Animals are ____________that ingest their food
heterotrophs
All animals can trace their lineage to a common ancestor that lived in the _____
Neoproterozoic era
Which of the following is (are) unique to animals?
nervous conduction and muscular movement
Animal cells are held together by structural proteins such as___________
collagen
________ are groups of cells that have a common structure, function, or both
Tissues
Most animals reproduce sexually, with the _______ stage usually dominating the life cycle
diploid
Cleavage leads to formation of a multicellular, hollow _________
blastula
The blastula undergoes __________, forming a ________ with different layers of embryonic tissues
gastrulation, gastrula
A ______ is sexually immature and morphologically distinct from the adult; it eventually undergoes ___________
larva, metamorphosis
A _________resembles an adult, but is not yet sexually mature
juvenile
Most animals, and only animals, have _______ that regulate the development of body form
Hox genes
Although the Hox family of genes has been highly conserved, it can produce a wide diversity of ___________
Animal morphology
The common ancestor of living animals (675-800 MYA) may have resembled modern _________, protists that are the closest living relatives of animals
choanoflagellates
The common ancestor is likely to have been a protist that lived during the _________.
Neoproterozoic
Early members of the animal fossil record include the _________, which dates from 565 to 550 million years ago
Ediacaran biota
The ____________ (535 to 525 million years ago) marks the earliest fossil appearance of many major groups of living animals
Cambrian explosion
The beginning of the_________ era followed mass extinctions of both terrestrial and marine animals. These extinctions included the large, nonflying dinosaurs and the marine reptiles
Cenozoic
Zoologists sometimes categorize animals according to a _________, a set of morphological and developmental traits
body plan
In some species, such as worms, sea urchins, and vertebrates, the protein ________ marks the site of gastrulation and activates the transcription of genes necessary for the process.
-catenin
Some animals have _________, with no front and back, or left and right
radial symmetry
Two-sided symmetry is called _________
bilateral symmetry
Bilaterally symmetrical animals have
A dorsal (top) side and a ventral (bottom) side
A right and left side
Anterior (head) and posterior (tail) ends
__________, the development of a head
Cephalization
Radial animals are often _____or __________
sessile, planktonic
________ is the germ layer covering the embryo’s surface
Ectoderm
_________ is the innermost germ layer and lines the developing digestive tube, called the archenteron
Endoderm
Sponges and a few other groups lack ______
true tissues
________animals have ectoderm and endoderm
These include cnidarians and comb jellies
Diploblastic
_______ animals also have an intervening ______ layer (develops into the lining of the coelom, muscles, skeleton, gonads, kidneys and circulatory system); these include all bilaterians
Triploblastic, mesoderm
Most triploblastic animals possess a _______
body cavity
A true body cavity is called a ________ and is derived from mesoderm
coelom
________ are animals that possess a true coelom
Coelomates
A ________ is a body cavity derived from the mesoderm and endoderm
pseudocoelom
Triploblastic animals that possess a pseudocoelom are called ___________
pseudocoelomates
Triploblastic animals that lack a body cavity are called _________
acoelomates
_________ is a clade of animals with true tissues
Eumetazoa
Most animal phyla belong to the clade ________ and are called __________
Bilateria, Bilaterians
What distinguishes a coelomate animal from a pseudocoelomate animal is that coelomates
a body cavity completely lined by mesodermal tissue, whereas pseudocoelomates do not.
The morphology-based tree divides bilaterians into two clades _______ and _________
deuterostomes, Protostomes
Ecdysozoans shed their exoskeletons through a process called _____. Example Cicada.
ecdysis
There are several hypotheses regarding the cause of the cambrian explosion and decline of Edicaran Biota
- New Predator-prey relationship
- A rise in atmospheric oxygen
- The evoulution of the HOX gene Complex