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I found this on a forest in Mexico City. It was kind of a warm day (around 15°C). It had been raining a few days prior and it was quite humid, but not suffocating.
This orange thing was on top of a rotting tree. I thought it could be Dictydiaethalium… maybe.
When I moved it it produced an orange slime.
Could these be Mycetozoa? - Biology
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Welcome to Ask A Biologist. This site has a large collection of biology learning materials that includes stories, games, activities, videos, and a podcast.
How life evolved: 10 steps to the first cells
We may never be able to prove beyond any doubt how life first evolved. But of the many explanations proposed, one stands out – the idea that life evolved in hydrothermal vents deep under the sea. Not in the superhot black smokers, but more placid affairs known as alkaline hydrothermal vents.
This theory can explain life’s strangest feature, and there is growing evidence to support it.
Earlier this year, for instance, lab experiments confirmed that conditions in some of the numerous pores within the vents can lead to high concentrations of large molecules. This makes the vents an ideal setting for the “RNA world” widely thought to have preceded the first cells.
If life did evolve in alkaline hydrothermal vents, it might have happened something like this&colon
Water percolated down into newly formed rock under the seafloor, where it reacted with minerals such as olivine, producing a warm alkaline fluid rich in hydrogen, sulphides and other chemicals – a process called serpentinisation.
This hot fluid welled up at alkaline hydrothermal vents like those at the Lost City, a vent system discovered near the Mid-Atlantic Ridge in 2000.
Unlike today’s seas, the early ocean was acidic and rich in dissolved iron. When upwelling hydrothermal fluids reacted with this primordial seawater, they produced carbonate rocks riddled with tiny pores and a “foam” of iron-sulphur bubbles.
Inside the iron-sulphur bubbles, hydrogen reacted with carbon dioxide, forming simple organic molecules such as methane, formate and acetate. Some of these reactions were catalysed by the iron-sulphur minerals. Similar iron-sulphur catalysts are still found at the heart of many proteins today.
The electrochemical gradient between the alkaline vent fluid and the acidic seawater leads to the spontaneous formation of acetyl phosphate and pyrophospate, which act just like adenosine triphosphate or ATP, the chemical that powers living cells.
These molecules drove the formation of amino acids – the building blocks of proteins – and nucleotides, the building blocks for RNA and DNA.
Thermal currents and diffusion within the vent pores concentrated larger molecules like nucleotides, driving the formation of RNA and DNA – and providing an ideal setting for their evolution into the world of DNA and proteins. Evolution got under way, with sets of molecules capable of producing more of themselves starting to dominate.
Fatty molecules coated the iron-sulphur froth and spontaneously formed cell-like bubbles. Some of these bubbles would have enclosed self-replicating sets of molecules – the first organic cells. The earliest protocells may have been elusive entities, though, often dissolving and reforming as they circulated within the vents.
The evolution of an enzyme called pyrophosphatase, which catalyses the production of pyrophosphate, allowed the protocells to extract more energy from the gradient between the alkaline vent fluid and the acidic ocean. This ancient enzyme is still found in many bacteria and archaea, the first two branches on the tree of life.
Some protocells started using ATP as well as acetyl phosphate and pyrophosphate. The production of ATP using energy from the electrochemical gradient is perfected with the evolution of the enzyme ATP synthase, found within all life today.
Protocells further from the main vent axis, where the natural electrochemical gradient is weaker, started to generate their own gradient by pumping protons across their membranes, using the energy released when carbon dioxide reacts with hydrogen.
This reaction yields only a small amount of energy, not enough to make ATP. By repeating the reaction and storing the energy in the form of an electrochemical gradient, however, protocells “saved up” enough energy for ATP production.
Once protocells could generate their own electrochemical gradient, they were no longer tied to the vents. Cells left the vents on two separate occasions, with one exodus giving rise to bacteria and the other to archaea.
Transgender Ideology Is Riddled With Contradictions. Here Are the Big Ones.COMMENTARY BY
Former Senior Research FellowNow, activists claim that gender identity is destiny, while biological sex is the social construct. itakdalee/Getty Images
People say that we live in a postmodern age that has rejected metaphysics. That’s not quite true.
We live in a postmodern age that promotes an alternative metaphysics. As I explain in “When Harry Became Sally,” at the heart of the transgender moment are radical ideas about the human person—in particular, that people are what they claim to be, regardless of contrary evidence. A transgender boy is a boy, not merely a girl who identifies as a boy.
