1. The document describes a system designed to meet the basic needs of a family of four living in the tropics. The system generates fuel gas from bacterial fermentation of urine and feces. It uses solid waste from the fermenter as fertilizer and grows leguminous plants such as beans and peanuts. Fish that feed on algae are stocked in the pond rather than carnivorous fish.
2. Candidates were asked questions about various parts of the system. For example, how the nitrogen cycle makes nitrogen in urine and feces available to plants, the advantages of growing legumes, and the benefits of stocking the pond with algae-feeding fish rather than carnivorous fish.
1. The document describes a system designed to meet the basic needs of a family of four living in the tropics. The system generates fuel gas from bacterial fermentation of urine and feces. It uses solid waste from the fermenter as fertilizer for crops and stocks the pond with fish that feed on algae rather than carnivorous fish.
2. The document discusses student responses to questions about the nitrogen cycle and leguminous plants. It notes confusion between nitrogen fixing and denitrifying bacteria. It also notes that students have difficulty with the sequence of changes in the nitrogen cycle and defining nitrogen compounds.
3. The document evaluates student essays on relationships between animals and plants. It finds the scientific
UC Davis EVE161 Lecture 17 by @phylogenomicsJonathan Eisen
This document contains slides from a lecture on metagenomics given by Jonathan Eisen at UC Davis in winter 2014. The lecture discusses shotgun metagenomics and analyzing metagenomic functions and gene content from environmental samples without genome assemblies. It provides an example of a comparative metagenomics study of various microbial communities that identified habitat-specific genes and metabolic profiles reflecting the different environments. The slides include figures and references from a 2005 Science paper on this topic. Problem set 4 for the class involves selecting a relevant paper for presentation the following week.
The document contains slides from a course on microbial phylogenomics taught by Jonathan Eisen at UC Davis in winter 2016. The slides discuss various topics relating to metagenomics including the environmental genome shotgun sequencing of the Sargasso Sea, methods for binning sequences from metagenomic data like aligning to reference genomes or assembly, and examples of projects that used shotgun sequencing like the Wolbachia and glassy-winged sharpshooter projects. It also discusses challenges with assembly for metagenomic data due to variations in coverage and the DeLong lab's early work characterizing uncultured marine microbes.
Deciphering the nature of the coral–Chromera association. Mohamed et al-2018-...Amin Mohamed
Since the discovery of Chromera velia as a novel coral-associated microalga, this organism has attracted interest because of its unique evolutionary position between the photosynthetic dinoflagellates and the parasitic apicomplexans. The nature of the relationship between Chromera and its coral host is controversial. Is it a mutualism, from which both participants benefit, a parasitic relationship, or a chance association? To better understand the interaction, larvae of the common Indo-Pacific reef-building coral Acropora digitifera were experimentally infected with Chromera, and the impact on the host transcriptome was assessed at 4, 12, and 48 h post-infection using Illumina RNA-Seq technology. The transcriptomic response of the coral to Chromera was complex and implies that host immunity is strongly suppressed, and both phagosome maturation and the apoptotic machinery is modified. These responses differ markedly from those described for infection with a competent strain of the coral mutualist Symbiodinium, instead resembling those of vertebrate hosts to parasites and/or pathogens such as Mycobacterium tuberculosis. Consistent with ecological studies suggesting that the association may be accidental, the transcriptional response of A. digitifera larvae leads us to conclude that Chromera could be a coral parasite, commensal, or accidental bystander, but certainly not a beneficial mutualist.
BIS2C. Biodiversity and the Tree of Life. 2014. L8. Intro to Microbial Divers...Jonathan Eisen
BIS2C. Biodiversity and the Tree of Life.
At UC Davis Spring 2014.
Lecture 8.
Introduction to Microbial Diversity, part 2.
Slides for Lectures by Jonathan Eisen
This document summarizes a biodiversity study of diatoms from the Ganga River and a residential pond in India. Diatoms are single-celled algae with unique silica cell walls that come in many shapes and sizes, and play an important role in carbon fixation and oxygen production. The study involved collecting samples from both water sources, cleaning the diatoms, observing them under a microscope, and classifying the different types found based on their morphology. The document discusses the importance of diatoms and some of their applications, such as for nutrition, industry, and nanotechnology. It concludes that future genetic manipulation could make diatom biotechnology more viable and profitable.
1. The document describes a system designed to meet the basic needs of a family of four living in the tropics. The system generates fuel gas from bacterial fermentation of urine and feces. It uses solid waste from the fermenter as fertilizer for crops and stocks the pond with fish that feed on algae rather than carnivorous fish.
2. The document discusses student responses to questions about the nitrogen cycle and leguminous plants. It notes confusion between nitrogen fixing and denitrifying bacteria. It also notes that students have difficulty with the sequence of changes in the nitrogen cycle and defining nitrogen compounds.
3. The document evaluates student essays on relationships between animals and plants. It finds the scientific
UC Davis EVE161 Lecture 17 by @phylogenomicsJonathan Eisen
This document contains slides from a lecture on metagenomics given by Jonathan Eisen at UC Davis in winter 2014. The lecture discusses shotgun metagenomics and analyzing metagenomic functions and gene content from environmental samples without genome assemblies. It provides an example of a comparative metagenomics study of various microbial communities that identified habitat-specific genes and metabolic profiles reflecting the different environments. The slides include figures and references from a 2005 Science paper on this topic. Problem set 4 for the class involves selecting a relevant paper for presentation the following week.
The document contains slides from a course on microbial phylogenomics taught by Jonathan Eisen at UC Davis in winter 2016. The slides discuss various topics relating to metagenomics including the environmental genome shotgun sequencing of the Sargasso Sea, methods for binning sequences from metagenomic data like aligning to reference genomes or assembly, and examples of projects that used shotgun sequencing like the Wolbachia and glassy-winged sharpshooter projects. It also discusses challenges with assembly for metagenomic data due to variations in coverage and the DeLong lab's early work characterizing uncultured marine microbes.
Deciphering the nature of the coral–Chromera association. Mohamed et al-2018-...Amin Mohamed
Since the discovery of Chromera velia as a novel coral-associated microalga, this organism has attracted interest because of its unique evolutionary position between the photosynthetic dinoflagellates and the parasitic apicomplexans. The nature of the relationship between Chromera and its coral host is controversial. Is it a mutualism, from which both participants benefit, a parasitic relationship, or a chance association? To better understand the interaction, larvae of the common Indo-Pacific reef-building coral Acropora digitifera were experimentally infected with Chromera, and the impact on the host transcriptome was assessed at 4, 12, and 48 h post-infection using Illumina RNA-Seq technology. The transcriptomic response of the coral to Chromera was complex and implies that host immunity is strongly suppressed, and both phagosome maturation and the apoptotic machinery is modified. These responses differ markedly from those described for infection with a competent strain of the coral mutualist Symbiodinium, instead resembling those of vertebrate hosts to parasites and/or pathogens such as Mycobacterium tuberculosis. Consistent with ecological studies suggesting that the association may be accidental, the transcriptional response of A. digitifera larvae leads us to conclude that Chromera could be a coral parasite, commensal, or accidental bystander, but certainly not a beneficial mutualist.
BIS2C. Biodiversity and the Tree of Life. 2014. L8. Intro to Microbial Divers...Jonathan Eisen
BIS2C. Biodiversity and the Tree of Life.
At UC Davis Spring 2014.
Lecture 8.
Introduction to Microbial Diversity, part 2.
