BIOL 1070 Midterm 1
BIOL 1070 Midterm 1 Unit 1 Online Invasive Species • The water has become much clearer as the quantity of particulate matter in the water column has been greatly reduced. This is one of the byproducts of the huge abundance of zebra mussels, whose filter-feeding activities cycle massive amounts of water every day. • Zebra mussles are able to attach to just about any solid surface has made them a real menace as they clog pipes and cover industrial equipment, docks, and boats. • It has been estimated that the economic damage by zebra mussels and the efforts to control them have already cost billions of dollars Here are the questions about zebra mussels that struck me as being important: o o o o
Where did zebra mussels come from? When and where did they first arrive, and how have they spread so quickly? What impacts are they having on the native fauna and ecosystem? Why have they been so successful at spreading into new lakes and rivers?
Peer-reviewed scientific publications, also known as the “primary literature” are the means by which scientists share their results with other researchers. As members of the University of Guelph, you have access to an extraordinary number of peer-reviewed journals through the library, most of them with electronic access. Search engines such as Google Scholar, PubMed, and Web of Science can all be used to locate papers on any topic.
Zebra Mussels • The zebra mussel (Dreissena polymorpha) is native to eastern Eurasia, specifically the Black Sea and Caspian Sea. • Mode of transport across the Atlantic was in the ballast water of an ocean liner.
• • •
First reported in North America in 1988 in Lake St. Clair, in a peer-reviewed paper by Hebert et al. (1989). o Prof. Hebert is the Director of the Biodiversity Institute of Ontario here at the University of Guelph. This is not the first time the zebra mussel has invaded new environments — it also invaded western Europe in the late 1700s and early 1800s There has since been a second invasion by a related mussel, the quagga mussel (Dreissena rostriformis)
Native Mussel Fauna In Ontario, the native mussels are all members of the family Unionidae, but within this there are several distantly related subfamilies. Zebra mussels and other factors (especially agricultural practices) are having a significant impact on the native mussels of the region. Freshwater mussels are among the most endangered organisms in North America. Unionids are particularly interesting because of their complex life cycle, which includes a component of obligate parasitism (i.e., they must parasitize a host at some stage to complete their reproductive cycle).
Most of the species in Ontario are dioecious (“two houses”), meaning that they have separate males and females. o Males release their sperm into the water through their exhalant siphon, which are then taken up by females downstream through their inhalant siphon. Fertilization is internal (i.e., inside the female’s body), and the embryos develop inside modified pouches of the female’s gills called a marsupium. o The embryos mature into specialized larvae called glochidia (singular glochidium), and it is these that represent the parasitic life stage. o Glochidia must attach to the gills of a fish in order to continue their development. o The mantle tissue acts as a “lure” that resembles a fish or invertebrate prey that attracts the host. Key Points in Unit 1 1. The invasive zebra mussel (Dreissena polymorpha) has had an enormous economic, aesthetic, and biological impact on the Great Lakes watershed. It originated from eastern Eurasia and is thought to have been transported by an ocean vessel sometime before 1988. 2. Peer-reviewed primary literature is the standard means by which scientists share their research findings. It is typically a well regulated system where two or more external referees read and critique the manuscript providing a recommendation to the journal editor to publish or reject the study. 3. There are 41 native freshwater mussels in Ontario, many of them are endangered. Unionids are obligate parasites where glochidia (larvae) are released and must attach to the gills of a fish host to complete their development. 4. Native and invasive mussel species are studied by a variety of different people: undergraduates, graduates, professors and government scientists. These people explore mussel diversity, adaptations, distribution, phylogenetics and conservation issues. Unit 2 – Online Taxonomic Level: Domains – eukaryotes Kingdoms – Animilia (animals) Phyla (singular: Phylum) - Mollusca (mollusks) Classes – Mammilia (mammals) Orders – Primates (apes) Families -Hominidae (great apes) Genera (singular: Genus) - Homo (humans and extinct relatives, e.g., Neanderthals) Species (singular is also species, not specie) - sapiens (humans) Biologists use the word “diversity” to refer to the number of species in a taxonomic group or a geographical area. Differences Within Species: Sexual Dimorphism and Age Each species has morphological (physical) traits that can be used to distinguish it from other mussels. Our development — what biologists call “ ontogeny” — involves significant changes in morphology from youth to old age. This is also true of mussels! Like humans, mussels may exhibit clear differences among individuals within species due to sexual dimorphism (in some species) and age. Finding gravid females and juveniles is a good sign that recruitment (production of the next generation) is succeeding Female mussels have a wider posterior while males come to a point. Differences Within Species II: Morphology The scientific name conveys important information about the species itself- .Dreissena polymorpha (zebra mussel), is one such example: “polymorpha” means “many forms”. Differences Within Species: Cryptic Variation To be evolutionarily relevant, variation among individuals must be heritable. In other words, there must be a genetic basis for the observed trait such that it will be passed on in similar form to offspring. Cases in which the same set of genes (genotype) can result in differing features (phenotype) according to environmental conditions are known as “ phenotypic plasticity”. Abundance vs. Variation vs. Diversity vs. Disparity Morphological and genetic variation (differences among individuals within a species) diversity (number of species) Whereas diversity is a measure of the number of different species, disparity refers to how physically different those species are from each other.