It’s understandable why activists make these claims. An argument about transgender identities will be much more persuasive if it concerns who someone is, not merely how someone identifies. And so the rhetoric of the transgender moment drips with ontological assertions: People are the gender they prefer to be. That’s the claim.
Transgender activists don’t admit that this is a metaphysical claim. They don’t want to have the debate on the level of philosophy, so they dress it up as a scientific and medical claim. And they’ve co-opted many professional associations for their cause.
Thus the American Psychological Association, in a pamphlet titled “Answers to Your Questions about Transgender People, Gender Identity, and Gender Expression,” tells us, “Transgender is an umbrella term for persons whose gender identity, gender expression, or behavior does not conform to that typically associated with the sex to which they were assigned at birth.”
Notice the politicized language: A person’s sex is “assigned at birth.” Back in 2005, even the Human Rights Campaign referred instead to “birth sex” and “physical sex.”
The phrase “sex assigned at birth” is now favored because it makes room for “gender identity” as the real basis of a person’s sex.
In an expert declaration to a federal district court in North Carolina concerning H.B. 2, Dr. Deanna Adkins stated, “From a medical perspective, the appropriate determinant of sex is gender identity.” Adkins is a professor at Duke University School of Medicine and the director of the Duke Center for Child and Adolescent Gender Care (which opened in 2015).
Adkins argues that gender identity is not only the preferred basis for determining sex, but “the only medically supported determinant of sex.” Every other method is bad science, she claims: “It is counter to medical science to use chromosomes, hormones, internal reproductive organs, external genitalia, or secondary sex characteristics to override gender identity for purposes of classifying someone as male or female.”
This is a remarkable claim, not least because the argument recently was that gender is only a social construct, while sex is a biological reality. Now, activists claim that gender identity is destiny, while biological sex is the social construct.
Adkins doesn’t say if she would apply this rule to all mammalian species. But why should sex be determined differently in humans than in other mammals? And if medical science holds that gender identity determines sex in humans, what does this mean for the use of medicinal agents that have different effects on males and females? Does the proper dosage of medicine depend on the patient’s sex or gender identity?
But what exactly is this “gender identity” that is supposed to be the true medical determinant of sex? Adkins defines it as “a person’s inner sense of belonging to a particular gender, such as male or female.”
Note that little phrase “such as,” implying that the options are not necessarily limited to male or female. Other activists are more forthcoming in admitting that gender identity need not be restricted to the binary choice of male or female, but can include both or neither. The American Psychological Association, for example, defines “gender identity” as “a person’s internal sense of being male, female, or something else.”
Adkins asserts that being transgender is not a mental disorder, but simply “a normal developmental variation.” And she claims, further, that medical and mental health professionals who specialize in the treatment of gender dysphoria are in agreement with this view.
These notions about sex and gender are now being taught to young children. Activists have created child-friendly graphics for this purpose, such as the “Genderbread Person.” The Genderbread Person teaches that when it comes to sexuality and gender, people have five different characteristics, each of them falling along a spectrum.
There’s “gender identity,” which is “how you, in your head, define your gender, based on how much you align (or don’t align) with what you understand to be the options for gender.” The graphic lists “4 (of infinite)” possibilities for gender identity: “woman-ness,” “man-ness,” “two-spirit,” or “genderqueer.”
The second characteristic is “gender expression,” which is “the way you present gender, through your actions, dress, and demeanor.” In addition to “feminine” or “masculine,” the options are “butch,” “femme,” “androgynous,” or “gender neutral.”
Third is “biological sex,” defined as “the physical sex characteristics you’re born with and develop, including genitalia, body shape, voice pitch, body hair, hormones, chromosomes, etc.”
The final two characteristics concern sexual orientation: “sexually attracted to” and “romantically attracted to.” The options include “Women/Females/Femininity” and “Men/Males/Masculinity.” Which seems rather binary.
The Genderbread Person tries to localize these five characteristics on the body: gender identity in the brain, sexual and romantic attraction in the heart, biological sex in the pelvis, and gender expression everywhere.
The Genderbread Person espouses the latest iteration of transgender ideology. (Photo: Sam Killerman/It’s Prounounced Metrosexual)
The Genderbread Person presented here is version 3.3, incorporating adjustments made in response to criticism of earlier versions. But even this one violates current dogma. Some activists have complained that the Genderbread Person looks overly male.
