Unit 3 Test Review PDF

Unit 3 Test Review Adaptation vs. variation ​ Adaptations help an organism survive and reproduce in a particular ecosystem ​ Variations are differences between individuals, which may be structural, functional, or physiological Types of adaptations - structural, physiological, behavior...

Unit 3 Test Review Adaptation vs. variation ​ Adaptations help an organism survive and reproduce in a particular ecosystem ​ Variations are differences between individuals, which may be structural, functional, or physiological Types of adaptations - structural, physiological, behavioral 1.​ Structural Adaptations ​ Physical feature of an organism that enables them to survive in their environment. 2.​ Physiological Adaptation ​ Internal or cellular features of an organism that enables it to survive in its environment ​ Ex: Hibernation - allows species to reduce their metabolism to save energy which prolongs survival ​ Ex. Snakes produce venom to ward off predators and to capture prey 3.​ Behavioural Adaptation ​ Actions of an organism that enables them to survive in their environment. ​ Ex. Animal migration -​ enables them to find a suitable ecosystem if there is a lack of food or severe weather ​ Travelling in large groups protects them from predators Camouflage & mimicry ​ Examples of structural adaptations ​ Camouflage -​ when organism can blend in with its environment it increases its chances of survival -​ ex. stick insects ​ Mimicry -​ Mimicry is when a harmless species resembles a harmful species in colouration or structure -​ Predators that avoid the harmful species will also avoid the mimic since they look alike -​ E.g. Monarch (harmful) vs.viceroy butterfly (harmless) -​ by catching and eating a monarch (harmful & tastes bad) , it causes the predators to learn to avoid both English Peppered Moth - example of variation to adaptation The English Peppered Moth ​ Colour Variation of Moths ​ Greyish-white with black dots (flecked or peppered moth) ​ Black (melanic moth) ​ Moths are active at night ​ During the day, they rest in trees and are potential prey for birds  Unit 3 Test Review Before the Industrial Revolution ​ England, 1800s, trees were covered with light-coloured lichen ​ Lichen provide camouflage for lighter coloured flecked peppered moths ​ Black moths were easily seen and preyed upon ​ In 1848, black moths were very rare (only 2% of moth population) During the Industrial Revolution ​ Air pollution killed the lichen and soot began to cover the trees ​ As a result, flecked moths were seen and easily eaten by birds ​ More black moths survived as they were camouflaged by the soot. They now had the selective advantage ​ The black moths reproduced and passed on their genes to their offspring, causing their numbers to rise ​ Within a span of 50 years, by 1889, black moths became increasingly more common and made up 95% of the moth population. Thelight-coloured flecked moths were now very rare Post Industrial Revolution ​ Environmental protection policies were put into place to reduce pollution and soot. ​ Lichen grew back, trees become light coloured again ​ Black moths once again stood out and were preyed upon ​ Lighter flecked moth population increased again as they were now camouflaged and had the selective advantage ​ By 1985, 50% were black, dropped to 30% four years later and is estimated that they are very rare today ​ NOTE: It is important to understand the ratio of flecked to black moths in the population changed over time, individual moths did not change from flecked to black Variation Within Species Arises From Our Genes ​ There is a huge number of possible combinations of genes that offspring can inherit from their parents ​ This results in genetic variation among individuals within a population Mutations & selective advantage Mutations Lead to Genetic Variation ​ A mutation is a permanent change in the genetic material (DNA) of an organism ​ Mutations are the only source of new genetic variation (new phenotypes) ​ Occur randomly ​ Can be caused by UV radiation, viruses or exposure to chemicals Mutations in Cells ​ In somatic (body) cells, the mutation will disappear from the population when the organism dies  Unit 3 Test Review ​ In gametes, if the cell survives, the mutation may be passed on into future generations, creating a new variation Mutations Can Provide Selective Advantage ​ Selective Advantage: a genetic advantage that improves an organism’s chance of survival ​ Generally, selective advantage helps an organism survive and reproduce under changing environmental conditions Selective pressure ​ Environmental factors