During which period of Earth's history did four-legged animals appear on land?

The diagram shows a fossil of an ancient whale skull and a skull of a present-day whale. the ancient whale is extinct and is believed to be an ancestor of the present-day whale. what do these skulls most likely show that supports darwin’s theory of evolution? all populations can adapt and survive. only some organisms have a common ancestor. populations change slowly over time. populations rapidly become extinct.

Turtle hatchling survivorship rate is low in many turtle species due to predation. amanda researched the predatory rate on a species of turtle eggs in the red river. the eggs were harvested from trapped turtles and the egg's cloaca film (reproductive discharge) was either washed off or left on once gathered. research suggests that predators use the female's cloaca scent to locate the eggs. the eggs were only handled when wearing gloves and then reburied along islands where the turtles were trapped. the nests were monitored by cameras and manually on foot and data on nest predation were recorded. a. based on the experimental design, what is the dependent variable? b. based on the experimental design, what is the independent variable? c. based on the experimental design, what is the control?

What initially causes a nerve impulse? release of enzymes out of the neuron movement of chemicals into the dendrites of the neuron pathogens attacking the dendrites of the neuron red blood cells bathing the neuron