chapter 22 a darwinian view of life
Overview
The 22nd chapter of the textbook describes evidence for Darwin's theory of evolution through natural selection and how this explains adaptations of organisms to their surroundings. Adaptations are inherited characteristics that enhance survival and/or reproduction in certain environments. Natural selection is when individuals with certain advantageous inherited traits survive/reproduce at higher rates than other organisms.
Charles Darwin observed and reasoned that (1) genetic variation exists within populations, (2) these variations in traits are heritable, (3) all species can make more offspring than will survive, and (4) there is competition for resources. Some evidence for natural selection includes homologous structures, which exhibit similar structures that were present in a common ancestor, but have different functions. The image below depicts some examples of homology. In contrast, analagous structures are similar in function, but do not share common ancestry because convergent evolution occurred. The textbook shows how evolution is supported by scientific evidence, but also that natural selection is not the only mechanism responsible for evolution.
The 22nd chapter of the textbook describes evidence for Darwin's theory of evolution through natural selection and how this explains adaptations of organisms to their surroundings. Adaptations are inherited characteristics that enhance survival and/or reproduction in certain environments. Natural selection is when individuals with certain advantageous inherited traits survive/reproduce at higher rates than other organisms.
Charles Darwin observed and reasoned that (1) genetic variation exists within populations, (2) these variations in traits are heritable, (3) all species can make more offspring than will survive, and (4) there is competition for resources. Some evidence for natural selection includes homologous structures, which exhibit similar structures that were present in a common ancestor, but have different functions. The image below depicts some examples of homology. In contrast, analagous structures are similar in function, but do not share common ancestry because convergent evolution occurred. The textbook shows how evolution is supported by scientific evidence, but also that natural selection is not the only mechanism responsible for evolution.
Big Ideas
1.A.1 Natural selection is a major mechanism of evolution.
1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics.
Artifact
View the experiment fitting to this chapter on tHesE wOrDs.
Also, see the Virtual Lab Notebook section on this site to view a brief description of the Pom-Pom Lab.
Reflection
The Pom-Pom Lab was a suitable way to present an example of how natural selection works on organisms in populations. Students used forks, knives, spoons, carpets, and fluffy pom-pom balls to model a small ecosystem and examine how the predator and prey populations evolved after several generations. I found that observing exactly how the populations changed, documenting, and graphing our results was very beneficial in becoming knowledgeable about natural selection and Darwin's theory of evolution. I felt accomplished after understanding how the chapter information applied to organisms.
1.A.1 Natural selection is a major mechanism of evolution.
1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics.
Artifact
View the experiment fitting to this chapter on tHesE wOrDs.
Also, see the Virtual Lab Notebook section on this site to view a brief description of the Pom-Pom Lab.
Reflection
The Pom-Pom Lab was a suitable way to present an example of how natural selection works on organisms in populations. Students used forks, knives, spoons, carpets, and fluffy pom-pom balls to model a small ecosystem and examine how the predator and prey populations evolved after several generations. I found that observing exactly how the populations changed, documenting, and graphing our results was very beneficial in becoming knowledgeable about natural selection and Darwin's theory of evolution. I felt accomplished after understanding how the chapter information applied to organisms.
chapter 23 evolution of populations
Overview
This chapter goes into specific detail on how populations vary, evolve, and adapt. Since genetic variation exists within populations, natural selection has the freedom to choose the traits most advantageous, so to speak. Geographic variation means that there are differences in genetic composition of populations separated by a geographic axis, which can produce a cline, or graded change in a character. Formation of new alleles through mutation, alteration of gene position, rapid reproduction, and sexual reproduction all contribute to genetic variation.
This chapter also explains the Hardy-Weinberg principle, a very important concept for biology students. If a population is in Hardy-Weinberg equilibrium, it is not evolving and five conditions must be fulfilled: (1) no mutations, (2) random mating, (3) no natural selection, (4) large population, and (5) no gene flow. Here are the equation that can be used to calculate gene frequencies in a population:
This chapter goes into specific detail on how populations vary, evolve, and adapt. Since genetic variation exists within populations, natural selection has the freedom to choose the traits most advantageous, so to speak. Geographic variation means that there are differences in genetic composition of populations separated by a geographic axis, which can produce a cline, or graded change in a character. Formation of new alleles through mutation, alteration of gene position, rapid reproduction, and sexual reproduction all contribute to genetic variation.
