Reproduction in Animals• Important to survival of a species• Two Types: – Asexual – one parent; offspring are clones • Bacteria, plants, amoebas, and simple organisms – Sexual – joining of gametes (egg + sperm); increases genetic variation • Some plants, many animals
Asexual vs. Sexual Reproduction ASEXUAL SEXUAL One parent Two parents Offspring are clones of parent Egg + Sperm = Offspring Offspring/cell’s DNA same as Offspring DNA different from parent parents and each other Same parental genes passed New combinations of genes down Less/no genetic diversity Increase in genetic diversity Could be disadvantage if Offspring/species better able to environment changes evolve and adapt to changing environment Egg/Sperm produced by Meiosis
Examples of Asexual Reproductionregeneration parthenogenesis vegetative budding fission
Fertilization and Development• Fertilization – joining of egg and sperm Internal vs. External• Development – differentiation and maturation of fertilized egg Internal vs. External
Fertilization and Development in AnimalsFertilization Requirements Advantages Disadvantage Examples sExternal - Large # of Parents don’t Less chance Frogs, coral,- gametes join gametes need to be in sponges,outside of body - Water of fertilization the same many fish place - Specialized - chance ofInternal fertilization Parents must Birds, reptiles,- gametes join organs be close mammals, - Mating rituals - Lower # ofinside of body together some fish gametesDevelopment Requirements Advantages Disadvantage Examples sExternal No parental Low chance Frogs, many- growth outside Water or Shell care needed fish, reptiles, of survivalof parents’ body birds Specialized chance ofInternal organs support offspring Pregnancy is Mammals,- growth inside survival demanding some sharks &of parent’s body developing snakes egg
Reproductive Adaptations in Animals Amplexus in Frogs Eggs prevent reptiles from drying out on land Specialized organs in damselflies
The Amniotic Egg • Evolutionary adaptation that allowed fertilized eggs to develop on dry land • Shell and membranes protect embryo • Produced by reptiles, birds, and some mammals
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