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Asexual Reproduction. Genes all come from one parent Common to many invertebrates Advantages Enables animals to live in isolation – no need to locate mates Organism can create numerous offspring in a short amount of time – rapidly colonize habitat

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Asexual Reproduction

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Asexual reproduction l.jpg

Asexual Reproduction

  • Genes all come from one parent

  • Common to many invertebrates

  • Advantages

    • Enables animals to live in isolation – no need to locate mates

    • Organism can create numerous offspring in a short amount of time – rapidly colonize habitat

    • Advantageous in __________, favorable environments

      • Perpetuates successful genotypes precisely


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Forms of Asexual Reproduction

  • _____________

    • separation of parent into two or more individuals of approximately equal size.

  • _____________

    • new individuals split off from existing ones

  • __________________

    • Broken off body part grows into new individual

    • Regeneration of body parts

  • _________________

    • Eggs develop without being fertilized

Queen Worker Drone


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Forms of Asexual Reproduction

  • Parthenogenosis

    • Egg develops ___________ being fertilized

    • Adults produced by parthenogenesis are _____________

      • Example: drone (male) bees form from single unfertilized egg and do not need to undergo meiosis to make their own new reproductive cells

    • SOMETIMES, in certain species, whether parthenogenesis occurs may be determined by season/conditions

      • Favorable conditions leads to asexual repro.

        • Everythings going well, why change?

      • Environmental stress leads to sexual repro

        • If conditions are bad, better hope some variety will come up with a solution!


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Sexual Reproduction

  • Creation of offspring by fusion of haploid gametes to form a zygote

  • Increases genetic variation

  • Probably enhances reproductive success when pathogens or other environmental factors ________ rapidly

    • If there’s variety, chances are better than someone will have a genetic solution to an environmental problem


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Hermaphrodites

  • Each individual has both male and female reproductive systems

    • NOT ASEXUAL

    • Helps when finding a mate is not easy

      • Every individual encountered is a potential ___________ (as opposed to just ½ the individuals encountered)

    • Each partner donates sperm to female repro organs of the other.


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TWO Types of Fertilization

  • ____________ fertilization

    Requires environment where egg/zygote can develop without drying out.

    • The eggs are unprotected and vulnerable to water loss, etc.

    • Thus, almost always occurs in ____________ areas


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External Fertilization

  • Parents may not even make physical contact

    • Eggs/sperm released into water

    • Timing is still important

    • Some do use specific mates and mating behaviors

    • __________________ are used to draw animals together


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External Fertilization

  • GENERAL rule

    • _______ of zygotes produced

    • _________ parental care

    • Have lots of babies and hope at least a few of them survive

    • Very small proportion of zygotes survive to full development


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Internal Fertilization

  • Protects _________________

    • Neither sperm nor egg is ever exposed to environment

    • Sperm placed directly inside the female

  • Protects _______________

    • Embryos develop either:

      • Inside shelled eggs

      • Inside the female

    • Don’t come out until they can survive dry environment


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Internal Fertilization

  • ALL internal fertilization requires

    • Sophisticated reproductive systems including organs that

      • deliver sperm

      • receptacles that receive, store and transport sperm to ripe eggs.

    • Cooperativebehaviors leading to copulation

      • Uncharacteristic sexual behaviors are eliminated by ____________________________

      • Example – female spiders eat males if they don’t use the proper reproductive signals


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Internal Fertilization

  • Generally produces _______________ zygotes than external

  • But proportion of zygotes that develop and survive is ____________. This is because of:

    • greater protection of eggs/zygotes/embryos

      • Within a shell OR

      • Within the female

    • Due to better parental care of eggs and offspring

      • Don’t abandon young


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Internal Fertilization

  • Two possible outcomes:

    • _______________ to be laid on land

      • Reptiles, Birds

      • And 1 very small mammal group – montremes (platypus and spiny echidna)

    • Embryos develop _______________________

      • Mammals (placental and marsupial)

  • Both animal types are called ______________ due to the embryonic structures they share in common


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AMNIOTES

  • Amniotic eggs

    • Shell is NOT the only part that protects

    • EXTRAEMBRYONIC MEMBRANES make the anmiontic egg successful

      • AMNION

        • surrounds baby with water

        • “little ocean”

      • Yolk Sac

        • Stored Food

      • Allantois

        • Waste sac

      • Chorion

        • Functions with allantois in GAS EXCHANGE


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AMNIOTES

Amnion

  • Internal Development

  • Mammals –

    • both placental and marsupial

    • NOT monotremes (EGG LAYERS!)