We are all Related You are a member of a lineage of ancestors and descendants that has never once been broken in more than 3.8 billion years of life on Earth. Ways in which living things are related to one another through their common ancestors: a field known as “ phylogenetics”. Anatomy Of A Phylogeny The closest relatives descended from a single recent ancestor are even called “sister taxa” — again, there are important parallels between phylogenies and pedigrees. This order of branching, what biologists call “ topology”, reflects the ancestor-descendant relationships, and that is the most important information contained in a tree diagram. The ancestors and descendants on a phylogeny are usually species. The root (common ancestor shared by all species depicted), branches (connections between ancestors and descendants), and “tips” (or “ terminal nodes”). The terminal nodes usually represent living species, whereas internal nodes are usually extinct ancestors. Evolutionary Classification The approach to classification that is based strictly on evolutionary relationships is known as “cladistics”, and the evolutionary groups that it considers worthy of naming are called “ clades”. A clade is any group of species that includes the last ancestor that they shared and all its descendants. Valid clades, which include the last shared ancestor and all its descendants, are known as “ monophyletic” groups (meaning “one lineage”). When one of the descendants is left out, which creates what cladists call a “ paraphyletic” group. For example, the term “reptile”, which includes lizards, snakes, turtles, and crocodiles but not birds is a paraphyletic group. It is not a clade, because it leaves out birds. Mussles Mussels inhabiting fast-moving rivers exhibit a variety of adaptations to remaining anchored in the substrate at the bottom. This includes various configurations of bumps, ridges, or wings. This sort of feature has evolved more than once in independent lineages as a similar adaptation under similar environmental pressures, a process known as “ convergent evolution”. Sharing ancestral traits is called “ homology”, whereas having traits that are similar but evolved independently is called “ homoplasy” (convergent evolution).
Unit 3 – Online Adaptation and Specialization Mutation (the origin of new genetic variation) Genetic drift (changes due to chance, specifically founder effects and population bottlenecks) Gene flow (movement of genes among populations) Natural selection: Non-random differences in survival and/or reproduction among individual entities on the basis of differences in heritable characteristics. Adaptation: 1) a characteristic that enhances the survival and/or reproduction of organisms that bear it, relative to alternative (especially ancestral) character states; 2) a physical, physiological, behavioural, or other characteristic evolved through natural selection. Adaptation is NOT the change undergone by an individual organism during its lifetime in response to external conditions. Population: for sexual species, a group of interbreeding individuals and their offspring. Alleles: alternate (i.e., different and mutually exclusive) forms of a gene. e.g., “B” (brown eyes) versus “b” (blue eyes). Genotype: the set of genes possessed by an organism. Phenotype: the physical expression of the genotype (in combination with the environment). Frequency: the proportional representation of a phenotype, genotype, gamete, or allele in a population. e.g., 6 out of 10 have blue eyes = 60% = a frequency of 0.6. The Basis Of Natural Selection
When it comes specifically to adaptive changes among species and the traits of organisms that allow them to survive successfully in their environments, natural selection is indeed the only known mechanism that can provide a scientific explanation. 1. Individuals within populations are variable. That not every individual is identical in a population is obvious for humans 2. This variability among individuals is at least partly heritable. Offspring tend to look more like their parents than like unrelated members of the population 3. Not everyone survives and reproduces, and some individuals are more successful than others. Many more offspring are produced in each generation than could possibly survive, a phenomenon known as “overproduction”. 4. The differential survival and reproduction of individuals is associated with the heritable variation among individuals (i.e., it is non-random). This is the key to natural selection, that the individuals who do manage to reach adulthood and have offspring of their own are, on average, better suited to surviving and reproducing in their particular environment because of traits that they inherited from their parents. 