Gonads are sex organs that produce gametes. Male gonads are the testes, which produce sperm and male sex hormones. Female gonads are the ovaries, which produce eggs (ova) and female sex hormones.
The answer is B) the science of heredity
Only eukaryotes contain upper three but all cells contain "Contractile Vacuoles"
In short, Your Answer would be Option D
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Evolution:
. Natural selection
. prehistoric times
. fossils
. certain body parts
. animals that are different but have similar traits
As food reaches the end of the esophagus, it enters the stomach through a muscular valve called the lower esophageal sphincter. The stomach secretes acid and enzymes that digest food. Ridges of muscle tissue called rugae line the stomach. The stomach muscles contract periodically, churning food to enhance digestion.Mar 4, 2016