# About embryonic and genetic evidence of evolution?

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My question here is about evidence for evolution from Embryology and from Genetics.

1. Mammals do have similar Embryos, but is it the case that for each species there is an embryonic development that occurs in earlier species, has such relationship been observed?

What I mean for example if we generally conceive of having species$$Sp_1,Sp_2,… ,Sp_n$$ where each $$Sp_{i+1}$$ being evolved from $$Sp_i,$$ then is it the case that the embryonic development stages of $$Sp_{i+1}$$ contains some of the embryonic development stages of all of its ancestor species.

2. Similar question to 1 but regarding Genetics, is it the case that every species has a genetic thumbprint of its ancestors that lie there in the non-functional sections of its DNA, i.e. is it the case that all the genetic history of our evolution is recorded in the non-functional section of our DNA. So do human DNA have some portions of the DNA of some dinosaurs for example?

Question 1 asks whether ontogeny recapitulates phylogeny. It is striking that the when observing e.g. human embryo development, the embryo seems to go through stages that its ancestral species would go through, but where those 'lower' species would terminate at a specific stage. In other words, embryonic development seems to recapitulate a species' evolutionary lineage.

This is the recapitulation theory, which is outdated and incorrect, but a great example from the history of science. The most prominent of these was Ernst Haeckel's biogenetic law and the Meckel-Serres Conception. There were many problems with this, especially because they focused on noting similarities rather than differences, and several exceptions exist to the rule. They were not very scientific. It also incorrectly presumes that complex organisms have more predecessors. However, it is a compelling piece of evidence to elegantly show that evolution acts incrementally on existing embryological processes.

Question 2 asks whether there is evidence of ancestral DNA in our genome. The answer is yes. Where to begin? We share almost all of our genes with close relatives (e.g. chimpanzees and bonobos) and progressively fewer with more distant relatives. 50% of a banana's genes (and indeed most other plants') can be found in the human genome. But remember, logically, that doesn't necessarily mean that 50% of human genes are found in bananas, though, because of the way divergence works. The human genome also contains a record of many viruses that have inserted themselves over tens of millions of years. Though they are not ancestors, they have been added 'horizontally' as opposed to the 'vertically' that ancestor DNA is modified over a species lineage.

It's very possible to answer your questions from many, many different angles, and present countless pieces of evidence in favor, but I think this should suffice.

S Pr's answer is very good, I'll just elaborate on a few points.

1) Evolution acts incrementally on existing embryological processes -> the insight here is that organisms don't come out fully formed, they develop. When we say a gene, say, "codes for" a tail, it doesn't make a tail magically appear: its action happens during the organism's development, where it acts on the development process such that the adult organism will have a tail.

This means that when organisms change over time via evolution, the way these changes are actually implemented are as changes to an existing development process; obviously the development process isn't going to be reset each time. So for example, it might make sense that since snakes don't have limbs as adults, they should never have limbs at any point in their development because what would be the point? But they evolved as a variation on organisms that did have limbs, and whose embryological development included the development of limbs. Evolutionarily speaking there's little reason why you should change that by preventing the development of limbs at stage 0, as opposed to, say, halting their development at stage 10 and destroying the limb buds. Either way you end up with a limbless adult snake! On the other hand if you destroy the limbs at stage 10, you're hardly going to have them come back at stage 19. In other words, you can end up with a pattern of later evolutionary changes happening later in development on average even if the changes occur at a random point in development, simply because a change at one stage of development also changes the later stages, but keeps the earlier stages intact. So earlier stages are more likely to be unchanged on average, i.e. similar to how they were in the ancestors. In practice the changes don't happen randomly in the development process of course, which is one reason "ontogeny recapitulates phylogeny" actually has tons of exceptions. This textbook "Developmental Biology" has a cool companion site with a chapter that discusses the history of the idea. This Wikipedia page also discusses some evolution in the view of evolution and development, talking about the "hourglass model" vs the "funnel model". The funnel model is this idea that the earliest stages are most similar to ancestral forms (and thus similar between related species), but the hourglass model points out that actually there is one specific stage (the "phylotypic stage") that stays similar between species, but there are differences both in earlier and in later stages.

