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Heterochrony takes on a few different forms.
In Predisplacement, a character begins developing earlier in the descendent lineage than it did in the ancestor.
On the flip side, Postdisplacement is when a character begins developing at a later stage in the descendent lineage when compared to the ancestor.
In both cases, the character does not change, only the timing of developmental events.
In Acceleration, the character develops at a faster rate in the descendent than in the ancestor.
On the flip side, Neoteny is when the character develops at a slower rate in the descendent lineage when compared to the ancestor.
In both cases, the character itself is not affected; rather the growth rate is.
With Hypermorphosis, a character continues developing beyond the point at which it stopped in the ancestral lineage.
On the flip side, Progenesis is when the development of the descendent's character stops progressing before the point at which it stops in the ancestral lineage.
In both cases, the character itself will change.
Hypothetical Example:
The tail of an ancestral feline species grows to 27 inches in 2.0 years. The feline species splits into 2 descendent lineages. One feline descendent lineage splits into a species(we will call it 'Species X') that maintains the 27 inch growth and the 2.0 year growth time; AND a species(we will call it 'Species Y') that maintains the 2.0 year growth time but the tail grows to 29 inches. This is an example of Heterochrony, specifically an example of Heterochrony through a combination of Hypermorphosis(more growth) and Acceleration(increased growth rate).
If it were just Hypermorphosis, the tail would take more time to grow to 29".
If it were just Acceleration, the tail would reach 27"... just sooner.
Thus; it is a combination. Happens more often than you would think. :)
What else can I help you with?
What is an evolutionary change in the rate or timing of developmental events?
heterochrony
What has the author Michael L McKinney written?
Michael L. McKinney has written: 'Readings for Environmental Literacy' 'Evolution of life' -- subject(s): Origin, Evolution (Biology), Life, Human evolution 'Environmental Science Note Taking Guide' 'Readings for Environmental Literacy 1998' 'Heterochrony' -- subject(s): Heterochrony (Biology)
What is the history and development of biology by identifying famous foreign biology?
Developmental biology - or 'embryology' - is a subject with a long and distinguished, but uneven, history. It is remarkable for the list of leading scientists and philosophers who have contributed to it from antiquity up to the present era. Because embryos are typically minute and inaccessible direct study and understanding has been slow and relatively recent: before the mid-nineteenth century theories of reproduction and the origin of living forms were largely speculative. Since then embryology has varied greatly in its importance within mainline biological thinking. At one time it provided key evidence for evolution; later for early theories of genetics. Recently, and even now it can be argued, biologists are divided and unclear about how best to demarcate the subject because it overlaps with many other biological themes as diverse as reproduction, malformation, aging and cancer. Today it tends to be approached through the techniques of molecular biology and molecular genetics, and has acquired renewed interest in the context of fertility enhancement, stem cells and genetic engineering. Key Concepts:Historically, developmental biology has at times been central to biological thinking: for example as key evidence for change and succession in body forms during evolution.The historical theme of whether, in part, 'ontogeny recapitulates phylogeny' remains an open question to this day.Investigative embryology created some of the most elegant and decisive experimental designs in the history of biology.Developmental biology remains the repository of some of the greatest remaining challenges within biology: for example how to account for the complexity and dynamic properties of living systems.The concepts of allometry and heterochrony have their origins in the study of embryos.Developmental biology remains a crucial challenge to the currently dominant explanation of biological systems in terms of molecular genetics: it demonstrates the equal importance of frequently overlooked 'epigenetic' considerations in accounting for biological form.IVF, the stem cells concept and the potential of regenerative medicine have their theoretical base in the standard concepts derived from developmental biologyKeywords: developmental biology; embryology; recapitulation; experimentalism; reductionism; organiser; genetic engineering
Word beginning with the letter h?
Officially, yes. Most teachers/professors will accept it either way. ANSWER In American English, it depends on whether or not the "h" is sounded. In "hour," it is not sounded; therefore, we say, "an hour." In "hostage," it is sounded; therefore, we say, "a hostage." [Some U.S.A. dialects use "a" in some words even when the "h" is not sounded. In the South, for example, one hears, "I'll be back in a (h)our."] That view rests on the general rule that if a word begins with a vowel we use "an," if it begins with a consonant, we use "a." Some h-words have alternate pronunciations, with the h and without. For example, the word "homage" is homage or omage -- or, in modern film lingo "ohMAGE." In America, we would say, "a homage"; "an omage"; "an ohMAGE." [spelvin]
Which is real creation or evolution?