Slides for Lectures by Jonathan Eisen
This document summarizes a biodiversity study of diatoms from the Ganga River and a residential pond in India. Diatoms are single-celled algae with unique silica cell walls that come in many shapes and sizes, and play an important role in carbon fixation and oxygen production. The study involved collecting samples from both water sources, cleaning the diatoms, observing them under a microscope, and classifying the different types found based on their morphology. The document discusses the importance of diatoms and some of their applications, such as for nutrition, industry, and nanotechnology. It concludes that future genetic manipulation could make diatom biotechnology more viable and profitable.
BIS2C. Biodiversity and the Tree of Life. 2014. L14. FungiJonathan Eisen
The document is a set of lecture slides about fungi. It discusses several types of fungi, including microsporidia, chytrids, zygospore fungi, glomeromycota, and dikarya. It provides details on the characteristics, life cycles, and evolution of these groups. It specifically examines the life cycles of sac fungi, noting they have a haploid stage, form a dikaryotic mycelium through plasmogamy, undergo karyogamy and meiosis within ascocarps to produce haploid ascospores.
A renewed need for a genomic field guide to microbesJonathan Eisen
This document discusses the need for a genomic field guide to microbes. It outlines several challenges to creating such a guide, including the small size and diversity of microbes, as well as difficulties observing and collecting data on them in natural environments. Potential solutions proposed include advances in DNA sequencing technologies that have enabled large-scale cataloging and identification of microbes. Components suggested for inclusion in a field guide are phylogenetic catalogs, functional profiles, biogeography data, identification methods, and information on applications like pathogen detection. Citizen science initiatives are also presented as a way to engage the public in microbiology. The talk concludes by advocating the creation of a comprehensive genomic field guide to microbes.
The document provides assessment statements related to evolution for a student. It covers four main topics: the origin of life on Earth, species and speciation, human evolution, and the Hardy-Weinberg principle. For each topic, it lists multiple learning objectives that describe key concepts and theories the student should understand, such as the processes needed for the spontaneous origin of life, mechanisms of speciation like allopatric and sympatric speciation, evidence from fossils that trace human evolution, and how to apply the Hardy-Weinberg principle to calculate genotype and allele frequencies. It also includes statements about uncertainties in the fossil record and debates around scientific theories of the past.
Impact of Silicon Dioxide Nanoparticle on Fresh Water Fish Clarius Batrachusijtsrd
Clarias batrachus, a freshwater Indian air breathing catfish is one of the important fish species. It is treated as a typical example to deal with the alimentary canal of a teleost and a test animal in many laboratories of Indian Universities . However, the effect of silicon dioxide nanoparticles on Indian Air breathing fishes is lacking. Therefore, the present work was designed to evaluate the median lethal dose of silicon dioxide nanoparticles on Clarias batrachus. The work will help in deciding the toxicity level of silicon dioxide nanoparticles for the higher yield of this fish. Nanotechnology an advanced tool to synthesis atomic level particles. Increased application of silicon dioxide nanoparticles results in the bioaccumulation of these particles in the environment. The fate and effect of nanomaterials in the environment has raised concern about their environmental risk to aquatic organisms. Silica nanoparticles SiO2 NPs find its uses in various fields and are inevitably released into the environment. However, the ecotoxicological effects of SiO2 NPs on the freshwater fish remain poorly understood. Pooja Shree Somani | Dr. Ranu Sharma "Impact of Silicon Dioxide Nanoparticle on Fresh Water Fish Clarius Batrachus" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd31275.pdf Paper Url :https://www.ijtsrd.com/biological-science/zoology/31275/impact-of-silicon-dioxide-nanoparticle-on-fresh-water-fish-clarius-batrachus/pooja-shree-somani
The document is a set of slides for a lecture on deuterostomes, specifically echinoderms and hemichordates. It includes a phylogenetic tree of animals showing the relationships between major groups like sponges, cnidarians, protostomes, deuterostomes. It also notes some of the key innovations along the branches, such as the development of multicellularity and tissues in the common ancestor of all animals.
This document contains slides from a lecture on chordates and vertebrate evolution. The slides cover topics like the phylogeny of chordates and vertebrates, innovations in vertebrate evolution like jaws and limbs, and examples of key vertebrate groups like lampreys and hagfish. The document emphasizes how scientists use comparative biology and phylogenetic trees to study relationships between organisms and infer ancestral traits.
The document summarizes a lecture on the human microbiome. It discusses how humans are colonized by vast numbers of microbes, forming complex microbial ecosystems. There is enormous variation in microbiome composition both within and between individuals, and this variation is associated with health states and phenotypes. Research has identified some possible causes of microbiome variation and suggests it may be possible to alter or restore microbiome composition.
BIS2C. Biodiversity and the Tree of Life. 2014. L12. Symbioses and the Human ...Jonathan Eisen
This document contains lecture slides about symbiosis and the human microbiome. It discusses the evolution of the human microbiome and how history is important for understanding ecosystems. It also summarizes some of the key functions of the microbiome, including digestion, immune system management, and vitamin production. Finally, it outlines different types of symbiotic relationships and provides examples of pathogenic bacteria and eukaryotes.
This study found high concentrations of viruses in water samples from the Chesapeake Bay. Virus counts ranged from 2.6 x 106 to 1.4 x 108 viruses per ml and averaged 2.5 x 107 viruses per ml. Virus counts were usually at least three times higher than bacterial counts from the same samples. Virus concentrations were highest in August and October and lowest in April and September. The high virus counts suggest that viruses may be an important factor influencing bacterial populations in the Chesapeake Bay through infection.
Sulphate and Hardness_Elphick et al_ET&CGuy Gilron
This document presents the results of a study evaluating the chronic toxicity of sulfate in various aquatic organisms. A variety of test species, including invertebrates, fish, algae, moss, and an amphibian, were exposed to sulfate under different water hardness conditions. The results show that sulfate toxicity decreases with increasing water hardness. Based on these findings, the authors calculated water quality guidelines for sulfate separately for soft, moderately hard, and hard water. The guidelines ranged from 75 to 725 mg/L sulfate depending on the water hardness and calculation method. The study provides a robust dataset that can be used to establish scientifically defensible sulfate guidelines that account for the modifying effect of water hardness.
Otolith Poster - Melissa Pappas.pptx - Google SlidesMelissa Pappas
This study compared the effectiveness of oxytetracycline (OTC) and calcein for marking fish otoliths to aid in age validation. Juvenile pinfish were immersed in various concentrations of OTC or calcein for different time periods. Their otoliths were later examined under fluorescence microscopy. Results showed calcein produced stronger marks than OTC. Higher calcein concentrations and using a NaCl solution improved mark strength. Calcein marks remained clearly visible over several months. This technique can help scientists accurately determine the age of fish by marking otoliths at a known time.
BIS2C. Biodiversity and the Tree of Life. 2014. L13. FungiJonathan Eisen
This document contains lecture slides about fungi. It begins with an outline of the lecture topics, which are an introduction to fungi, their diversity of forms, phylogenetic diversity, and symbioses. The slides then cover the defining characteristics of fungi, examples of fungal diversity including yeasts, molds, and mushrooms, fungal reproduction through spores and sexual reproduction, the phylogeny of fungi, and a classification table of major fungal groups. Practice exam questions are also included about topics covered in previous lectures.
This document summarizes a lecture on how different parts of genomes and cells can have different evolutionary histories. It discusses how endosymbiosis led to the origins of mitochondria and chloroplasts from ancient bacteria. Phylogenetic analysis of mitochondrial and chloroplast genes supports a single origin for each from ancient endosymbiotic events, though some lineages have since lost these organelles. The distribution and trees of chloroplasts and mitochondria do not always match the nuclear genome tree.