2) There is no such thing as "dormant" DNA. There is active DNA (that codes for genes, regulatory regions, etc) and non-functional DNA. Non-functional DNA can be a few mutations away from being functional, and thus become functional as a result of chance mutations, but "dormant" suggests regions of DNA that are deactivated with the intent of reactivating them in the future; this isn't a process that occurs in evolution, which has no such future-looking intent.

Now it is the case that a) all DNA is subject to mutation, and b) we have a whole lot of DNA, and the mutation rate is quite low. This means that a lot of DNA is indeed more or less the same as it was in our faraway ancestors. Having said that, non-functional DNA is less likely to remain the same than functional DNA is, because nothing prevents mutations to those parts from being passed down through the generations. The DNA sequences that are the most unchanged ("conserved") are those that are used in such basic functions of life that they evolved very early in the history of life, and any change to them kills the resulting organism, which means that natural selection will make sure they don't change, or change very little. Here is a paper "The Genetic Core of the Universal Ancestor" that looks at such DNA sequences that are the same in all organisms ("universally conserved") to infer what genes the common ancestor of all living things had.

Finally, while this does mean that humans share a lot of their genome with dinosaurs, those shared genes mostly come from the fact both humans and dinosaurs share genes with their common ancestor, which was one of the earliest reptiles. Dinosaurs are not ancestors to humans.

Question 1

Mammals do have similar Embryos, but is it the case that for each species there is an embryonic development that occurs in earlier species, has such relationship been observed?

Technically, we do not observe much from the embryology from ancestral lineages. They don't exist anymore, so we can't make many observations from their embryology. The question is rather whether related lineages have similar embryogenesis.

The answer is yes. Mammals develop like mammals, birds develop like birds, angiosperms develop like angiosperms. For example, in all protostomes (insects, spiders, crustaceans, molluscs,… ), the blastopore becomes the mouth while in all deuterostomes (sea urchins, sea cucumber, vertebrates incl. birds, mammals, turtles, lizards, sharks, etc… ), the blastopore becomes the anus.

Question 2

Genetics is our main tool for inferring our phylogenetic trees. So, it makes more sense to ask whether other things match the genetics than the other way around. But yes, things match. Fossil records, ontogeny, phenotypic variation and genetics. Everything match to tell a similar story of the phylogenetic relationships among species.

In the mid-1800s, Charles Darwin and Alfred Wallace independently concluded that inherited variations in traits, such as a bird's beak shape, may provide better odds of survival in a given niche. Organisms without the advantageous variation are less likely to survive and pass on their genes.

Since the heyday of Darwinism, considerable scientific evidence has emerged supporting the theory of evolution, including embryology, although the mechanisms of mutation and change are more complex than previously understood.

## About embryonic and genetic evidence of evolution? - Biology

Biogeography is the study of the geographic distribution of living things and the abiotic factors that affect their distribution. Abiotic factors, such as temperature and rainfall, vary based on latitude and elevation, primarily. As these abiotic factors change, the composition of plant and animal communities also changes.

### Patterns of Species Distribution

Ecologists who study biogeography examine patterns of species distribution. No species exists everywhere for example, the Venus flytrap is endemic to a small area in North and South Carolina. An endemic species is one which is naturally found only in a specific geographic area that is usually restricted in size. Other species are generalists: species which live in a wide variety of geographic areas the raccoon, for example, is native to most of North and Central America.

Since species distribution patterns are based on biotic and abiotic factors and their influences during the very long periods of time required for species evolution, early studies of biogeography were closely linked to the emergence of evolutionary thinking in the eighteenth century. Some of the most distinctive assemblages of plants and animals occur in regions that have been physically separated for millions of years by geographic barriers. Biologists estimate that Australia, for example, has between 600,000 and 700,000 species of plants and animals. Approximately 3/4 of living plant and mammal species are endemic species found solely in Australia.

Australia: Australia is home to many endemic species. The (a) wallaby (Wallabia bicolor), a medium-sized member of the kangaroo family, is a pouched mammal, or marsupial. The (b) echidna (Tachyglossus aculeatus) is an egg-laying mammal.

