Lecture 5 - sponges Flashcards
what do sponges originate from?
from colonial flagellates 700mya
what is the colonial theory?
a group of unicellular organisms all lived together in a colony and took on different roles in the colony - stick together functioning as a unit
4 pieces of evidence for colonial theory
1) flagellated cells found in metazoans
2) many flagellates form colonies
3) molecular link with sponges
4) choanoflagellates are though to be similar to ancestors
what is the phylum sponges are in?
porifera
features
simple structure
no symmetry
no sophisticated features
is it a successful phylum?
yes very widespread an ancient group
sponges have a common origin with the ancestral choanoflagellates but diverged separately how?
diverged from Eumetazoa into parazoa
what level of organisation have they got?
cellular level - no organs or tissues but cells can perform different functions
where are sponges found?
most are marine a few are freshwater
describe their movement
not much movement - some use other forms of movement e.g. on other animals
how do they feed?
most are filter feeders but some are carnivorous (deep sea)
how do they help coral reefs?
deposit carbon in digestible ways for other organisms
describe reproduction
1) able to regenerate
2) asexual by budding or gemmules
3) sexual - hermaphrodites
immunorecognition
can tell which cells of 2 different sponges are which - know their own cells
describe reproduction by gemmules
when the conditions are bad they may dry out or freeze forming gemmules (structure surrounded by spiccules with amoebocytes inside) - can form into any other cell types of the sponge when conditions are more favourable