Evolution of microbiomes and the evolution of the study and politics of micro...Jonathan Eisen
The document discusses the evolution of microbiomes and the study of microbiomes. It notes that microbiomes can be both overhyped yet underappreciated. It provides background on the rise of interest in microbiomes since the 2000s due to technological advances enabling their study as well as appreciation of their important functions. The author then discusses their own research focusing on using phylogenomic methods to study microbial communities and symbioses, especially how microbes and microbiomes help hosts adapt to stress. Examples discussed include chemosymbioses, pathogen resistance, environmental changes, and more.
This document is a dissertation submitted in partial fulfillment of a Bachelor's degree in environmental sciences. It presents the results of a study monitoring the phytoplankton communities in a eutrophic Irish lake over a 6-month period from January to July 2012. Phytoplankton assemblages were found to follow clear seasonal successional patterns related to changing water quality and nutrient conditions. Their composition supported the lake's status as healthy but bordering on mesotrophic/eutrophic. The study evaluated phytoplankton as biological indicators for monitoring water quality and ecological status under the EU Water Framework Directive.
This document contains slides from a lecture on chordates. It discusses the key characteristics of chordates like the notochord and dorsal hollow nerve cord. It covers the three major chordate groups: lancelets, tunicates, and vertebrates. Lancelets retain many chordate features throughout life. Tunicates resemble chordates as larvae but undergo metamorphosis and lose most features as adults. Many slides show examples of symbiosis in chordates and other animals.
This document discusses exam responses on topics related to carbon and nitrogen cycling. It provides feedback on common mistakes and omissions in student answers. For example, many students stated carbon is converted to oxygen during photosynthesis rather than being used to produce organic molecules. The document also notes better responses incorporated appropriate scientific terminology and integrated knowledge from the passage with their own biological understanding.
1. Most candidates understood how species conservation could result from selective logging but had difficulty clearly expressing these ideas. Some incorrectly imagined minerals redistributing over long distances from unlogged to logged areas. Most recognized the importance of sufficient time for tree regrowth.
2. Many candidates confused fertilizers and pesticides. Most explained ladybird consumption of greenflies accumulating insecticide but some incorrectly suggested insecticide increasing from greenfly reproduction. Patterns of population changes were often described poorly.
3. Candidates correctly identified interspecific competition but had difficulty calculating growth rate differences between spruce and heather in a control experiment.
BIS2C. Biodiversity and the Tree of Life. 2014. L14. FungiJonathan Eisen
The document is a set of lecture slides about fungi. It discusses several types of fungi, including microsporidia, chytrids, zygospore fungi, glomeromycota, and dikarya. It provides details on the characteristics, life cycles, and evolution of these groups. It specifically examines the life cycles of sac fungi, noting they have a haploid stage, form a dikaryotic mycelium through plasmogamy, undergo karyogamy and meiosis within ascocarps to produce haploid ascospores.
A renewed need for a genomic field guide to microbesJonathan Eisen
This document discusses the need for a genomic field guide to microbes. It outlines several challenges to creating such a guide, including the small size and diversity of microbes, as well as difficulties observing and collecting data on them in natural environments. Potential solutions proposed include advances in DNA sequencing technologies that have enabled large-scale cataloging and identification of microbes. Components suggested for inclusion in a field guide are phylogenetic catalogs, functional profiles, biogeography data, identification methods, and information on applications like pathogen detection. Citizen science initiatives are also presented as a way to engage the public in microbiology. The talk concludes by advocating the creation of a comprehensive genomic field guide to microbes.
The document provides assessment statements related to evolution for a student. It covers four main topics: the origin of life on Earth, species and speciation, human evolution, and the Hardy-Weinberg principle. For each topic, it lists multiple learning objectives that describe key concepts and theories the student should understand, such as the processes needed for the spontaneous origin of life, mechanisms of speciation like allopatric and sympatric speciation, evidence from fossils that trace human evolution, and how to apply the Hardy-Weinberg principle to calculate genotype and allele frequencies. It also includes statements about uncertainties in the fossil record and debates around scientific theories of the past.
Impact of Silicon Dioxide Nanoparticle on Fresh Water Fish Clarius Batrachusijtsrd
Clarias batrachus, a freshwater Indian air breathing catfish is one of the important fish species. It is treated as a typical example to deal with the alimentary canal of a teleost and a test animal in many laboratories of Indian Universities . However, the effect of silicon dioxide nanoparticles on Indian Air breathing fishes is lacking. Therefore, the present work was designed to evaluate the median lethal dose of silicon dioxide nanoparticles on Clarias batrachus. The work will help in deciding the toxicity level of silicon dioxide nanoparticles for the higher yield of this fish. Nanotechnology an advanced tool to synthesis atomic level particles. Increased application of silicon dioxide nanoparticles results in the bioaccumulation of these particles in the environment. The fate and effect of nanomaterials in the environment has raised concern about their environmental risk to aquatic organisms. Silica nanoparticles SiO2 NPs find its uses in various fields and are inevitably released into the environment. However, the ecotoxicological effects of SiO2 NPs on the freshwater fish remain poorly understood. Pooja Shree Somani | Dr. Ranu Sharma "Impact of Silicon Dioxide Nanoparticle on Fresh Water Fish Clarius Batrachus" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd31275.pdf Paper Url :https://www.ijtsrd.com/biological-science/zoology/31275/impact-of-silicon-dioxide-nanoparticle-on-fresh-water-fish-clarius-batrachus/pooja-shree-somani
The document is a set of slides for a lecture on deuterostomes, specifically echinoderms and hemichordates. It includes a phylogenetic tree of animals showing the relationships between major groups like sponges, cnidarians, protostomes, deuterostomes. It also notes some of the key innovations along the branches, such as the development of multicellularity and tissues in the common ancestor of all animals.
This document contains slides from a lecture on chordates and vertebrate evolution. The slides cover topics like the phylogeny of chordates and vertebrates, innovations in vertebrate evolution like jaws and limbs, and examples of key vertebrate groups like lampreys and hagfish. The document emphasizes how scientists use comparative biology and phylogenetic trees to study relationships between organisms and infer ancestral traits.
The document summarizes a lecture on the human microbiome. It discusses how humans are colonized by vast numbers of microbes, forming complex microbial ecosystems. There is enormous variation in microbiome composition both within and between individuals, and this variation is associated with health states and phenotypes. Research has identified some possible causes of microbiome variation and suggests it may be possible to alter or restore microbiome composition.
BIS2C. Biodiversity and the Tree of Life. 2014. L12. Symbioses and the Human ...Jonathan Eisen
This document contains lecture slides about symbiosis and the human microbiome. It discusses the evolution of the human microbiome and how history is important for understanding ecosystems. It also summarizes some of the key functions of the microbiome, including digestion, immune system management, and vitamin production. Finally, it outlines different types of symbiotic relationships and provides examples of pathogenic bacteria and eukaryotes.
This study found high concentrations of viruses in water samples from the Chesapeake Bay. Virus counts ranged from 2.6 x 106 to 1.4 x 108 viruses per ml and averaged 2.5 x 107 viruses per ml. Virus counts were usually at least three times higher than bacterial counts from the same samples. Virus concentrations were highest in August and October and lowest in April and September. The high virus counts suggest that viruses may be an important factor influencing bacterial populations in the Chesapeake Bay through infection.
Sulphate and Hardness_Elphick et al_ET&CGuy Gilron
This document presents the results of a study evaluating the chronic toxicity of sulfate in various aquatic organisms. A variety of test species, including invertebrates, fish, algae, moss, and an amphibian, were exposed to sulfate under different water hardness conditions. The results show that sulfate toxicity decreases with increasing water hardness. Based on these findings, the authors calculated water quality guidelines for sulfate separately for soft, moderately hard, and hard water. The guidelines ranged from 75 to 725 mg/L sulfate depending on the water hardness and calculation method. The study provides a robust dataset that can be used to establish scientifically defensible sulfate guidelines that account for the modifying effect of water hardness.
