Chapter 32 - Overview of Animal Diversity Flashcards
What are animals?
multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers
What kinds of tissues are unique to animals?
Nervous tissue and muscle tissue
What do animals’ cells have instead of cell walls?
Structural proteins like collagen
What is cleavage?
When a zygote undergoes rapid cell division after fertilization
What does cleavage lead to?
the formation of a multicellular, hollow blastula
What is gastrulation?
when a blastula forms a gastrula with different layers of embryonic tissues
What is a larva?
sexually immature and morphologically distinct from the adult stage of animal development
What is a juvenile?
the stage of animal development when it resembles an adult, but is not sexually mature yet
What are Hox genes?
genes that regulate the development of body form
How are choanoflagellates and animals similar?
They have sequence similarities in the genes involved in adherence and attachment that were required with the advent of multicellularity.
What was the Cambrian explosion?
the earliest fossil appearance of animals
List the characteristics of bilaterians
Bilaterally symmetric form, complete digestive tract, one-way digestive system
What is a body plan?
a set of morphological and developmental traits that is used to categorize animals
What is radial symmetry?
when animals have a top and a bottom but no front, back, left, or right; the type of symmetry found in a flowerpot
What is bilateral symmetry?
when animals have a dorsal (top) side and a ventral (bottom) side, a right side, a left side, an anterior (front) and a posterior (back)
Compare the movements of radially and bilaterally symmetrical animals.
Radial animals are sessile or planktonic; they drift or swim weakly. Bilateral animals move actively and heave a central nervous system.
What are tissues?
collections of specialized cells isolated from other tissues by membranous layers
How are tissues formed?
From three germ layers during development
What is the ectoderm?
the germ layer covering the embryo’s surface
What is the endoderm?
the innermost germ layer lining the archenteron (developing digestive tube)
What are diploblastic animals?
Animals with only an ectoderm and an endoderm
What are triploblasic animals?
animals that have an ectoderm, an endoderm, and a mesoderm; includes all bilaterally symmetrical animals
What is a mesoderm?
an intermediate tissue layer between the ectoderm and the endoderm
What is a coelom?
a true body cavity, derived from the mesoderm
What are coelomates?
animals with a true coelom (body cavity)
What is a pseudocoelom?
a false body cavity that isn’t lined on both sides because its derived from the mesoderm and the endoderm
What are pseudocoelomates?
triploblastic animals with a pseudocoelom
What are acoelomates?
triploblastic animals that lack a body cavity
What are the functions of a body cavity?
Fluid cushions suspended organs; fluid acts like a skeleton against which the muscles can work; Enables internal organs to grow and move independently of the outer body wall
What is a grade?
a group whose members share key biological features
What is a clade?
a group consisting of an ancestor and all of its descendants
What happens in protostome development?
the cleavage is spiral and determinate
What is a determinate cleavage?
when the developmental fate of embryonic cells is determined early in development
What is deuterostome development?
the cleavage is radial and indeterminate
What is an indeterminate cleavage?
when each cell in the early stage of cleavage retains the capacity to develop into a complete embryo; makes identical twins and embryonic stem cells possible
What is the difference in coelom formation between protostomes and deuterostomes?
In protostomes, the splitting of solid masses of the mesoderm forms the coelom; in deuterostomes, the mesoderm buds from the wall of the archenteron to form the coelom
What does the blastopore do?
Connects the archenteron to the exterior of the gastrula
When is the blastopore formed?
during gastrulation
What is eumetazoa?
the clade of animals with tissues; “true animals”
What is the only clade of bilaterian animals that includes vertebrates?
Chordata
What are invertebrates?
animals that lack a backbone
What are vertebrates?
animals with a backbone
What are the three clades of bilaterians?
Deuterostomia, Ecdysozoa, and Lophotrochozoa
Which clade of bilaterians includes vertebrates and invertebrates?
Deuterostomia
Which clade of bilaterians secretes external skeletons?
Ecdysozoa
What is ecdysis?
when Ecdysozoans shed their exoskeletons
Which clades of bilaterians only have invertebrates?
Ecdysozoa and Lophotrochozoa
What is a lophophore?
a feeding structure
What bilaterian clade can undergo the trochophore larva stage?
Lophotrochozoa
