Odd Stuff

One is a limpet and the other barnacle. Which is which?

From Evol 2 again

Qn23: clarification. It is onto not ortho-logy.
Ontology is developmental biology:
The theory of recapitulation, also called the biogenetic law or embryological parallelism, and often expressed as "ontogeny recapitulates phylogeny.
But is of course refuted on many fronts (so is not important)
The recapitulation theory claims that each successive stage in the development of an individual represents one of the adult forms that appeared in its evolutionary history.
(This idea is too extreme! If this is true, we will have real gills which close up later during embryo devt!)
Modern observation
Species which have an evolutionary relationship typically share the early stages of embryonal development and differ in later stages. Examples include:
• The backbone, the common structure among all vertebrates such as fish, reptiles and mammals, appears as one of the earliest structures laid out in all vertebrate embryos.
If a structure vanished in an evolutionary sequence, then one can often observe a corresponding structure appearing at one stage during embryonic development, only to disappear or become modified in a later stage. Examples include:
• Whales, which have evolved from land mammals, don't have legs, but tiny remnant leg bones lie buried deep in their bodies. During embryonal development, leg extremities first occur, then recede. Similarly, whale embryos have hair at one stage (like all mammalian embryos), but lose most of it later.
• The common ancestor of humans and monkeys had a tail, and human embryos also have a tail at one point; it later recedes to form the coccyx.
In other words: there is embryological devt does not show us the actual evol history.


Qn7: The simplest organism is found at the end of a tree. Which end?(hint: How does a real tree look like?) – towards the pointed end of a V-shape

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Jane was asking about some questions on the cloning and gene therapy MCQs. I will post it up once i have time. Seemed like I have to do it while overseas cos i am really rushed for time here :P

H3 bio also......

Let me pack first k? I havent even settle lodging yet so.....shucks!!!!!