Lecture 4: Animal Diversity Flashcards
The Animal Kingdom
- beetles make up the greatest amount
- history more than half a billion years
- great diversity of living species
common ancestor of animals may have resembled
choanoflagellates (which are sister taxa)
choanoflagellates are the sister group to
Metazoa (animals)
Choanoflagellate cells are morphologically similar to
collar cells of sponges
there are similar cells to choanoflagellates in
cndiarians, flatworms, echinioderms
DNA sequences indicate that
choanoflagellates and animals are sister taxa
Animal characteristics
multicellular, chemoheterotrophic eukaryotes with tissues that develop from embryonic layers
3 main animal characteristics
- nutritional mode
- cell structure and specialization
- reproduction and development
Animals, unlike plants, cannot
construct all of their own organic molecules
Animals do not feed by
absorption
Animal structure
- lack cell walls
- bodies are held together by structural proteins
- nervous tissue and muscle tissue are unique to animals
how do animals reproduce
- sexually, with the diploid stage dominating the life cycle
- zygote undergoes rapid cell division called cleavage
- cleavage forms a blastula
- blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues
What specific genes do animals have that regulate the development of body form
hox genes
hox genes are highly
conserved; passed on
radial symmetry
can be cut into two planes
bilateral symmetry
two-sides symmetry
bilaterally symmetrical animals have
- a dorsal (top) and a ventral (bottom) side
- right and left side
- anterior (head) & posterior (tail) ends
- cephalization, development of a head
animal body plans vary according to
the organization of the animal’s tissues
tissues are collections of
specialized cells isolated from other tissues by membranous layers
three germ layers
ectoderm, endoderm, mesoderm
ectoderm
germ layer covering the embryo’s surface
endoderm
innermost germ layer which lines the archenteron (digestive tube)
diploblastic animals
have ectoderm and endoderm
triploblastic animals have
a mesoderm layer; including all bilaterians