BIO 121 Lecture Notes - Lecture 26: Prophase, Sexual Reproduction, Germ Cell
24 Jul 2020
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Lay eggs in ext enviro w/o drying out. Amnion large sac that surrounds fetus watery chamber for fetus to develop nutritious & protects. Hard shell prevent egg from drying out. 4 key features: sweat glands, mammary glands, hair, four-chambered heart. 3 main groups: prototherians (monotremes), metatherians (marsupials), eutherians (placentals) No genetic diversity problem if organism needs to adapt to changing enviro. Budding like regeneration occurs w/o damage, gives rise to individuals/colonies. Regeneration repairs damage to body involves mitosis & differentiation. Parthenogenesis egg develops w/o fertilisation new indiv can be haploid/diploid. Sexual reproduction: gametogenesis (making sex cells, spawning/mating (getting sex cells together, fertilisation (sex cells fusing) Germ cells need to proliferate & undergo meiosis exchange genetic materials & half chromosome # Meiosis consists of 2 nuclear divisions that decrease chromo # to haploid nucleus divides twice but dna replicated once: prod 4 genetically diff haploid cells.
