Well 44 yrs old and I remember going to school and we sang allegiance to the flag, and other songs. My one teacher told us to sit out of sing that morning. We was like why she say that if we didn't want to we didn't have to I was so my. Question why don't they sing in schools today.
When I was little, I went to my great aunt's funeral. And I still remember the pastor/priest saying "Where is she now? In heaven? In hell? No one knows!" I would guess there was some philosophical point he was trying to make, but my little brain stopped listening after that thinking just how rude he was to say something like that at someone's literal funeral.
I mean not truly knowing if someone is truly in heaven or hell is a Christian belief but mentioning that at a funeral is very inappropriate because the whole point is that you hope they are in heaven
Grandpa not going to heaven because he's and adult (has lots of ladies), just killed me. The things that kids misinterpret/mispronounce is hilarious. Reminded me of when my middle daughter was young, hollerin' at her siblings not to yell and make a ruckus because we live in a canon (canyon) and the noise travels. lol Kids are such awesome little people. Ms. Chang, you're an awesome teacher.
Thats the best way to do it when the conversation goes somewhere you don't want it too. Try to divert there attention back to whatever they were doing before it started.
I’m a piano teacher with a lot of Indian families in my studio. One of my little boys came in telling me about how they learned about Shiva in religion class today (my response: cool!) but what broke my heart was his adamant follow-up that Shiva was real (my response: of course he is!). I had not challenged or rejected this in any way - after having grown up multicultural I believe most every path has some truth in it - but it just seemed like he said it because he must be used to kids at school mocking his beliefs. It made me so sad.
🥹🥹🥹 I feel like it means he’s used to adults questioning him too so it’s so special that you validated his beliefs! I love that for him. I hope every adult in his life from now on is more like you.
I love this. Facts are for public school, ideologies are for at home. I wish more teachers addressed all ideologies the way you’ve handled religious ideology in this skit.
I LOVE most about this is how you emphasize all beliefs are equally valid. This is what we need most in a world where religious extremists are such a dominant factor in our laws, rights, and safety as human beings on this entire planet.
If I were still young enough to have kids, or if I pretty much needed to address any degree of socio -religious kind of question to anyone, I would want Jere Chang firmly in my corner. Big Hug!! ❤️
Lol, where I live in the South (not far from Georgia!), religion and sex education are THE hot-button topics. I work with kids, and don't touch those topics with a 10-foot poll:P
My mom and I were in this once. I was 16/17 and my mom and I were volunteer CCD teachers for 4th-6th graders. We were teaching Christmas in our Catholic Church and the question of Santa came up by one girl. We did the whole “St. Nick” spiel which we thought would satisfy any kid. Well this kid took it to mean that Santa wasn’t real and we got a nasty (Karen-level) email about it. Fortunately the CCD board was on our side but it turned me off to the entire idea of religion as a practice since questions were met with persecution towards the asker and/or the preacher due to miscommunication
In England, it’s mandatory for schools to teach children about religion. Parents can request their child is removed from these classes, but most don’t.
@@Martehoffmann8 Interesting. We do it from primary though high school - so 4-15 or 16 (it depends if you decided to take full courses GCSE instead of short course).
@@sophiefrancis8295we learn that in the US too (probably depends on the state) but it’s not taught like “this is real and you need to believe this” it’s taught in history to give context to wars and regions around the world.
Are you in a religious school and this is religion class or is it a “World Religions” class? I understand that it sucks to have to learn about faith if your parents send you to a religious school and you’re an atheist or agnostic. I’ve taught at a religious school and I tried really hard to make Bible class non-judgy. Ultimately I left because it doesn’t sit well with me to have a captive audience.
That's like telling someone to prove Santa Claus doesn't exist. The burden of proof lies with one who makes a positive claim about something, such as "god is very real."
Yeshua Hamashiach is God in the flesh, the Son of God, the Word of God, and he died so that you may be presented blameless in the sight of the Father. And so you may inherit his kingdom. The LORD Yeshua Hamashiach is the only way to the Father and his kingdom. Repent of your sins, turn to Yeshua and accept him into your life as your LORD and Savior before it's too late, every day is not guaranteed. John 14:6 Jesus said to him, “I am the way, and the truth, and the life; no one comes to the Father except through Me. May God bless you all.