The geographic distribution of organisms on the planet follows patterns that are best explained by evolution in conjunction with the movement of tectonic plates over geological time. Broad groups that evolved before the breakup of the supercontinent Pangaea (about 200 million years ago) are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, such as the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana. The presence of Proteaceae in Australia, southern Africa, and South America is best explained by the plant family’s presence there prior to the southern supercontinent Gondwana breaking up.

Biogeography: The Proteacea family of plants evolved before the supercontinent Gondwana broke up. Today, members of this plant family are found throughout the southern hemisphere (shown in red).

## Biogeography

The geographic distribution of organisms on the planet follows patterns that are best explained by evolution in conjunction with the movement of tectonic plates over geological time. Broad groups that evolved before the breakup of the supercontinent Pangaea (about 200 million years ago) are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, for example the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana. The presence of Proteaceae in Australia, southern Africa, and South America is best explained by the plant family’s presence there prior to the southern supercontinent Gondwana breaking up ([Figure 4]).

Figure 4: The Proteacea family of plants evolved before the supercontinent Gondwana broke up. Today, members of this plant family are found throughout the southern hemisphere (shown in red). (credit “Proteacea flower”: modification of work by “dorofofoto”/Flickr)

The great diversification of the marsupials in Australia and the absence of other mammals reflects that island continent’s long isolation. Australia has an abundance of endemic species—species found nowhere else—which is typical of islands whose isolation by expanses of water prevents migration of species to other regions. Over time, these species diverge evolutionarily into new species that look very different from their ancestors that may exist on the mainland. The marsupials of Australia, the finches on the Galápagos, and many species on the Hawaiian Islands are all found nowhere else but on their island, yet display distant relationships to ancestral species on mainlands.

## What is the genetic evidence for human evolution?

In the last couple of decades, our understanding of genetics has grown dramatically, providing overwhelming evidence that humans share common ancestors with all life on earth. Here are some of the main types of genetic evidence for common ancestry.

1. Genetic Diversity. Human children inherit 3 billion base pairs of DNA from each parent, but they are not an exact duplicate. The rate of change has been measured precisely to an average of 70 bases (out of our 6 billion total) per generation. So as we go back on the family tree, there are more and more genetic differences between us and our ancestors. For example, there would be about 140 differences between your DNA and that of your four grandparents, and 210 differences between you and your eight great-grandparents, and so on. That enables us to make a prediction from the amount of genetic diversity between two species about the time since their common ancestor population lived. Using non-genetic evidence, the common ancestor between humans and chimpanzees was estimated to have lived about 6 million years ago. The calculation from genetic differences gives a figure remarkably close to the estimated value.

2. Genetic “scars”. Just as scars stay on our bodies as reminders of past events, the DNA code contains “scars” and these are passed on from generation to generation. DNA scars result from the deletion or insertion of a block of bases (not just single base changes as in the previous section). Because we have a lot of these (hundreds of thousands) and they can be precisely located, they serve as a historical record of species. If we have the same scar as chimpanzees and orangutans, then the deletion or insertion must have occurred before these species diverged into separate populations. If we and chimpanzees have a certain scar but orangutans do not, we can conclude the deletion or insertion must have occurred after the common ancestor of chimps and humans separated from our common ancestor with orangutans. In this way we can create a detailed family tree of common ancestors.

3. Genetic synonyms. In a certain context, the words “round” and “circular” mean the same thing to an English speaker—they are synonyms. So too, there are “synonyms” in the genetic code—different sequences of DNA bases that mean the same thing to cells (that is, they cause the production of the same proteins). Mutations in the genetic code are often harmful, resulting in an organism not being able to successfully reproduce. But if the mutation results in a “synonym”, the organism would function the same and continue passing on its genes. Because of this we would expect the synonymous changes to be passed on much more effectively than non-synonymous changes. That is exactly what we find among the DNA of humans and chimpanzees: there are many more synonymous differences between the two species than non-synonymous ones. This is exactly what we would expect if the two species had a common ancestor, and so it provides further evidence that humans and chimpanzees were created through common descent from a single ancestral species.

The more research that is done on DNA, the more evidence we find that all life is related.

Last updated on March 11, 2019

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## Similarities During Development

Embryology, the study of biological development from the time of conception, is another source of independent evidence for common descent. Barnacles, for instance, are sedentary crustaceans with little apparent similarity to such other crustaceans as lobsters, shrimps, or copepods. Yet barnacles pass through a free-swimming larval stage in which they look like other crustacean larvae. The similarity of larval stages supports the conclusion that all crustaceans have homologous parts and a common ancestry.

