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Divergent Evolution

Annelida and Protoannelida are marine worms that have diverged from a common ancestor.  They’re both arthropods that lived in ocean sediment during the Cambrian period.  They we’re very similar and we’re both symmetrical, had soft bodies and we’re multi segmented. But, structural difference showed that they most likely evolved into two different species from an annelid ancestor 600 million years ago.

Coevolution

An example is rhizocephalan, which is a barnacle parasite on decapods like crabs and shrimp.  The rhizocephalan enters the host and grows throughout the digestive system.  It then plants a sac like externa for reproduction.  Once fused it produces male and female eggs.  The host thinks the externa is its own egg sac and cares for it.  Over time, these organism evolve to fit to others needs together.  The rhizocephalan has evolved so much that it's barely recognizable as a member of the cerripedia group and is hard to tell it’s not part of the host.

Convergent Evolution

The complex eyes of crustaceans are very similar and perform the same function as the eyes of arthropods and cephalopods.  But, they evolved separately.

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Protein

Tropomyosin is a protein found in crustaceans.  It’s common in almost every crustacean and in insects, arachnids and mollusks.  It’s responsible for contraction of skeletal muscle and makes up the exoskeleton.  The fact that this is found in all of these organisms proves that they have evolved from a common ancestor, considering not all these organisms aren’t crustaceans.

Carbohydrate

Chitin is a polysaccharide that makes up the exoskeleton of crustaceans.  It protects delicate tissues.  It is not only found in crustaceans but also many arthropods like insects and spiders. This proves that they may have come from a common ancestor because they all use the same substance for protection.

http://www.wisegeekhealth.com/what-is-a-tropomyosin.htm

http://www.ncbi.nlm.nih.gov/pubmed/10474029

https://docs.google.com/document/d/1Yt15XLsJaUy_ma2HXAWrn4DQr9YGR-Q4vyRLzXP1FVA/edit#

http://www.encyclopedia.com/topic/chitin.aspx

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link

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prawn shrimp

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krill

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crab

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A lobster have 100 chromosomes.  A crab has 104 chromosomes.  The amount of chromosomes for barnacles depends on the species and can be anywhere from 12 to 200.  There’s not much to account for the difference in barnacles except that they’re not as similiaras crabs and lobsters are.  Both crabs and lobsters have many similiarites and it only made sense they had a similiar numberof chromosomes.  This supports the evolution of crustaceans because these similiar organisms were formed around the same time from a common ancestor.
Source 1   Source 2

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Topic 5

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Topic 4

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Topic 3

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Topic 2

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Topic 1

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Lobster

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Shrimp

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Homologous Structure
A homologous structure in the animal kingdom is the maxillae.  In ants they’re used for breaking food up so the ants can swallow it.  In grasshoppers they are used to move the food into the mouth.  In crayfish, which is a crustacean, they are used to move food into the mouth and water into the gill chamber.  It makes up the jaw of dogs and humans

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Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.

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I believe crustaceans have gone through punctuated evolution.  Crustaceans have not changed much since 600 million years ago.  This was shown in my fossils.  Compound eyes haven’t changed much which means that the rest of the organisms hasn’t.  There wasn’t a gradual change in the eyes, it was not predictable.  There isn’t that much variation in traits and most crustaceans live in groups.  Punctuated equilibrium is also supported by DNA sequences.  The atyidae shrimp and paelimonidae shrimp have the same DNA strands and base in different orders.  They have evolved from a common ancestor or from each other, but it wasn’t gradual.  The phylogeny tree based on morphology shows evolutionary relationships between the crustaceans but it doesn’t follow a set pattern is is punctual.  Crustacean evolution has followed a punctuated equilibrium process.

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Although crustaceans are one of the least evolved subphylum to exist, there is still evolution present.  Over millions of years natural selection has caused the organism to change and break into new species, which is shown in the phylogenetic tree.  Some are considered living fossils and haven't evolved much like horseshoe crabs.  Other crustaceans like mantis shrimp have evolved significantly.  From similiar DNA sequences in shrimp, identical biochemistry, related embryology in lobster and shrimp, and fossils that map the evolution of the compund eye, there is plenty of evidence to crustacean evolution.  All three types of natural selection are changing crustaceans over time and wil continue to change them. (Natural selection examples in document.)

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This tree shows the relationships between many different crustaceans.  It shows the evolution of crustaceans based on their morphology (relationship between their features).  Crustaceans started with the blind class of crustaceans called remipedia.  Then through evolution they grew into the maxillopada class.  Through more and more evolution they grew more complex into phyllopoda and malacostraca.

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Phylogenetic Tree

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The current of the Mediterranean Sea will push Hemimysis margalefi into different caves.  Since the population is splitting up this will change their gene pool.   Since the population of the cave dwelling crustacean is being split up and separated, small amounts of Hemimysis margalefi will be found in some caves.  Since there isn't as many alleles, gene flow will affect these smaller populations more and they’re more susceptible to major changes.
Source

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Different clusters of paramysis laccustris have appeared in different parts of the Black and Caspian Sea. Because of these seas, it appears that there are isolated clusters of paramysis lacustris that have differences because of higher mutation rates and large population. There is a gene flow coming from the east and the Caspian Sea disperses it into different clusters of the crustacean. The Caspian sea has high salinity water.
Source

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The atyidae is a family of shrimp, alpheidae is a family of snapping shrimp that resembles a lobster, and palaemonidae is a genus of caridean shrimp.  All of these shrimp are very similiar and most likely evolved from a common ancestor.  This is supported by their DNA.  All of these shrimp have the same DNA strands in different orders.  This shows that over time DNA changed in crustaceans.  But, since its all the same strands in a different order, the organisms are very similiar.

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The atyidae is a family of shrimp, alpheidae is a family of snapping shrimp that resembles a lobster, and palaemonidae is a genus of caridean shrimp.  All of these shrimp are very similiar and most likely evolved from a common ancestor.  This is supported by their DNA.  All of these shrimp have the same DNA strands in different orders.  This shows that over time DNA changed in crustaceans.  But, since its all the same strands in a different order, the organisms are very similiar.

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DNA ANALYSIS

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Both
shrimp and lobsters share similarities in development.  They both hatch in eggs and developed in the
eggs.  Towards the beginning they appear
very similar because they are both just blobs that fill up the egg.  They continue to look similar because the
blobs begin to divide into two half’s of a body in each embryo.  You can then see the eyes appear towards the
front in both embryos. The lobster appears more complex once it hatches than
the shrimp, but since they both are invertebrates from eggs, they are very similar
towards the beginning of development. 

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Both
shrimp and lobsters share similarities in development.  They both hatch in eggs and developed in the
eggs.  Towards the beginning they appear
very similar because they are both just blobs that fill up the egg.  They continue to look similar because the
blobs begin to divide into two half’s of a body in each embryo.  You can then see the eyes appear towards the
front in both embryos. The lobster appears more complex once it hatches than
the shrimp, but since they both are invertebrates from eggs, they are very similar
towards the beginning of development. 

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The fossils show evolution in eyes.  515 million years ago, the super predator has compound eyes with 16,000 lenses and one inch in length.  500 million years ago, not much changed appeared in the compound eyes except that they were on stalks.   Then 390 million years ago in Trilobites, complex eyes appeared.  Underneath their compound eyes, there were sensory cells wired to the brain.  160 million years ago in the Jurassic period crustaceans were found with a high performance eye like that of a dragonfly.  Later in the Quaternary period the mantis shrimp had complex eyes.  There was not that much changed since 515 million years ago.

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Characteristics, Exemplary Organisms and Taxonomy