I went to Christian school k-6 . I’m thankful for it . Evolution shouldn’t be taught in schools. Although we did have many questionable teachers. Once the music teacher prayed loudly for the devil to leave the room. In his defense my sixth grade class was so bad our regular teacher quit mid year. It definitely was overpriced .
Evidence for evolution comes from many different areas of biology: Anatomy: Species may share similar physical features because the feature was present in a common ancestor (homologous structures). Molecular biology: DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are. Biogeography: The global distribution of organisms and the unique features of island species reflect evolution and geological change. Fossils: Fossils document the existence of now-extinct past species that are related to present-day species. Direct observation: We can directly observe small-scale evolution in organisms with short lifecycles (e.g., pesticide-resistant insects). Evolution happens on large and small scales *Before we look at the evidence, let's make sure we are on the same page about what evolution is. Broadly speaking, evolution is a change in the genetic makeup (and often, the heritable features) of a population over time.* Biologists sometimes define two types of evolution based on scale: Macroevolution, which refers to large-scale changes that occur over extended time periods, such as the formation of new species and groups. Microevolution, which refers to small-scale changes that affect just one or a few genes and happen in populations over shorter timescales. Microevolution and macroevolution aren’t really two different processes. They’re the same process (evolution) occurring on different timescales. Microevolutionary processes occurring over thousands or millions of years can add up to large-scale changes that define new species or groups. Anatomy and embryology Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations. He proposed that the evolutionary history of life forms a branching tree with many levels, in which all species can be traced back to an ancient common ancestor. In this tree model, more closely related groups of species have more recent common ancestors, and each group will tend to share features that were present in its last common ancestor. We can use this idea to "work backwards" and figure out how organisms are related based on their shared features. Homologous features If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor. Physical features shared due to evolutionary history (a common ancestor) are said to be homologous. To give one classic example, the forelimbs of whales, humans, birds, and dogs look pretty different on the outside. That's because they're adapted to function in different environments. However, if you look at the bone structure of the forelimbs, you'll find that the pattern of bones is very similar across species. It's unlikely that such similar structures would have evolved independently in each species, and more likely that the basic layout of bones was already present in a common ancestor of whales, humans, dogs, and birds. Some homologous structures can be seen only in embryos. For instance, all vertebrate embryos (including humans) have gill slits and a tail during early development. The developmental patterns of these species become more different later on (which is why your embryonic tail is now your tailbone, and your gill slits have turned into your jaw and inner ear). Homologous embryonic structures reflect that the developmental programs of vertebrates are variations on a similar plan that existed in their last common ancestor. Sometimes, organisms have structures that are homologous to important structures in other organisms but that have lost their major ancestral function. These structures, which are often reduced in size, are known as vestigial structures. Examples of vestigial structures include the tailbone of humans (a vestigial tail), the hind leg bones of whales, and the underdeveloped legs found in some snakes. Analogous features To make things a little more interesting and complicated, not all physical features that look alike are marks of common ancestry. Instead, some physical similarities are analogous: they evolved independently in different organisms because the organisms lived in similar environments or experienced similar selective pressures. This process is called convergent evolution. (To converge means to come together, like two lines meeting at a point.) For example, two distantly related species that live in the Arctic, the arctic fox and the ptarmigan (a bird), both undergo seasonal changes of color from dark to snowy white. This shared feature doesn’t reflect common ancestry - i.e., it's unlikely that the last common ancestor of the fox and ptarmigan changed color with the seasons. Instead, this feature was favored separately in both species due to similar selective pressures. That is, the genetically determined ability to switch to light coloration in winter helped both foxes and ptarmigans survive and reproduce in a place with snowy winters and sharp-eyed predators. Determining relationships from similar features In general, biologists don't draw conclusions about how species are related on the basis of any single feature they think is homologous. Instead, they study a large collection of features (often, both physical features and DNA sequences) and draw conclusions about relatedness based on these features as a group. We will explore this idea further