Similarly, a wide variety of organisms from fruit flies to worms to mice to humans have very similar sequences of genes that are active early in development. These genes influence body segmentation or orientation in all these diverse groups. The presence of such similar genes doing similar things across such a wide range of organisms is best explained by their having been present in a very early common ancestor of all of these groups.

When Charles Darwin first proposed the idea that all new species descend from an ancestor, he performed an exhaustive amount of research to provide as much evidence as possible. Today, the major pieces of evidence for this theory can be broken down into the fossil record, embryology, comparative anatomy, and molecular biology.

This is a series of skulls and front leg fossils of organisms believed to be ancestors of the modern- day horse.

1.Give two similarities between each of the skulls that might lead to the conclusion that these are all related species.

the pointy bone on top of the muzzle of the horse and the triangular shape of the head and the gap between front and rear teeth

2.What is the biggest change in skull anatomy that occurred from the dawn horse to the modern horse?

Increase in the size of the skull a shift from cusps to complex ridges on the grinding surface of the premolars and molars, elongation of the face and of the space between the incisors and cheek teeth, an anterior shift of the cheek teeth so they lie forward of the eye a deep lower jaw bone

1. What is the biggest change in leg anatomy that occurred from the dawn horse to the modern horse?

Fifty five million years ago, there was an animal the size of a small dog, called Hyracotherium (sometimes called Eohippus). Its front feet had four toes, and its back feet had three. Modern horse feet have a single hoof. We see the reduction and loss of the side toes and enlargement of the terminal phalanx (hood) elongation and enlargement of the central metapodial (the longest bone in the foot)

Organisms that are closely related may also have physical similarities before they are even born! Take a look at the six different embryos below:

These are older, more developed embryos from the same organisms.

Hypothesize which embryo is from each of the following organisms:

These are embryos at their most advanced stage, shortly before birth.

Describe how the embryos changed for each of these organisms from their earliest to latest stages.

Species Anatomical Changes From Early to Late Stages

Developed limbs, defined features in face, neck, ears, loss of tail, tiny fingers present

the individual development of an animal occurs through a series of stages that paint a broad picture of the evolutionary stages (phylogeny) of the species to which it belongs. &quotOntogeny recapitulates Phylogeny&quot, Haeckel

Shown below are images of the skeletal structure of the front limbs of 6 animals: human, crocodile, whale, cat, bird, and bat. Each animal has a similar set of bones. Color code each of the bones according to this key:

For each animal, indicate what type of movement each limb is responsible for.

Human Using tools, picking up and holding objects

Cat running, walking, jumping

Bat flying, flapping wings

Crocodile swimming, walking/crawling

Comparison to Human Arm in Function Animal Comparison to human arm in form Comparison to Human Arm in function

whale Whale has a much shorter and thicker humerus, radius, and ulna. Much longer metacarpals.

Whale fin needs to be longer to help in movement through water. Thumbs are not necessary, as they don’t need to pick up and grasp things.

cat Curved humerus, shorter thinner humerus and ulna and radius, smaller metacarpals and phalanges

Movement of cat involves jumping and running, smaller for agility and balancing on small ledges, no thumbs for grasping since they use claws and teeth for this.

bat Thinner humerus, ulna, radius, smaller carpals, longer and thinner metacarpals and phalanges

Bones are smaller so that there is less weight in flight, long metacarpals and phalanges to extend wings

bird Slightly shorter humerus, ulna, radius metacarpals fused together, fewer but pointy phalanges

Bones are thinner for flight, more aerodynamic and light

crocodile Shorter, thicker humerus, ulna and radius, larger carpals, pointy phalanges

Thicker legs to support heavy weight and long metacarpals for swimming

Compare the anatomy of the butterfly and bird wing below.

1. Give an example of an analogous structure from this activity: Butterfly and bird wing or bat wing

Vestigial structures are anatomical remnants that were important in the organism’s ancestors, but are no longer used in the same way.