Otolith Poster - Melissa Pappas.pptx - Google SlidesMelissa Pappas
This study compared the effectiveness of oxytetracycline (OTC) and calcein for marking fish otoliths to aid in age validation. Juvenile pinfish were immersed in various concentrations of OTC or calcein for different time periods. Their otoliths were later examined under fluorescence microscopy. Results showed calcein produced stronger marks than OTC. Higher calcein concentrations and using a NaCl solution improved mark strength. Calcein marks remained clearly visible over several months. This technique can help scientists accurately determine the age of fish by marking otoliths at a known time.
BIS2C. Biodiversity and the Tree of Life. 2014. L13. FungiJonathan Eisen
This document contains lecture slides about fungi. It begins with an outline of the lecture topics, which are an introduction to fungi, their diversity of forms, phylogenetic diversity, and symbioses. The slides then cover the defining characteristics of fungi, examples of fungal diversity including yeasts, molds, and mushrooms, fungal reproduction through spores and sexual reproduction, the phylogeny of fungi, and a classification table of major fungal groups. Practice exam questions are also included about topics covered in previous lectures.
This document summarizes a lecture on how different parts of genomes and cells can have different evolutionary histories. It discusses how endosymbiosis led to the origins of mitochondria and chloroplasts from ancient bacteria. Phylogenetic analysis of mitochondrial and chloroplast genes supports a single origin for each from ancient endosymbiotic events, though some lineages have since lost these organelles. The distribution and trees of chloroplasts and mitochondria do not always match the nuclear genome tree.
Evolution of microbiomes and the evolution of the study and politics of micro...Jonathan Eisen
The document discusses the evolution of microbiomes and the study of microbiomes. It notes that microbiomes can be both overhyped yet underappreciated. It provides background on the rise of interest in microbiomes since the 2000s due to technological advances enabling their study as well as appreciation of their important functions. The author then discusses their own research focusing on using phylogenomic methods to study microbial communities and symbioses, especially how microbes and microbiomes help hosts adapt to stress. Examples discussed include chemosymbioses, pathogen resistance, environmental changes, and more.
This document is a dissertation submitted in partial fulfillment of a Bachelor's degree in environmental sciences. It presents the results of a study monitoring the phytoplankton communities in a eutrophic Irish lake over a 6-month period from January to July 2012. Phytoplankton assemblages were found to follow clear seasonal successional patterns related to changing water quality and nutrient conditions. Their composition supported the lake's status as healthy but bordering on mesotrophic/eutrophic. The study evaluated phytoplankton as biological indicators for monitoring water quality and ecological status under the EU Water Framework Directive.
This document contains slides from a lecture on chordates. It discusses the key characteristics of chordates like the notochord and dorsal hollow nerve cord. It covers the three major chordate groups: lancelets, tunicates, and vertebrates. Lancelets retain many chordate features throughout life. Tunicates resemble chordates as larvae but undergo metamorphosis and lose most features as adults. Many slides show examples of symbiosis in chordates and other animals.
This document discusses exam responses on topics related to carbon and nitrogen cycling. It provides feedback on common mistakes and omissions in student answers. For example, many students stated carbon is converted to oxygen during photosynthesis rather than being used to produce organic molecules. The document also notes better responses incorporated appropriate scientific terminology and integrated knowledge from the passage with their own biological understanding.
1. Most candidates understood how species conservation could result from selective logging but had difficulty clearly expressing these ideas. Some incorrectly imagined minerals redistributing over long distances from unlogged to logged areas. Most recognized the importance of sufficient time for tree regrowth.
2. Many candidates confused fertilizers and pesticides. Most explained ladybird consumption of greenflies accumulating insecticide but some incorrectly suggested insecticide increasing from greenfly reproduction. Patterns of population changes were often described poorly.
3. Candidates correctly identified interspecific competition but had difficulty calculating growth rate differences between spruce and heather in a control experiment.
This document contains summaries of exam responses on topics related to ecology and succession:
1) Many candidates incorrectly described industrial effluent or slurry spillage instead of the provided explanation of weathered rock for shoreline deposits. Few could apply knowledge of succession to explain climax communities.
2) Most calculated diversity indices correctly but responses varied in interpreting the results. Better responses recognized adaptations allowing Fucus spiralis to outcompete others in its habitat.
3) Some wrote too much about succession where not required, failing to distinguish key points about changes in species numbers and individuals. Most described pioneer species roles but some unnecessary detailed climax communities.
4) Many misinterpreted the provided graph and did
This document provides information about the June 2004 Biology exam for the Cambridge O Level qualification. It includes the following:
1) Details of the multiple choice (Paper 1) and core and extended papers (Papers 2 and 3), including the number and types of questions.
2) Summaries of candidate performance on specific multiple choice questions, identifying common misconceptions or areas of difficulty.
3) Comments on candidate responses to questions on Papers 2 and 3, noting both strengths and weaknesses in understanding of various biology concepts assessed.
This document provides a summary of exam results for a chemistry exam, including statistics on student performance and comments on specific exam questions. It reports that the average student score was 24.35 out of 40, with a standard deviation of 7. Some questions were answered correctly by over 75% of students, while the most difficult question saw many students choosing incorrect answers. Weaker students struggled most with questions involving temperature changes, acid-base reactions, and the sources of nitrogen oxides. The summary identifies common mistakes and misconceptions revealed by students' answers.
This document discusses the increasing recognition of microorganisms in groundwater systems and their impact. It notes that groundwater microbiology is a newly developing field, as groundwater was long considered sterile. Microorganisms are now known to influence groundwater chemistry and the performance of wells. The document outlines some of the functions of microorganisms in groundwater, such as degrading pollutants and impacting water quality. It emphasizes that more understanding is needed of microbial communities and activities in groundwater systems to effectively manage this important water resource.
The document discusses the nitrogen and phosphorus cycles in soil. Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia which is then nitrified by other bacteria into nitrates usable by plants. Phosphorus is slowly released from rocks into soil by weathering and can be added through fertilizer application. The phosphorus cycle has a much lower turnover rate than the nitrogen cycle. Agricultural practices can disrupt these cycles by removing nutrients in crops or excess fertilizer running into rivers, causing eutrophication.
QUESTION 1Atmospheric chemists think that Earth’s first atmosphe.docxJUST36
QUESTION 1
Atmospheric chemists think that Earth’s first atmosphere
A.
contained no oxygen atoms.
B.
was very similar to today’s atmosphere.
C.
consisted of carbon in the form of carbon dioxide.
D.
contained nitrogen in the form of ammonia and nitrogen gas.
E.
consisted of carbon in the form of carbon monoxide.
5 points
QUESTION 2
Paleontologists have found fossils dating back 3.6 billion years. These closely resemble
A.
fungi.
B.
today’s simplest plants.
C.
small invertebrate animals.
D.
blue-green algae present today.
E.
nothing alive today.
5 points
QUESTION 3
Kelps are a form of what group of protists?
A.
dinoflagellates
B.
slime molds
C.
ciliates
D.
water molds
E.
brown algae
5 points
QUESTION 4
Some bacteria can form resting structures called ___________ that can withstand extremes in temperature, moisture, and radiation.
A.
prions
B.
capsids
C.
viroids
D.
endospores
E.
symbionts
5 points
QUESTION 5
Oxygen built up in the atmosphere approximately 2 billion years ago and
A.
could not have occurred without the oxygen coming from outer space.