determine whether certain traits of an organism are suitable for survival -​ Traits that are suitable are selected for and those that are not are selected against ​ Abiotic (environmental) factors: -​ availability of light, water, temperature, soil composition, etc. ​ Biotic (environmental) factors: -​ predation, competition between organisms (food, mates, habitat), parasites, etc. Selective Pressure Example: Trees in Low Light Dense Forest ​ Environmental Factor – little available sunlight ​ Trees able to survive in the shade will reproduce and pass on the alleles to survive those conditions ​ In future generations, these alleles will increase in the population since more of these individuals that can survive in shady conditions will survive and reproduce ​ If the environment changes, like an increase in sunlight levels, this trait may no longer be an advantage and these shade-loving trees may not survive any longer Selective advantage ​ Selective Advantage: a genetic advantage that improves an organism’s chance of survival ​ Generally, selective advantage helps an organism survive and reproduce under changing environmental conditions ​ Can be provided from genetic mutations Process of natural selection ​ The process in which characteristics of a population change over many generations as organisms with heritable traits survive and reproduce Natural Selection ​ Natural selection has no purpose or direction (situational) ​ It is situational because a trait that is advantageous in one situation may not be in another ​ If the trait is “naturally selected for”, then over time there will be more of those individuals and they will reproduce ​ Thus the outcome is changing populations (who are better adapted to their environment) ​ For natural selection to occur, there must be  Unit 3 Test Review 1.​ genetic variability (diversity within a species as seen with the peppered moth and antibiotic resistance examples in 7.1) 2.​ heritability (traits passed onto offspring) 3.​ selective pressure (conditions that select for or against certain traits) ​ Environment plays a role in an individual’s survival and it is naturally occurring ​ No ultimate goal in mind ​ Ex: Peppered moth – change occurred naturally in the population in response to changes in the environment Artificial selection ​ Selective pressure exerted by humans on populations in order to improve or change particular desirable traits ​ Artificial selection and selective breeding are forms of biotechnology ​ Has a huge impact on human’s ability to survive ​ E.g. most grains, fruits, vegetables, meat and milk have been selectively bred ​ Humans are selectively choosing traits to pass on to individuals ​ Has an ultimate goal ​ Ex: breeders can select for cows that produce more milk ​ Example: -​ The wild mustard seed has been selectively bred -​ Different parts of the flower have been modified to create a variety of crops -​ All the different plants are part of the same species, they are just variations of the wild mustard seed Comte de Buffon/Leclerc ​ French naturalist ​ First to imply that species change over time ​ Suggested that similarities between humans and apes might mean they have a common ancestor ​ Also suggested that the Earth was older than believed ​ Later on, his work influenced Cuvier and Lamarck Anning ​ Worked as a fossil hunter and uncovered the first plesiosaur (aquatic reptile) ​ She was very skilled at collecting fossils ​ As a result, she made many important contributions to the field of paleontology Cuvier ​ Known as the founder of paleontology (study of ancient life through the examination of fossils) ​ Confirmed Annin’s work ​ Discovered that each stratum (layer) of rock held a unique group of fossil species (new species appeared and others disappeared over time) ​ Came up with the theory of Catastrophism  Unit 3 Test Review -​ Proposes that natural catastrophes killed many species and that these events corresponded to the boundaries between the fossil layers ​ Deep rock strata are older than strata closer to the surface ​ Different species of fossilized organisms are found in different rock strata ​ This is evidence that not all life forms came into existence at the same time Lyell ​ Proposed theory of UNIFORMITARIANISM ​ Idea that the Earth’s surface has always changed and continues to change through similar, uniform, and very gradual, slow processes (not catastrophic) ​ These slow continuous changes result in large changes over time Lamarck ​ Proposed the Theory of Acquired Characteristics -​ Characteristics acquired (gained) during an organism’s lifetime can be passed onto offspring. -​ example: bodybuilders will have children with large muscles ​ He hypothesized that over time, organisms become better adapted to their environment until they achieved perfection in an ideal form ​ Lamarck believed that as the environment changed, so did the needs of the species and the organism’s structure would be modified by use ​ The trait could then be passed on to their offspring ​ Example: Giraffes stretching their necks led to them having longer necks ​ Lamarck also suggested that body parts that are not used would eventually disappear (idea of use and disuse) ​ Example for idea of use: -​ Toes of water birds -​ Water birds gained elongated, webbed toes from years of straining their toes to swim through water ​ Example for idea of disuse ​ Penguins have small wings ​ Their wings are smaller than those of other birds because penguins do not use them to fly ​ Lamarck’s theory is NOT TRUE however he was the first one to show that the environmental challenges could cause changes in a species trait -​ Darwin built on this idea Malthus' contribution to Darwin's theory ​ An economist who wrote “Essay on the Principles of Population” that explained how populations might change over time ​ Key idea was that populations produce far more offspring than their environments can support ​ Eventually, the population will be reduced by starvation or disease  Unit 3 Test Review Darwin's theory of evolution by natural selection ​ Darwin publishes his ideas in 1859 in the book called The Origin of Species ​ competition for limited resources would select individuals with favourable traits that allow them to survive ​ Ideas summarized in The Origin of Species 1)​ Organisms produce more offspring than can survive. Therefore, organisms compete for limited resources. 2)​ Individuals of a population vary extensively and much of this variation is heritable. 3)​ Individuals that are better suited to local conditions survive to produce more offspring. 4)​ Processes for change are slow and gradual. ​ 22 year old naturalist → Voyage to South America in 1831 → HMS Beagle → 5 yr journey ​ Observed, recorded and collected specimens of rocks, minerals, plants and animals ​ Later devised the Theory of Evolution by Natural Selection -​ Explains how life has changed and continues to change, due to natural pressures ​ He stopped in the Galapagos islands, which includes more than 20 volcanic islands, located about 100 km off the coast of Ecuador ​ They were all formed around the same time and have similar abiotic conditions ​ Returned in 1836 to analyze the evidence he collected on the voyage Survival of the fittest ​ Darwin’s process of natural selection is the same as the idea of “survival of the fittest” ​ Evolutionary fitness isn’t a measure of physical fitness but of reproductive fitness ​ Organisms that are “fittest” leave the most fertile offspring, so those organisms win the struggle for survival Descent with modification ​ Darwin never used the term “evolution” as it implied progress. He spoke of “descent with modification” ​ Darwin’s theory doesn’t demonstrate progress, but instead a species’ ability to survive local conditions at a specific time ​ According to Darwin evolution has no set direction, it does NOT demonstrate progress ​ It results from the ability of individuals in a population to survive in a particular environment ​ Individuals that are better suited (fitted) to local conditions survive to produce more offspring and pass on those traits that will allow their offspring to survive ​ The process of change is gradual Know the 5 sources of evidence for evolution 1.​ Evidence from the Fossil Record ​ Fossils found in young, shallower layers of rock (closer to the surface) are much more similar to species alive today, than fossils of older, deeper layers. ​ Fossils appear in chronological order in the rock layers.  Unit 3 Test Review ​ Not all organisms appear in the fossil record at the same time. (Fishes, amphibians, reptiles, mammals, birds → order of vertebrate evolution). Slow changes that took millions of years. 2.​ Evidence from Biogeography ​ Darwin and Wallace used biogeography (the study of past and present geographical distribution of species populations) to develop their theories. They hypothesized that species evolve in one location and then spread to other regions. Some examples that support this theory include: a)​ Geographically close environments are more likely to be populated by related species than are locations that are geographically separate but environmentally similar b)​ Animals found on islands often closely resemble animals found on the closest continent. Therefore the animals on the island have evolved from the mainland animals, and the population has adapted over time to the island environment. c)​ Fossils of the same species can be found on the coastline of neighbouring continents. Therefore the continents are not in a fixed location, they were once closer together and they are slowly moving away from each other. ​ 200 million years ago all of the present-day continents combined to form a single supercontinent called Pangea. 