BIO 3:Animal Reproduction

8/7/2019 BIO 3:Animal Reproduction

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Animal Reproduction

All animals have a DIPLONTIC lifecycle.

The only haploid cells are the sex cellsor GAMETES.

Reproduction is very important in thesurvival of the species and inachieving diversity (variation)


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Asexual Reproduction

Involves one parent

Results into an offspring with identical

genotype and phenotype DISADVANTAGE: NO VARIATION.

EXAMPLES:

Budding Regeneration

Parthenogenesis


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Budding- newindividuals form

as outgrowths ofthe bodies ofolder animals(buds form bymitotic divisions)



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Regeneration- usually thought of as the

replacement of damaged tissues or lostlimbs, but in some cases pieces of anorganism can regenerate completeindividuals (echinoderms)



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Parthenogenesis - is the developmentof offsprings from unfertilized eggs

(arthropods, fish, amphibians and reptiles). Can also be a part of a mechanism in

determining sex (hymenopterans: bees, wasps,ants)

EX: in the bee colony: males develop fromunfertilized eggs(n), females also from unfertilizedeggs (2n) and sterile, but a few are chosen to be thequeen



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Parthenogenesis


Queen Worker

(female)

Drone

(male)


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a large portion of time and energy is spent in

mating which exposes them to predation, can

cause physical damage, and detracts them

from other essential activities like feeding and

caring for their existing offsprings

Despite the disadvantages, mating provides an

evolutionary advantage: it produces GENETIC

DIVERSITY (raw material for natural selection).

Sexual Reproduction


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Involves three basic steps:

GAMETOGENESIS (by meiosis; the variation

in genetic content are made in the crossing-over of homologous chromosomes, and the

independent assortment of chromosomes)

MATING

FERTILIZATION

Sexual Reproduction


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Gametogenesis

Occurs in the GONADS (male: testes,

female: ovaries)

Gametes:

SPERM (males)- flagellated: motile

EGG/OVUM- non-motile

GERM cells- origin of the gametes; they are

produced at the embryonic stage of theorganism and continually divide mitotically

producing oogonia and spermatogonia (2n)


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Mating

Gets eggs and sperm closeenough together so that

fertilization can occur The simplest distinction in mating

systems is whether fertilizationoccurs externally or internally.


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External Fertilization In an aquatic environment, animals can bring their

gametes together by simply releasing them intothe water.

To maximize potential for fertilization theyconsider : the day length, changes in temperature,or changes in weather to time their productionand release of gametes.

Social stimulation is also used. They tend torelease gametes when others in the population

also release them.


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External Fertilization


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Hermaphrodites An earthworm is an

example of a simultaneoushermaphrodite, meaning

that it is both male andfemale at the same time.When two earthworms

mate, they exchange

sperm, and as a result, theeggs of each are fertilized


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Male Reproductive System


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Artificial Fertilization

Artificial

insemination


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Documents

BIO 3:Animal Reproduction