Chapter 2_reproduction Part 1 201415 Latest

CHAPTER 2: REPRODUCTIVE SYSTEM

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Learning Objectives

1) Identify and describe the different stages ofmitosis and meiosis.

2) Compare and describe asexual and sexualreproduction process.

3) Compare and describe external and internalfertilization.

4) Describe reproduction in vertebrates.

5) Describe the human gametogenesis process.

6) Describe pregnancy and human developement.

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REPRODUCTIVE SYSTEM

5.Human

Reproductive

System

6.Pregnancy and

Human

Development

1.Cell Division

Mitosis Meiosis

2.Asexual

Reproduction

Fragmentation Budding Parthenogenesis Hermaphroditism

3.Sexual Reproduction

Fertilization- internal/external

Embryonic development- oviparity- ovoviviparity- viviparity

4.Reproduction in

Vertebrates

Fishes/amphibians Reptiles/birds Mammals

Male Female

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1. CELL DIVISION:MITOSIS

Process in which one cell duplicates itschromosomes to generate two identical

cells with an equal distribution of

organelles and other cellular components.

Followed by cytokinesis which dividesthe cytoplasm and cell membrane.

Mitosis maintains the diploid

condition.(2n)

In multicellular organisms, the somaticcells undergo mitosis, while germ cells

divide in a process called meiosis.

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Parent cellDiploid (2n)

Daughter cellDiploid (2n)

Daughter cellDiploid (2n)

5CELL DIVISION : MITOSIS & CELL CYCLE

Cell cycle has two parts:

1) Growth and preparation (Interphase)

2) Cell division:

i) Mitosis (nuclear division)

ii)Cytokinesis (cytoplasm division)

STAGES1- Interphase (G1,S,G2)2- Prophase3- Prometaphase4- Metaphase5- Anaphase6- Telophase7- Cytokinesis

Can be divided into three subphases:

i) G1 Cell acquires and synthesisesmaterials such as proteins for celldivision. New organelles are beingformed

ii)S Synthesis of DNA andchromosomes undergo replication.Each chromosome consist of twoidentical sister chromatids

iii)G2 Cell continues to grow andremains metabolically active.Enzymes and proteins aresynthesised for cell division. The cellsaccumulates energy

Is the longest part of the cycle.

Cell grows and copies thechromosomes in preparation of celldivision 7

CELL DIVISION: INTERPHASE

CELL DIVISION:

INTERPHASE (G1 Phase)

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The cell just finished dividingso in Gap 1 the cell is recovering

from mitosis.

In this stage, cell grows andproduces protein for DNA

synthesis

CELL DIVISION:

INTERPHASE (S Phase)

This is the synthesis phasewhere DNA replicates.

Amount of DNA double.

Called Gap 2 Phase.

Single centrosome (an organellethat organize cellsmicrotubules) replicates andremain near the nucleus.

Organelles also replicated.

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CELL DIVISION: INTERPHASE (G2 Phase)

Chromatin condensed intochromosomes.

Duplicated chromosomes appear astwo identical sister chromatids.

Nucleolus disappears.

Mitotic spindle begins to form.

Centrosome move apart from eachother.

Nuclear envelope starts break up10

CELL DIVISION: MITOSIS (Prophase)

Chromosomes attach to spindlefibers.

Nuclear membrane disappears.

Microtubules invade the nucleararea.

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CELL DIVISION: MITOSIS

(Prometaphase)

Longest stage in mitosis

The chromosomes arealigned at metaphaseplate

kinetochores attached tomicrotubules

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(Metaphase)

Centromere divides into two

Sister chromatids separateand move towards oppositepoles

End of anaphase whenchromosomes reach thepoles.

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(Anaphase)

Spindle fibers disappear.

Two daughter cells begin to form.

Chromosomes less condensed.

Nuclear envelope and nucleolusreform.

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(Telophase)

Vesicles which contain cell wall materialare formed from Golgi apparatus

Move to the middle of the cell

Grow and enlarged until the membranefuses with the plasma membrane.

Cleavage furrow shallow groove nearthe old plate

Deepens until the cell pinches into twodaughter cell.

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CELL DIVISION: CYTOKINESIS

(Animal Cell)

CELL DIVISION: CYTOKINESIS

(Plant Cell)

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CELL DIVISION:

The Importance of Mitosis

Mitosis is important for;

i) Cell Growth

ii) Tissue Repair

iii) Reproduction

Meiosis is the process by which onediploid (2n)eukaryotic cell divides togenerate four haploid (n) cellscalled gametes.

Division of the nucleus occur twice(meiosis I and meiosis II) andfollowed by cytokinesis.

