Hippos likely evolved from a group of anthracotheres about 15 million years ago, the first whales evolved over 50 million years ago, and the ancestor of both these groups was terrestrial. These first whales, such as Pakicetus, were typical land animals. They had long skulls and large carnivorous teeth. Hope I’ve helped ;)
Answer:True
Explanation:
Nerve impulse must reach a certain threshold in a neuron before action potential can be generated to intiate conduction of action potential.
Therefore if mutiple impulses are generated and these are not upto thresholds , no matter how strong the stimulI are-NO ACTION POTENTIAL WILL BE GENERATED.
THIS IS ALL OR NONE PRINCIPLE
The all or none hypotheses can be best explain with flushing of the water closet after using it. If required volume of water is not pumped into the water closet storage above, no matter how long the handle is push, FLUSHING WILL NOT TAKE PLACE.Thus the threshold volume of water must be met.
Answer:
Penguins in general are distributed close to each other to be able to withstand the extreme cold, characteristic of the ecosystems they inhabit. They also group together to incubate their eggs.
They perform a series of coordinated movements that help them fight low temperatures, being careful to drop the egg.
Answer:
Sympathetic nervous system
Explanation:
The sympathetic nervous system of the autonomic division prepares the body for stress or emergency conditions by generating the “fight-or-flight” responses. The sympathetic nervous system triggers the release of stress hormones from the adrenal medulla to generate the set of physiological responses.
There is dilation of the pupil, and an increased rate of heartbeat and increased blood pressure. Other responses include dilation of airways and dilation of blood vessels that supply blood to skeletal muscles, heart muscles, liver, etc. Under the given emergency condition, the sympathetic nervous system of Meghan was activated to generate the fight or flight response.
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