Give an example of a vestigial structure from this activity: Thumb of a whale fin

Below are some vestigial structures found in humans. For each, hypothesize what its function may have been. Structure Possible function

Wisdom teeth Extra grinding ability for vegetation

Appendix Store “good” bacteria to fight infections or digest cellulose like the caecum in rabbits

Muscles for moving the ear Better hearing by changing direction of ears

Body hair Keeping warm Stop pathogens from getting to mucous membranes Trap pheromones/oil on body

Little toe Balance/clinging on rocks/trees

Tailbone Rear stabilizing limb, balance

1. How are vestigial structures an example of evidence of evolution? Vestigial organs are often homologous to organs that are useful in other species. The vestigial tailbone in humans is homologous to the functional tail of other primates. Thus vestigial structures can be viewed as evidence for evolution: organisms having vestigial structures probably share a common ancestry with organisms in with organisms in which the homologous structure is functional.

Cytochrome c is a protein found in mitochondria. It is used in the study of evolutionary relationships because most animals have this protein. Cytochrome c is made of 104 amino acids joined together. Below is a list of the amino acids in part of a cytochrome protein molecule for 9 different animals. Any sequences exactly the same for all animals have been skipped.

For each non-human animal, take a highlighter and mark any amino acids that are different than the human sequence. When you finish, record how many differences you found in the table on the next page.

Animal Number of Amino Acid Differences Compared to Human Cytochrome C

Animal Number of Amino Acid Differences Compared to Human Cytochrome C

Molecular Biology – Summary Questions

2.Do any of the organisms have the same number of differences from human Cytochrome C? In situations like this, how would you decide which is more closely related to humans?

None of the organisms have the same number of difference from the human Cytochrome C. In situations like this, we can decide which is more closely related to humans by comparing anatomy structures, evolutionary tree or comparing them to the human genes by using another protein.

1.Charles Darwin published his book On the Origin of Species in 1859. Of the different types of evidence that you have examined, which do you think he relied upon the most, and why?

Darwin relied on the similar anatomies of species to link them. He also had some fossil evidence that showed slight changes in the body structure of the species over time, often leading to vestigial structures.

1. Given the amount of research and evidence available on evolution, why is it classified as a theory?

The scientific definition of the word &quottheory&quot is different from the colloquial sense of the word. Colloquially, or in everyday language, &quottheory&quot can mean a hypothesis, a conjecture, an opinion, or a speculation that does not have to be based on facts or make testable predictions. However, in science, the meaning of theory is more rigorous. A theory is a hypothesis corroborated by observation of facts, which makes testable predictions. In science, a current theory is a theory that has no equally acceptable or more acceptable alternative theory.

## Introduction

volution, the overarching concept that unifies the biological sciences, in fact embraces a plurality of theories and hypotheses. In evolutionary debates one is apt to hear evolution roughly parceled between the terms "microevolution" and "macroevolution". Microevolution, or change beneath the species level, may be thought of as relatively small scale change in the functional and genetic constituencies of populations of organisms. That this occurs and has been observed is generally undisputed by critics of evolution. What is vigorously challenged, however, is macroevolution. Macroevolution is evolution on the "grand scale" resulting in the origin of higher taxa. In evolutionary theory, macroevolution involves common ancestry, descent with modification, speciation, the genealogical relatedness of all life, transformation of species, and large scale functional and structural changes of populations through time, all at or above the species level (Freeman and Herron 2004 Futuyma 1998 Ridley 1993).

Universal common descent is a general descriptive theory concerning the genetic origins of living organisms (though not the ultimate origin of life). The theory specifically postulates that all of the earth's known biota are genealogically related, much in the same way that siblings or cousins are related to one another. Thus, universal common ancestry entails the transformation of one species into another and, consequently, macroevolutionary history and processes involving the origin of higher taxa. Because it is so well supported scientifically, common descent is often called the "fact of evolution" by biologists. For these reasons, proponents of special creation are especially hostile to the macroevolutionary foundation of the biological sciences.

This article directly addresses the scientific evidence in favor of common descent and macroevolution. This article is specifically intended for those who are scientifically minded but, for one reason or another, have come to believe that macroevolutionary theory explains little, makes few or no testable predictions, is unfalsifiable, or has not been scientifically demonstrated.