B.
helped to form the ozone layer that is so important to life today.
C.
destroyed ozone forming more oxygen.
D.
occurred because aerobic organisms required the oxygen.
E.
occurred due to carbon dioxide being split by lightning strikes.
5 points
QUESTION 6
Of the following, which kingdom contains the most diversity in terms of DNA sequences?
A.
Animalia
B.
All of these are approximately equivalently diverse.
C.
Fungi
D.
Plantae
E.
Protista
5 points
QUESTION 7
All but one of the following are false regarding protists. Identify the true statement.
A.
Protists are prokaryotic.
B.
Protists do not have the ability to move on their own.
C.
All protists are single-celled organisms.
D.
Most protists are single-celled organisms; some are multicellular.
E.
Protists have cell walls composed mainly of peptidoglycans.
5 points
QUESTION 8
During which geological era did Pangea break apart?
A.
Paleozoic
B.
Archean
C.
Cenozoic
D.
Proterozoic
E.
Mesozoic
5 points
QUESTION 9
Eukaryotic cells are thought to have
A.
evolved before prokaryotic cells.
B.
first appeared as parts of multicellular organisms.
C.
first appeared with tough cell walls.
D.
developed when mitochondria grew much larger in size that they had been previously.
E.
appeared about 2.1 billion years ago.
5 points
QUESTION 10
When taxonomists classify organisms using a phylogenetic approach, they are most concerned with
A.
ancestral traits.
B.
ingroups.
C.
derived traits.
D.
outgroups.
E.
cladists.
5 points
QUESTION 11
What term is used to indicate a characteristic that is shared and inherited from a common ancestor?
A.
derived trait
B.
homologous trait
C.
outgroups
D.
cladistic trait
E.
analogous trait
5 points
QUESTION 12
The endosymbiont hypothesis suggests that the mitochondria of eukaryotic cells are descended from captured
A.
aerobic bacteria.
B.
eukaryotic algae.
C.
archaebacteria.
D.
chemoautotr ...
l) Give several pieces of evidence that RNA preceded proteins and DNA.pdfezzi552
Given the following information for Nugget Corporation, answer the questions below.
November
December
January
February
March
Sales
$300,000
$250,000
$275,000
$325,000
$350,000
Cash collected in month of sale
10%
Credit collections:
Collected in month of sale
10%
Collected in month following the sale
75%
Collected in second month following the sale
15%
Each question should have one amount in the answer field.
You must format your answers as follows: $x,xxx
Total collections from cash sales for the quarter ending March 31, 2018.
Total collections from credit sales for the quarter ending March 31, 2018.
November
December
January
February
March
Sales
$300,000
$250,000
$275,000
$325,000
$350,000
Solution
1) Total collections from cash sales for the quarter ending March 31, 2018 $ 95,000
Working: January February March Total Sales $ 2,75,000
$ 3,25,000 $ 3,50,000 Cash Sales @ 10% $ 27,500 $ 32,500 $
35,000 $ 95,000 2) Total collections from credit sales for the
quarter ending March 31, 2018 $ 5,27,625 Working: November December
January February March Total Sales $ 3,00,000 $ 2,50,000 $ 2,75,000 $ 3,25,000 $
3,50,000 Credit Sales @ 90% $ 2,70,000 $ 2,25,000 $ 2,47,500 $ 2,92,500 $
3,15,000 Collection of credit sales in the month of: November
$ 27,000 December $ 2,02,500 $ 22,500 January $ 40,500
$ 1,68,750 $ 24,750 February $ 33,750 $ 1,85,625 $ 29,250 March
$ 37,125 $ 2,19,375 $ 31,500 Total $ 2,47,500 $ 2,48,625 $ 31,500 $
5,27,625.
QUESTION 1Which ecological niche described below possesses the gre.pdfeyevisioncare1
QUESTION 1
Which ecological niche described below possesses the greatest number of prokaryotic cells
(select one)?
A.
Oceanic and Terrestrial sub-surfaces
B.
In or on non-prokaryotic organisms (humans, animals and plants)
C.
Dry land
D.
Lakes, rivers and oceans
E.
Earth stratosphere
1 points Saved
QUESTION 2
Which organism was primarily responsible for oxygenation of the earth approximately 2 billion
years ago (select one)?
A.
cyanobacteria
B.
Wooly mammoths
C.
Green sulfur bacteria
D.
Thermophilic archaea
E.
algae
1 points Saved
QUESTION 3
The earliest microorganisms were likely restricted to deep ocean and sub-surface ecological
niches until which of the following (select one)?
A.
Ozone layer developed
B.
Aquatic life carried them to land
C.
Phototrophy evolved
D.
Chemolithotrophy developed
E.
The development of chemoorganotrophy
1 points Saved
QUESTION 4
Two tubes are inoculated from one test tube of a bacterial culture. The cultures are then
transferred every day for 2 months. All of the media and growth conditions are the same in every
tube. After 2 months of cultivation, the fitness and genotype frequencies of the populations in the
two tubes are compared. The fitness of the two cultures is the same, but the genotype frequencies
are very different in the two cultures. How is this possible?
A.
This result is not possible because different genotype frequencies would result in different
fitness levels under the same growth conditions.
B.
Genetic drift within the small populations in the test tubes resulted in different genotype
frequencies.
C.
It is highly unlikely that any bacterial culture could be maintained for 2 months
D.
Natural selection caused the evolution of different genotype frequencies within the separate test
tubes.
E.
Two months is not long enough for different fitness levels to evolve even if the genotype
frequencies change.
1 points Saved
QUESTION 5
If you allowed 20 identical parallel Listeria cultures to evolve for 20,000 generations under new
growth conditions with very little nitrogen, the parallel cultures would do which of the following
(select one)?
A.
Direct mutations to occur in nitrogen utilization and uptake genes in order to adapt rapidly to the
culture conditions
B.
Each parallel culture would accumulate different random mutations resulting in different
adaptations to use the nitrogen in the media.
C.
Evolve identical adaptations to use the nitrogen source provided in the media
D.
Not change or adapt significantly over this small number of generations
E.
Each culture would evolve to use arsenic in place of nitrogen
1 points Save Answer
QUESTION 6
Which of the following statements are correct about the early formation of life on earth (select all
that apply)?
A.
Lateral gene transfer is one plausible explanation as to why organisms in Archaea, Bacteria, and
Eukarya still share so many genes among such distinct domains.
B.
The domains of life arose as barriers between gene exchange evolved between organisms
C.
W.
This document is a 16-page exam paper for Life Sciences P2 from February/March 2010. It contains instructions for the exam, which is divided into two sections worth a total of 150 marks and takes 2.5 hours. Section A contains multiple choice and short answer questions testing concepts related to evolution, ecology, genetics and the timeline of life on Earth. Section B includes several longer answer questions requiring explanations and descriptions related to topics like natural selection, Lamarckism, water pollution and plant uses.
test bank Principles of Life Digital Update, 3e by David Hillis, Mary Price, ...NailBasko
This document provides a test bank with questions and answers for Chapter 1 of the textbook "Principles of Life Digital Update, 3e by David Hillis, Mary Price, Richard Hill, David Hall, Marta Laskowski". It includes 53 multiple choice questions testing foundational concepts in biology, such as the definition of life, cellular structure, evolution, and the tree of life. The questions cover topics like the basic unit of life (the cell), the early evolution of life on Earth, the emergence of eukaryotes and multicellular organisms, and the three domain system of classifying life.
