Study Questions for my Biology Exam !!?

I don't have a key to compare my answers to and I am new to this class so I don't know anyone else in it. Some feedback on these questions would be so helpful for me to see if I'm on the right track for my exam. Thanks!

Compare function and level of development of the coelom in annelids, molluscs, arthropods, echinoderms and chordates. Explain why differences exist.

How have arthropods and chordates adapted to terrestrial living? In what ways are their solutions similar? Different? Explain how those adaptations may have contributed to the groups’ success.

What are the four unique chordate characteristics? What is the significance of each structure (i.e., how did it aid in the group’s success)? How are these traits involved in locomotion and feeding in larvae or adults?

What traits allow craniates to be more active than other chordates? How did those traits contribute to higher activity levels?

Why is external fertilization more common in aquatic environments and internal fertilization more common in terrestrial environments?

Draw a phylogenetic tree for the major clades of animals. Indicate the origins of important derived traits on the trees. Discuss structure, function, and evolutionary significance of those traits.

1 Answer

  • Anonymous
    9 years ago
    Favorite Answer

    Bio II with Maher? Hope this helps.

    1. Coelom development in annelids etc:

    In annelids, produced by shizogony. Forms a hydrostatic skeleton and a space for egg storage.

    In molluscs, the coelom forms a hydrostatic skeleton and provides suspension for the internal organs.

    In arthropods, secondarily depricated as there is no need for a hydrostatic skeleton. Mostly replaced by haemocoel, but coelom still houses the reproductive organs.

    In echinoderms, secondarily depricated and forms the basis of a circulatory system.

    In chordates, well-developed and complete. Also not involved in hydrostatic skeleton.

    Present in all five groups. The first three are protostomes (spiral determinate cleavage and shizogony) and the last two are deuterostomes (radial indeterminate cleavage and enterocoely)

    2. Arthropod and chordate adaptations to terrestrial life:

    Present in general: Coelom, skeleton, nervous system, respiration. The coelom facilitates differential growth rates of internal organs and can be the basis for the digestive system, etc. Skeleton provides support to counteract gravity, which is felt more strongly in a non-buoyant environment. Nervous system and cephalization (concentration of sense organs at the anterior end of the animal) facilitate higher activity levels and the ability to seek out food, identify threats, react to the environment. Respiration / gas exchange is also necessary for aerobic metabolism.

    Major differences:

    Coelom - present and developed in both but not part of respiration in arthropods (that role taken by haemocoel). Respiration by diffusion limits arthropod size. Houses internal organs in both.

    Skeleton - Exoskeleton in arthropods, muscles on the inside. Made of chitin. Has to molt to grow. Limits arthropod size due to pronounced effects of gravity. Endoskeleton in chordates, with muscles outside it. Can grow a lot more, segmented muscle attachment allows for fine motor control.

    Nervous system and cephalization - Derived in both, not ancestral to common ancestor. Formed by concentration of sense organs at the anterior end of the nerve cord in chordates, but through compression of trunk segments in arthropods. Accomplishes the same task in both: pharynx and sense organs are co-located on the anterior end of the animal, facilitating food seeking and threat response.

    3. Four unique characteristics of chordates (always found at some stage of development, but one or more may be absent in the adult):

    Notochord - Present in all chordates, located ventrally from the dorsal hollow nerve cord. Forms the developmental basis for the segmented body plan in chordates. Eventually surrounded by the vertebral colum and remains as the discs between the vertebrae.

    Dorsal hollow nerve cord - Typically, the spinal cord. Located dorsal to the notochord, forms the basis of the nervous system. Cerebrates have sense organs concentrated at the anterior end, which forms the head in craniates.

    Pharyngeal slits / pouches - Form the gills in fish, eustachian tubes in humans, ear bones in some other organisms, suspension feeding apparatus in lancelets, etc. Provides a versatile basis for various feeding apparatus and sense organs.

    Post-anal tail - Categorically, a tail located posterior to the anus. Assists with balance in quadrupeds and locomotion in marine / freshwater tetrapods (fish, etc).

    Also worth mentioning are segmented muscles (think abdominal muscles) attached to an endoskeleton, which allows for much finer motor control than, for example, arthropods with internal muscles and an exoskeleton.

    Source(s): Principally from lecture notes.
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