A more serious fault in the eyes of many activists is the use of the term “biological sex.” Time magazine drew criticism for the same transgression in 2014 after publishing a profile of Laverne Cox, the “first out trans person” to be featured on the cover.
At least the folks at Time got credit for trying to be “good allies, explaining what many see as a complicated issue,” wrote Mey Rude in an article titled “It’s Time for People to Stop Using the Social Construct of ‘Biological Sex’ to Defend Their Transmisogyny.” (It’s hard to keep up with the transgender moment.)
But Time was judged guilty of using “a simplistic and outdated understanding of biology to perpetuate some very dangerous ideas about trans women,” and failing to acknowledge that biological sex “isn’t something we’re actually born with, it’s something that doctors or our parents assign us at birth.”
Today, transgender “allies” in good standing don’t use the Genderbread Person in their classrooms, but opt for the “Gender Unicorn,” which was created by Trans Student Educational Resources. It has a body shape that doesn’t appear either male or female, and instead of a “biological sex” it has a “sex assigned at birth.”
Those are the significant changes to the Genderbread Person, and they were made so that the new graphic would “more accurately portray the distinction between gender, sex assigned at birth, and sexuality.”
According to Trans Student Education Resources, “Biological sex is an ambiguous word that has no scale and no meaning besides that it is related to some sex characteristics. It is also harmful to trans people. Instead, we prefer ‘sex assigned at birth’ which provides a more accurate description of what biological sex may be trying to communicate.”
The Gender Unicorn is the graphic that children are likely to encounter in school. These are the dogmas they are likely to be catechized to profess.
The Gender Unicorn is used to avoid using a male or female body as default. (Photo: Landyn Pan and Anna Moore/Trans Student Educational Resources)
While activists claim that the possibilities for gender identity are rather expansive—man, woman, both, neither—they also insist that gender identity is innate, or established at a very young age, and thereafter immutable.
Dr. George Brown, a professor of psychiatry and a three-time board member of the World Professional Association for Transgender Health, stated in his declaration to the federal court in North Carolina that gender identity “is usually established early in life, by the age of 2 to 3 years old.”
Addressing the same court, Adkins asserted that “evidence strongly suggests that gender identity is innate or fixed at a young age and that gender identity has a strong biological basis.” (At no point in her expert declaration did she cite any sources for any of her claims.)
If the claims presented in this essay strike you as confusing, you’re not alone. The thinking of transgender activists is inherently confused and filled with internal contradictions. Activists never acknowledge those contradictions. Instead, they opportunistically rely on whichever claim is useful at any given moment.
Here I’m talking about transgender activists. Most people who suffer from gender dysphoria are not activists, and many of them reject the activists’ claims. Many of them may be regarded as victims of the activists, as I show in my book.
Many of those who feel distress over their bodily sex know that they aren’t really the opposite sex, and do not wish to “transition.” They wish to receive help in coming to identify with and accept their bodily self. They don’t think their feelings of gender dysphoria define reality.
But transgender activists do. Regardless of whether they identify as “cisgender” or “transgender,” the activists promote a highly subjective and incoherent worldview.
On the one hand, they claim that the real self is something other than the physical body, in a new form of Gnostic dualism, yet at the same time they embrace a materialist philosophy in which only the material world exists. They say that gender is purely a social construct, while asserting that a person can be “trapped” in the wrong gender.
They say there are no meaningful differences between man and woman, yet they rely on rigid sex stereotypes to argue that “gender identity” is real, while human embodiment is not. They claim that truth is whatever a person says it is, yet they believe there’s a real self to be discovered inside that person.
They promote a radical expressive individualism in which people are free to do whatever they want and define the truth however they wish, yet they try ruthlessly to enforce acceptance of transgender ideology.
It’s hard to see how these contradictory positions can be combined. If you pull too hard on any one thread of transgender ideology, the whole tapestry comes unraveled. But here are some questions we can pose:
If gender is a social construct, how can gender identity be innate and immutable? How can one’s identity with respect to a social construct be determined by biology in the womb? How can one’s identity be unchangeable (immutable) with respect to an ever-changing social construct? And if gender identity is innate, how can it be “fluid”?
The challenge for activists is to offer a plausible definition of gender and gender identity that is independent of bodily sex.
