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Human Reproduction

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Submitted By iwanAzlan
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ANIMAL REPRODUCTION &
DEVELOPMENT

Dr Ilma

• The two earthworms in this picture are mating
• Each worm produces both sperm and eggs, which will fertilize
– And in a few weeks, new worms will hatch

Asexual And Sexual Reproduction
• Both occur in the animal kingdom
• Asexual reproduction is the creation of new individuals – Whose genes all come from one parent
• Sexual reproduction is the creation of offspring – By the fusion of male and female gametes to form a zygote

Mechanisms of Asexual Reproduction
• Many invertebrates reproduce asexually by fission – The separation of a parent into two or more individuals of approximately the same size

Mechanisms of Asexual Reproduction
• Budding
– In which two new individuals arise from outgrowths of existing ones
• A two-step process
– Fragmentation
• The breaking of the body into several pieces, some or all of which develop into complete adults

– Regeneration
• Follows fragmentation
• the regrowth of lost body parts

• Some animals reproduce by parthenogenesis
– A process in which an egg develops without being fertilized

• Among vertebrates, several genera of fishes, amphibians, and lizards, including whiptail lizards
– Reproduce exclusively by a complex form of parthenogenesis Ovary size (a) Both lizards in this photograph are C. uniparens females. The one on top is playing the role of a male. Every two or three weeks during the breeding season, individuals switch sex roles.

Hormones

Ovulation
Estrogen

Ovulation
Progesterone

Behavior

Time

Femalelike

Malelike

Femalelike

Malelike

(b) The sexual behavior of C. uniparens is correlated with the cycle of ovulation mediated by sex hormones. As blood levels of estrogen rise, the ovaries grow, and the lizard behaves like a female. After ovulation, the estrogen level drops
abruptly,

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