. Notable scientists
3.1. GEORGES-LOUIS LECLERC, COMTE DE BUFTON 1707-1788 (histoire naturlle)
3.1.1. Bufton noted the simularities between apes and humans, suspecting that they had a common ancestor. However he didn't believe in evolution, and instead believed that animals developed from a "perfect state" and into what they are now. (So basically evolving backwards)
3.2. JEAN-BAPITISTE LAMARK 1744 - 1829 (the theory of acquired characteristics)
3.2.1. evidence does not support lamarks theory.
3.2.1.1. Lamark's theory was hinged upon the assumption that all evolution would lead to a species' "perfection" which is untrue and that an organism would develop mutations within their lifetime.
3.2.2. Lamark proposed that organisms gain or lose physical characteristics through over/under use. (acquired characteristics)
3.2.2.1. EX: ancestoral giraffs stretched their necks to reach higher branches of tree (overuse of chacateristic) and therefore their children would have slightly longer necks, and their children would have slightly more longer necks.
3.3. GEORGE CUVIER 1769-1832 (catastrophism)
3.3.1. Proposed the idea that Earth had experienced many destructive natural events which he called "revolutions". Cuvier suggested these catastrophes corresponded to the boundaries between strata, this is how he explained fossils of species that no longer existed. BELIEVED THE EARTH WAS MORE THAN 6000 YEARS OLD.
3.4. CHARLES LYELL 1797-1875 (uniformatarianism)
3.4.1. Lyell believed geographic changes were made slowly over time rather than catastrophically (suddenly). Believed Earth was older than 6,000 years old. His geographic ideas inspired Darwin to think about slow biological changes within organisms.
3.5. CHARLES DARWIN 1809 - 1882 (the father of evolution and the creator of the theory of evolution by mechanism of natural selection)
3.5.1. Darwin explained that natural selection would result in small changes within a population of species from one gen to the next
3.5.2. These changes would eventually accumulate over long periods of time and lead to the origin of a new species (descent with modification)
3.6. ALFRED RUSSELL WALLACE 1923 - 1913 (the theory of evolution and contribution)
3.6.1. reached a very similar conculsion to Darwin, was only a few days behind in publishing and therefore forgotten by the majority of people. poor guy.
4. NATURAL SELECTION
4.1. DARWIN'S 5 POSTULATES
4.1.1. 1. There is genetic variation (and phenotypic variation) among individuals in a population of species due to mutations and sexual reproductions
4.1.2. 2. Over time populations get exposed to different selective pressures, which will cause individuals to compete for resources or be exposed to predation, parasites, diease, or natural disasters
4.1.3. 3. Competition leads to the death of some individuals, the ones with advantagous variations (adaptations) will survive
4.1.4. 4. Ones that are more likely to survive will reproduce and tehrefore contribute more genes to the population
4.1.5. 5. Eventually the adpation becomes a part of the species
4.2. Definition: the process by which the characteristics of a population change over time due to dertain inherited traits that allow individuals to survive and reproduce in their enviornment better than others.
4.2.1. Natural selection acts on individuals. Evolution occurs in populations.
4.2.2. Natural sleection is not forward looking and does not lead to perfection.
4.3. Selective pressures: the enviornmental conditions that select for certain characteristics over others
4.3.1. Abiotic selective pressures: factors such as climate, amount of food/water, that put pressure onto a group of organisms
4.3.2. Biotic selective pressures: factors such as predators, parasites, and competition for resources that put pressure upon a group of organisms.
4.3.3. Genetic diversity within a population allows some individuals to survive while others die in the face of the enviornment. If there's not enough genetic diversity and none of the population survives the changes in an enviornmental conditions, this will result in extinction.
4.4. Fitness: individuals in a population have inherited benefical adaptation which allows them to survive and produce more offspring. (more fit = more reproductively viable offspring)
4.4.1. The genetic traits of "fit" individuals become more common or frequent over time
4.4.2. Survival of the fittest.
4.5. Genetic/phenotypic variation:
4.5.1. differences between individuals (structural, behavioural, or physiological)
4.5.1.1. ADAPTATIONS: result from gradual and accumulative changes that help an organism survive and reproduce.
4.5.1.1.1. Behavioural adaptations: ways in which an organism acts that increases the organism's ability to survive
4.5.1.1.2. Physiological adaptations: internal body processes that increase the ability of an organism to surive and reproduce in it's environment. (INTERNAL ADAPTATIONS)
4.5.1.1.3. Structural adaptations: a physical feature of an organism that increases the ability of an organism to survive and reproduce in its environment.