Is there a gender binary or not? Somehow, it both does and does not exist, according to transgender activists. If the categories of “man” and “woman” are objective enough that people can identify as, and be, men and women, how can gender also be a spectrum, where people can identify as, and be, both, or neither, or somewhere in between?
What does it even mean to have an internal sense of gender? What does gender feel like? What meaning can we give to the concept of sex or gender—and thus what internal “sense” can we have of gender—apart from having a body of a particular sex?
Apart from having a male body, what does it “feel like” to be a man? Apart from having a female body, what does it “feel like” to be a woman? What does it feel like to be both a man and a woman, or to be neither?
The challenge for the transgender activist is to explain what these feelings are like, and how someone could know if he or she “feels like” the opposite sex, or neither, or both.
Even if trans activists could answer these questions about feelings, that still wouldn’t address the matter of reality. Why should feeling like a man—whatever that means—make someone a man? Why do our feelings determine reality on the question of sex, but on little else? Our feelings don’t determine our age or our height. And few people buy into Rachel Dolezal’s claim to identify as a black woman, since she is clearly not.
If those who identify as transgender are the sex with which they identify, why doesn’t that apply to other attributes or categories of being? What about people who identify as animals, or able-bodied people who identify as disabled? Do all of these self-professed identities determine reality? If not, why not?
And should these people receive medical treatment to transform their bodies to accord with their minds? Why accept transgender “reality,” but not trans-racial, trans-species, and trans-abled reality?
The challenge for activists is to explain why a person’s “real” sex is determined by an inner “gender identity,” but age and height and race and species are not determined by an inner sense of identity.
Of course, a transgender activist could reply that an “identity” is, by definition, just an inner sense of self. But if that’s the case, gender identity is merely a disclosure of how one feels. Saying that someone is transgender, then, says only that the person has feelings that he or she is the opposite sex.
Gender identity, so understood, has no bearing at all on the meaning of “sex” or anything else. But transgender activists claim that a person’s self-professed “gender identity” is that person’s “sex.”
The challenge for activists is to explain why the mere feeling of being male or female (or both or neither) makes someone male or female (or both or neither).
Gender identity can sound a lot like religious identity, which is determined by beliefs. But those beliefs don’t determine reality. Someone who identifies as a Christian believes that Jesus is the Christ. Someone who identifies as a Muslim believes that Muhammad is the final prophet. But Jesus either is or is not the Christ, and Muhammad either is or is not the final prophet, regardless of what anyone happens to believe.
So, too, a person either is or is not a man, regardless of what anyone—including that person—happens to believe. The challenge for transgender activists is to present an argument for why transgender beliefs determine reality.
Determining reality is the heart of the matter, and here too we find contradictions.
On the one hand, transgender activists want the authority of science as they make metaphysical claims, saying that science reveals gender identity to be innate and unchanging. On the other hand, they deny that biology is destiny, insisting that people are free to be who they want to be.
Which is it? Is our gender identity biologically determined and immutable, or self-created and changeable? If the former, how do we account for people whose gender identity changes over time? Do these people have the wrong sense of gender at some time or other?
And if gender identity is self-created, why must other people accept it as reality? If we should be free to choose our own gender reality, why can some people impose their idea of reality on others just because they identify as transgender?
The challenge for the transgender activist is to articulate some conception of truth as the basis for how we understand the common good and how society should be ordered.
As I document in depth in “When Harry Became Sally,” the claims of transgender activists are confusing because they are philosophically incoherent. Activists rely on contradictory claims as needed to advance their position, but their ideology keeps evolving, so that even allies and LGBT organizations can get left behind as “progress” marches on.
At the core of the ideology is the radical claim that feelings determine reality. From this idea come extreme demands for society to play along with subjective reality claims. Trans ideologues ignore contrary evidence and competing interests, they disparage alternative practices, and they aim to muffle skeptical voices and shut down any disagreement.
The movement has to keep patching and shoring up its beliefs, policing the faithful, coercing the heretics, and punishing apostates, because as soon as its furious efforts flag for a moment or someone successfully stands up to it, the whole charade is exposed. That’s what happens when your dogmas are so contrary to obvious, basic, everyday truths.
A transgender future is not the “right side of history,” yet activists have convinced the most powerful sectors of our society to acquiesce to their demands. While the claims they make are manifestly false, it will take real work to prevent the spread of these harmful ideas.