This chapter also explains the Hardy-Weinberg principle, a very important concept for biology students. If a population is in Hardy-Weinberg equilibrium, it is not evolving and five conditions must be fulfilled: (1) no mutations, (2) random mating, (3) no natural selection, (4) large population, and (5) no gene flow. Here are the equation that can be used to calculate gene frequencies in a population:
p + q = 1
p^2 + 2pq + q^2 = 1
p^2 + 2pq + q^2 = 1
Usually, populations do not find themselves in Hardy-Weinberg equilibrium because natural selection, genetic drift, and gene flow can alter allele frequencies. Genetic drift causes unpredictable fluctuations in allele frequencies from one generation to the next, most dramatically in small populations. Gene flow means that alleles transfer into or out of a population due to movement of individuals.
Other types of selection exist as well. Sexual selection, when individuals with certain characteristics are more likely to get mates, also contributes to adaptive evolution. Directional selection favors individuals on one extreme of a phenotypic range, while stabilizing selection acts against both extremes and favors the intermediate trait. Disruptive selection favors individuals at both extremes over the intermediates. Please study the images below to visualize these concepts.
Other types of selection exist as well. Sexual selection, when individuals with certain characteristics are more likely to get mates, also contributes to adaptive evolution. Directional selection favors individuals on one extreme of a phenotypic range, while stabilizing selection acts against both extremes and favors the intermediate trait. Disruptive selection favors individuals at both extremes over the intermediates. Please study the images below to visualize these concepts.
Big Ideas
1.A.1 Natural selection is a major mechanism of evolution.
1.A.2 Natural selection acts on phenotypic variations in populations.
1.A.3 Evolutionary change is also driven by random processes.
3.C.1 Changes in genotype can result in changes in phenotype.
4.C.3 The level of variation in a population affects population dynamics.
4.C.4 The diversity of species within an ecosystem may influence the stability of an ecosystem.
Artifact
Click on the files below to see a list of important terms and images as well as questions and answers from the reading guide for this chapter.
1.A.1 Natural selection is a major mechanism of evolution.
1.A.2 Natural selection acts on phenotypic variations in populations.
1.A.3 Evolutionary change is also driven by random processes.
3.C.1 Changes in genotype can result in changes in phenotype.
4.C.3 The level of variation in a population affects population dynamics.
4.C.4 The diversity of species within an ecosystem may influence the stability of an ecosystem.
Artifact
Click on the files below to see a list of important terms and images as well as questions and answers from the reading guide for this chapter.
ch23_terminology.pdf | |
File Size: | 293 kb |
File Type: |
ch23_readingguide.pdf | |
File Size: | 1370 kb |
File Type: |
Reflection
Both the list of terms that needed to be defined and the reading guide with questions and images helped me tremendously to understand this chapter. The reading guide gave a short overview of the most important aspects of the chapter, while the list of terminology gave a shorter one still. This reading guide truly helped me to grasp the Hardy-Weinberg principle, because after reading and even taking notes on that section, I did not understand it fully. The reading guide almost always gives me more clear perception of the info.
Both the list of terms that needed to be defined and the reading guide with questions and images helped me tremendously to understand this chapter. The reading guide gave a short overview of the most important aspects of the chapter, while the list of terminology gave a shorter one still. This reading guide truly helped me to grasp the Hardy-Weinberg principle, because after reading and even taking notes on that section, I did not understand it fully. The reading guide almost always gives me more clear perception of the info.
chapter 24 the origin of species
Overview
Speciation : process by which one species splits into two or more. Reproductive isolation is when biological factors prevent different species from interbreeding. Prezygotic barriers block fertilization or mating and postzygotic barriers prevent development or the fertility of hybrids. If two populations become reproductively isolated, they will experience speciation.
Allopatric speciation occurs when gene flow between populations becomes interrupted after division into geographically isolated subpopulations. Geographic separation causes a divergence in the gene pools. Reproductive isolation increases as distance between populations increases. Sympatric speciation, on the other hand, occurs in populations of the same area and is also less common. Polyploidy, or extra sets of chromosomes, may sometimes cause species differentiation (mostly in plants). Autopolyploidy could produce a tetraploid that can self-pollinate or mate with other tetraploids. Allopolyploidy could result from two different species making sterile offspring, which could reproduce asexually, and tehn make a fertile polyploid in subsequent generations. Habitat differentiation and sexual selection can also contribute to sympatric speciation.
