Bio1331 Animals - Evolution - Chordates And Jawless Fishes (Lecture Seven)

All chordates have a notochord. This is because a notochord is a defining characteristic of chordates. It is a flexible rod-like structure that provides support and serves as a precursor to the backbone in vertebrates. While the notochord may be present only during the embryonic stage in some chordates, it is still present in all chordates at some point in their life cycle. Therefore, it is true that all chordates have a notochord.

The correct answer is "This one!" because lancelets, also known as cephalochordates, are a type of marine chordate that have a long, slender body and a notochord that extends the length of their body. The given answer implies that one of the options presented is a lancelet, but without additional information or context, it is not possible to determine which option is being referred to as "this one."

They only have a notochord during larval stages.

Ernest Haeckel developed the Recapitulation Theory. This theory, also known as the Biogenetic Law, suggests that the development of an organism from embryo to adult recapitulates or mirrors the evolutionary history of its species. Haeckel proposed that the stages of embryonic development in different organisms resemble the adult forms of their evolutionary ancestors, providing evidence for the theory of evolution. His work had a significant impact on the field of evolutionary biology and embryology.

The correct answer is Tunicates, Lancelets, Cephalochordates, Urochordates. These are all different variations of the clade of chordates. Tunicates and Urochordates refer to the same group of marine animals, which includes sea squirts. Lancelets and Cephalochordates also refer to the same group, which includes small, fish-like marine animals. Both variations of the names are valid and commonly used to describe these clades of chordates.

Lancelets, also known as cephalochordates, are a chordate clade that may have resembled ancestral chordates. These small, fish-like marine animals possess many of the key characteristics of chordates, including a notochord, a dorsal nerve cord, and pharyngeal slits. They are considered to be the closest living relatives to the vertebrates and provide valuable insights into the evolutionary history of chordates. Tunicates, or urochordates, are another chordate clade but are more derived and have undergone significant evolutionary changes compared to lancelets. Therefore, lancelets/cephalochordates are a more likely candidate for resembling ancestral chordates.

Recapitulation Theory is the name given to the theory that claims an organism's biological/embryological development mirrors its species' evolutionary development. This theory suggests that during its development, an organism goes through stages that resemble the evolutionary stages of its ancestors. This theory was proposed by Ernst Haeckel in the late 19th century and has since been revised and refined. It suggests that the development of an organism from embryo to adult can provide insights into its evolutionary history.

The notochord of Lancelets/Cephalochordates is a flexible rod-like structure that extends the entire length of the Lancelet body. It is present throughout the entire life of the Lancelet and provides support and structure. This distinguishes Lancelets from other chordates, such as vertebrates, where the notochord is only present during embryonic development and is later replaced by the vertebral column.

The correct answer is Myxini, Myxinis, Hagfish, Hagfishes, Pentromyzontida, Lamprey. These are all names of clades of vertebrates. Myxini refers to the clade that includes hagfish, while Lamprey refers to the clade that includes lampreys. Hagfishes and Pentromyzontida are alternative names for the clade that includes hagfish.

The traits that are commonly associated with vertebrates include a rigid, internal skeleton, 2 pairs of appendages, an anterior skull, a large brain, an advanced circulatory system, and internal organs suspended in a large coelom. These traits are characteristic of vertebrates and distinguish them from other organisms.

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