10 Things about Natural Selection 1. Natural selection by itself does not create new traits, it only changes the proportion of variation that is already present in the population. Most often, natural selection reduces the amount of variation in a population because some variants are eliminated. 2. Mutation, not natural selection, is the source of new variation. The repeated twostep interaction of mutation and natural selection is what leads to the evolution of new adaptive features. 3. Mutation is random with respect to fitness — that is, it occurs without regard for what happens to the organism. It is simply a genetic error. Natural selection is, by definition, nonrandom with respect to fitness. This means that, overall, it is a serious misconception to consider adaptation as happening “by chance”. 4. Mutations occur with all three possible outcomes: neutral (no phenotypic effect), deleterious (bad effects), and beneficial (positive effects). Beneficial mutations may be rare and deliver only a minor advantage, but these can nonetheless increase in proportion in the population over many generations by natural selection. The occurrence of any particular beneficial mutation may be very improbable, but natural selection is very effective at causing these individually unlikely improvements to accumulate. Natural selection is an improbability concentrator. 5. No organisms change as the population adapts. Rather, this involves changes in the proportion of beneficial traits across multiple generations. 6. The direction in which change occurs is dependent on the environment. A change in environment can make previously beneficial traits neutral or detrimental and vice versa. 7. Adaptation does not result in optimal characteristics. It is constrained by historical, genetic, and developmental limitations and by tradeoffs among features. 8. It does not matter what an “ideal” adaptive feature might be – the only relevant factor is that variants that happen to result in greater survival and reproduction relative to alternative variants are passed on more frequently. As Darwin wrote in a letter to Joseph Hooker (11 Sept. 1857), “I have just been writing an audacious little discussion, to show that organic beings are not perfect, only perfect enough to struggle with their competitors.” 9. The process of adaptation by natural selection is not forwardlooking, and it cannot produce features on the grounds that they might become beneficial sometime in the future. In fact, adaptations are always to the conditions experienced by generations in the past. 10. Natural selection is not the only mechanism of evolution. Mutation, genetic drift, and gene flow can also change the proportion of variants in a population Lures - Mantle tissue, which is the tissue that produces the shell. All mussels have mantle tissue, and it predates the evolution of lures. Male mussels have mantle tissue, and obviously they do not produce lures because they do not have brood larvae that need to be transferred to a fish host. Two large-scale evolutionary processes: the origin of new species (speciation) and the loss of existing species (extinction). “Biological Species Concept”, which states that “species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” That is, species are defined based on their reproductive boundaries.
Two organisms that could, at least in principle, successfully produce fertile offspring are considered members of the same species. Species are groups of organisms that share genes with each other, but for which there is little or no gene flow to or from other groups. There have been six major mass extinction events over the past 600 million years or so of the history of animal life. The Cretaceous-Tertiary (K-T) event of 65 million years ago, in which the dinosaurs (other than their descendants: birds) disappeared after more than 150 million years of success, is surely the best known of these. The End Permian event of about 250 million years ago, otherwise known as “The Great Dying”. About 95% of species are thought to have vanished during this event: in other words, multicellular life nearly disappeared the End Permian event of about 250 million years ago, otherwise known as “The Great Dying”. About 95% of species are thought to have vanished during this event: in other words, multicellular life nearly disappeared. At present, we find ourselves in the midst of another mass extinction event. This one, known as the Holocene extinction event, is being caused almost entirely by anthropogenic factors — that is, by human activity.