4.5.2. Not all variations develop into adaptaions
4.5.3. If the variation increases the ability of an organism to survive in its enviornment, that variation is more likely to be passed on to the next generation. This will result in the variation becoming more frequent and eventually become a trait of the population.
4.5.4. Over time the gene that provided the selective advantage (benefical variation) will become more common.
5. ARTIFICAL SELECTION: selection imposed by humans on other organisms.
5.1. Humans apply selective pressure by choosing to modify particular traits to achieve a purpose. (humans select the traits from the organisms they want most like friendliest animals)
5.1.1. Can cause inbreeding and medical issues when humans focus too much on only the traits they desire.
5.2. Using selective breeding, humans can choose for different traits in groupd of organims such as pet traits or increased plant yield and/or nutritional value in plants
5.2.1. Ex. Wild mustard is a significant example of how humans selectively breed plants. Many different plants we eat regularly such as brocolli, cauliflower, etc, all originate from the wild mustard plant.
5.2.2. Ex. bulldogs are also an example of artifical selection, specifically the consequences of it. Bulldogs are very inbred and have a lot of health problems (heart, hip, breathing, etc)
5.2.2.1. Artifical selection can lead to a huge decrease in genetic diversity and the creation of monoculture.
5.2.2.1.1. Monoculture: the cultivation of a single crop in a large area. This makes it very easy for all of the crops in one given area to be destroyed, as there is very little genetic diversity so the crops cannot properly resist the pressure.
5.2.2.1.2. Example of monoculture: irish potato famine
5.3. Relies heavily on biotechnology
6. SOURCES OF EVIDENCE OF EVOLUTION
6.1. Fossil records: fossils are sedimentary rocks that show different kinds of speices alive in the past.
6.1.1. Fossils in young layers of rock are more similar to species today, while fossils in older layers get less similar. Fossils appear chronologically in rock layers, the older ones are usually deeper.
6.1.2. Older fossils show simpler organisms; younger fossils show more complex life
6.1.3. Transitional fossils show a mix of traits of ancestoral populations and novel traits of later descendants
6.1.3.1. Ex. archaeoptreryx shows both reptile (claws, sharp teeth, etc) and bird like (feathers, wings) characteristics
6.2. Biogeography: the study of past and present geographic distribution of organisms
6.2.1. Geographically close enviornments are more likely to be populated with related species
6.2.2. Animals found on islands often resemble organisms on the closest landforms and fossils of the same species can be found on the coastlines of neighbouring continents
6.2.2.1. Before pangea went poof the same species the population lived in the area but even as it seperated the speices that died there could still be found as fossils
6.3. Anatomy: physical or phyisological structures within a living organism
6.3.1. Vestigial structures: when there is leftover evidence of an organism's ancestor remaining in an organism that has no further use but is still leftover. fossils allow scientists to identify vestigial structures.
6.3.1.1. Ex. Whales have vestigial bones used for walking on land, but seeing as how whales cannot walk this is a vestigial structure that is evidence that whales had a common ancestor on land before evolving to live in the water
6.3.2. Analogous structures: structures that different organisms share. The structures preform similar functions but the organisms DO NOT HAVE A COMMON ANCESTOR. Functional simularities do not imply that the speices are closely related. this is called CONVERGENT EVOLUTION. (unrelated species develop analogous structures that help them occupy similar niches)
6.3.2.1. Ex. Bats and butterflies both have wings but are not related, they have the same function, different structure.
6.3.3. Homologus structures: structures that different organisms share. These structures do not look exactly the same or have the same function, but are STRUCTURALLY SIMILAR. Organisms that have a homologous structure will SHARE A COMMON ANCESTOR. This is called DIVERGENT EVOLUTION. (species related by a common ancestor share homologous structures as they occupy similar niches.) LOOK DIFFERENT BUT STRUCTURALLY SIMILAR
6.3.3.1. Ex. All forelimbs of mammals have the same bone pattern, indicating a common ancestor. Humans, cats, whales, and bats all have similar forebone structures even if they vary from wings, to arms, to front legs, to flippers.
