1. That starts with anisogamy , which arose long before mammals appeared. 2. Here, fusion of 2 dissimilar gametes occurs, known as anisogamy . 3. Anisogamy is the fertilization of gametes of dissimilar morphology by sexual reproduction.4. Anisogamy unequal sized gamonts is present.5. There are several types of anisogamy . 6. Some trophozoites enlarge and become macrogamete, whereas others divide repeatedly to form microgametes ( anisogamy ). 7. Many anisogamous external fertilizers select for different traits due to anisogamy due to the nature of their fertilization. 8. The " two-fold cost of sex " may more accurately be described as the cost of anisogamy . 9. In several lineages, this form of reproduction independently evolved to anisogamy with gametes of male and female types to oogamy. 10. This is a result of anisogamy , where sperm are smaller and much less costly ( energetically ) to produce than eggs. 
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