Unit 4 –Online Majestic Pine Woods
Old Field Woods
Maple Ridge Woods
Biodiversity: Biodiversity is often used as a non-technical term, which refers to the different scales of biological variation. 1) the Convention on Biological Diversity, also known as the Rio Summit, defines biodiversity as “the variability among living organisms from all sources including, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.” 2) The Canadian Biodiversity Strategy, defines biodiversity as “the variety of species and ecosystems on Earth and the ecological processes of which they are a part”. In general, biodiversity comprises three scales of variation: genetic, species, and ecosystem. Species Richness: Species richness is defined as the number of species present in a defined area such as a community or ecosystem. Sampling species richness is complete when the species area curve is saturated Abundance: Species abundance refers to how common a species is in a defined area and can be measured as percent cover, biomass or frequency of individuals per species Relative abundance: is a term that refers to the comparison of the species abundance within a defined area and relates to the “evenness” of distribution of individuals among species in a community. Abiotic: Abiotic factors are the physical and chemical features of an environment. Abiotic factors include light (radiation), temperature, water (availabilty, composition, flow), atmospheric gases (including pollution), and soil factors such as nutrients and porosity. Biotic: Biotic factors refer to the living things that live within and shape an ecosystem. This usually includes producers (plants that convert the sun’s energy into chemical food), consumers (organims that eat other plants and/or animals) and decomposers (organisms such as bacteria or fungi that feed off dead biota, decomposing large organic molecules into smaller units). Population: A populations refers to the colllection of individuals of a single species within a defined area at a specified point in time. Community: A community refers to the collection of species (each with its own population) living in a given area at a particular point in time.
Community: A community refers to the collection of species (each with its own population) living in a given area at a particular point in time.
Lecture Notes Biodiversity is the variety of genes, species and ecosystems. Evolution is decent with modification from common ancestors Darwin wasn’t any good at school, at a young age his father sent him to Edinburgh University. He wrote “The Origin Of Species” Unionids Larval form – glochidium Host dependent – Yes Larval dispersal – dispersed by host Dreissenids Larval form – veligers Host dependent – No Larval dispersal –dispersed in water Freshwater Bivalves develop in 3 ways 1. Early development as a parasitic stage on a host (by pasing) – Unionids 2. By producing veliger larval (Zebra Mussels) 3. By releasing fully developed young mussels (rare) Strategy for infecting fish host Conglutinates – Glochidia enclosed in membranous capsules that mimic host prey Leures – Modified mantle tissue mimics fish or invertebrate prey item to attract fish host Host Capture – Mussel may physically grip host and pump glochidia over the gills of the fish Zebra Mussel life cycle is much simpler and uses external fertilization techniques.
Causes of variation – Genetics and environment When it comes to phylogenetic trees you can’t asses what is more ‘primitive’ What matters is the pattern of branching (“topology”). The order of the tips (“terminal nodes”) is arbitrary. The lineages of all living (“ extant” ) species have been evolving for exactly the same amount of time because they all go back to a shared ancestor There is no “main line” since we can rotate branches. - Related though ancestors
The formation of new species is called speciation. Most often, this involves an ancestral species splitting or branching into two descendant species. This is called cladogenesis Gene - A molecular unit of heredity in a living organism. It is made up of stretches of DNA and RNA that may code for a type of protein or have a function in the organism. Found in the nucleus, mitochondria, and chloroplast.
Allele - is a form of a gene or group of genes. Different alleles may result in different traits, such as eye or flower petal color. However, different alleles may give rise to the same trait resulting in genetic variation in alleles with little or no variation in traits. The Primary source of genetic variation is mutation Mutations are errors in DNA replication. They occur at random. Mutations do NOT occur in order to benefit the organism. A secondary source of genetic variation is recombination. Gene Flow – Movement of genes amoung populations. Genetic Drift – Is the random change in frequency of gene variants (alleles) in a population. It is evolution by chance through many generations. Founder effects- loss of genetic variation that occurs when a new, smaller population is established
Difference : Genetic drift: in allele frequencies in a population Natural Selection is NON-RANDOM – Differences in•Random survival changes and/or reproduction among individual entitiesdue onto chance. Gene flow: the basis of differences in heritable characteristics. •Sharing of alleles among populations.
Mantle: folding of the body wall that lines shell; secretes shell substance (CaCo3). Mantle cavity: houses gills.
Adaptation is the evolutionary change over thousands of generations, enhances survival and reproduction through natural selection. “Co-option” of a functional tissue into a new & additional function.
Exinction : 1) Failure to adapt to a changing physical environment or to find new suitable habitat. (Not enough variation? No gene flow?) 2) Failure to keep up with the evolution of a competitor, predator, host, pathogen, etc. 3) Being driven to extinction by a newly encountered competitor, pathogen, or predator. 4) Losing an essential host, prey, or partner species. Speciation: What matters most for speciation is that there is a barrier to gene flow, which allows one species to split into two.