Could these be Mycetozoa? - Biology
Graphing Trigonometric Functions
In this section we will explore the graphs of the six trigonometric functions, beginning with the graph of the cosine function.
Graphing y = cos x
To sketch a graph of y = cos x we can make a table of values that we can compute exactly:
We can plot these points and sketch a smooth curve going through them:
Since the domain of the cosine function is all real numbers, we place arrows on the graph to indicate that the graph repeats itself exactly in both directions. The fact that the cosine function repeats itself means that that it is periodic. In particular, y = cos x is periodic with period 2&pi . This means that if the point (x, y) lies on the graph, then the point (x+2k&pi, y) will also lie on the graph where k is any integer. For example, (x + 2&pi, y) and (x &minus 2&pi, y) will both lie on the graph.
Graphing y = sin x
To sketch a graph of y = sin x we can make a table of values that we can compute exactly:
We can plot these points and sketch a smooth curve going through them:
Since the domain of the sine function is all real numbers, we place arrows on the graph to indicate that the graph repeats itself exactly in both directions. Like the cosine function, the sine function is also 2&pi periodic.
Graphing y = tan x
To sketch a graph of y = tan x we can make a table of values that we can compute exactly:
Notice that we now have some undefined functional values graphically, these correspond to vertical asymptotes. We can sketch y = tan x as follows:
In the above graph, the dashed lines indicate vertical asymptotes. We place arrows on the graph to indicate that the function increases to &infin. For example, tan x &rarr &infin as x &rarr (&pi/2) - (i.e. as x approaches &pi/2 from the left) and tan x &rarr &minus&infin as x &rarr (&pi/2) - (i.e. as x approaches &pi/2 from the right). Unlike the sine and cosine functions, the tangent function is &pi periodic. That is, if the point (x, y) lies on the graph of y = tan x so will the point (x + k&pi , y) where k is any integer.
Recall that the secant, cosecant, and cotangent functions are the reciprocals of the cosine, sine, and tangent functions, respectively. You are less likely to encounter these graphs in your studies of the life sciences. We are including these graphs for completeness.
Transforming y = cos x and y = sin x
We will now look at graphical transformations of y = cos x and y = sin x. We can write a transformed cosine and sine function as follows,
We call |a| the amplitude of the function. The amplitude is the distance from the minimum functional value to the maximal functional value divided by 2. The period of the above functions is 2&pi/b (notice when b = 1, the period is 2&pi). When modeling a particular quantity or phenomenon using a sine or cosine function, the amplitude and period are two important features defining the behavior. You can refer to the transformations section to examine the other transformations more closely.
Studying Environmental Science: What is it like and where can it take you?
In a world where global warming, air pollution, and plastic waste are major topical issues, environmental science is becoming an increasingly valued and relevant degree. Although it is a relatively new field, it combines elements of the key traditional fields of chemistry and biology, and is widely recognised as a rigorous and academic degree. However, due to its newness, many people have questions about what studying environmental science is like and where it can lead. This article will answer these questions and a number of other common questions about environmental science.
Environmental science is an interdisciplinary subject, so it will involve studying elements of biology, chemistry, physics, geography and social sciences this can be a challenge as each of these fields requires different skills and knowledge. However, by combining an understanding of all of these areas, students are better able to study the environment from an integrated perspective.
Fieldwork is a key part of studying environmental science. How far you travel for fieldwork is related to your areas of interest – it could involve travelling to different countries to experience a range of habitats and climates or it could be focussing on a particular ecosystem and involve a significant amount of work in a single location.
Laboratory work is also a core element of studying environmental science – as part of the degree, you will learn how to test analyse different samples and interpret the results.
It is also common to do work placements or voluntary work as part of the degree the environmental sector is extremely competitive, and work experience develops valuable skills which are invaluable when job hunting.
As mentioned above, environmental science is interdisciplinary, so topics will draw on different fields to develop understanding.
Core elements of most courses include atmospheric sciences, ecology, environmental chemistry and geosciences.
Atmospheric sciences involves studying the atmosphere, typically covering the chemistry and physics of the atmosphere, and the impact changes can have on ecosystems all over the world. You may also study meteorology.
Ecology focuses on how organisms interact with the environment and each other. This can connect to social sciences as well as biology. Environmental chemistry centres around the impact humans have on the environment and how contamination happens, what its effects are and how it can be prevented.
