Which of these would be evidence that cyanobacteria evolved the ability to perform photosynthesis and released oxygen as a byproduct over 2 billion years ago? a) the presence of iron oxides (rust) in sedimentary rock layers that are 2 billion years old b) the presence of an iridium-rich layer in sedimentary rock dating from times of mass extinctions c) the presence of chloroplasts in fossilized eukaryotes from fossils dating from 2 billion years ago forward d) the formation of stromatolite rock structures from aggregates of cyanobacteria dating 3.5 billion years ago

A) The presence of iron oxides (rust) in sedimentary rock layers that are 2 billion years old.

Explanation:

Cyanobacteria perform photosynthesis using sunlight, water and carbon dioxide to produce carbohydrates as well as oxygen. In fact, to this day, all plants on Earth contain cyanobacteria - known as chloroplasts - that participate in photosynthesis. This is how oxygen arrived on earth over 2 billion years ago.

A great evidence of this moment is the presence of iron oxides (rust) in 2 billion year old sedimentary rock layers. Since it is the first report of an element that has oxygen in its composition.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products