Option 1: Allopatric speciation Meaning “different place”. Species is split due to a geographic barrier or because some individuals move to a separate place. Option 2: Sympatric speciation - does not require physical separation to reduce gene flow between two different groups within a population.
Where did zebra mussels come from? When and where did they first arrive, and how have they spread so quickly? What impacts are they having on the native fauna and ecosystem? Why have they been so successful at spreading into new lakes and rivers?
Peer-reviewed scientific publications, also known as the “primary literature” are the means by which scientists share their results with other researchers. As members of the University of Guelph, you have access to an extraordinary number of peer-reviewed journals through the library, most of them with electronic access. Search engines such as Google Scholar, PubMed, and Web of Science can all be used to locate papers on any topic.
Zebra Mussels • The zebra mussel (Dreissena polymorpha) is native to eastern Eurasia, specifically the Black Sea and Caspian Sea. • Mode of transport across the Atlantic was in the ballast water of an ocean liner.
• • •
First reported in North America in 1988 in Lake St. Clair, in a peer-reviewed paper by Hebert et al. (1989). o Prof. Hebert is the Director of the Biodiversity Institute of Ontario here at the University of Guelph. This is not the first time the zebra mussel has invaded new environments — it also invaded western Europe in the late 1700s and early 1800s There has since been a second invasion by a related mussel, the quagga mussel (Dreissena rostriformis)
Native Mussel Fauna In Ontario, the native mussels are all members of the family Unionidae, but within this there are several distantly related subfamilies. Zebra mussels and other factors (especially agricultural practices) are having a significant impact on the native mussels of the region. Freshwater mussels are among the most endangered organisms in North America. Unionids are particularly interesting because of their complex life cycle, which includes a component of obligate parasitism (i.e., they must parasitize a host at some stage to complete their reproductive cycle).
Most of the species in Ontario are dioecious (“two houses”), meaning that they have separate males and females. o Males release their sperm into the water through their exhalant siphon, which are then taken up by females downstream through their inhalant siphon. Fertilization is internal (i.e., inside the female’s body), and the embryos develop inside modified pouches of the female’s gills called a marsupium. o The embryos mature into specialized larvae called glochidia (singular glochidium), and it is these that represent the parasitic life stage. o Glochidia must attach to the gills of a fish in order to continue their development. o The mantle tissue acts as a “lure” that resembles a fish or invertebrate prey that attracts the host. Key Points in Unit 1 1. The invasive zebra mussel (Dreissena polymorpha) has had an enormous economic, aesthetic, and biological impact on the Great Lakes watershed. It originated from eastern Eurasia and is thought to have been transported by an ocean vessel sometime before 1988. 2. Peer-reviewed primary literature is the standard means by which scientists share their research findings. It is typically a well regulated system where two or more external referees read and critique the manuscript providing a recommendation to the journal editor to publish or reject the study. 3. There are 41 native freshwater mussels in Ontario, many of them are endangered. Unionids are obligate parasites where glochidia (larvae) are released and must attach to the gills of a fish host to complete their development. 4. Native and invasive mussel species are studied by a variety of different people: undergraduates, graduates, professors and government scientists. These people explore mussel diversity, adaptations, distribution, phylogenetics and conservation issues. Unit 2 – Online Taxonomic Level: Domains – eukaryotes Kingdoms – Animilia (animals) Phyla (singular: Phylum) - Mollusca (mollusks) Classes – Mammilia (mammals) Orders – Primates (apes) Families -Hominidae (great apes) Genera (singular: Genus) - Homo (humans and extinct relatives, e.g., Neanderthals) Species (singular is also species, not specie) - sapiens (humans) Biologists use the word “diversity” to refer to the number of species in a taxonomic group or a geographical area. Differences Within Species: Sexual Dimorphism and Age Each species has morphological (physical) traits that can be used to distinguish it from other mussels. Our development — what biologists call “ ontogeny” — involves significant changes in morphology from youth to old age. This is also true of mussels! Like humans, mussels may exhibit clear differences among individuals within species due to sexual dimorphism (in some species) and age. Finding gravid females and juveniles is a good sign that recruitment (production of the next generation) is succeeding Female mussels have a wider posterior while males come to a point. Differences Within Species II: Morphology The scientific name conveys important information about the species itself- .Dreissena polymorpha (zebra mussel), is one such example: “polymorpha” means “many forms”. Differences Within Species: Cryptic Variation To be evolutionarily relevant, variation among individuals must be heritable. In other words, there must be a genetic basis for the observed trait such that it will be passed on in similar form to offspring. Cases in which the same set of genes (genotype) can result in differing features (phenotype) according to environmental conditions are known as “ phenotypic plasticity”. Abundance vs. Variation vs. Diversity vs. Disparity Morphological and genetic variation (differences among individuals within a species) diversity (number of species) Whereas diversity is a measure of the number of different species, disparity refers to how physically different those species are from each other.
