biology 26.1
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26.1 Introduction to the Animal Kingdom
Invertebrate
• Animal that does not have a backbone, or vertebral column.
vertebrate
• Animal that has a vertebral column, or backbone
Feedback inhibition
• Process in which the product or result stops or limits the process.
blastula
• Hollow ball of cells formed when a zygote undergoes a series of divisions.
protostome
• Animal whose mouth is formed from its blastopore.
deuterostome
• Animal whose anus is formed from the blastopore of a blastula.
anus
• Opening through which wastes leave the digestive tract.
endoderm
• Innermost germ layer of most animals; develops into the linings of the digestive tract and much of the respiratory system.
mesoderm
• Middle germ layer of most animals; gives rise to muscles and much of the circulatory, reproductive, and excretory systems.
ectoderm
• Outermost germ layer of most animals; gives rise to outer layer of the skin, sense organs, and nerves.
Radial symmetry
• Body plan in which body parts repeat around the center of the body; characteristic of sea anemones and sea stars.
Bilateral symmetry
• Body plan in which only a single, imaginary line can divide the body into two equal halves; characteristics of worms, arthropods, and chordates.
cephalization
• Concentration of sense organs and nerve cells at the front of an animal’s body.
Key Concept
• Animals, members of the kingdom Animalia, are multicellular, eukaryotic heterotrophs whose cells lack cell walls.
Key Concept
• Animals carry out the following essential functions: feeding, respiration, circulation, excretion, response, movement, and reproduction.
Key Concept
• Complex animals tend to have high levels of cell specialization and internal body organization, bilateral body symmetry, a front end or head with sense organs, and a body cavity.
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