Occur in germ cell such as inovaries and testes.

Essential for sexual reproductiontherefore occurs in all eukaryotes 18

1.CELL DIVISION: MEIOSIS

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CELL DIVISION: MEIOSIS

(Terminology)

Diploid - two sets of chromosomes (2n), in humans 23 pairs or 46 total

Haploid - one set of chromosomes (n) - gametes or sex cells, in humans23 chromosomes

Homologous pair-each chromosome in pair are identical to theother ( carry genes for same trait) only one pair differs - sexchromosomes X or Y

Synapsis - pairing of homologous chromosomes forming a tetrad.

Crossing over - chromatids of tetrad exchange parts.

Chromosome replicate in S phase (remainuncondensed)

Each chromosome contain twogenetically identical sister chromatid

Centrosome replicates forming twocentrosomes

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CELL DIVISION:

MEIOSIS

(INTERPHASE)

Chromosome condensed.

Spindle apparatus forms.

No crossing over.

Nucleolus and nuclear envelopes disappear.

Spindle microtubules form and centrosomes move apart.

Homologues chromosomes condense and pair each other (Synapsis-contains 4 sister chromatids)

Crossing over at chiasmata.

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CELL DIVISION:

MEIOSIS(Prophase I)

CELL DIVISION:

MEIOSIS(Prophase II)

Duplicated chromosome lineup on the metaphase plate.

Sister chromatids are no longergenetically identical

Homologous chromosome lineup on the metaphase plate atthe center of cell.

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CELL DIVISION:

MEIOSIS

(Metaphase I)

CELL DIVISION:

MEIOSIS

(Metaphase II)

Sister chromatids separate andmove towards the opposite poles.

Centromere divides into two.

The homologous chromosomesseparate and move towards theopposite poles.

Sister chromatids attached at thecentromere and move as single unit.

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CELL DIVISION:

MEIOSIS

(Anaphase I)

CELL DIVISION:

MEIOSIS

(Anaphase II)

Nuclei and nuclear envelopes reform.

Chromosomes decondensed.

Cytokinesis.

Four haploid (n) daughter cells form.

Genetically distinct from the eachother and from the parent cells.

Cytokinesis

Each homologous chromosome hasreached the opposite poles.

Each homologous chromosomeconsists of two non-identical sisterchromatids.

The 2 daughter cells now is haploid

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CELL DIVISION:

MEIOSIS

(Telophase II)

CELL DIVISION:

MEIOSIS

(Telophase I)

Crossing Over

Genetic variation cause by the unique combination of traits in each member of a species.

It occur during meiosis and fertilization.

Independent Assortment

Random Fertilization

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The Genetic Variation

Cause of Genetic Variation

Occurs in Prophase I when 2 pairs of non-sister chromatids cross each other.

Involved a combination of DNA from two parents into a single chromosome.

Produce recombinant chromosomes.

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Crossing Over

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Independent Assortment

The pairs of homologous chromosomeseparate, or assort randomly.

At metaphase I, each homologous pairof chromosomes aligns on themetaphase plate. Each pair consists ofone maternal and one paternalchromosome.

All of the maternal chromosomes willnot be separated into one cell, whilethe all paternal chromosomes areseparated into another.

Instead, after meiosis occurs, eachhaploid cell contains a mixture of genesfrom the organism's mother and father.

Fusion of gametes (spermand ovum) produce a zygote withdiploid condition.

In humans, when individual ovumrepresentative of one of eightmillion possible chromosomecombinations is fertilized by asperm cell, which also representsone of eight million possibilities,the resulting in varieties ofzygote.

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Random Fertilization

MITOSIS MEIOSIS

MITOSIS MEIOSIS

Occurs in somatic cells Occurs in germ cells.

Produce 2 daughter cells from one parents.

Produce 4 daughter cells from one parents.

Number of chromosome is similar to their parents.

Number of chromosomes are half or the parents.

Daughter cells are genetically identical tothe parents.

Daughter cells have different genetic composition from the parents.

Synapsis did no occur.Synapsis occur between two homologous chromosome during prophase meiosis I.

No bivalent or tetrads are formed. Bivalent or tetrads is formed.

Involve one nuclear division. Nuclear division occur twice.

Important in growth and worn out tissue repair.

Important in genetic variation among gametes.

Sister chromatids separate during anaphase

Homologous chromosome separate during anaphase I

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2. ASEXUAL REPRODUCTION

OVERVIEW

Involve only one parent.

No fertilization occur means no fusion of sperm andegg.

Using mitotic division.

