Answer:
 gills
Explanation: A fish without a jaw was the first vertebrate to evolve. These fish used filtration to capture their food and sucked water and debris from the sea through their mouths and then released the water and trash through their gills. Some features are as follows:
1. They have a notocorda that serves as support through the back of the fish.
2. Gill bags. These organs are responsible for filtering the oxygen in the water.
3. A pineal eye that is sensitive to light
4. A cartilaginous skeleton
 
        
                    
             
        
        
        
The abiotic factor that is essential for all aquatic ecosystem with the exception of hydro thermal vent is SUNLIGHT, THIS IS BECAUSE IT PROVIDES A SOURCE OF ENERGY. 
Sunlight is very essential for aquatic ecosystems because it is the principal source of energy from which aquatic plants trap energy to make their food and provided mean of sustenance for themselves and other organisms in the water.
        
             
        
        
        
Answer:
1) Brown, 2)Tall with a 25% chance of short 3) Rough 4) 50% chance of solid 50% chance of stripes
Explanation:
The big letters are the dominant. Dominant always shows up if its part of it. The genetic squares show that any square with a Big letter will present the big letters trait. i didnt really understand so i hope this is what you're looking for