Chapter 32 Flashcards
what are the three aspects that depict an animal
nutritional mode, animal structure and specialization, and reproduction and development
describe the nutrition of animals
heterotrophs that ingest their food
describe the structure and specialization of animals
they are multicellular eukaryotes that lack cell walls, bodies held together by proteins such as collagen, also contain nervous and muscle tissue
describe the reproduction and development of animals
most reproduce sexually, with diploid stage dominating life cycle, zygote undergoes cleavage after fertilization, cleavage forms blastula, blastula forms gastrula
define larva
sexually immature and morphologically distinct from the adult - undergoes metamorphosis
how long ago did the common ancestor of living animals live and what is it believed to have resembled
between 675 and 875 million years - modern choanoflagellates
this happened 535 to 525 million years ago and marks the earliest fossil appearance of many major groups of living organisms
Cambrian explosion
three hypotheses regarding the cause of the Cambrian explosion
new predator-prey relationships, a rise in atmospheric oxygen, and the evolution of the hox gene complex
first land animals about 460 million years ago
protostomes - blastopore becomes mouth, arthropods, mollusk, annelid worms
vertebrates made the transition to land about ____ years ago
360 million
what marked the beginning of the Cenozoic era
mass extinctions of terrestrial and marine animals
this is a set of morphological and developmental traits
body plan
two sided symmetry
bilateral symmetry
the development of a head
cephalization
collections of specialized cells isolated from others by membranous layers
tissues
the germ layer covering the embryo’s surface
ectoderm
the innermost germ layer and lines the developing digestive tube
endoderm
the developing digestive tube
archenteron
these have and ectoderm and an endoderm
diploblastic
triploblastic animals have a ______
middle layer - mesoderm
a true body cavity
coelom
a body cavity derived from the mesoderm and endoderm
hemocoelom
triploblastic animals that lack a body cavity
acoelomates
in protostome development cleavage is ______ and ______
spiral and determinate
in deuterostome development, cleavage is ______ and ______
radial and indeterminate
what happens with indeterminate cleavage
each cell in the early stages of cleavage retains the capacity to develop into a complete embryo