This thesis examines the impact of nitrogen on microbial diversity and function in aquatic environments. Chapter 1 provides background on the nitrogen cycle, which is driven by assimilatory and dissimilatory processes conducted primarily by prokaryotes. Human activities have increased the influx of nutrients like nitrogen into waterways through fertilizer use, fossil fuel combustion, and legume cultivation. This can lead to eutrophication and decreased biodiversity. The thesis focuses on the Caloosahatchee River estuary system, which experiences varying freshwater discharge levels affecting nutrient inputs that can disturb biological organization.
This study examined the ability of three bacterial strains - Streptomyces 1, Streptomyces 2, and Bacillus 1 - to precipitate calcite under alkaline conditions. The bacteria were cultured in different media formulations to determine which conditions promoted optimal calcite production while maintaining alkalinity. B4 media with varied carbon, nitrogen, and calcium sources was used. Results showed peptone-based media had higher pH but lower calcite precipitation than glucose-based media. Higher calcium concentration and an alternative media may be needed to further increase calcite formation under alkaline conditions.
This document contains answers to questions about photosynthesis, reproduction in flowering plants, adaptations to habitats, ecosystems, human influences on the environment, and classification and variation from the Cambridge Checkpoint Science Workbook 3. The questions cover topics such as the process of photosynthesis, parts of flowers, dispersal of seeds, food webs, water and air pollution, intensive farming, and indicators of pollution. Diagrams, tables, and graphs are included as part of some answers.
This document discusses restrictions on sharing and distributing an article from a journal published by Elsevier. It can be used by the author for non-commercial research and education purposes, including instruction and sharing with colleagues, but other uses like reproduction, distribution, selling, licensing copies or posting online are prohibited without permission. The document provides a link for authors to check Elsevier's policies on archiving and manuscripts. It then presents the abstract of a research article on using multiple tracers to assess nitrate sources and fate in shallow groundwater of an agricultural area.
1 Humans dogs cats and all species of plant in my garden.pdfaadhi2009
1. Humans, dogs, cats, and all species of plant in my garden can perform anaerobic respiration. a.
TRUE b. FALSE 2. Respiration necessarily involves... a. Air b. Carbohydrates c. An
electrochemical gradient across a membrane d. Oxygen e. All of the above f. None of the above 3.
Over the 4-billion-year history of life on Earth, plants have been mostly responsible for all of the
photosynthesis that has taken place. a. TRUE b. FALSE 4. In the Cyanobacteria lineage, a way of
using H2O as an electron donor evolved. What's the big deal about this? Why was this significant?
Select all that apply. a. It changed the water cycle forever b. It created a source of Oxygen, which
spurred the evolution of other metabolisms that could use it c. It created a source of Oxygen,
which, once it became abundant, changed the redox chemistry of the Earth forever d. Never
before had organisms been able to use light energy as a source of energy and reduced
compounds like NADPH e. This form of photosynthesis would go on to become the dominant form
of carbon fixation on the planet 5. It's unlikely that we'd find the Calvin Cycle in any deep-sea
organisms, down where there is no sunlight to absorb. a. TRUE b. FALSE6. Which of the following
terms would describe an organism that harnesses energy from the sun but does not synthesize its
own carbon-based biomolecules from inorganic sources, such as CO2 ? a. Autotroph b.
Photoautotroph c. Chemoautotroph d. Photoheterotroph e. None of the above 7. Which of the
following should return the most results in a search on Web of Science? a. behavior OR color b.
behavio$r AND colo$r c. behavio $r OR colo$r d. behav* AND colo* e. behav* OR colo* f.
behavior AND color 8. I'm writing my own paper, and I want to cite a paper by Pardis Sabeti and
16 of her colleagues. The reference will appear at the end of my paper in the Works Cited section
as: Sabeti, P. C., Reich, D. E., Higgins, J. M., Levine, H. Z., Richter, D. J., Schaffner, S. F., ... &
Ackerman, H. C. (2002). Detecting recent positive selection in the human genome from haplotype
structure. Nature, 419(6909),832. Which of the following would be an appropriate way to cite this
paper in an in-text citation? Select all that apply. a. We adapted methods used to identify partial
selective sweeps at SNPs (Sabeti et al. 2002). b. We adapted methods used to identify partial
selective sweeps at SNPs (Sabeti, Reich, Higgins, et al. 2002). c. We adapted methods used to
identify partial selective sweeps at SNPs. (Sabeti et al. 2002) d. A variation on this theme was
proposed by (Sabeti et al. 2002) who considered the increase in the number of distinct haplotypes
away from the location of a putative selective sweep. e. A variation on this theme was proposed by
Sabeti et al. (2002) who considered the increase in the number of distinct haplotypes away from
the location of a putative selective sweep.f. A variation on this theme was proposed by Sabeti et
al. (2002) who considered the increase in the.
The document outlines the key processes thought to be necessary for the spontaneous origin of life on Earth: 1) The synthesis of simple organic molecules, as demonstrated by the Miller-Urey experiment; 2) The assembly of these molecules into polymers like polypeptides; 3) A mechanism for inheritance, proposed to be self-replicating RNA; 4) The development of membranes. These processes are hypothesized to have led to the formation of "protobionts", early cell-like structures surrounded by membranes. The endosymbiotic theory proposes that eukaryotic cells arose from engulfed prokaryotes that evolved to become organelles like mitochondria and chloroplasts. Early prokaryotes also produced oxygen as
The study examined the effects of added nitrogen in the form of ammonium sulfate on soil arthropod populations and plant growth. Samples were taken from both a treatment plot with added nitrogen and a control plot without nitrogen over the course of several months. Results showed that mite and springtail populations, soil moisture levels, plant diversity, and plant growth increased to a greater degree in the treatment plot compared to the control. However, more samples would be needed to draw definitive conclusions due to sources of error like inconsistent soil sampling methods between researchers.
1. Energy transfer from forests is disrupted when trees are removed, impacting soil stability, carbon dioxide levels, biodiversity, and rainfall patterns. Deforestation harms local ecosystems.
2. Chemical insecticides accumulate in ladybird bodies through eating greenflies and cannot be excreted, increasing their numbers. Biological control using ladybirds is more stable as numbers fluctuate less with seasons and plants.
3. Two plant species interact through competing for limited resources like light or nutrients. Heather provides nitrogen fixing bacteria that stimulates spruce growth while inhibiting heather.
This document describes a system designed to meet the basic needs of a family of four living in the tropics. The system includes crop plants, solid and liquid waste, cattle, chickens, algae in a shallow pond, and fish. Urine, feces, and crop waste are recycled through various processes involving bacteria, plants, and animals to provide nutrients to crops and meet other needs in a sustainable cycle.
1. Nitrogen cycles through ecosystems via organic compounds, ammonium, nitrites, and nitrates due to the actions of saprophytic bacteria and nitrifying bacteria. Nitrogen-fixing bacteria in root nodules of legumes convert nitrogen to organic compounds that fertilize the plant.
2. Decomposer bacteria release ammonia and nitrifying bacteria convert it to nitrites and nitrates via nitrification. There is competition between microbes for these nitrogen sources.
3. The document outlines scientific marking schemes for content, breadth, relevance, presentation, and use of technical vocabulary. It provides example questions and marking schemes related to ecology, biogeochemical cycles, microbes, and earthworm
The document describes a system designed to meet the basic needs of a family of four living in the tropics. The system uses natural processes to cycle nutrients between different components. Urine and feces from humans and livestock are used to fertilize crop plants through the nitrogen cycle. A fermenter containing bacteria breaks down liquid waste, while solid waste is used directly as fertilizer. Algae in a shallow pond produce carbon dioxide and oxygen, and are eaten by fish which provide a source of protein. This sustainable system recycles resources to grow crops and raise animals.