We are all Related You are a member of a lineage of ancestors and descendants that has never once been broken in more than 3.8 billion years of life on Earth. Ways in which living things are related to one another through their common ancestors: a field known as “ phylogenetics”. Anatomy Of A Phylogeny The closest relatives descended from a single recent ancestor are even called “sister taxa” — again, there are important parallels between phylogenies and pedigrees. This order of branching, what biologists call “ topology”, reflects the ancestor-descendant relationships, and that is the most important information contained in a tree diagram. The ancestors and descendants on a phylogeny are usually species. The root (common ancestor shared by all species depicted), branches (connections between ancestors and descendants), and “tips” (or “ terminal nodes”). The terminal nodes usually represent living species, whereas internal nodes are usually extinct ancestors. Evolutionary Classification The approach to classification that is based strictly on evolutionary relationships is known as “cladistics”, and the evolutionary groups that it considers worthy of naming are called “ clades”. A clade is any group of species that includes the last ancestor that they shared and all its descendants. Valid clades, which include the last shared ancestor and all its descendants, are known as “ monophyletic” groups (meaning “one lineage”). When one of the descendants is left out, which creates what cladists call a “ paraphyletic” group. For example, the term “reptile”, which includes lizards, snakes, turtles, and crocodiles but not birds is a paraphyletic group. It is not a clade, because it leaves out birds. Mussles Mussels inhabiting fast-moving rivers exhibit a variety of adaptations to remaining anchored in the substrate at the bottom. This includes various configurations of bumps, ridges, or wings. This sort of feature has evolved more than once in independent lineages as a similar adaptation under similar environmental pressures, a process known as “ convergent evolution”. Sharing ancestral traits is called “ homology”, whereas having traits that are similar but evolved independently is called “ homoplasy” (convergent evolution).
Unit 3 – Online Adaptation and Specialization Mutation (the origin of new genetic variation) Genetic drift (changes due to chance, specifically founder effects and population bottlenecks) Gene flow (movement of genes among populations) Natural selection: Non-random differences in survival and/or reproduction among individual entities on the basis of differences in heritable characteristics. Adaptation: 1) a characteristic that enhances the survival and/or reproduction of organisms that bear it, relative to alternative (especially ancestral) character states; 2) a physical, physiological, behavioural, or other characteristic evolved through natural selection. Adaptation is NOT the change undergone by an individual organism during its lifetime in response to external conditions. Population: for sexual species, a group of interbreeding individuals and their offspring. Alleles: alternate (i.e., different and mutually exclusive) forms of a gene. e.g., “B” (brown eyes) versus “b” (blue eyes). Genotype: the set of genes possessed by an organism. Phenotype: the physical expression of the genotype (in combination with the environment). Frequency: the proportional representation of a phenotype, genotype, gamete, or allele in a population. e.g., 6 out of 10 have blue eyes = 60% = a frequency of 0.6. The Basis Of Natural Selection
When it comes specifically to adaptive changes among species and the traits of organisms that allow them to survive successfully in their environments, natural selection is indeed the only known mechanism that can provide a scientific explanation. 1. Individuals within populations are variable. That not every individual is identical in a population is obvious for humans 2. This variability among individuals is at least partly heritable. Offspring tend to look more like their parents than like unrelated members of the population 3. Not everyone survives and reproduces, and some individuals are more successful than others. Many more offspring are produced in each generation than could possibly survive, a phenomenon known as “overproduction”. 4. The differential survival and reproduction of individuals is associated with the heritable variation among individuals (i.e., it is non-random). This is the key to natural selection, that the individuals who do manage to reach adulthood and have offspring of their own are, on average, better suited to surviving and reproducing in their particular environment because of traits that they inherited from their parents. 10 Things about Natural Selection 1. Natural selection by itself does not create new traits, it only changes the proportion of variation that is already present in the population. Most often, natural selection reduces the amount of variation in a population because some variants are eliminated. 2. Mutation, not natural selection, is the source of new variation. The repeated twostep interaction of mutation and natural selection is what leads to the evolution of new adaptive features. 3. Mutation is random with respect to fitness — that is, it occurs without regard for what happens to the organism. It is simply a genetic error. Natural selection is, by definition, nonrandom with respect to fitness. This means that, overall, it is a serious misconception to consider adaptation as happening “by chance”. 