During sperm competition, two or more spermatozoa from different males compete to fertilize the same egg. It can occur when the female has multiple potential mating partners. Which of the following states the downside of this process for each individual male?

During gastrulation, the blastula reorganizes into two primary germ layers. The inner layer is called _________, and the outer layer is called _________.

The corpus luteum is a mass of cells that forms in the ovary and produces the hormone ___________ during the early stages of pregnancy.

Secondary oocytes complete meiosis II if fertilised by sperm. Identify at which phase of meiosis II secondary oocytes is arrested.

Which of the following examples demonstrates a parthenogenesis reproduction? 

Which of the following statements about the menstrual cycle is false? 

Which of the following is an enzyme-filled structure at the tip of sperm that allows it to penetrate barriers around the egg?