Evolution and Development Flashcards
What is the difference between triploblasts and diploblasts?
Triploblasts have three germ layers
Diploblasts only have two germ layers
Why has it been speculated that multicellular organisms have developed?
Size: Avoid predation
Survival of enviromental adverse conditions eg cells could sacrifice themselves as food
Differentiation, communication and cell death
Why has the evolution of gastrulation occured?
Came from the advantage of having specialised surface/cavity that could aid in digesting large chunks of food
What is trichoplax?
May represent a primitive metazoan
Trichoplax moves towards a nutrient particle
It forms a digestive cavity around the nutrient particle. digesting it externally
Where is the circulatory system in drosophila?
Dorsal side
Hermichordates may show what?
How the body plan has twisted
Known as acorn worms which usually in the sea bed
Molecular studies show BMP is expressed on the dorsal side of the animal and chordin ventrally
It has the same orientation as the arthropods
Shows that chordates to which vertebrates belong underwent inversion
What is the phylotypic stage?
Where vertebrate embryos are the most similar
Stages before are changed by reproductive adpatations eg changes in egg sizes between species
Changes after show more and more specific adaptation
How did diversity develop?
Mainly changes in control regions of control and target genes; not changes in protein function
Modification of existing mechanisms, not invention of new ones
Which molecular changes drive evolution?
Duplication and divergence
Timing and level of gene transcription
Changes in proteins are much rarer
Genome duplications
What is the basic role of Hox genes?
They specify positional identity of cells along the AP axis
How many sets of Hox genes do drosophila and mammals have?
d = 1 m = 4
How many species of fish are there and why?
> 33,000
This is because they duplicated their genome 3 times so they have extra genes which have provided the raw gene material for rapid evolution
Snakes have an extension of which Hox gene and what is it responsible for in the chick?
Hoxc6
Flank of the embryo
Hox 6 boundaries correlate to what?
The level of the neck/thorax
