A = acoelomate, P = pseudocoelomate, C = eucoelomate For the three major clads o
ID: 98378 • Letter: A
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A = acoelomate, P = pseudocoelomate, C = eucoelomate For the three major clads of bilaterians, what can be inferred about whether the common ancestor of the clade had a true coelom? ________________ On the evolutionary tree above, which organisms are characterized by having jointed appendages?_________ Instructions: Read this passage and write "yes" or "no" in each box for whether each group has the characteristic or not. Construct a phylogenetic tree for mammals. Don't forget to add shared characteristics (synapomorphies) to your tree.Explanation / Answer
10. It is documented that the ancestor of Bilaterians appeared at the end of the Vendian period the last geological period of the Neoproterozoic Era preciding the Cambrian period. This is approximately 635 to 541 million years ago.
11. The Arthopoda is the group of invertebrate animals having an exoskeleton, body divided into segments each segment with a pair of jointed appendages or limbs. These organisms have cuticle made of chitin mineralized by calcium carbonate. This group is traditionally divided into five subgroups:- trilobites, chelicerates, myriads, crustaceans and hexapods.
This chelicerates is distinguished by their claw-like jointed appendage which is called chelicerae from which this group name is derived. Most of the marine chelicerates are extinct while a few members have survived.
The crustaceans have appendages with two branches at the tips and the term birame is used to describe the members. The extant species are mainly aquatic animals and also there are some terrestrial species.
The hexapods are the largest extant subgroup with unique characteristics like having only one pair of sensory antennae and their appendages are unbranched or uniramous. The hexapods include the Class Insecta with twenty-six order
12. Monotremes are one of the three groups of mammals. The other groups are Eutheria or placentals and marsupials.
They have hair on their body, they have mammary glands to feed the young ones. They have short gestation period and no placenta. An example of monotreme is platypus or echidna.
The marsupials have a pouch in which they carry their young ones.
They have hair, mammary glands, short gestation period. The marsupials do not have placenta.
The Eutheria or placentals have all the traits mentioned-true hairs, mammary glands. They have placenta and have long gestation period.
13. Cladistics is a method to hypothesize the relationships among organisms and to reconstruct evolutionary trees on the basis of such information. The basis of cladistics is data on the characters or traits of the organisms in which we are interested.
While constructing a phylogenetic tree the species of interest are shown at the tips of the tree’s branches. The branches represent the evolutionary history of a species that means how they evolved from a common ancestor through the process of divergence.
Each branch point represents the most common ancestor shared by all the species from which they descended.
In building a phylogenetic tree, the species are organized into nested groups based on derived traits different from those of group’s ancestor.
Synapomorphy: A trait present in an ancestral species which is shared exclusively by its descendants during the course of evolution.
This trait is derived from ancestors and therefore used in determining phylogenetic relationships.
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