Lecture 19 Biology 2

Lecture 19 Biology 2 - Reproduction Lecture outline 1)...

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Reproduction Lecture outline 1) Asexual reproduction 2) Sexual reproduction 3) Human reproduction - male reproductive anatomy - female reproductive anatomy - conception - fetal development - contraception Asexual Reproduction No fusion of sperm and egg Haploid offspring come from single parent Offspring identical to parent - clones
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Types of Asexual Reproduction Parthenogenesis Budding/Fission - benefits: rapid and cheap - costs: loss of genetic diversity Sexual Reproduction Fusion of haploid gametes (egg and sperm) into a diploid offspring Gametes formed by meiosis Offspring are genetically different from their parents Sexual reproduction is expensive time/energy to find mate time/energy to court mate mate selection mate guarding parental care meiosis
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Mating displays Male bowerbirds courtship rituals Sex is dangerous! Seeking mates can make you more conspicuous Fireflies may attract males of another species and eat them. Carnivorous bats may be attracted to mating calls of prey species
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Why have sex? Reasons for sexual reproduction Offspring will be more variable and better able to adapt to a changing environment Offspring will be different from their parents Mutations can build up in asexual species and recombination is necessary to over-ride these Where to fertilize. .. External Fertilization - eggs expelled by female, sperm expelled by male - eggs fertilized by sperm in the environment Eggs
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Internal Fertilization Internal Fertilization - sperm deposited into female reproductive tract - requires cooperation (most of the time) Reproduction in Vertebrates and most other animals 2 different sexes Egg is larger and doesn’t move around Sperm are smaller and motile Many more sperm are produced than eggs Sex/Gender determination in Vertebrates: Three types of sex determination: 1. Genotypic—most common 2. Temperature-dependent 3. Behavioral
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1. Genotypic sex determination There are differences in 1 pair of chromosomes = sex chromosomes Homogametic sex - the chromosomes are the same e.g., Mammals, females are XX Heterogametic sex - the chromosomes are different e.g., Mammals, males are XY Not all animals are this way
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Lecture 19 Biology 2 - Reproduction Lecture outline 1)...

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