when we examine phylogenetic trees. Molecular biology Like structural homologies, similarities between biological molecules can reflect shared evolutionary ancestry. At the most basic level, all living organisms share: -The same genetic material (DNA) -The same, or highly similar, genetic codes -The same basic process of gene expression (transcription and translation) -The same molecular building blocks, such as amino acids These shared features suggest that all living things are descended from a common ancestor, and that this ancestor had DNA as its genetic material, used the genetic code, and expressed its genes by transcription and translation. Present-day organisms all share these features because they were "inherited" from the ancestor (and because any big changes in this basic machinery would have broken the basic functionality of cells). Although they're great for establishing the common origins of life, features like having DNA or carrying out transcription and translation are not so useful for figuring out how related particular organisms are. If we want to determine which organisms in a group are most closely related, we need to use different types of molecular features, such as the nucleotide sequences of genes. Homologous genes Biologists often compare the sequences of related genes found in different species (often called homologous or orthologous genes) to figure out how those species are evolutionarily related to one another. The basic idea behind this approach is that two species have the "same" gene because they inherited it from a common ancestor. For instance, humans, cows, chickens, and chimpanzees all have a gene that encodes the hormone insulin, because this gene was already present in their last common ancestor. In general, the more DNA differences in homologous genes (or amino acid differences in the proteins they encode) between two species, the more distantly the species are related. For instance, human and chimpanzee insulin proteins are much more similar (about 98% identical) than human and chicken insulin proteins (about 64% identical), reflecting that humans and chimpanzees are more closely related than humans and chickens. Biogeography The geographic distribution of organisms on Earth follows patterns that are best explained by evolution, in combination with the movement of tectonic plates over geological time. For example, broad groupings of organisms that had already evolved before the breakup of the supercontinent Pangaea (about 200 million years ago) tend to be distributed worldwide. In contrast, broad groupings that evolved after the breakup tend to appear uniquely in smaller regions of Earth. For instance, there are unique groups of plants and animals on northern and southern continents that can be traced to the split of Pangaea into two supercontinents (Laurasia in the north, Gondwana in the south). The evolution of unique species on islands is another example of how evolution and geography intersect. For instance, most of the mammal species in Australia are marsupials (carry young in a pouch), while most mammal species elsewhere in the world are placental (nourish young through a placenta). Australia’s marsupial species are very diverse and fill a wide range of ecological roles. Because Australia was isolated by water for millions of years, these species were able to evolve without competition from (or exchange with) mammal species elsewhere in the world. The marsupials of Australia, Darwin's finches in the Galápagos, and many species on the Hawaiian Islands are unique to their island settings, but have distant relationships to ancestral species on mainlands. This combination of features reflects the processes by which island species evolve. They often arise from mainland ancestors - for example, when a landmass breaks off or a few individuals are blown off course during a storm - and diverge (become increasingly different) as they adapt in isolation to the island environment. (Part 1 of 2)
Fossil record Fossils are the preserved remains of previously living organisms or their traces, dating from the distant past. The fossil record is not, alas, complete or unbroken: most organisms never fossilize, and even the organisms that do fossilize are rarely found by humans. Nonetheless, the fossils that humans have collected offer unique insights into evolution over long timescales. How can the age of fossils be determined? First, fossils are often contained in rocks that build up in layers called strata. The strata provide a sort of timeline, with layers near the top being newer and layers near the bottom being older. Fossils found in different strata at the same site can be ordered by their positions, and "reference" strata with unique features can be used to compare the ages of fossils across locations. In addition, scientists can roughly date fossils using radiometric dating, a process that measures the radioactive decay of certain elements. Fossils document the existence of now-extinct species, showing that different organisms have lived on Earth during different periods of the planet's history. They can also help scientists reconstruct the evolutionary histories of present-day species. For instance, some of the best-studied fossils are of the horse lineage. Using these fossils, scientists have been able to reconstruct a large, branching "family tree" for horses and their now-extinct relatives. Changes in the lineage leading to modern-day horses, such as the reduction of toed feet to hooves, may reflect adaptation to