Geoscience is a very broad field, but focuses on the earth’s natural processes in environmental science, this will involve learning more about the earth to ensure you have a good scientific basis for understanding environmental changes.>
Environmental science is academically rigorous and involves developing a wide range of transferable skills that are very useful in the job market.
It also offers the opportunity to study multiple branches of science and take part in lab and fieldwork as well as more traditional study.
Top universities register a high employment rate for environmental science, and the US Bureau of Labour and Statistic calculates that the growth outlook is higher than average.
If you are interested in working in a related field or even going on to further study, then environmental science is an excellent degree choice.
If your main interest is in biology, a pure biology degree may be a better choice. There will still be the opportunity to choose modules that are related to environmental science, and it will reduce the number of different sciences you are learning about.
However, if you are happy with interdisciplinary study and you are committed to working in the environmental sector then environmental science might be a better option.
It is also important to consider that a pure biology degree will enable you to access some biology-related careers that an environmental science degree wouldn’t qualify you for. This is because studying a single science will result in a much greater understanding of that specific field than a multi-disciplinary approach.
Environmental science is a degree with excellent career prospects, as well as opportunities for further study – around a fifth of students go on to postgraduate study or research. This may also be necessary if you wish to pursue a career in law or graduate education.
Working as an environmental scientist or in a career directly related to the field may require further study, as their person specifications often require a high degree of specialisation. More information about top careers in environmental science can be found here.
However, due to the interdisciplinary nature of the degree, and the range of transferable skills you develop, there is a wide range of career opportunities outside the environmental science field. Common routes for environmental science graduates include resource management, environmental advocacy, teaching and planning and development. These careers allow you to utilize the skills you have developed, but definitely allow you to engage with immediate real-world problems, rather than researching in a laboratory.
Jobs in the environmental sector are typically very competitive and can require specialised study and significant work experience. However, the sector is growing rapidly, and there are a number of careers, such as environmental engineer or scientist where demand is extremely high. Moreover, as the impact of environmental issues such as plastic waste are studied further, the demand for graduates who are able to support sustainability targets is likely to increase.
Moreover, many countries are likely to need to undergo major infrastructure upgrades in the next decade, and environmental considerations will be a major concern.
New graduates are likely to have good career opportunities but will likely join companies in more junior roles in order to be trained up, as many careers have very specific knowledge and skill requirements. This means that starting salaries may be relatively low, but there will be good opportunities to progress and earn more in the future.
One of the things people are often keen to know is whether they ‘need’ a degree in environmental science to start a career in the environmental sector. This may be because they already have a degree or because they’ve started a degree in another subject but have developed an interest in environmental science.
Firstly, it is important to note that many careers in the sector require further study, so it may be possible to pursue a postgraduate qualification in environmental science without an undergraduate degree in the subject. So if your degree isn’t in environmental science but you want to work in the field, there are still options available.
Secondly, an environmental science degree is only advantageous if you want to work in a scientific role. There are many jobs in the green sector which do not require a science background and are accessible to any graduate, with the right volunteer work and enthusiasm.
So if you are in the process of selecting a degree, are keen to study a scientific subject and committed to working in the green sector then an environmental science degree might be the best choice for you. However, it is not the only route into the field: so if you are passionate about the environment and happy to do volunteer work and potentially further study, then you may not need an environmental science degree.
A change in the sequence of bases in DNA or RNA is called a mutation. Does the word mutation make you think of science fiction and bug-eyed monsters? Think again. Everyone has mutations. In fact, most people have dozens or even hundreds of mutations in their DNA. Mutations are essential for evolution to occur. They are the ultimate source of all new genetic material - new alleles - in a species. Although most mutations have no effect on the organisms in which they occur, some mutations are beneficial. Even harmful mutations rarely cause drastic changes in organisms.
Types of Mutations
There are a variety of types of mutations. Two major categories of mutations are germline mutations and somatic mutations.
- Germline mutations occur in gametes. These mutations are especially significant because they can be transmitted to offspring and every cell in the offspring will have the mutation.
- Somatic mutations occur in other cells of the body. These mutations may have little effect on the organism because they are confined to just one cell and its daughter cells. Somatic mutations cannot be passed on to offspring.