## First Genetic Evidence Uncovered Of How Major Changes In Body Shapes Occurred During Early Animal Evolution

Biologists at the University of California, San Diego have uncovered the first genetic evidence that explains how large-scale alterations to body plans were accomplished during the early evolution of animals.

In an advance online publication February 6 by Nature of a paper scheduled to appear in Nature, the scientists show how mutations in regulatory genes that guide the embryonic development of crustaceans and fruit flies allowed aquatic crustacean-like arthropods, with limbs on every segment of their bodies, to evolve 400 million years ago into a radically different body plan: the terrestrial six-legged insects.

The achievement is a landmark in evolutionary biology, not only because it shows how new animal body plans could arise from a simple genetic mutation, but because it effectively answers a major criticism creationists had long leveled against evolution-the absence of a genetic mechanism that could permit animals to introduce radical new body designs.

"The problem for a long time has been over this issue of macroevolution," says William McGinnis, a professor in UCSD's Division of Biology who headed the study. "How can evolution possibly introduce big changes into an animal's body shape and still generate a living animal? Creationists have argued that any big jump would result in a dead animal that wouldn't be able to perpetuate itself. And until now, no one's been to demonstrate how you could do that at the genetic level with specific instructions in the genome."

The UCSD team, which included Matthew Ronshaugen and Nadine McGinnis, showed in its experiments that this could be accomplished with relatively simple mutations in a class of regulatory genes, known as Hox, that act as master switches by turning on and off other genes during embryonic development. Using laboratory fruit flies and a crustacean known as Artemia, or brine shrimp, the scientists showed how modifications in the Hox gene Ubx-which suppresses 100 percent of the limb development in the thoracic region of fruit flies, but only 15 percent in Artemia-would have allowed the crustacean-like ancestors of Artemia, with limbs on every segment, to lose their hind legs and diverge 400 million years ago into the six-legged insects.

"This kind of gene is one that turns on and off lots of other genes in order to make complex structures," says Ronshaugen, a graduate student working in William McGinnis' laboratory and the first author of the paper. "What we've done is to show that this change alters the way it turns on and off other genes. That's due to the change in the way the protein produced by this gene functions."

"The change in the mutated protein allows it to turn off other genes," says William McGinnis, who discovered with two other scientists in 1983 that the same Hox genes in fruit flies that control the placement of the head, thorax and abdomen during development are a generalized feature of all animals, including humans. "Before the evolution of insects, the Ubx protein didn't turn off genes required for leg formation. And during the early evolution of insects, this gene and the protein it encoded changed so that they now turned off those genes required to make legs, essentially removing those legs from what would be the abdomen in insects."

The UCSD team's demonstration of how a mutation in the Ubx gene and changes in the corresponding Ubx protein can lead to such a major change in body design undercuts a primary argument creationists have used against the theory of evolution in debates and biology textbooks. Their specific objection to the idea of macroevolutionary change in animals is summed up in a disclaimer that the Oklahoma State Textbook Committee voted in November, 1999 to include in that state's biology textbooks: "The word evolution may refer to many types of change. Evolution describes changes that occur within a species. (White moths, for example, may evolve into gray moths). This process is microevolution, which can be observed and described as fact. Evolution may also refer to the change of one living thing into another, such as reptiles and birds. This process, called macroevolution, has never been observed and should be considered a theory."

"The creationists' argument rests in part on the fact that animals have two sets of chromosomes and that in order to get big changes, you'd need to mutate the same genes in both sets of chromosomes," explains McGinnis. "It's incredibly unlikely that you would get mutations in the same gene in two chromosomes in a single organism. But in our particular case, the kind of mutation that's in this gene is a so-called dominant mutation, so you only need to mutate one of the chromosomes to get a big change in body plan."

The discovery of this general mechanism for producing major leaps in evolutionary change has other implications for scientists. It may provide biologists with insights into the roles of other regulatory genes involved in more evolutionarily recent changes in body designs. In addition, the discovery in the UCSD study, which was financed by the National Institute of Child Health and Human Development, of how this particular Hox gene regulates limb development also may have an application in improving the understanding human disease and genetic deformities.