changes in the environment. Direct observation of microevolution In some cases, the evidence for evolution is that we can see it taking place around us! Important modern-day examples of evolution include the emergence of drug-resistant bacteria and pesticide-resistant insects. For example, in the 1950s, there was a worldwide effort to eradicate malaria by eliminating its carriers (certain types of mosquitos). The pesticide DDT was sprayed broadly in areas where the mosquitoes lived, and at first, the DDT was highly effective at killing the mosquitos. However, over time, the DDT became less and less effective, and more and more mosquitoes survived. This was because the mosquito population evolved resistance to the pesticide. Emergence of DDT resistance is an example of evolution by natural selection. How would natural selection have worked in this case? 1. Before DDT was applied, a tiny fraction of mosquitos in the population would have had naturally occurring gene versions (alleles) that made them resistant to DDT. These versions would have appeared through random mutation, or changes in DNA sequence. Without DDT around, the resistant alleles would not have helped mosquitoes survive or reproduce (and might even have been harmful), so they would have remained rare. 2. When DDT spraying began, most of the mosquitos would have been killed by the pesticide. Which mosquitos would have survived? For the most part, only the rare individuals that happened to have DDT resistance alleles (and thus survived being sprayed with DDT). These surviving mosquitoes would have been able to reproduce and leave offspring. 3. Over generations, more and more DDT-resistant mosquitoes would have been born into the population. That's because resistant parents would have been consistently more likely to survive and reproduce than non-resistant parents, and would have passed their DDT resistance alleles (and thus, the capacity to survive DDT) on to their offspring. Eventually, the mosquito populations would have bounced back to high numbers, but would have been composed largely of DDT-resistant individuals. In parts of the world where DDT has been used extensively in the past, many of the mosquitoes are now resistant. DDT can no longer be used to control the mosquito populations (and reduce malaria) in these regions. Why are mosquito populations able to evolve rapid resistance to DDT? Two important factors are large population size (making it more likely that some individuals in the population will, by random chance, have mutations that provide resistance) and short lifecycle. Bacteria and viruses, which have even larger population sizes and shorter lifecycles, can evolve resistance to drugs very rapidly, as in antibiotic-resistant bacteria and drug-resistant HIV. Summary Multiple types of evidence support the theory of evolution: -Homologous structures provide evidence for common ancestry, while analogous structures show that similar selective pressures can produce similar adaptations (beneficial features). -Similarities and differences among biological molecules (e.g., in the DNA sequence of genes) can be used to determine species' relatedness. -Biogeographical patterns provide clues about how species are related to each other. -The fossil record, though incomplete, provides information about what species existed at particular times of Earth’s history. -Some populations, like those of microbes and some insects, evolve over relatively short time periods and can observed directly. (Part 2 of 2. Shamelessly plagiarized from Khan Academy.)
I love how you leave it open to the families instead of trying to teach them a personal belief
It really is kinda simple 🥹
@@mschanggifted simple and wise.
Well 44 yrs old and I remember going to school and we sang allegiance to the flag, and other songs. My one teacher told us to sit out of sing that morning. We was like why she say that if we didn't want to we didn't have to I was so my. Question why don't they sing in schools today.
I don't think it's legal to tell kids one religion is real
@@Hepoxni But kids don’t know that
“My worm went to heaven” Oh my gosh🥺🥺🥺protect that child(and worm, wherever it is) at all costs
Not grandpa getting kicked out of heaven for having too many ladies 😂😂😂
That killed me😂😂
💀
This is one of your best skits. I like how you addressed religious beliefs and did it with Mary Sue and the gang. I wish more teachers were like you.
Thank you
When I was little, I went to my great aunt's funeral. And I still remember the pastor/priest saying "Where is she now? In heaven? In hell? No one knows!" I would guess there was some philosophical point he was trying to make, but my little brain stopped listening after that thinking just how rude he was to say something like that at someone's literal funeral.
Oh dear, I hope she haunts that pastor!!
I mean not truly knowing if someone is truly in heaven or hell is a Christian belief but mentioning that at a funeral is very inappropriate because the whole point is that you hope they are in heaven
Mary Sue over here outing her Grandpa for being an adulterer, and then Bill cracking a joke about it. LOL
Grandpa not going to heaven because he's and adult (has lots of ladies), just killed me. The things that kids misinterpret/mispronounce is hilarious. Reminded me of when my middle daughter was young, hollerin' at her siblings not to yell and make a ruckus because we live in a canon (canyon) and the noise travels. lol Kids are such awesome little people. Ms. Chang, you're an awesome teacher.