1. Organic nitrogen is converted to ammonium compounds by decomposers and then to nitrates by nitrifying bacteria for uptake by plant roots. Nitrogen-fixing bacteria convert nitrogen to compounds used by legumes, reducing the need for fertilizer. Shorter food chains produce greater fish yields due to less energy loss between trophic levels.
2. Random quadrats are used to sample plant diversity. Heather affects diversity by providing habitat. Nitrogen is used for non-photosynthetic plant parts and eaten by grouse. Younger plants are more productive. Enzymes are proteins that catalyze reactions without being used up.
3. Earthworm taxonomy is given. Enzymes are not
Deforestation, especially in tropical rainforests over the past 60 years, has contributed to both local decreases in biodiversity and global climate effects. Deforestation and the burning of fossil fuels have increased carbon dioxide levels in the atmosphere and global temperatures. New ideas to address global warming include planting trees on farms to offset industry emissions by acting as carbon sinks, and reducing plowing which allows soil to store more carbon.
This document contains information about nitrogen cycling in soil and forests. It discusses:
1. The roles of decomposers and nitrifying bacteria in breaking down organic matter and converting ammonia to nitrates.
2. How burning forests releases more carbon dioxide into the atmosphere since trees are no longer removing carbon through photosynthesis.
3. Various factors that allow hardwood trees to regenerate more easily than softwoods in areas where forests have been cleared, such as competition for light, temperature and moisture regulation, and nutrient recycling.
Large-scale deforestation leads to environmental problems like soil erosion and decreased biodiversity. Sustainable logging of tropical rainforest helps conserve the ecosystem by only removing mature trees from sectors in sequence, allowing regeneration. Integrated pest management uses both chemical and biological controls, along with other practices, to manage pests in a balanced way while reducing chemical use. Enhancing environmental conditions in greenhouses, like carbon dioxide levels and temperature, can increase crop yields. However, overuse of fertilizers can pollute water sources with nitrates.
This document discusses several topics related to agriculture and ecology:
1. Deforestation can lead to soil erosion, increased carbon dioxide levels, and loss of biodiversity.
2. Using chemical versus biological pest control methods: chemicals fluctuate over time but biological controls are more constant; chemicals may not reach all plants.
3. Interspecific competition was shown between spruce and heather over light and nutrients; spruce grows better when heather is controlled.
4. Speciation occurs when populations become isolated and develop differences over time due to varying environments and natural selection, allowing them to breed but not mix ecologically. Increased diversity supports more niches and food sources.
5. Beach
1. 1. A diagram was provided that showed part of a system designed to meet all basic needs of a
family of four living in the tropics. The system was based in part on the generation of fuel gas
by bacterial fermentation of urine and faeces.
(a) Candidates were asked to describe how processes which naturally formed part of the
nitrogen cycle could make nitrogen contained in urine and faeces available to crop plants.
There were many competent answers that showed detailed knowledge of the relevant
parts of the nitrogen cycle and scored full marks. There were also very weak accounts,
however, that included unselective descriptions of the whole of the nitrogen cycle
including inappropriate references to denitrification and nitrogen fixation. The average
type of response tended to include one or other of the following faults: the assertion that
ammonia was present in urine or faeces; use of the term “nitrogen” in a very loose way
with little reference to specific forms; errors in the sequence of nitrite and nitrate
production; confusion in the nomenclature of the microorganisms involved; lack of
precision concerning uptake of nitrate by plants.
(b) In the system, solid waste from the fermenter was used as fertiliser for crop plants and
candidates were asked to explain the advantage of growing leguminous plants such as
groundnuts or beans. It was evident that many candidates were unfamiliar with
leguminous plants. Answers were often quite weak, with scoring limited to mention of
root nodules (root “noodles” were held to be nutritious, but unacceptable here) and
nitrogen fixing bacteria (with the latter frequently misidentified). There was widespread
belief that nitrate was the product of nitrogen fixation and, in some cases, that the plant
itself fixed the nitrogen. Few candidates appreciated that remains of the legumes would
need to be decomposed before releasing material that could be converted to nitrates and
consequently there were many vague answers such as “legumes return goodness to the
soil”. Ironically, some of those who had discussed nitrogen fixation entirely out of
context in part (a) did not repeat this material which was now relevant.
The question concluded by asking candidates to explain the advantage in the system of
stocking the pond with fish that feed on algae rather than with carnivorous fish. Most
candidates chose to refer, sometimes at undue length, to prevention of eutrophication.
Very few, however, discussed trophic levels in relation to relative energy loss but some
did suggest that stocking with fish that feed on algae would produce a greater yield of
fish. A large number of obscure answers suggested that carnivorous fish would need to be
fed by “bringing meat in” and there was even the occasional idea that the cattle and
chickens would be fed to these fish.
2. In part (a) it was obvious that some candidates had actually done this sort of exercise as they
described in detail how random numbers are generated and used with a grid on the ground to
place the quadrats. A minority of students still described throwing random quadrats but this
method is prone to bias and is not random. The most common error was to omit the method of
generating random numbers.
Hyde Clarendon Sixth Form College 1
2. Many wrote at length in part (b)without focusing on the stages of heather growth given in the
diagram, or failed even to offer an indication of the heather’s age, and vaguely used the terms
‘early’ and ‘late’. The diversity of heather and not of the whole community was a popular
misunderstanding. Some candidates agreed that the diversity would change but failed to say
whether it would get greater or less. Although many did use the information in the table to
explain that increased cover offered by the heather, blocked light and affected diversity. Many
offered other factors such as more nutrients in the soil, but could not easily rationalise how that
occurred.
In part (c)(i) some candidates did manage to calculate the rate but this caused problems for
many. Some demonstrated misunderstandings with the correct notation of SI units. Few read the
question in part (c)(ii)so many did not relate age of the heather to the changing distribution of
green shoots and older woody ones. The most common incorrect response involved a discussion
of the death of parts of the plant. In part (iii) the availability of extra food for grouse was
frequently given, but few related the fact that burning heather eventually increased cover, which
provided the grouse with somewhere to hide. In part (d)(i) many students failed to show an
understanding of the term ‘organic’. This can be the only explanation for responses such as
ammonia, soil, humus, bone and root. Some however did offer protein and few even gave DNA.
Candidates really had a problem with (d)(ii) as phosphate, sodium, and hydrogen ions were
given, this suggested that the candidates read the question as “name an ion” rather than “name
an ion containing nitrogen”. Ammonia and the correct named ion, but with an incorrect
chemical formula, were common mistakes.
In part (e) there was still a great deal of confusion over the role of the bacteria and the sequence
of the nitrogen-containing compounds. The relative positions of ammonium, nitrite and nitrate
ions were regularly switched. Many candidates did, however, correctly name the bacteria
involved in the nitrogen cycle and gave complete and accurate accounts. Saprobiotic bacteria
were rarely mentioned and often the pathway began with the ammonium ions, but with no
mention as to how they were created from organic nitrogenous compounds. Inappropriate
bacteria such as the nitrogen-fixing bacteria were often mentioned, candidates being unable to
identify the relevant parts of the nitrogen cycle and so found it necessary to include everything
they knew.
In part (f) most candidates realised that the table showed changing amounts of nitrogen in the
soil and heather plants, but they were at a loss to explain the reason for burning heather after 8
rather than after 15 years. Few realised the significance of creating gaseous oxides of nitrogen
during burning and thought that burning would place nitrogen directly into the soil.
3. (a) There was a strong centre bias to this part of the question. Candidates were either familiar
with the ways in which organisms were classified or their answers appeared t6 be based
largely on guesses.