4. Mutations occur with all three possible outcomes: neutral (no phenotypic effect), deleterious (bad effects), and beneficial (positive effects). Beneficial mutations may be rare and deliver only a minor advantage, but these can nonetheless increase in proportion in the population over many generations by natural selection. The occurrence of any particular beneficial mutation may be very improbable, but natural selection is very effective at causing these individually unlikely improvements to accumulate. Natural selection is an improbability concentrator. 5. No organisms change as the population adapts. Rather, this involves changes in the proportion of beneficial traits across multiple generations. 6. The direction in which change occurs is dependent on the environment. A change in environment can make previously beneficial traits neutral or detrimental and vice versa. 7. Adaptation does not result in optimal characteristics. It is constrained by historical, genetic, and developmental limitations and by tradeoffs among features. 8. It does not matter what an “ideal” adaptive feature might be – the only relevant factor is that variants that happen to result in greater survival and reproduction relative to alternative variants are passed on more frequently. As Darwin wrote in a letter to Joseph Hooker (11 Sept. 1857), “I have just been writing an audacious little discussion, to show that organic beings are not perfect, only perfect enough to struggle with their competitors.” 9. The process of adaptation by natural selection is not forwardlooking, and it cannot produce features on the grounds that they might become beneficial sometime in the future. In fact, adaptations are always to the conditions experienced by generations in the past. 10. Natural selection is not the only mechanism of evolution. Mutation, genetic drift, and gene flow can also change the proportion of variants in a population Lures - Mantle tissue, which is the tissue that produces the shell. All mussels have mantle tissue, and it predates the evolution of lures. Male mussels have mantle tissue, and obviously they do not produce lures because they do not have brood larvae that need to be transferred to a fish host. Two large-scale evolutionary processes: the origin of new species (speciation) and the loss of existing species (extinction). “Biological Species Concept”, which states that “species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” That is, species are defined based on their reproductive boundaries.
Two organisms that could, at least in principle, successfully produce fertile offspring are considered members of the same species. Species are groups of organisms that share genes with each other, but for which there is little or no gene flow to or from other groups. There have been six major mass extinction events over the past 600 million years or so of the history of animal life. The Cretaceous-Tertiary (K-T) event of 65 million years ago, in which the dinosaurs (other than their descendants: birds) disappeared after more than 150 million years of success, is surely the best known of these. The End Permian event of about 250 million years ago, otherwise known as “The Great Dying”. About 95% of species are thought to have vanished during this event: in other words, multicellular life nearly disappeared the End Permian event of about 250 million years ago, otherwise known as “The Great Dying”. About 95% of species are thought to have vanished during this event: in other words, multicellular life nearly disappeared. At present, we find ourselves in the midst of another mass extinction event. This one, known as the Holocene extinction event, is being caused almost entirely by anthropogenic factors — that is, by human activity.
Unit 4 –Online Majestic Pine Woods
Old Field Woods
Maple Ridge Woods
Biodiversity: Biodiversity is often used as a non-technical term, which refers to the different scales of biological variation. 1) the Convention on Biological Diversity, also known as the Rio Summit, defines biodiversity as “the variability among living organisms from all sources including, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.” 2) The Canadian Biodiversity Strategy, defines biodiversity as “the variety of species and ecosystems on Earth and the ecological processes of which they are a part”. In general, biodiversity comprises three scales of variation: genetic, species, and ecosystem. Species Richness: Species richness is defined as the number of species present in a defined area such as a community or ecosystem. Sampling species richness is complete when the species area curve is saturated Abundance: Species abundance refers to how common a species is in a defined area and can be measured as percent cover, biomass or frequency of individuals per species Relative abundance: is a term that refers to the comparison of the species abundance within a defined area and relates to the “evenness” of distribution of individuals among species in a community. Abiotic: Abiotic factors are the physical and chemical features of an environment. Abiotic factors include light (radiation), temperature, water (availabilty, composition, flow), atmospheric gases (including pollution), and soil factors such as nutrients and porosity. Biotic: Biotic factors refer to the living things that live within and shape an ecosystem. This usually includes producers (plants that convert the sun’s energy into chemical food), consumers (organims that eat other plants and/or animals) and decomposers (organisms such as bacteria or fungi that feed off dead biota, decomposing large organic molecules into smaller units). Population: A populations refers to the colllection of individuals of a single species within a defined area at a specified point in time. Community: A community refers to the collection of species (each with its own population) living in a given area at a particular point in time.