I loved the, “Can we get back to work” when the convo really started going sideways 😂😂
Thats the best way to do it when the conversation goes somewhere you don't want it too. Try to divert there attention back to whatever they were doing before it started.
Worms in heaven, but not the grandpa!😂😂
How do you think these things up??!!
This is great! I wish more teachers were like you! ❤
I’m a piano teacher with a lot of Indian families in my studio. One of my little boys came in telling me about how they learned about Shiva in religion class today (my response: cool!) but what broke my heart was his adamant follow-up that Shiva was real (my response: of course he is!). I had not challenged or rejected this in any way - after having grown up multicultural I believe most every path has some truth in it - but it just seemed like he said it because he must be used to kids at school mocking his beliefs. It made me so sad.
🥹🥹🥹
I feel like it means he’s used to adults questioning him too so it’s so special that you validated his beliefs! I love that for him. I hope every adult in his life from now on is more like you.
That was so funny lol kids say the darndest things
This is a TV show I would binge on lol Adorable ❤
I love this. Facts are for public school, ideologies are for at home. I wish more teachers addressed all ideologies the way you’ve handled religious ideology in this skit.
I LOVE most about this is how you emphasize all beliefs are equally valid. This is what we need most in a world where religious extremists are such a dominant factor in our laws, rights, and safety as human beings on this entire planet.
So I have been recommended a lot of your videos on here, but this one takes the cake! I HAD to subscribe. You’re great. I love how you talk.
"But not with your grandpa" Bill saw his shot and took iy
If I were still young enough to have kids, or if I pretty much needed to address any degree of socio -religious kind of question to anyone, I would want Jere Chang firmly in my corner. Big Hug!! ❤️
you are a great teacher
Lol, where I live in the South (not far from Georgia!), religion and sex education are THE hot-button topics. I work with kids, and don't touch those topics with a 10-foot poll:P
In my country it’s actually part of the curriculum.
I thought basic sex education was taught every where especially since some parents don't want to discuss it
"my grandpa isn't going to heaven because he's an adult"
Ikr 😂😂😂 ☠️
I know, late to comment but I really really heart this. Let's just all respect each other!
I was just thinking to myself I hadn't seen your videos in awhile and wondering if you'd created any new content. Yay 😊
My mom and I were in this once. I was 16/17 and my mom and I were volunteer CCD teachers for 4th-6th graders. We were teaching Christmas in our Catholic Church and the question of Santa came up by one girl. We did the whole “St. Nick” spiel which we thought would satisfy any kid. Well this kid took it to mean that Santa wasn’t real and we got a nasty (Karen-level) email about it. Fortunately the CCD board was on our side but it turned me off to the entire idea of religion as a practice since questions were met with persecution towards the asker and/or the preacher due to miscommunication
Glad I has Spiritual teachers!
As the parent of a gifted 3rd grader this very much seems legit.
Thank you for capitalizing the G in God.
I probably would’ve just said that we don’t know what happens after you die, because no one has ever come back from it to tell us
In England, it’s mandatory for schools to teach children about religion. Parents can request their child is removed from these classes, but most don’t.
What kind of religion are they taught?
@@Nan-59 The six main world religions, usually. That is: Christianity, Judaism, Hinduism, Buddhism, Islam and Sikhism.
We usually learn religion in hs here
@@Martehoffmann8 Interesting. We do it from primary though high school - so 4-15 or 16 (it depends if you decided to take full courses GCSE instead of short course).
@@sophiefrancis8295we learn that in the US too (probably depends on the state) but it’s not taught like “this is real and you need to believe this” it’s taught in history to give context to wars and regions around the world.
Tough situation to be in!
Bill is a terror😂
"ha,but not your grandpa huh?" FOUL.
Yes God is real people believing and not believing doesn't change the fact of his existence it's never ok to not believe in God.
I'm glad that he isn't trying to disrespect us Christians but I hope that he gets to know Jesus as Lord and saviour 🙏🏽
@@shaniaault6646who’s “he?”
What credible and verifiable evidence do you have to prove your particular god exists?
@@ga6589 What evidence do you have shows that's he's doesn't
@@ga6589 what “viable and credible” evidence is there to prove he doesn’t?
and look around you. what other evidence do you need?