Hybrid zones, regions in which members of different populations meet and mate, show mating patterns, differences in allel frequencies, and the development of species. In reinforcement, natural selection strengthens prezygotic barriers if hybrids turn out less fit than the original species. In fusion, reproductive barriers lessen and the populations can fuse into one. In a stable situation, hybrids will continue to be formed because they survive well or barriers to reproduction change.
Big Ideas
1.C.1 Speciation and extinction have occurred throughout the Earth's history.
1.C.2 Speciation may occur when two populations become reproductively isolated from each other.
1.C.3 Populations of organisms continue to evolve.
2.E.2 Timing and coordination of physiological events are regulated by multiple mechanisms.
Artifact
Click below to see a list of terms and pictures for Chapter 24.
Speciation : process by which one species splits into two or more. Reproductive isolation is when biological factors prevent different species from interbreeding. Prezygotic barriers block fertilization or mating and postzygotic barriers prevent development or the fertility of hybrids. If two populations become reproductively isolated, they will experience speciation.
Allopatric speciation occurs when gene flow between populations becomes interrupted after division into geographically isolated subpopulations. Geographic separation causes a divergence in the gene pools. Reproductive isolation increases as distance between populations increases. Sympatric speciation, on the other hand, occurs in populations of the same area and is also less common. Polyploidy, or extra sets of chromosomes, may sometimes cause species differentiation (mostly in plants). Autopolyploidy could produce a tetraploid that can self-pollinate or mate with other tetraploids. Allopolyploidy could result from two different species making sterile offspring, which could reproduce asexually, and tehn make a fertile polyploid in subsequent generations. Habitat differentiation and sexual selection can also contribute to sympatric speciation.
Hybrid zones, regions in which members of different populations meet and mate, show mating patterns, differences in allel frequencies, and the development of species. In reinforcement, natural selection strengthens prezygotic barriers if hybrids turn out less fit than the original species. In fusion, reproductive barriers lessen and the populations can fuse into one. In a stable situation, hybrids will continue to be formed because they survive well or barriers to reproduction change.
Big Ideas
1.C.1 Speciation and extinction have occurred throughout the Earth's history.
1.C.2 Speciation may occur when two populations become reproductively isolated from each other.
1.C.3 Populations of organisms continue to evolve.
2.E.2 Timing and coordination of physiological events are regulated by multiple mechanisms.
Artifact
Click below to see a list of terms and pictures for Chapter 24.
ch24_terminology.pdf | |
File Size: | 312 kb |
File Type: |
Reflection
For the chapters on evolution, students defined a number of terms and drew pictures to represent these terms. A large poster was made with each term and picture on it. This was very useful, because students worked together cooperatively to create images that would explain the term in a coherent way. Thinking and working together to understand the terms in Chapter 24 contributed to a well-rounded learning technique. The poster also served as a study tool if needed.
For the chapters on evolution, students defined a number of terms and drew pictures to represent these terms. A large poster was made with each term and picture on it. This was very useful, because students worked together cooperatively to create images that would explain the term in a coherent way. Thinking and working together to understand the terms in Chapter 24 contributed to a well-rounded learning technique. The poster also served as a study tool if needed.
chapter 25 the history of life on earth
Overview
The conditions on early Earth made the origin of life possible. Organic compounds needed to be made, macromolecules had to come about, and protocells had to spontaneously form to allow for the beginning of life on Earth. RNA formed and was stable enough to persist and even act as a ribozyme.
The fossil record helps to document the history of life. It shows when different organisms lived and died through the application of radiometric dating. Of course it is very incomplete because only some organisms could become fossilized and studied later on.
Important events in life's history are the origins of unicellular and multicellular organisms, as well as the colonization of land. The first organisms were prokayotes, which evolved to perform photosynthesis and respiration after the oxygen revolution. The first eukaryotes came along and created a mutually beneficial relationship with prokaryotes, called the endosymbiont theory (see image below!). The earliest multicellular organisms were small algae, ca. 1.5 billion years ago. The Cambrian explosion was the sudden appearance fo present-day animal phyla in fossils from about 525 million years ago. The colonization of land obviously presents a very important step in the evolution of life on Earth.
