What causes genetic variation during human sexual reproductive processes?

the zygote cell divides many times through mitosis to form a blastocyst during embryo formation.

adjacent chromatids in homologous chromosomes cross over during meiosis in sperm and egg formation.

mitochondria, containing mitochondrial dna, collect in the midpiece of sperm cells during sperm formation.

spindle fibers form between centrioles before attaching to chromosomes during meiosis in gamete formation.

Which conditions are necessary for natural selection to occur? select all of the answers that apply. a. inheritable adaptations vary among individuals. b. the population size is increasing. c. more individuals are born than can survive. d. fitness varies among individuals. e. the environment changes suddenly and drastically.

Long term exposure to waves can cause sunburns and skin cancer.

Toorale man murder mystery < - your lab link 1. how was the toorale man found? 2. what did archaeologists learn about the burial? why is the burial important? 3. what information were the scientists able to learn from the skeleton itself? 4. why is the question of whether the injuries came from a stone or steel weapon important? how could scientists distinguish between the different types of weapons? 5. what did the carbon dating and soil testing tell scientists about toorale man? why are the dates interesting for scientists?