It's Billy Idol
MS.CHANGG!! MY COUSIN GOES TO UR SCHOOL!!!
I believe in Jesus
I'm an Athiest and my teacher still makes me do RE worksheets.....it sucks (I support christians don't come at me)
Are you in a religious school and this is religion class or is it a “World Religions” class? I understand that it sucks to have to learn about faith if your parents send you to a religious school and you’re an atheist or agnostic. I’ve taught at a religious school and I tried really hard to make Bible class non-judgy. Ultimately I left because it doesn’t sit well with me to have a captive audience.
@@muriel5826 I'm in my final year at primary so I have different subjects in just 1 classroom,I don't actually mind it its just a bit annoying.
Can you please reply to my comment? Thank you. I’ve been watching you for a long time.
Google parasocial relationship
But not with your grandpa 😂
Yo God is fr very real, prove me wrong
That's like telling someone to prove Santa Claus doesn't exist. The burden of proof lies with one who makes a positive claim about something, such as "god is very real."
Yeshua Hamashiach is God in the flesh, the Son of God, the Word of God, and he died so that you may be presented blameless in the sight of the Father. And so you may inherit his kingdom. The LORD Yeshua Hamashiach is the only way to the Father and his kingdom. Repent of your sins, turn to Yeshua and accept him into your life as your LORD and Savior before it's too late, every day is not guaranteed.
John 14:6
Jesus said to him, “I am the way, and the truth, and the life; no one comes to the Father except through Me.
May God bless you all.
I went to Christian school k-6 . I’m thankful for it . Evolution shouldn’t be taught in schools. Although we did have many questionable teachers. Once the music teacher prayed loudly for the devil to leave the room. In his defense my sixth grade class was so bad our regular teacher quit mid year. It definitely was overpriced .
Evolution is real. I’m sorry your education failed you.
@@Kirsten_is_cursed10not how textbooks claim . We did not come from monkeys and there was no Big Bang . The Bible is real.
Evidence for evolution comes from many different areas of biology:
Anatomy: Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
Molecular biology: DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
Biogeography: The global distribution of organisms and the unique features of island species reflect evolution and geological change.
Fossils: Fossils document the existence of now-extinct past species that are related to present-day species.
Direct observation: We can directly observe small-scale evolution in organisms with short lifecycles (e.g., pesticide-resistant insects).
Evolution happens on large and small scales
*Before we look at the evidence, let's make sure we are on the same page about what evolution is. Broadly speaking, evolution is a change in the genetic makeup (and often, the heritable features) of a population over time.* Biologists sometimes define two types of evolution based on scale:
Macroevolution, which refers to large-scale changes that occur over extended time periods, such as the formation of new species and groups.
Microevolution, which refers to small-scale changes that affect just one or a few genes and happen in populations over shorter timescales.
Microevolution and macroevolution aren’t really two different processes. They’re the same process (evolution) occurring on different timescales. Microevolutionary processes occurring over thousands or millions of years can add up to large-scale changes that define new species or groups.
Anatomy and embryology
Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations. He proposed that the evolutionary history of life forms a branching tree with many levels, in which all species can be traced back to an ancient common ancestor.
In this tree model, more closely related groups of species have more recent common ancestors, and each group will tend to share features that were present in its last common ancestor. We can use this idea to "work backwards" and figure out how organisms are related based on their shared features.
Homologous features
If two or more species share a unique physical feature, such as a complex bone structure or a body plan, they may all have inherited this feature from a common ancestor. Physical features shared due to evolutionary history (a common ancestor) are said to be homologous.
To give one classic example, the forelimbs of whales, humans, birds, and dogs look pretty different on the outside. That's because they're adapted to function in different environments. However, if you look at the bone structure of the forelimbs, you'll find that the pattern of bones is very similar across species. It's unlikely that such similar structures would have evolved independently in each species, and more likely that the basic layout of bones was already present in a common ancestor of whales, humans, dogs, and birds.
Some homologous structures can be seen only in embryos. For instance, all vertebrate embryos (including humans) have gill slits and a tail during early development. The developmental patterns of these species become more different later on (which is why your embryonic tail is now your tailbone, and your gill slits have turned into your jaw and inner ear). Homologous embryonic structures reflect that the developmental programs of vertebrates are variations on a similar plan that existed in their last common ancestor.