Community: A community refers to the collection of species (each with its own population) living in a given area at a particular point in time.
Lecture Notes Biodiversity is the variety of genes, species and ecosystems. Evolution is decent with modification from common ancestors Darwin wasn’t any good at school, at a young age his father sent him to Edinburgh University. He wrote “The Origin Of Species” Unionids Larval form – glochidium Host dependent – Yes Larval dispersal – dispersed by host Dreissenids Larval form – veligers Host dependent – No Larval dispersal –dispersed in water Freshwater Bivalves develop in 3 ways 1. Early development as a parasitic stage on a host (by pasing) – Unionids 2. By producing veliger larval (Zebra Mussels) 3. By releasing fully developed young mussels (rare) Strategy for infecting fish host Conglutinates – Glochidia enclosed in membranous capsules that mimic host prey Leures – Modified mantle tissue mimics fish or invertebrate prey item to attract fish host Host Capture – Mussel may physically grip host and pump glochidia over the gills of the fish Zebra Mussel life cycle is much simpler and uses external fertilization techniques.
Causes of variation – Genetics and environment When it comes to phylogenetic trees you can’t asses what is more ‘primitive’ What matters is the pattern of branching (“topology”). The order of the tips (“terminal nodes”) is arbitrary. The lineages of all living (“ extant” ) species have been evolving for exactly the same amount of time because they all go back to a shared ancestor There is no “main line” since we can rotate branches. - Related though ancestors
The formation of new species is called speciation. Most often, this involves an ancestral species splitting or branching into two descendant species. This is called cladogenesis Gene - A molecular unit of heredity in a living organism. It is made up of stretches of DNA and RNA that may code for a type of protein or have a function in the organism. Found in the nucleus, mitochondria, and chloroplast.
Allele - is a form of a gene or group of genes. Different alleles may result in different traits, such as eye or flower petal color. However, different alleles may give rise to the same trait resulting in genetic variation in alleles with little or no variation in traits. The Primary source of genetic variation is mutation Mutations are errors in DNA replication. They occur at random. Mutations do NOT occur in order to benefit the organism. A secondary source of genetic variation is recombination. Gene Flow – Movement of genes amoung populations. Genetic Drift – Is the random change in frequency of gene variants (alleles) in a population. It is evolution by chance through many generations. Founder effects- loss of genetic variation that occurs when a new, smaller population is established
Difference : Genetic drift: in allele frequencies in a population Natural Selection is NON-RANDOM – Differences in•Random survival changes and/or reproduction among individual entitiesdue onto chance. Gene flow: the basis of differences in heritable characteristics. •Sharing of alleles among populations.
Mantle: folding of the body wall that lines shell; secretes shell substance (CaCo3). Mantle cavity: houses gills.
Adaptation is the evolutionary change over thousands of generations, enhances survival and reproduction through natural selection. “Co-option” of a functional tissue into a new & additional function.
Exinction : 1) Failure to adapt to a changing physical environment or to find new suitable habitat. (Not enough variation? No gene flow?) 2) Failure to keep up with the evolution of a competitor, predator, host, pathogen, etc. 3) Being driven to extinction by a newly encountered competitor, pathogen, or predator. 4) Losing an essential host, prey, or partner species. Speciation: What matters most for speciation is that there is a barrier to gene flow, which allows one species to split into two.
Option 1: Allopatric speciation Meaning “different place”. Species is split due to a geographic barrier or because some individuals move to a separate place. Option 2: Sympatric speciation - does not require physical separation to reduce gene flow between two different groups within a population.