Hyde Clarendon Sixth Form College 2
3. (b) In part (i) most candidates appeared to be of the opinion that digestive enzymes were
present in worm casts so that digestion could continue in the soil. Some were of the
opinion that, as worms were primitive animals, they had short guts. They therefore
ingested the casts and passed them through the gut a second time. There were relatively
few references to the key points that the enzymes were not themselves digested and being
proteins they were too large to be absorbed through the gut wall. Some of the answers to
part (ii)showed a good understanding of the basic principles of experimental design, but
far too many simply assumed that demonstration of the presence of reducing sugar or the
absence of starch in worm casts proved the presence of amylase.
(c) Many candidates were content to take the lack of earthworms at face value and made no
attempt to link it in any sensible way to the use of fungicide. Some realised that the
information in the passage about breaking the leaves into smaller pieces was relevant, but
few went on to develop this point further and describe the effect of increased surface area
on the rate of microbial decomposition.
(d) The answers to this part of the question were generally poor. Although there were some
references in part (i) to nitrate and ammonium ions, mineralised nitrogen was rarely
described as being more than “nitrogen in mineral form”. The tendency to repeat the
question also characterised many of the answers to part (ii) with excretory nitrogen
generally described as being “nitrogen in excreted products”. Where the answer was
amplified, excretory nitrogen was usually identified as the nitrogen found in faeces.
Evidence from the answers to this part of the question, and elsewhere in the paper, point
to few candidates understanding the differences between the processes of secretion,
excretion and egestion.
(e) The number of times that ammonia appeared in the answer to part (i) suggested that either
few candidates understood the meaning of the word “organic” or that ammonia was
genuinely regarded as an example of an organic compound. Where both of the examples
offered were organic, lipids and carbohydrates often featured. There were, in addition,
many inappropriate references to cells and tissues. Although there were some excellent
answers to part (ii), others reflected a fundamental lack of knowledge on the part of the
candidates concerned or were totally unselective in the material they presented. The
production of ammonia was often omitted, the terms “nitrifying” and “nitrogen-fixing”
were frequently confused and nitrates were too often described as being converted into
nitrites.
(f) In part (i) most candidates showed understanding that the behaviour of earthworms in dry
conditions led to a smaller surface area over which water could be lost. Some,
unfortunately, linked this behaviour to saving energy through a lower rate of respiration,
while others referred to reduced rates of sweating. There were also many sound answers
to part (ii).
Hyde Clarendon Sixth Form College 3
4. (g) Many candidates understood the difficult concept that lowering the C : N ratio could be
achieved either by removing carbon or by adding nitrogen. Unfortunately, the
explanations of how these effects were achieved Were often insufficiently clear to gain
credit. Once again, far too much use was made of unqualified pronouns and many
members of the examining team commented on difficulties in deciding to what “it” was
referring.
4. (a) Weak answers followed the stem of the question and only referred to carbon rather than
considering the form it would take in the atmosphere, namely carbon dioxide. Unclear
responses proposed that ‘slash and burn’ would increase its concentration without
explaining whether it was the ‘slash’, the removal of trees, or ‘burn’, the combustion of
trees, that was responsible for the change. Not all candidates used the allocation of marks
to construct their answer and generally included only the increase due to release of carbon
dioxide from burning. Better candidates identified the reduced uptake of carbon dioxide
since there would be fewer photosynthesising organisms.
(b) The concept tested in this question was secondary succession. Where the role of pioneer
species was identified, clarification was needed since soil already existed from the earlier
presence of organisms. Weak responses produced unnecessary descriptions of primary
succession. Better candidates recognised that recolonisation would occur with seeds and
spores from neighbouring areas although this was not always well expressed. Many
achieved credit by explaining the process of succession and the resultant re-establishment
of a climax community, but there were also many who appeared unfamiliar with the
concept or who could not communicate the main ideas adequately.
(c) This question allowed candidates to demonstrate their ability to interpret information and
apply their knowledge. Thus, good candidates could identify the source of ammonium
compounds in manure, which soil bacteria would be relevant, and what was meant by
crop yield. Many showed a good knowledge of the nitrogen cycle but only the better
candidates considered the role of nitrogen-fixing bacteria. It was not necessary to name a
specific nitrifying bacterium, but where this was done, the bacterium had to be linked to
the appropriate reaction to secure credit.
(d) It was pleasing to see so many candidates familiar with environmental concerns and
conservation, although candidates often failed to express themselves clearly. A large
proportion considered the view of what would be lacking if a forest ecosystem was
removed, rather than the advantages of conserving one, but examiners sought to credit the
concepts. There was a limited appreciation of forests as sustainable resources but frequent
reference to habitats, carbon sinks, species diversity and food chains allowed maximum
credit to be obtained by many.
5. Once again, the nitrogen cycle proved a weak link in the understanding of a large number of
candidates.
Hyde Clarendon Sixth Form College 4
5. (a) More candidates were able to identify process P as denitrification than were able to
identify process Q as nitrogen fixation. Nitrification was a common wrong answer, as
was ammonification, since this refers to the conversion of nitrogen in organic compounds
to ammonia.
(b) Many candidates misread the questions and did not realise that they had to account for the
apparent discrepancy between the amount of ammonia converted to nitrates and the
amount formed by nitrogen fixation. Good candidates knew that ammonia is also formed
by the decomposition of proteins, amino acids, urea and other organic compounds in the
detritus that contain nitrogen.
(c) Most candidates realised that hydrogen is lost and oxygen is gained in the conversion of
ammonia to nitrate.
6. (a) Most candidates knew the mark-release-recapture technique, and were able to describe
the various steps. However, they did not always explain the reasons behind the steps. For
example, they did not always explain that the released insects should be left for a suitable
period of time to allow them to re-integrate with the rest of the population.
(b) (i) Nearly all candidates knew that there would be only one degree of freedom.
(ii) Most candidates knew that the 0.05 level of probability is that most commonly
used in biological analysis to judge statistical significance.
(iii) Responses to this section were generally disappointing. Most candidates were
unable to reason that, because the value for χ2 is greater than the critical value,
then there is a probability of less than one in one thousand that the results are due
to chance. They were uncertain as to whether the difference in values of χ2 implied
that the differences in results are due to chance or due to some biological cause.
They wrote about rejecting a null hypothesis which had not been stated and also
merely that ‘the results are statistically significant’. Candidates should be aware of
2
the logic that, if χ is greater than the critical value, there is only a probability of
(usually one in twenty) that the results are due to chance as the basis for rejecting
any null hypothesis and accepting the experimental hypothesis.
(c) (i) A number of candidates realised that some of the biomass produced in
photosynthesis would be respired by the plant, but very few actually explained that
biomass is lost in the form of carbon dioxide. Most of those who involved
respiration in their answers suggested that energy is lost, which is true, but loss of
energy does not account for the difference in biomass between gross primary
production and net primary production.
Hyde Clarendon Sixth Form College 5
6. (ii) Nearly all knew that a higher net primary production would lead to more dead
plants and so more food for the detritivorous insects.
(iii) Most candidates realised that decomposers would respire compounds from the dead
plant remains, releasing carbon dioxide, which could be taken in by plants to be
used in photosynthesis.
However, only better candidates knew that the decomposers were saprobionts and
supplied details of extra-cellular digestion.
7. (i) Most candidates gained credit for the fact that the fertiliser had leached into the river, but
only the more able explained that it is excess fertiliser that leaches in this way.
(ii) The vast majority of candidates scored highly by correctly recounting the standard
sequence of events in eutrophication.
Hyde Clarendon Sixth Form College 6