Sometimes, organisms have structures that are homologous to important structures in other organisms but that have lost their major ancestral function. These structures, which are often reduced in size, are known as vestigial structures. Examples of vestigial structures include the tailbone of humans (a vestigial tail), the hind leg bones of whales, and the underdeveloped legs found in some snakes.
Analogous features
To make things a little more interesting and complicated, not all physical features that look alike are marks of common ancestry. Instead, some physical similarities are analogous: they evolved independently in different organisms because the organisms lived in similar environments or experienced similar selective pressures. This process is called convergent evolution. (To converge means to come together, like two lines meeting at a point.)
For example, two distantly related species that live in the Arctic, the arctic fox and the ptarmigan (a bird), both undergo seasonal changes of color from dark to snowy white. This shared feature doesn’t reflect common ancestry - i.e., it's unlikely that the last common ancestor of the fox and ptarmigan changed color with the seasons. Instead, this feature was favored separately in both species due to similar selective pressures. That is, the genetically determined ability to switch to light coloration in winter helped both foxes and ptarmigans survive and reproduce in a place with snowy winters and sharp-eyed predators.
Determining relationships from similar features
In general, biologists don't draw conclusions about how species are related on the basis of any single feature they think is homologous. Instead, they study a large collection of features (often, both physical features and DNA sequences) and draw conclusions about relatedness based on these features as a group. We will explore this idea further when we examine phylogenetic trees.
Molecular biology
Like structural homologies, similarities between biological molecules can reflect shared evolutionary ancestry. At the most basic level, all living organisms share:
-The same genetic material (DNA)
-The same, or highly similar, genetic codes
-The same basic process of gene expression (transcription and translation)
-The same molecular building blocks, such as amino acids
These shared features suggest that all living things are descended from a common ancestor, and that this ancestor had DNA as its genetic material, used the genetic code, and expressed its genes by transcription and translation. Present-day organisms all share these features because they were "inherited" from the ancestor (and because any big changes in this basic machinery would have broken the basic functionality of cells).
Although they're great for establishing the common origins of life, features like having DNA or carrying out transcription and translation are not so useful for figuring out how related particular organisms are. If we want to determine which organisms in a group are most closely related, we need to use different types of molecular features, such as the nucleotide sequences of genes.
Homologous genes
Biologists often compare the sequences of related genes found in different species (often called homologous or orthologous genes) to figure out how those species are evolutionarily related to one another.
The basic idea behind this approach is that two species have the "same" gene because they inherited it from a common ancestor. For instance, humans, cows, chickens, and chimpanzees all have a gene that encodes the hormone insulin, because this gene was already present in their last common ancestor.
In general, the more DNA differences in homologous genes (or amino acid differences in the proteins they encode) between two species, the more distantly the species are related. For instance, human and chimpanzee insulin proteins are much more similar (about 98% identical) than human and chicken insulin proteins (about 64% identical), reflecting that humans and chimpanzees are more closely related than humans and chickens.
Biogeography
The geographic distribution of organisms on Earth follows patterns that are best explained by evolution, in combination with the movement of tectonic plates over geological time. For example, broad groupings of organisms that had already evolved before the breakup of the supercontinent Pangaea (about
200 million years ago) tend to be distributed worldwide. In contrast, broad groupings that evolved after the breakup tend to appear uniquely in smaller regions of Earth. For instance, there are unique groups of plants and animals on northern and southern continents that can be traced to the split of Pangaea into two supercontinents (Laurasia in the north, Gondwana in the south).
The evolution of unique species on islands is another example of how evolution and geography intersect. For instance, most of the mammal species in Australia are marsupials (carry young in a pouch), while most mammal species elsewhere in the world are placental (nourish young through a placenta). Australia’s marsupial species are very diverse and fill a wide range of ecological roles. Because Australia was isolated by water for millions of years, these species were able to evolve without competition from (or exchange with) mammal species elsewhere in the world.
The marsupials of Australia, Darwin's finches in the Galápagos, and many species on the Hawaiian Islands are unique to their island settings, but have distant relationships to ancestral species on mainlands. This combination of features reflects the processes by which island species evolve. They often arise from mainland ancestors - for example, when a landmass breaks off or a few individuals are blown off course during a storm - and diverge (become increasingly different) as they adapt in isolation to the island environment.
