Shallow groove on the surface of the cortex is called a

Shallow groove on the surface of the cortex is called sulcus.

Cortex means the outer layer of an inner organ. The outer layer of the cerebrum is called cerebral cortex, where cerebrum occupies the biggest part of the brain. A human being has four lobes of the cerebral cortex which include temporal lobe, parietal lobe, occipital lobe, and frontal lobe.

Cortex has six layers of different types of neurons which are responsible for higher information processing and thinking. Cerebral cortex controls general movement, behavioural reactions, perception and visceral functions. We term the grooved layer as the brain itself.Cerebral cortex consists of large amounts of sulci and gyri(sulcus and gyri in singular). The number of gyri correlates to the processing ability of the animal.A man has big gyri compared to a rat.

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.

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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.