Biodiversity (Animals) Flashcards
Features that define an animal’s body plan
- number of tissue types in embryos
- type of body symmetry
- presence or absence of a fluid-filled cavity
- way the earliest events of embryo development proceed
All animals have tissues except
sponges
Diploblasts
Embryos have 2 types of tissues or germ layers
- Ectoderm
- Endoderm
Triploblasts
Embryos have 3 types of tissues
- Ectoderm
- Endoderm
- Mesoderm
Germ layers develop into distinct adult tissues
Cleavage
Rapid cell division following fertilization
Blastula
Multicellular, hollow ball of cells formed from the cleavage
Gastrulation
Process blastula undergoes which forms a gastrula with different layers of embryonic tissues
Examples of diploblasts
Cnidarians and ctenophores
Radial symmetry
At least two planes of symmetry
Bilateral Symmetry
A single plain of symmetry
Face their environment in one direction
Dorsal
top side
Ventral
bottom side
Anterior
head
Posterior
tail
Cephalization
development of a head
Larva
sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis, transforming the animal into an adult
A body cavity may be present or absent in a
triploblastic animal
Coelomates
- Have a true body cavity
- All are bilaterally symmetric except adult echinoderms
- 3 embryonic tissue layers
Bilateria
- Protostomes - mouth formed first
(arthropods, mollusks, segmented worms) - Deuterostomes - mouth formed second
(chordates, echinoderms)
Hox genes
Developmental genes that regulate the expression of other genes
Closest living relative to animals
Choanoflagellates
Cambrian explosion
marks the earliest fossil appearance of many major groups of living things
Bilaterians
- Bilaterally symmetric
- Complete digestive tract
- One-way digestive system
- Most animal phyla belong to the clade Bilateria
Eumetazoa
clade of animals with tissues