Zoo-Lab (Sem-1) Chapter 6: An Introduction to Animal Diversity

animals

multicellular, heterotrophic eukaryotes with tissues that develop embryonic layers; over 1.3 million living species identified; lack cell walls; held together by structural proteins such as collagen; uniquely have nervous and muscle tissue; mostly reproduce sexually

diploid stage

dominates the life cycle of animals

cleavage

rapid cell division of zygote after fertilization

blastula

hollow ball of cells formed during cleavage

gastrulation; gastrula

the blastula undergoes ____________, forming a ________ with different layers of embryonic tissues

larva

sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis

metamorphosis

a biological change of form

Hox genes

found in all animals and only animals; regulate the development of body form

675 and 875 million years ago

when the common ancestor of living animals may have lived

choanoflagellates

protists that are the closest living relatives of animals that resembled the common ancestor of all living animals

Mawsonites spriggi

consist of a rounded diamond shape, made up from lobes radiating out from a central circle roughly 12 cm in diameter

Spriggina floundersi

the official fossil emblem of South Australia; it has been found nowhere else

Cambrian explosion (535-525 MYA)

marks the earliest fossil appearance of many major groups of living animals

new predator-prey relationships; rise in atmospheric oxygen; evolution of the Hox gene complex

hypothesized cause of the Cambrian explosion

Mesozoic Era (251-65.5 MYA)

animals began to make land impact by 460 MYA; vertebrates reached land (360 MYA); emergence of coral reefs; dinosaurs were the dominant terrestrial vertebrates; first mammals emerged

Cenozoic Era (65.5 MYA - Present)

mass extinctions of both terrestrial and marine animals; extinctions included the large, nonflying dinosaurs and the marine reptiles; diversification of modern mammal orders and insects

body plan

a way to categorize animals; a set of morphological and developmental traits

grade

a group whose members share key biological features

symmetry

a way to categorize animals according to the ________ of their bodies, or lack of it

radial symmetry

body plan in which body parts repeat around the center of the body

bilateral symmetry

two-sided symmetry; have a dorsal (top) and ventral (bottom side; a right and left side; anterior (head) and posterior (tail) ends; and cephalization, development of a head

cephalization

development of a head (brain)

ectoderm; endoderm; mesoderm

embryonic germ layers

ectoderm

germ layer covering the embryo's surface

endoderm

innermost germ layer and lines the developing digestive tube, called the archenteron

archenteron

the primitive gastric cavity of an embryo; developing digestive tube

diploblastic

animals with an ectoderm and endoderm

triploblastic

animals with all three embryonic germ layers; includes all bilaterians

mesoderm

middle germ layer; develops into muscles, and much of the circulatory, reproductive, and excretory systems

coelom

true body cavity derived from mesoderm

coelomates

animals that possess a true coelom

pseudocoelom

a body cavity derived from the mesoderm and endoderm

acoelomates

triploblastic animals that lack a body cavity

protostome development

cleavage is spiral and determinate

deuterostome development

cleavage is radial and indeterminate

indeterminate cleavage

each cell in the early stages of cleavage retains the capacity to develop into a a complete embryo; makes possible identical twins and embryonic stem cells

common ancestor

all animals share a ______ ________

basal animals

sponges are _____ _______

Eumatazoa

a clade of animals - eumetazoans with true tissues

Bilateria

a.k.a. bilaterians; where most animal phyla belong to

Deuterostomia

where chordates and other phyla belong to

ecdysis

Ecdysozoans shed their exoskeletons through a process called _______

lophophore

a feeding structure present in lophotrochozoans

trochophore larva

distinctive larval stage observed in some lophotrochozoan animals, including some annelids and molluscs.