Answer:
1. False
2. True
3. True
4. False
Explanation:
In mammals, the contraction of the heart muscle is caused by pacemaker cells localized within the sinoatrial (SA) node. These cells rhythmically generate slow electrically-induced action potentials due to their slow rate of depolarization. The pacemaker cells generate the action potentials that propagate through the heart and trigger the contraction of myocyte cells (i.e., myocytes simply conduct the action potential waves). The slow depolarization of pacemaker cells occurs during diastole, i.e., during the period of relaxation of the heart muscle.
 
        
             
        
        
        
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Answer: elevation,  landforms
, relief
Explanation:
Area's topography can be defined as the physical features with which the area of the land is associated with. These features are mountains, lakes, valleys and rivers. 
The following are the elements of the parts of the area's topography:
Elevation: The elevation describes the height above the given level. This can be used to measure the height of the mountain.
Landforms: Landforms are the features of the Earth's surface that includes the parts like hills, plains and mountains. 
Relief: A relief gives an idea of elevation from the concerned point in a landform. 
 
        
             
        
        
        
Answer:
It's the lowest level of biological organization that can survive and reproduce as long as appropriate conditions are achieved.
Explanation:
 
        
             
        
        
        
Here is your answer......
Explanation:
Monotremes are mammals that lay eggs. Monotremes are warm blooded with a fast metabolism. They have hairy bodies to keep warm.
Marsupials are mammals that give birth to live young.  These mammals have a pouch where their young grow and develop. Marsupials are hairy, warm blooded, and produce milk. One of the biggest differences between marsupials and placental mammals is that marsupials give birth quite early and rely less on the nourishment of the placenta. Some examples of marsupials are kangaroo and opossums.
Placental mammals are mammals that give birth to fully developed live young.  They differ from marsupials in that the baby spend more time being nourished in-utero by the placenta. These mammals are hairy and warm blooded as well. Some examples are mice, rats, and bats
Hope it helps.....