Sperm are reproductive cells produced by testicles containing 23 chromosomes. Each sperm has head, neck, and tail for egg penetration. Spermatogenesis takes 74 days, producing 100-200 million daily. Males can produce up to 1 trillion sperm cells throughout life
Sperm can survive 15-30 minutes on skin or surfaces. Temperature and moisture affect sperm survival rate. Sperm becomes dead once semen dries. Chances of pregnancy are extremely low
Fertilization occurs when sperm and egg nuclei unite to form an embryo. Primitive fertilization involves genetic material exchange between cells. Membrane fusion creates channels for cell-to-cell material transfer
Dolphins are members of Cetacea family, found worldwide. They live in pods ranging from family units to hundreds. Most species practice polygamy with multiple partners
Gametogenesis involves cell division to form mature haploid gametes. Can occur through meiosis or mitosis depending on organism's life cycle. Alternation of generations exists between meiosis and gametogenesis
Humans evolved from chimpanzees 8-4 million years ago. Modern humans emerged in Africa 300,000 years ago. First behavioral modernity appeared 160,000-60,000 years ago. Humans migrated out of Africa, replacing archaic populations