3. Evidence from Anatomy ​ Homologous structures - are structures that have similar structure and origin but have a different function -​ Ex. Vertebrate forelimbs are homologous structures. They are used for different functions (flying, running or swimming) but they all contain the same set of bones, organized in similar ways. This means they must have originated from a common ancestor. ​ Analogous structures - are structures of organisms that do not have a common evolutionary origin but perform similar functions -​ Ex. Wings of insects, birds, and bats are similar in function but not in structure. For example, bones support bird wings whereas a tough material called chitin makes up insect wings. 4. Evidence from Embryology ​ Embryology is the study of early, pre-birth stages of an organism's development. ​ Embryos of different organisms exhibit similar stages of embryonic development. This can be used to determine evolutionary relationships. ​ Similarities between embryos in related groups (such as vertebrates) point to a common ancestral origin. ​ Similarities in the embryos of fish, birds, and mammals provide evidence of evolution of species from a common ancestor 5. Evidence from DNA ​ Evolutionary relationships between species are reflected in their DNA  Unit 3 Test Review ​ Scientists can determine how closely related two organisms are by comparing their DNA sequences ​ The more similar the sequences are, the greater the likelihood that they came from a common ancestor ​ Darwin’s theory is supported by genetic evidence and our understanding of genetic inheritance Transitional fossils ​ Transitional fossil - is a fossil that shows intermediary links between groups of organisms and shares characteristics common to two separate groups. ​ They have helped scientists to better understand the relationships between groups of organisms, linking the past with the present. ​ Example: Fossils of whales from 36 to 55 million years ago linked present day whales to terrestrial ancestors. ​ Whales had a tiny pelvis and hind limbs but since they led aquatic lives, these parts were useless. Their presence, although in a reduced form, showed a link between the terrestrial animal and whales today -​ This pelvic bone is called a vestigial structure, which is a reduced form of a structure that was functional in the organism's early ancestor -​ Today, baleen whales still have this vestigial pelvic bone Macroevolution vs. Microevolution ​ Microevolution: -​ Relatively small changes to the allele frequency in a population that lead to evolution WITHIN a species population -​ Allele frequency looks at the number of copies of an allele compared to the total number of alleles in a population ​ Macroevolution -​ Microevolution eventually leads to macroevolution as it is many small changes over a period of time Mutations ​ RANDOM ​ A change that occurs in DNA of an individual will randomly introduce new alleles into a population ​ This will change allele frequencies and could potentially change the entire gene pool if mutation becomes prevalent ​ The more genetic variation there is in a population, the greater the chance of a selective advantage to some individuals in a changing environment ​ Mutation Example: Effect of warfarin on rats -​ Warfarin is a rat poison that was used to control rat populations -​ Before its use, a few rats had a mutation that made them resistant to the warfarin’s effects  Unit 3 Test Review -​ When they began using it, these rats survived and passed on the resistance, increasing the population of warfarin-resistant rats Gene Flow ​ RANDOM ​ Begins with two different interbreeding populations that have different allele frequencies ​ Animals that migrate to a neighbouring group to mate will introduce new alleles to that population which can cause ​ A change in allele frequencies in one or both of the populations ​ ​ Through gene flow, modeled here, genetic information is exchanged between individuals of different populations Genetic Drift ​ RANDOM ​ The change in allele frequencies by chance due to random events in a small breeding population ​ The smaller the population, the