Both are real, and neither contradicts the other. This is somewhat true: we are created. We have a Creator. Anyone who disagrees with me can talk to me and I will prove that we indeed have a Creator. There is no other explanation for the amazing and intricate detail that is in our body. The cells, all the systems in the body, and how we have been given exactly what we need. If you have studied life science then you can see how completely impossible it would be to get the intricate and amazing systems which we contain, from a simple explosion. Think of it this way: you have just received a new box of Legos and you shake them really hard. You just can't expect to open the box and see the intricate Tower of London that the kit was supposed to make. If you do expect this you are either brainwashed or insane. Now whether or not our Creator used the process of evolution is not clarified in the Bible so people have different beliefs.Another answer: To say that those who believe in evolution are insane or brainwashed, we can say that the finger points both ways. There is no way to prove the creationism view point. Through the process of descent with modification, the common ancestor of life on Earth gave rise to the fantastic diversity that we see documented in the fossil record and around us today. Evolution means that we're all distant cousins: humans and oak trees, hummingbirds and whales. It all began with the Big Bang around 14 billion years ago. Thinking man first was seen more than 500,000 years ago. What started the Big Bang...no one knows even if they would like to think that they know. At least scientists can admit that they still don't know it all.To say that shaking a box of Legos and expecting them to form into the Tower of London is not what evolution is about. We are saying that life evolved from single cells and then organisms that have as few has 800 cells into larger and more complex organisms all under the response to the environment.Another answer:A Jewish answer is that we have an unbroken national tradition of 3300 years to the Revelation at Sinai. God states that He created the universe (Genesis 1:1; Exodus 20:10). This tradition is accepted by Christianity and Islam also. Not to mention, that Evolutionists have not put forth any putative proofs that would undermine the tradition.God's creation of the universe explains the vast wisdom found within it.There are some people who believe in Creation without quoting the Bible. Their reasoning includes:1) The glaring lack of transitional fossils has been noted by the evolutionists themselves, such as this statement from the famous paleontologist and evolutionist George G. Simpson; quote: "The regular lack of transitional fossils is not confined to primates alone, but is an almost universal phenomenon.""The lack of transitional series cannot be explained as being due to the scarcity of material. The deficiencies are real; they will never be filled" (Nilsson, N. Heribert)."To the unprejudiced, the fossil record of plants is in favor of special creation" (Corner, E.J.H., Contemporary Botanical Thought).Another answer:Many religious people, including theologians, feel that a deeper understanding of nature actually enriches their faith. Moreover, in the scientific community there are thousands of scientists who are devoutly religious and also accept evolution.It can not be both ways. Besides mutations are harmful, helpful or neutral depending on the third base (wobble effect).The dates that radioactive clocks have put on evolutionary history are astonishing. Life is well over 3.5 billion years old, and until about 600 million years ago, the planet was dominated by microbes. Radioactive clocks have shown that evolution can change its pace. Almost all scientists agree.Harvard paleontologist Stephen Jay Gould drew attention back to embryos. He documented the history of scientific research that had led to so much confusion. The timing of development is controlled by two knobs. One controls the rate at which an organism grows. The other controls the rate at which it changes shape over time. Random mutation may end up changing the settings of each knob, thereby speeding up or slowing down the rate at which a species' embryos develop. These kinds of adjustments can alter the entire body of an organism, or individual organs. Gould predicted that with heterochrony, the genes that regulate other genes would hold the key to the evolution of embryos. His prediction has now been borne out.Junhyong Kim and his fellow Yale biologists compared the timing at which a crucial developmental gene became active in the fruit fly and two close relatives. They found that the gene (for timing) started to make its proteins at different rates in the 3 species led to differences in their anatomy - even though the developmental gene itself is identical in all three species.And Lastly: Though fishermen will always tell tall tales about the big one that got away, more and more evidence suggests that the "big ones" simply don't exist anymore and Dr. David O. Conover's work suggests why: many fish are evolving smaller body sizes. We are changing their environment by fishing for and selecting the larger. The genes that produce the smaller size are selected. This is natural selection at work now.One other thing that shows evolution at work today is the fact that some groups of peoples have higher numbers with one recessive gene for sickle cell anemia. They live in areas of the world where malaria is common. People with one copy of the gene live longer than those with none. People with two copies do not survive long. The environment, along with the mosquitoes, are selecting humans with the gene that allows them to live longer and reproduce more children. Both the fish and people are evolving right now at this time.