"If you compare this gene to many other related genes, you can see that they share certain regions in their sequences, which suggests that their function might be regulated like this gene," says Ronshaugen. "This may establish how, not only this gene, but relatives of this gene in many, many different organisms actually work. A lot of these genes are involved in the development of cancers and many different genetic abnormalities, such as syndactyly and polydactyly, and they may explain how some of these conditions came to be."

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## About embryonic and genetic evidence of evolution? - Biology

I. Fossils provide an objective record of evolution

A. fossils are preserved or mineralized remains or imprints of organisms that lived long ago

B. the fossil record supports three major conclusions

• Earth is about 4.5 billion years old
• organisms have inhabited Earth for most of its history
• all organisms living today share ancestry with earlier, simpler life-forms

C. example of new fossil evidence: whale evolution

• mesonychids, from about 60 million years ago, and about 2 meters long, are hypothesized to be the link between modern whales and hoofed mammals
• Ambulocetus natans, from about 50 million years ago, and about 3 meters long, apparently resembled modern sea lions
• Rodhocetus kasrani, from about 40 million years ago, have reduced hind limbs, flipper-like forelimbs, and were probably almost entirely aquatic
• modern whales have vestigal hind limbs and forelimbs that are flippers

D. the fossil record is incomplete

• most organisms lived and died in places where fossils do not easily form
• environments that produce fossils are wet lowlands, slow-moving streams, lakes, shallow seas, and areas where volcanic ash settles
• most remains of organisms decay or are eaten by scavengers
• some types of organisms, such as shelled organisms, fossilize more easily than others
• radiometric dating allows paleontologists, those who study fossils, to determine the age of fossils

II. Anatomy and development suggest common ancestry

A. homologous structures are those that share a common ancestor

B. the forelimbs of vertebrates are homologous, all containing the same set of bones, but in different proportions

• humerus (upper limb)
• radius and ulna (lower limb)
• carpals and metacarpals (wrist)
• phalanges (fingers/toes)

C. homologous structures during embryonic development reveal common ancestry

• all vertebrates share many stages and structures during embryonic development
• tail, limb buds, pharyngeal pouches

D. vestigial structures are reduced in size and have little or no function, but are homologous to structures in related organisms

## Evidence of Evolution

The earth has been around for millions of years and is constantly changing with time. Layers of the earth hold fossils of past animals that lived on Earth. Studying the fossils and their location in the earth's layers gives us a timeline of the animal's changes, called a fossil record. By using relative dating, scientists can figure out when the adaptations took place, and how they helped the animal survive better in it's enviornment

Dinosaur Fossil Record Mystery

Evidence of evolution is present in vertebrates to this day. Homologous structures are structures that have similar bone structure, and embryos. Most vertebrates have homologous structures, so this shows that they extend from a common ancestor, but their own species has evolved to suit it's own enviornment. An adaption that the species might have aquired is a vestigal organ, an organ that a species has, but doesn't have a use for. This provides evidence for evolution because the species has changed its body to survive better in it's conditions. Homologous structures have similar embryos. Many embryos in the early stages of devlopment look a lot alike, which proves that they have a common ancestor, but as the embryo matures, it shows how the species has changed.

Evidence of evolution is present in vertebrates to this day. Homologous structures are structures that have similar bone structure, and embryos. Most vertebrates have homologous structures, so this shows that they extend from a common ancestor, but their own species has evolved to suit it's own enviornment. An adaption that the species might have aquired is a vestigal organ, an organ that a species has, but doesn't have a use for. This provides evidence for evolution because the species has changed its body to survive better in it's conditions.

Natural & Artifical Selection

Anatomical Structures, Embryology & DNA

Suvival of the Fittest: Giraffes

On the other hand, their an analogous structures. Analogous structures are structures that look alike but are from different ancestors. This shows that even though they don't come from the same ancestor, they have evolved similarily to species with the same needs to survive in their enviornment. Many species are related through genetics. Phylogenetics is the study of the relationship of species through their macromolecules. It shows that organisms have a common relationship through their DNA, which it has evolved from to fit the species own needs.

All over the world, different species of animals exist, all slightly different from each other. Resreach has proved that all the continents used to be joined together in one super continent called Pangea. When all the continents spilt up, all the animals were separated. Then, the animals evolved and adapted to their new enviornments. Depending on where they lived, the animals devloped into different species that had variations that suited their location on the planet.