less likely it is that the parent gene pool will be reflected in the next generation ​ The failure of a few individuals to reproduce intensifies the effects of genetic drift ​ Conditions required for genetic drift: small populations. This will cause changes to appear drastic. ​ Larger populations appear stable ​ With small populations only a short period of time is required to have a significant effect on the gene pool The Bottleneck Effect ​ Change in gene distribution due to a sudden decline in population ​ Sometimes events (natural disasters, invasive species, overhunting) can greatly reduce a population (often to the point of extinction) ​ Since there’s only a few survivors, only a fraction of the original gene pool is present, which causes a decrease in diversity (allele frequencies change) ​ ​ Example: Colour Vision Deficiency -​ A typhoon devastated a small island part of Micronesia. -​ Only 30 survived, one of which carried a genetic mutation that causes colour vision deficiency.  Unit 3 Test Review -​ Today, 10% of the current population have the deficiency, while in the general population the condition is very rare. The Founder Effect ​ A few individuals occupy a new area & the population will have been started by a very limited number of members of a given species (occurs frequently on islands) ​ “Founders” may carry with them a genotype that is atypical of their species and it passes on to virtually all of the population ​ Allele frequencies change (compared to parent population) ​ ​ Example: Polydactylism, when a sixth finger or toe grows, is common in Amish populations where there is a lack of genetic diversity (founded by only a few families) Non-Random Mating ​ Involves mate selection, which is NOT random, based on preferred phenotypes or when in an inbreeding situation ​ Includes inbreeding and preferred phenotypes Non-Random Mating - Preferred Phenotypes ​ Choosing a mate based on physical attributes or behavioural traits. ​ Examples: -​ courtship displays (greater sage grouse strut display) -​ male-male competition (male caribou spar using their antlers), those that are successful more likely to reproduce Non-Random Mating - Inbreeding ​ When mating pairs are limited an organism is more likely to breed with an organism genetically similar to themselves. ex. self-fertilization in flowers ​ This doesn’t affect distribution of alleles directly but it causes more homozygous genotypes which may cause more harmful alleles to be expressed, causing disease ​ Inbreeding individuals have higher rates of producing offspring with more deformities, health issues and genetic diseases Natural Selection and its Types ​ Genetic information leads to the expression of a specific physical trait that provides selective advantage ​ Over time that physical trait will increase in frequency, causing a change in allele frequencies  Unit 3 Test Review which can lead to evolutionary change ​ Several types 1.​ Stabilizing Selection 2.​ Directional Selection 3.​ Disruptive Selection 4.​ Sexual Selection Stabilizing Selection ​ Selective pressure that favours intermediate phenotypes and selects against extremes ​ Distribution narrows ​ The population before natural selection (top) and after (bottom). The brown area shows the general population. ​ Example: Human Birth ​ Directional Selection ​ Selective pressure favours phenotypes that occupy ONE extreme but not another ​ Distribution shifts (peak shift) Disruptive Selection ​ Extremes of phenotypes are selected for while intermediate phenotypes are selected against ​ Twin peak distribution ​ Sexual Selection ​ Selection of a trait that increases the mating success of the individual ​ Often involves competition between males through combat or through visual displays ​ Such selection can lead to sexual dimorphisms (striking differences in the physical appearance of males and females) ​ Also involves the choice females make for mates ​ ex. physical traits like colour, song, strength...  Unit 3 Test Review What is Speciation? ​ Also called macroevolution ​ The formation of new species from existing species. ​ Two populations become reproductively isolated over time (i.e. become two different species). -​ Some members of a population change so much that they are no longer able to reproduce viable, fertile offspring with members of the original population. ​ With little or no gene flow between them, the populations become reproductively isolated from each other Reproductive Isolation Mechanisms ​ Keeping species distinct ​ Include geographical barriers and biological barriers to reproduction Pre-Zygotic Isolating Mechanisms (5) ​ mechanisms will not allow a zygote to form since they can -​ prevent mating between different species -​ prevent the eggs from being fertilized if different species attempt to mate. 1.