Mutations also differ in the way that the genetic material is changed. Mutations may change the structure of a chromosome or just change a single nucleotide.
Chromosomal alterations are mutations that change chromosome structure. They occur when a section of a chromosome breaks off and rejoins incorrectly or does not rejoin at all. Possible ways these mutations can occur are illustrated in Figure below. Go to this link for a video about chromosomal alterations: http://www.youtube.com/watch?v=OrXRSqa_3lU (2:18).
Chromosomal Alterations. Chromosomal alterations are major changes in the genetic material.
Chromosomal alterations are very serious. They often result in the death of the organism in which they occur. If the organism survives, it may be affected in multiple ways. An example of a human chromosomal alteration is the mutation that causes Down Syndrome. It is a duplication mutation that leads to developmental delays and other abnormalities.
A point mutation is a change in a single nucleotide in DNA. This type of mutation is usually less serious than a chromosomal alteration. An example of a point mutation is a mutation that changes the codon UUU to the codon UCU. Point mutations can be silent, missense, or nonsense mutations, as shown in Table below. The effects of point mutations depend on how they change the genetic code. You can watch an animation about nonsense mutations at this link:www.biostudio.com/d_%20Nonsen. 20Mutation.htm.
Type Description Example Effect Silent mutated codon codes for the same amino acid CAA (glutamine) &rarr CAG (glutamine) none Missense mutated codon codes for a different amino acid CAA (glutamine) &rarr CCA (proline) variable Nonsense mutated codon is a premature stop codon CAA (glutamine) &rarr UAA (stop) usually serious
A frameshift mutation is a deletion or insertion of one or more nucleotides that changes the reading frame of the base sequence. Deletions remove nucleotides, and insertions add nucleotides. Consider the following sequence of bases in RNA:
Now, assume an insertion occurs in this sequence. Let&rsquos say an A nucleotide is inserted after the start codon AUG:
Even though the rest of the sequence is unchanged, this insertion changes the reading frame and thus all of the codons that follow it. As this example shows, a frameshift mutation can dramatically change how the codons in mRNA are read. This can have a drastic effect on the protein product.
Polly Share A Cracker? Parrots Can Practice Acts Of Kindness, Study Finds
Recent research has explored "helping" behavior in species ranging from nonhuman primates to rats and bats. To see whether intelligent birds might help out a feathered pal, scientists did an experiment using African grey parrots like these. Henry Lok/EyeEm/Getty Images hide caption
Recent research has explored "helping" behavior in species ranging from nonhuman primates to rats and bats. To see whether intelligent birds might help out a feathered pal, scientists did an experiment using African grey parrots like these.
Henry Lok/EyeEm/Getty Images
Parrots can perform impressive feats of intelligence, and a new study suggests that some of these "feathered apes" may also practice acts of kindness.
African grey parrots voluntarily helped a partner get a food reward by giving the other bird a valuable metal token that could be exchanged for a walnut, according to a newly published report in the journal Current Biology.
"This was really surprising that they did this so spontaneously and so readily," says Désirée Brucks, a biologist at ETH Zürich in Switzerland who is interested in the evolution of altruism.
Children as young as 1 seem highly motivated to help others, and scientists used to think this kind of prosocial behavior was uniquely human. More recent research has explored "helping" behavior in other species, everything from nonhuman primates to rats and bats.
To see whether intelligent birds might help out a feathered pal, Brucks and Auguste von Bayern of the Max Planck Institute for Ornithology in Germany tested African grey parrots. They used parrots that had previously been trained to understand that specific tokens, in the form of small metal rings, could be traded for a food treat through an exchange window.
In their experiment, this exchange window was covered up and closed on one bird's cage, making it impossible for that bird to trade. The bird had a pile of tokens in its cage but no way to use them. Meanwhile, its neighbor in an adjacent cage had an open exchange window — but no tokens for food.
After sizing up the situation, the token-rich bird would help out its pal by passing tokens through an opening between the two bird enclosures. And the bird shared even though it didn't partake in the walnut payoff.
"The African greys gave the token beak-to-beak with their partner," Brucks says. "It was not just one token. Many of them transferred all 10 tokens, one after the other, always watching how their partner got the food for it, whereas they themselves did not get anything."
Later, scientists reversed birds' roles to see if the recipient of this generosity would pay back those favors. And the birds did.
