Chapter 32: Animal Diversity Flashcards
Most diverse animal group
terrestrial arthropods
animal
multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers
collagen
structural protein that supports cell walls
muscle cells
contractile cells to generate motion
nerve cells
conduct electrical impulses
methods of asexual reproduction
budding, fission, parthenogenesis (virgin birth)
dominant life cycle stage
diploid stage is dominant
sexual reproduction
typically a small flagellated sperm fertilizes a large egg; diploid adults produce haploid gametes
zygote
fertilized egg that develops into gastrula
cleavage
cell division without growth
blastula
hollow ball of cells with an internal cavity (blastocoel)
gastrulation
invagination of blastopore to form the beginning of the gut (different in sponges)
sponge cell characteristics
lack tissues; cells can de-differentiate into other cell types
archenteron
formed by invagination; gives rise to the gut
endoderm
tissue lining gut
ectoderm
outer layer of cells; skin and nervous system
diploblasts
only two tissue types; “fancy gastrula”
triploblasts
have a third germ layer known as the mesoderm that forms all other organs between gut and outer surface
direct development
offspring looks like a little version of the parent
indirect development
young offspring (larvae) are morphologically/ecologically different than the adult
clade that animals belong to
opisthokonts (like fungi)
closest relatives to animals
choanoflagellata: similar feeding cell type; analysis of DNA sequence data
neoproterozoic era
era in which animals arise
ediacaran biota
earliest large animal fossils
cambrian explosion
appearance in the fossil record of most animal phyla
bilaterians
most of the fossils from the cambrian explosion; bilaterally symmetric form with complete digestive tract
mesozoic era
age of dinosaurs; bounce back of animals after extinction
end-cretaceous extinction
wiped our dinosaurs and other groups
cenozoic era
modern era; diversification of large mammals
animal body plans
specific and conserved; development under control of Hox genes. 3 aspects: symmetry, tissue organization, and body cavities
sponge symmetry
asymmetrical
sea anemone symmetry
radially symmetrical
symmetry of most animals
bilateral symmetry; dorsal, ventral, anterior, posterior
cephalization
having a front end (head); typical of animals that move under own power
coelom
fluid-filled body cavity
coelomates
body cavity lined with mesoderm
pseudocoelmates
not completely lined with mesoderm
acoelomates
lack a body cavity
hydrostatic skeleton
fluid-filled body cavity serves as a hydrostatic skeleton to antagonize muscles
protosomes
solid masses of mesoderm form; expand to filled blastocoel. determinate spiral cleavage; blastopore becomes the mouth
deuterostomes
mesoderm buds off endoderm of archenteron; indeterminate radial cleavage; blastopore becomes anus
5 important points about relationships among living animals
- share a common ancestor
- sponges are sister group to all other animals
- eumetazoa is a clade of animals with tissue (all except sponges)
- most animal phyla belong to the bilateria clade
- 3 major clades of bilaterian animals: deuterostomia, ecdysozoa, lophotrochozoa
deuterostomia diversity
invertebrates or vertebrates; includes hemichordates, echinoderms, and chordates
ecdysozoa
all invertebrates; includes nematodes and arthropods; secrete an exoskeleton for growth (ecdysis)
lophotrochozoa
all invertebrates; named for features: lophophore and trochophore larvae
lophophore
crown of ciliated tentacles used for feeding; ie. ectoprocts
trochophore larva
developmental stage; ie. mollusks and annelids
porifera
sponges
cnidaria
jellyfish, sea anemones, coral
bilateria
animals with bilateral body symmetry