Mass exinctions shaped the history of life as well. Extinctions erased many species and also made room for new ones to radiate where old ones had been. The Cretaceous extinction (65.5 mya), for example, allowed mammals to radiate.
Developmental genes play a large role in major changes in body form. The regulation of these genes occurs and homeotic genes play a major part in that process. Changes in regulation may have resulted in different species. Also, just to put things into perspective for us humans, if the Earth's life of 4.6 billion years were downsized to 24 hours, then humans would have come around a couple of seconds ago. This Earth is bigger than us. And it will go on without us.
The conditions on early Earth made the origin of life possible. Organic compounds needed to be made, macromolecules had to come about, and protocells had to spontaneously form to allow for the beginning of life on Earth. RNA formed and was stable enough to persist and even act as a ribozyme.
The fossil record helps to document the history of life. It shows when different organisms lived and died through the application of radiometric dating. Of course it is very incomplete because only some organisms could become fossilized and studied later on.
Important events in life's history are the origins of unicellular and multicellular organisms, as well as the colonization of land. The first organisms were prokayotes, which evolved to perform photosynthesis and respiration after the oxygen revolution. The first eukaryotes came along and created a mutually beneficial relationship with prokaryotes, called the endosymbiont theory (see image below!). The earliest multicellular organisms were small algae, ca. 1.5 billion years ago. The Cambrian explosion was the sudden appearance fo present-day animal phyla in fossils from about 525 million years ago. The colonization of land obviously presents a very important step in the evolution of life on Earth.
Mass exinctions shaped the history of life as well. Extinctions erased many species and also made room for new ones to radiate where old ones had been. The Cretaceous extinction (65.5 mya), for example, allowed mammals to radiate.
Developmental genes play a large role in major changes in body form. The regulation of these genes occurs and homeotic genes play a major part in that process. Changes in regulation may have resulted in different species. Also, just to put things into perspective for us humans, if the Earth's life of 4.6 billion years were downsized to 24 hours, then humans would have come around a couple of seconds ago. This Earth is bigger than us. And it will go on without us.
Big Ideas
1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics.
1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organsims today.
1.C.1 Speciation and extinction have occured throughout the Earth's history.
1.D.1 There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence.
4.B.4 Distribution of local and global ecosystems changes over time.
Artifact
Reading guide for Chapter 25:
1.A.4 Biological evolution is supported by scientific evidence from many disciplines, including mathematics.
1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organsims today.
1.C.1 Speciation and extinction have occured throughout the Earth's history.
1.D.1 There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence.
4.B.4 Distribution of local and global ecosystems changes over time.
Artifact
Reading guide for Chapter 25:
ch25_readingguide.pdf | |
File Size: | 1297 kb |
File Type: |
Reflection
Reflecting on another reading guide does not make me happy. I would rather reflect on the insignificance of humans. Many of us believe that humans are the greatest thing that happened since oxygen. But honestly, humans have become an absolute nuisance for Earth and every other animal that lives here. Aside from some huge differences that we will subtly put aside here, the human species shares some significant qualities with viruses. Viruses invade a host, control its resources, multiply rapidly, and destroy the very thing that provides them with the ability to survive. Humans exploit all resources they believe belong to them, reproduce until they fill cities, towns, and large areas, and simultaneously ruin the home that they rely on. Nature does not need us. We need nature. And if we believe that we even have the ability to destroy the Earth, then we are being delusional. After five mass extinctions, Earth still exists and organisms still evolve. Earth will survive us. No question about it.
Reflecting on another reading guide does not make me happy. I would rather reflect on the insignificance of humans. Many of us believe that humans are the greatest thing that happened since oxygen. But honestly, humans have become an absolute nuisance for Earth and every other animal that lives here. Aside from some huge differences that we will subtly put aside here, the human species shares some significant qualities with viruses. Viruses invade a host, control its resources, multiply rapidly, and destroy the very thing that provides them with the ability to survive. Humans exploit all resources they believe belong to them, reproduce until they fill cities, towns, and large areas, and simultaneously ruin the home that they rely on. Nature does not need us. We need nature. And if we believe that we even have the ability to destroy the Earth, then we are being delusional. After five mass extinctions, Earth still exists and organisms still evolve. Earth will survive us. No question about it.