(Part 1 of 2)
Fossil record
Fossils are the preserved remains of previously living organisms or their traces, dating from the distant past. The fossil record is not, alas, complete or unbroken: most organisms never fossilize, and even the organisms that do fossilize are rarely found by humans. Nonetheless, the fossils that humans have collected offer unique insights into evolution over long timescales.
How can the age of fossils be determined? First, fossils are often contained in rocks that build up in layers called strata. The strata provide a sort of timeline, with layers near the top being newer and layers near the bottom being older. Fossils found in different strata at the same site can be ordered by their positions, and "reference" strata with unique features can be used to compare the ages of fossils across locations. In addition, scientists can roughly date fossils using radiometric dating, a process that measures the radioactive decay of certain elements.
Fossils document the existence of now-extinct species, showing that different organisms have lived on Earth during different periods of the planet's history. They can also help scientists reconstruct the evolutionary histories of present-day species. For instance, some of the best-studied fossils are of the horse lineage. Using these fossils, scientists have been able to reconstruct a large, branching "family tree" for horses and their now-extinct relatives. Changes in the lineage leading to modern-day horses, such as the reduction of toed feet to hooves, may reflect adaptation to changes in the environment.
Direct observation of microevolution
In some cases, the evidence for evolution is that we can see it taking place around us! Important modern-day examples of evolution include the emergence of drug-resistant bacteria and pesticide-resistant insects.
For example, in the 1950s, there was a worldwide effort to eradicate malaria by eliminating its carriers (certain types of mosquitos). The pesticide DDT was sprayed broadly in areas where the mosquitoes lived, and at first, the DDT was highly effective at killing the mosquitos. However, over time, the DDT became less and less effective, and more and more mosquitoes survived. This was because the mosquito population evolved resistance to the pesticide.
Emergence of DDT resistance is an example of evolution by natural selection. How would natural selection have worked in this case?
1. Before DDT was applied, a tiny fraction of mosquitos in the population would have had naturally occurring gene versions (alleles) that made them resistant to DDT. These versions would have appeared through random mutation, or changes in DNA sequence. Without DDT around, the resistant alleles would not have helped mosquitoes survive or reproduce (and might even have been harmful), so they would have remained rare.
2. When DDT spraying began, most of the mosquitos would have been killed by the pesticide. Which mosquitos would have survived? For the most part, only the rare individuals that happened to have DDT resistance alleles (and thus survived being sprayed with DDT). These surviving mosquitoes would have been able to reproduce and leave offspring.
3. Over generations, more and more DDT-resistant mosquitoes would have been born into the population. That's because resistant parents would have been consistently more likely to survive and reproduce than non-resistant parents, and would have passed their DDT resistance alleles (and thus, the capacity to survive DDT) on to their offspring. Eventually, the mosquito populations would have bounced back to high numbers, but would have been composed largely of DDT-resistant individuals.
In parts of the world where DDT has been used extensively in the past, many of the mosquitoes are now resistant. DDT can no longer be used to control the mosquito populations (and reduce malaria) in these regions.
Why are mosquito populations able to evolve rapid resistance to DDT? Two important factors are large population size (making it more likely that some individuals in the population will, by random chance, have mutations that provide resistance) and short lifecycle. Bacteria and viruses, which have even larger population sizes and shorter lifecycles, can evolve resistance to drugs very rapidly, as in antibiotic-resistant bacteria and drug-resistant HIV.
Summary
Multiple types of evidence support the theory of evolution:
-Homologous structures provide evidence for common ancestry, while analogous structures show that similar selective pressures can produce similar adaptations (beneficial features).
-Similarities and differences among biological molecules (e.g., in the DNA sequence of genes) can be used to determine species' relatedness.
-Biogeographical patterns provide clues about how species are related to each other.
-The fossil record, though incomplete, provides information about what species existed at particular times of Earth’s history.
-Some populations, like those of microbes and some insects, evolve over relatively short time periods and can observed directly.
(Part 2 of 2. Shamelessly plagiarized from Khan Academy.)
Not sure this is the right forum but thank you for the time and effort you put into your comment.
So bad.