  • Shelled egg not used, but

    • amnion present and

    • ________ extraembryonic membranes give rise to ____________, etc.


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Male Reproductive Organs

  • Testes

    • Seminiferous Tubules

      • Sperm production

  • Epididymis

    • Sperm maturation

  • Vas Deferens

    • Carry sperm to urethra

  • Urethra

    • exit body


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Seminiferous Tubules

  • Highly coiled tubes

    • Sperm are formed HERE

    • ____________ HAPPENS HERE!!

    • Also contain cells (Leydig cells) which make male hormones

      • Testosterone and other androgens

Cross section through Sem. Tubule


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___________________________

  • General term for creation of gametes

    • SEX CELLS

    • ___________________

    • TWO TERMS

      • Spermatogenesis

        • Gametogenesis (meiosis) in males

      • Oogenesis

        • Gametogenesis (meiosis) in females


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Spermatogenesis – MEIOSIS to create sperm

Least Mature

Also called

spermatogonium

Testis

Epididymis

Germ cell

(diploid)

Coiled

seminiferous

tubules

spermatocyte

(diploid)

MEIOSIS I

spermatocytes

(haploid)

MEIOSIS II

Vas deferens

Spermatids

(haploid)

Meiosis happens

Inside

Seminiferous

tubules

Most Mature

Spermatozoa

Cross-section of

seminiferous tubule


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Spermatogenesis

  • __________________________

    • Products of meiosis

    • ____ created from each primary spermatocyte

    • ____________________

    • Immature sperm

      • Tailess

    • Sertoli cells

      • Provide nourishment to spermatids as they further develop into sperm at center of seminiferous tubule


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Mature Sperm

  • Sperm structure

    • Head

      • ___________________

        • Contains enzymes to penetrate egg

      • Nucleus

        • Males genetic contribution

    • Mid-piece

      • Mitochondria

        • For energy - swimming

    • Tail

      • Microtubules

        • ____________


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Fertilization

  • Joining of sperm & egg

    • sperm head (nucleus) enters egg


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Female reproductive system

  • Ovaries

    • produces eggs & hormones

  • Uterus

    • nurtures fetus; lining builds up each month

  • Fallopian tubes

    • tubes for eggs to travel from ovaries to uterus

    • Called OVIDUCTS in every other animal

  • Cervix

    • opening to uterus, dilates 10cm (4 inches) for birthing baby

  • Vagina

    • birth canal


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Female Reproductive Organs

  • Ovaries

    • Each ovary contains many follicles

    • ___________________

      • One egg cell surrounded by folliclecells

      • Follicle cells nourish and protect developing egg

      • Follicle cells also produce primary female sex hormones

        • estrogens


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Oogenesis

  • Oogonia

    • Cells that create cells that undergo ________

    • ________________

    • Repeatedly divide to create _______ oogonia

      • ______________

  • Primary oocyte

    • Cell that has entered into _____________

  • Secondary oocyte

    • Cell that has entered into _____________

  • ____________


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Oogenesis

  • ________ divisions

    • Make one really good egg and ___ polar bodies

Meiosis 1 completed

during egg maturation

ovulation

Meiosis 2 completed

triggered by fertilization


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Reproductive hormones

LH &FSH

  • ______________

    • from testes

    • functions

      • sperm production

      • 2° sexual characteristics

  • _____________

    • from ___________

    • functions

      • egg production

      • prepare uterus for fertilized egg

      • 2° sexual characteristics

testesorovaries


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