Animal reproduction
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Animal Reproduction. Two Modes. Asexual – Invertebrates Fission Splitting into two Budding Splitting off parent Sponges produce gemmules Fragmentation Parent breaks into pieces Mature individuals are created through regeneration. Arm of a star fish create an adult. Sexual

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Animal Reproduction

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Animal reproduction

Animal Reproduction


Two modes

Two Modes

  • Asexual – Invertebrates

    • Fission

      • Splitting into two

    • Budding

      • Splitting off parent

        • Sponges produce gemmules

    • Fragmentation

      • Parent breaks into pieces

      • Mature individuals are created through regeneration.

        • Arm of a star fish create an adult.

  • Sexual

    • Involve a large non-motile cell

      • Ovum

    • Small Mobile Cell

      • Spermatazoan


Advantages and disadvantages of asexual reproduction

Advantages and Disadvantages of Asexual Reproduction

  • Advantages

    • Enables the animal to reproduce in an isolated environment.

    • Many offspring can produced very quickly and thus colonize a new habitat rapidly

    • Ideal for stable environments

  • Disadvantages

    • No genetic variability in case the environment changes

    • One disease can kill the entire population


Reproductive patterns vary

Reproductive Patterns Vary

  • Some animals will switch to sexual reproduction under environmental stress and reproduce asexually under favorable conditions.

  • Some animals only reproduce through parthenogenesis.

    • Adult develops from an unfertilized egg

    • Adults that develop in this manner are usually haploid

      • Whip tail lizards create a diploid zygote by doubling their chromosomes after meiosis

      • There are no males

      • Mating females switch roles and act male or female depending on the level of estrogen or progesterone in their bodies.


Sexual reproduction is a problem for sessile burrowing or parasitic animals

Sexual Reproduction is a Problem for Sessile, Burrowing or Parasitic animals.

  • Solution?

    • Hemaphroditism

      • Have both male and female reproductive organs.

    • Sequential Hemaphroditism

      • Species switch sexes during their lifetime.

        • Protogynous - female first

        • Protandrous - male first

        • Reef fish call wrasses switch from female to male based on size


Spermatogenesis

Spermatogenesis


The sperm

The Sperm


Oogenesis

Oogenesis


Menstral cycle preparing the endometrium

Menstral CyclePreparing the Endometrium

  • There are three phases

    • Proliferative - endometrium thickens

    • Secretory – endometrium becomes vascular and creates glandular structures.

    • Menstral flow – endometrium is expelled.


Ovarian cycle preparing the egg

Ovarian CyclePreparing the Egg

  • There are three phases

  • Follicular – several follicles begin to grow

    • Ovulation – one follicle matures and breaks out of the ovary

    • Luteal phase – remaining follicular tissue becomes glandular.

      • Secretes estrogen and progesterone to support the growing endometrim.


There are five hormones that synchronize the ovarian and menstral cycles

There are Five Hormones that Synchronize the ovarian and Menstral Cycles

  • GnRH, FSH, LH, Estrogen, and Progesterone

  • GnRH

    • Gonadotropin releasing hormone

    • Released by the hypothalamus

    • Causes the pituitary to releases FSH and LH

  • FSH

    • Follicle stimulating hormone

    • Respond to receptors on the follicle and encourage growth

    • Growing follicles secrete estrogen

    • Small amounts of estrogen inhibit the release of FSH and LH from the pituitary.

    • A steep rise in the release of estrogen from the follicle cause the opposite effect and stimulate the release of FSH and LH from the pituitary.

    • The follicle now respond to receptors for LH.


Animal reproduction

  • LH

    • Lutenizing Hormone

    • Cause the maturation of the follicle and it is released from the ovary

    • The follicular tissue left behind now becomes the corpus luteum which is glandular in function and secretes estrogen and progesterone.

  • Estrogen and Progesterone

    • An increase in the production of these hormones inhibit the hypothalamus and pituitary which inhibits the release of FSH and LH.

    • Progesterone supports the endometrium

    • Without LH the corpus luteum disintegrates

    • Without progesterone the endometrium disintegrates.

      • Blood vessels are choked off and the uterus undergoes spasms.

      • The endometrium is expelled

    • Without the corpus luteum the hypothalamus and pituitary can once again release FSH and LH and the follicular phases begins again.


Zygote formation

Zygote Formation


Placental circulation

Placental Circulation


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