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BIO 102 REVIEW TWO - B io 102 Review TWO REPRODUCTION(49 I...

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Bio 102 Review TWO REPRODUCTION (49) I. Asexual Reproduction- single parent; genes of offspring are identical to parent (except for parent) a. Benefits of Asexual i. Energy efficient (don’t have to have two cells, just one) ii. Successful in a stable environment (don’t change) iii. Don’t have to search for a mate iv. Genetic Stability b. Types of Asexual i. Fragmentation- each piece that breaks off becomes a new animal 1. Example- sea stars, flatworms, and annelids ii. Parthenogenesis- “virgin” birth; where an unfertilized egg becomes an adult and the adult is usually haploid 1. Example- common among honeybees and wasps and crustaceans 2. Also occurs in some invertebrate and vertebrate groups such as nematodes, gastropods, fishes, amphibians, and reptiles iii. Budding- a small part of the parent’s body separates from the rest and devels into a new individual 1. Example- sponges and cnidarians II. Sexual Reproduction- the fusion of gametes to produce a zygote (most animals reproduce this way) a. Benefits of Sexual i. Adaptive ii. Provides genetic diversity- each offspring has genes from mother and father 1. Allows for a new gene combo iii. Results in strong survivors (beneficial mutations) iv. Selects against harmful mutations b. Types of Fertilization i. External- release sperm and eggs into the water- frogs ii. Internal- male sperm delivered into female body- humans; terrestrial animals III. Hermaphroditism a. Occurs when a single animal produces both eggs and sperm b. 2 different individuals swap i. Examples: tapeworms, earthworms, tunicates
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c. Tape worm is capable of self-fertilization b/c it is difficult for it to find a mate, but most time self-fertilization is prevented (possibly by devel of testes and ovaries at different times) IV. Male Reproductive System a. Testes- contained in the scrotum as pair male gonads i. Cooling unit to keep sperm below body temperature ii. Connected to pelvic cavity by inguinal canals 1. Straining can cause a loop of intestine into scrotum (inguinal hernia) b. Seminiferous tubules (contained in the testes) i. Where spermatogenesis occurs ii. Interstitial cells- lie BETWEEN seminiferous tubules and secrete testosterone iii. Sertoli cells- ring the fluid-filled lumen of the seminiferous tubules a. Nourish sperm cells b. Phagocytose sperm’s cytoplasm which is discarded during development c. Tight junctions which prevent harmful substances from entering tubule 2. Beings with undifferentiated cells (spermatogonia) 3. Divide and some enlarge to become primary spermatocytes (diploid) 4. These divide by meiosis 5. Two secondary spermatocytes (haploid) 6. 2 nd meiosis four spermatids (haploid) 7. Then become 4 mature sperm iv. After maturing, the sperm are stored in the epididymis c. Sperm Structure i. Mitochondria are concentrated in the midpiece (used to provide flagella with energy) ii. (9+2) structure characterizes the structure of the flagella iii. The acrosome (head); contains enzymes that allows the sperm to penetrate the egg d. Conducting Ducts i. Ejaculation 1. Go from vas deferens 2.
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