​ Behavioural Isolation ​ Any special signals or behaviours that are species-specific will prevent interbreeding with closely related species. ​ Ex. bird songs differ for a specific species, courtship rituals of elk, pheromones (chemical signals) of insects 2.​ Temporal Isolation ​ Two species may occupy the same habitat but have timing barriers. ​ Ex. Different reproductive cycles for flowering of plants or animal mating occur at different times. 3.​ Habitat Isolation ​ Two species may live in the same general region but in different habitats, so they may rarely encounter each other ​ Ex. Ground squirrel species woodchucks live in fields at lower elevations while marmots live in alpine meadows in high elevations 4.​ Mechanical Isolation ​ Two closely related species may attempt to mate but are unsuccessful because their anatomy is incompatible ​ Ex: structural differences in reproductive organs → Insects - genitalia have very specific shapes that act as a lock and key. Even something that looks similar will not work 5.​ Gametic Isolation  Unit 3 Test Review ​ Gametes from two different species may meet but do not fuse to form a zygote ​ Ex. Sperm of male may not survive female reproductive tract ​ Ex. Giant clams release sperm & eggs into water and they will recognize each other by molecular markers Post-Zygotic Isolating Mechanisms (3) ​ In a few cases, animals of different species can overcome pre-zygotic barriers and will produce a hybrid offspring ​ 3 types of post-zygotic isolating mechanisms prevent hybrids from developing into viable, fertile individuals 1.​ Hybrid Inviability ​ Zygote dies shortly after fertilization due to genetic incompatibility ​ Normal mitosis is prevented from occuring after the zygote is formed ​ Ex: a zygote will form between a sheep and a goat but it never comes to term 2.​ Hybrid Sterility ​ Two species mate and produce hybrid offspring but it is sterile and thus cannot reproduce ​ Meiosis fails to produce normal gametes in the hybrid because the chromosome number or structure of the parent species differ ​ Ex. Sterile mules result from mating female horse with a male donkey 3.​ Hybrid Breakdown ​ The first generation of living hybrids CAN undergo meiosis properly to produce normal gametes but THEIR offspring cannot ​ The second generation offspring will die. They are too weak to live long or they are sterile What is Speciation? ​ The evolutionary process by which a new species arises ​ Once an isolating mechanism has prevented gene flow, populations must remain genetically isolated from each other for speciation to occur Modes of Speciation 1.​ Sympatric Speciation ​ Occurs when populations that live in the same habitat diverge genetically and become reproductively isolated. ​ More common in plants than animals ​ Chromosomal changes in plants or non-random mating in animals alters gene flow ​ The result is reproductive incompatibility without geographical isolation 2.​ Allopatric Speciation ​ More common  Unit 3 Test Review ​ Occurs when populations are separated by a geographical barrier and diverge genetically. ​ A type of speciation whereby two or more groups within a population are geographically isolated ​ Over time, the lack of gene flow and accumulation of mutations leads to genetically distinct populations ​ The original populations can no longer interbreed Divergent Evolution ​ Pattern of evolution where two species become distinct as they change in response to environmental conditions ​ Share many homologous structures ​ Ex. limbs of vertebrates ​ Forelimb of 4 different mammals. They are similar structures, which were present in the common ancestor. They persist in the diverged organisms although they have different functions Convergent Evolution ​ Pattern of evolution where similar traits arise in two species independently in response to similar conditions, not because they share a common ancestor ​ Share many analogous structures ​ Ex. Wings in bats, birds and bugs → Bones arranged differently but independently achieve the same function, flying ​ Different internal bone structures of wings in 1.​ Reptiles 2.​ Mammalian bats 3.​ Birds Speed of Evolutionary Change ​ Gradualism: change occurs slow and steady (big changes occur by accumulation of many small changes). ​ Punctuated Equilibrium: long periods of stasis (nothing happening, equilibrium) interrupted by bursts of divergence (big changes). ​ BOTH MODELS ARE AT WORK ​