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Animal Reproduction Reproduction Produce copies of self Continue survival of species Ensure survival of personal genetics.

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Presentation on theme: "Animal Reproduction Reproduction Produce copies of self Continue survival of species Ensure survival of personal genetics."— Presentation transcript:


2 Animal Reproduction

3 Reproduction Produce copies of self Continue survival of species Ensure survival of personal genetics

4 Asexual Reproduction Fragmentation Sponges, some annelids, starfish Organism breaks apart, pieces become new organisms

5 Asexual Reproduction Budding Hydras, cnidarians Creates bud that breaks off and becomes new organism Transverse fission Some protists, planaria Constricts, splits in half

6 Asexual Reproduction Parthenogenesis “virgin birth” Eggs produced by mitosis, not meiosis Egg not fertilized by male Some insects and arthropods (bees, ants, water fleas) Some reptiles (komodo dragons, geckos, whiptails) Some fish, sharks Same species can reproduce sexually as well

7 Sexual Reproduction More “costly” to make and care for gametes Potential mate needs to be found and possibly courted Pheromone production Time and energy in searching May be time & injury risk when competing Timing of gamete formation must synchronize between sexes Neural & hormonal mechanisms in both parents Overall more complex, more resources needed So why do it?

8 Sexual Reproduction Great genetic variation! Humans 22 pairs of homologous chromosomes (X & Y non- homologous) 8,388,608 combinations of homologous chromosomes 70,368,744,000,000 possible variations of offspring Including crossing over in meiosis I, there are 4,951,760,200,000,000,000,000,000,000 possible variations! IN ANY SINGLE CHILD!!! Many variations possible, some could enhance survival of organism

9 Sexual Reproduction External fertilization Sperm and egg unite outside of female Must be in very wet environment Sperm & eggs released into water Marine invertebrates Sperm deposited onto eggs Many fish, amphibians Internal fertilization Sperm and egg unite within female

10 Male Reproductive Systems Testes (internal or external) Sperm Motile, allows movement through fluid towards ova Copulatory organs For internal fertilization Penis—mammals Usually internal until copulation Most contain bone (baculum/os penis)

11 Male Reproductive Systems Copulatory organs (cont.) Clasper Chondricthyes Inserted into female Hemipenis (pl. hemipenes) Snakes, lizards Paired organs Often barbed Internal, everted into female during copulation

12 Male Reproductive Systems Copulatory organs (cont.) Cloaca Pass sperm through direct cloacal contact Most birds Waterfowl have penis-like organ (phallus)

13 Female Reproductive Systems Ovaries Oviduct (Fallopian tube) Uterus Eggs/Ova

14 Female Reproductive Systems Eggs Protect & nourish growing embryo Aquatic animals Gelatinous, thin-walled eggs Allow water to diffuse through egg wall Fish, amphibians

15 Female Reproductive Systems Eggs (cont.) Land animals Thick shell Water impermeable (prevent dehydration) Reptiles—leathery shell Usually buried or laid underground to preserve warmth Birds—hard shell Requires incubation (warmth from parent)

16 Female Reproductive System Eggs (cont.) Amnion—fluid sac to cushion & prevent dehydration Allantois—stores metabolic wastes Yolk sac—food source for embryo

17 Sexual Reproduction Hermaphrodite Animal has male and female sex organs Self-fertilization Inseminates itself Tapeworms Cross-fertilization Inseminate others Slugs, snails, earthworms

18 Sexual Reproduction Hermaphrodite (cont.) Sequential hermaphrodites Born as one sex, can change sex later in life Mostly fish, some crustaceans Clownfish harem Large female, several males Remove female, one male will become female Wrasses Largest fish always male When male dies, female may turn into male

19 Sexual Reproduction Oviparous Egg laying Little or no embryonic development within mother Young hatch from eggs Most insects, arachnids Most fish, reptiles, amphibians All birds, monotremes

20 Sexual Reproduction Viviparous Embryo develops within mother No egg around embryo Nourished by mother Live birth Most mammals Rare in other animals, but exists

21 Sexual Reproduction Ovoviviparous Eggs develop within mother Embryo nourished by yolk sac, not mother Live birth Some fish (guppies, mollies, swordtails)guppies Some sharks, reptiles, amphibians, invertebrates

22 Placenta Most mammals None in monotremes or marsupials Feeds & nourishes fetus Filters and eliminates wastes Blood does not directly connect between mother & fetus Produces progesterone to maintain pregnancy Specific shape and attachments vary between species

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