"In the very first trial, they could not have known that the roles would be reversed afterward," says Brucks, who notes that the parrots seemed to have an intrinsic desire to help out their partner. The eight birds tested all knew each other and lived in the same social group.
It seems that the birds weren't just being playful with the tokens, but really understood when and why the token was needed. That's because the birds would rarely pass a token over if the neighbor bird's exchange window was closed up.
This study is a starting point to explore what exactly is going on in the birds' minds, Brucks says.
A similar study in ravens did not find this effect. And when Brucks tested blue-headed macaws, they weren't helpful either. The macaws tried to bring the tokens as close as possible to the experimenter but did not transfer the token to the partner, Brucks says.
"We are really interested in this topic, and it's an important topic. The problem is it's very, very hard to design an experiment to truly demonstrate what is truly going on with these animals," says Irene Pepperberg, a Harvard researcher whose work with a famous African grey parrot named Alex helped reveal the sophisticated cognitive abilities of these birds.
Pepperberg has also done experiments to test African greys' willingness to help, using a different setup, and found that one parrot appeared to have some understanding of sharing — but it didn't seem like the parrots were spontaneously super-altruistic.
Still, Peggy Mason of the University of Chicago believes that this new study in parrots is striking.
"When they gave the token, the other bird was getting the food and they were not," Mason says. "I think they had the sense that this was a useful token, and that this token would turn into food for the other bird. It's very shocking. It's surprisingly giving, just because the only thing the bird doing it gets is that warm glow of helping."
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Examples of a Facultative Anaerobe
A common facultative anaerobe is yeast, used in various cooking applications such as making bread or beer. In either case, this facultative anaerobe must function without oxygen. Yet, the yeast can still survive, and must for these products to come out right.
In bread, yeast is responsible for making the bubbles in the dough. These pockets of air make the bread light and fluffy. Otherwise, the bread would bake into a solid mass more like a cake or brownie. Yeast creates these air pockets through the release of carbon dioxide, a byproduct of converting the glucose in the dough into energy. For a lighter, more airy dough chefs often let the dough “rise”. This term simply means setting the yeast-laden dough in a warm place, and allowing the facultative anaerobe to do its work. Over the course of an hour or so, the yeast will create large amounts of carbon dioxide within the dough, expanding it and making it lighter.
In beer, wine, and other alcoholic beverages, yeast is the key ingredient. The process of fermentation, or the creation of alcohol, occur in yeast when they have plenty of sugar but little oxygen. Brewers and wine-makers use this aspect of the facultative anaerobe to generate the alcohol within their products. Aerobic respiration completely reduces glucose to a few recyclable molecules and carbon dioxide. Fermentation, on the other hand, leaves a final product: ethanol. Beer and wine makers create the ethanol (an alcohol) in their products by strictly controlling the amount of sugar and oxygen in their fermentation tanks. In these conditions any facultative anaerobe will resort to fermentation, and put off ethanol as a byproduct. When the alcohol reaches the proper level in the mixture, the yeast are filtered out and the drink is bottled.
To solve their conundrum, mussels like those in the image above have evolved the abilities of a facultative anaerobe. Instead of relying on their normal aerobic respiration when the tide goes out, the mussels switch to a form of energy which breaks down amino acids. This allows the mussel to survive hours, or even days, without getting a fresh source of oxygen.
1. Humans muscles rely on aerobic respiration to produce the ATP necessary to work them. However, in times of stress and intense exercise, these muscles often run out of oxygen. In this case, the muscles must resort to a form of fermentation which produces lactic acid. Lactic acid can damage cells when it builds up, so the cells must quickly revert to aerobic respiration if they are to survive. Are humans facultative anaerobes?
2. What is the difference between a facultative anaerobe and an obligate anaerobe?
A. A facultative anaerobe only has anaerobic pathways.
B. An obligate anaerobe can survive the presence of oxygen.
C. A facultative anaerobe can survive and use oxygen.
3. While scientists used to believe that facultative anaerobe organisms were typically single-celled remnants of an earlier time, evidence has showed that many gut parasites are often facultative anaerobes. Which of the following provides an explanation of this fact?
A. These organisms have a constant access to oxygen.
B. Often, areas of the gut are anaerobic, forcing these organisms to use an anaerobic pathway.
C. These organisms do not represent a facultative anaerobe.
Watch the video: The Physarum Experiments, Study: Interspecies Encounter (October 2022).