6.4. Embryology: the study of early, pre-birth stages of an organism's development.
6.4.1. Simularities between embryos in a related group (vertebrates) provide evidence of a common ancestor
6.4.1.1. Ex. Lizard, pig, and human embryos look very similar, and as they are all vertebrates, share a common ancestor.
6.5. DNA: Evolutionary relationships between species are reflected in their DNA
6.5.1. Scientists can determine how related two organisms are by comparing the simularities in their DNA
6.5.1.1. Ex. Gene sequences show that dogs are bears are related.
7. MECHANISMS OF EVOLUTION
7.1. Mutation: random changes in DNA of an individual, which gives rise to new alleles for existing genes.
7.1.1. Mutations can be benefical, neutrual, or bad. When a mutation is naturally selected for or against, it causes changes in the allele frequency of the population.
7.2. Gene flow (migration): a group of individuals from one populations of a species moves to a new area and interbreds with another population of the same speices.
7.2.1. During the move, alleles are removed from one population and brought to another. May change allele frequencies in either population over time, usually REDUCES GENETIC DIFFERENCES BETWEEN POPULATIONS.
7.3. Genetic drift: A random change in genetic variation based on chance. (usually quite sudden or a large and rapid change). There are two kinds of genetic drift: founder's effect and bottleneck effect. Chance fluctuations can change allele frequencies in small populations. (changes in population can cause microevolution in small populations) Small populations will experience greater flucutations; it's less likely that the parent gene pool will be reflected in the next gen.
7.3.1. Founder effect: when a few individuals from a population start a NEW, ISOLATED POPULATION, resulting in a change in the gene pool.
7.3.1.1. Occurs frequently on islands since they're isolated habitats.
7.3.1.2. Ex. Afrikaner population: descendants of a small group of Dutch settlers in South Africa in the 17th century, the OG settlers carried the genes for Huntington's disease, which was inherited in future generations as individuals continued to interbreed.
7.3.2. Bottleneck Effect: change in the gene pool caused by a RAPID DECREASE in population size (natural disasters or human interference)
7.3.2.1. The survivours will carry a fraction of the alleles that were present in the initial population (loss of genetic diversity)
7.3.2.2. Ex. Northern elephant seals have a reduced physical size compared to their Southern counterparts, this is due to the fact that the Northern elephant seals were hunted to near extinction for their oil, and since the bigger ones were hunted only the smaller ones were left. EVen though the population has returned to over 30,000, the population is physically smaller.
7.4. Natural selection: the enviornment is responsible for selecting individuals best suited to survive and reproduce.
7.4.1. Stabilizing selection: Most common phenotypes (intermediate phenotypes) are most favoured by the environment.
7.4.1.1. Extreme phenotypes are selected against and the environment is stable.
7.4.1.1.1. Ex. # of eggs a robin lays. Too many eggs = not enough nutrients per egg, not enough eggs = higher chance none of them will survive)
7.4.2. Directional selection: GRADUALLY CHANGING enviornment favours individuals on ONE END of the extreme phenotypes over the other
7.4.2.1. Ex. Moths in England were significantly darker in colour during the industrial revolution because the smoke made the tree bark darker, therefore the lighter coloured moths had a harder time camoflauging and therefore, surviving.
7.4.3. Disruptive selection: FLUCTUATING enviornments favours individuals at BOTH EXTREMES
7.4.3.1. Polymorphism exists (emergence of 2 distinct forms)
7.4.3.1.1. Ex. Rabbit coat colour, multiple distinct forms (colours). Brown, black, white, etc.
7.5. Sexual Selection: Favours selection of any trait that influences the mating success of individuals. (2 types, intersexual and intrasexual)
7.5.1. Intersexual Selection: also known as "the female mate choice". Males of a species compete with each other (courtship displays, physical features, fights, etc) for the attention of a female.
7.5.1.1. Females get to choose their mate because they invest more in their offspring compared to the male. Females prefer the strongest male to ensure the survival of their offspring. This is why many species show sexual dimorphism (differences in physical characteristics of males vs females of the same species)
7.5.2. Intrasexual selection: also known as "male to male competition" males compete with each other agressively among themselves for acces to females.
7.5.2.1. Fighting and murder and shit
7.6. Non-random mating: every individual in population mates (unlike sexual selection) however populations demonstrate assortive mating. (like mates with like)
7.6.1. increases proportion of homozygous and decreases proportion of heterozygous in the population over time. This can be harmful as an individual with 2 recessive alleles will express the recessive trait. (genetic dieases)
7.6.1.1. *Sigh* inbreeding.
7.6.1.1.1. Individuals are more likely to mate with close relatives (i.e their neighbours) than with distant relatives. In nature, this is common in self fertilizing plants and small populations.
7.6.1.1.2. Inbreeding also occurs during selective breeding (domestication) of various species by humans. (i.e. cats, dogs, plants.) and in humans (royal families)