Sponges have collar cells that trap food and ingest it by or by the enzymes of lysosomes.

phagocytosis

Explanation:

Collar cells or choanocytes are found in inner portion of sponges. They line inner portion of spongocoel in simple sponges, body wall canal in complex sponges and chambers in most complex ones.

When the water flows through these structures, collar cells generate water currents. They trap and ingest food particles like algae and water borne bacteria by phagocytosis in which the plasma membrane engulfs the food particle finally trapping it in food vacuole.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.