lecture 16 Flashcards
(13 cards)
when did the first animals evolve?
700 million years ago
when did land animals appear?
400 million years ago
what are animals closely related to?
choanoflagellates
what did the earliest animals look like?
likely soft bodied, sessile, similar to sponges
when did animal diversity explode?
500 million years ago
what was a major driver in animal evolution?
methods used to capture and process food
how animals are typically classified
body plan/ symmetry
presence of hox genes
specialized tissues vs. no tissue
germ layers
embryotic development
presence of a notochord
which taxa’s include and dont include Hox genes?
do not contain:
porifera (sponges)
Ctenophora comb jellies)
the rest do contain hox genes
what do hox genes do?
regulate embryo development and determine the shape and function of different regions of the body plan
example of hox genes
determine how many appendages, and body segments an insect may have
(a sponge has no symmetry)
can animals reproduce asexually?
yes
parthenogenesis
what is bilateral symmetry in animals good for?
high mobility, suited well for predators
what is radial symmetry (starfish) good for?
sessile/slow animals
easier to sense predators and prey from all directions