Offspring have hereditary traits identical to theparents except in the case of mutation.

Asexual reproduction is the fastest and the mostefficient way of reproducing.

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BUDDING

FRAGMENTATION

PARTHENOGENESIS

FISSION

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2. ASEXUAL REPRODUCTION

Asexual reproductionGenetically identical cells are produced from a

single parent cell through mitosis

Fission bacteria, amoebaParent divides into two identical daughter

cells.Each part will become a separatebut identical organism.

Budding cnidarians, spongesNew individuals arise from outgrowths ofexisting ones.

Buds remain attached to parent or detached from parent, depending on species.

Asexual reproduction

Fragmentation flatworms, annelids, nematods

Breaking of the body into pieces, some or all of which develop into adults.

Fragmentation must be accompanied by regeneration, regrowth of lost body parts.

Asexual reproduction

Parthenogenesis honey bees, whiptail lizardsA female produce a new individual from an unfertilized egg.

Without sperm, the eggs developinto haploid male drones.

A queen bee mates only once andstores the sperm.She is in control of the releaseof sperm.

Fertilized eggs can develop intoother queens or sterile workerbees that are female.

Involves two parents/individuals through fusionof sperm and egg fromeach individual.

Egg: large and non-motile,with nutrients thatwill support thedevelopment of an embryo.

Sperm: small and motile,moving by propelling itsflagellum.

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3. SEXUAL REPRODUCTION

OVERVIEW

Sexual reproduction results in genetic recombination, which provides potential advantages

An increase in variation in offspring, providing an increase in the reproductive success of parents in

changing environments

An increase in the rate of adaptation

A shuffling of genes and the elimination of harmful genes from a population

2011 Pearson Education, Inc.

For many animals, finding a partner for sexual reproduction may be challenging

One solution is hermaphroditism, in which each individual has male and female reproductive systems

Two hermaphrodites can mate, and some hermaphrodites can self-fertilize

Individuals of some species undergo sex reversals

Some species exhibit male to female reversal (for example, certain oysters), while others exhibit female to male reversal (for example, a coral reef fish)

2011 Pearson Education, Inc.

Variation in Patterns of Sexual

Reproduction

INTERNAL EXTERNAL

SEXUAL REPRODUCTION

EXTERNAL VS INTERNAL FERTILIZATION

FERTILIZATION MODE

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Gametes meet outside the body.

Involve aquatic invertebrates

Eggs and sperm are simultaneously shed into the water and water help gametes to disperse rapidly.

Sperms swim through the water to fertilize the egg.

Depends on tidal length and temperature to coordinate gamete release.

Pheromones trigger gamete release.

Amplexus: the male rests atop the female, awaiting her release of eggs 44

SEXUAL REPRODUCTION:

EXTERNAL FERTILIZATION

Once adapting to terrestrial, the animalface problem of desiccation especiallyfor small and vulnerable gametes.

Therefore, the organism start to practiceinternal fertilization.

Male gametes are deposited straightinto the female reproductive tract.

Three strategies for embryonic andfoetal development.

i. Oviparity

ii. Ovoviviparity

iii. Viviparity

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SEXUAL REPRODUCTION:

INTERNAL FERTILIZATION

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OVIPARITY OVOVIVIPARITY

VIVIPARITY

EMBRYONIC

DEVELOPMENT

SEXUAL REPRODUCTION

INTERNAL FERTILIZATION

Eggs that are fertilized internallybut complete their developmentoutside the mothers body.

Depend on egg yolk fornourishment.

The eggs might be abandoned bythe parents (fishes) or cared bythe parents (birds).

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SEXUAL REPRODUCTION

INTERNAL FERTILIZATION(OVIPARITY)

The fertilized eggs are retainedwithin their mother to completetheir development.

The embryos obtain theirnourishment from the egg yolk.

Eggs hatch inside the body.

Found in some many reptiles andguppies.

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SEXUAL REPRODUCTION

INTERNAL FERTILIZATION(OVOVIVIPARITY)

The young develop within their mothers uterus.

Obtain nourishment from the mother via placenta.

The offspring are fully developed at birth.

Found in almost all mammals.

Cat giving bith Lemon shark giving birth, pup emerges tail first 49

SEXUAL REPRODUCTION

INTERNAL FERTILIZATION(VIVIPARITY)

4. VARIETIES OF REPRODUCTION IN VETEBRATE

FISHES/

AMPHIBIANS

REPTILES/

BIRDS

MAMMALS

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All are Internal fertilization

Some mammals are seasonal breeder where theyonly reproduce once a year.

Others have more frequent reproductive cycles. Thecycle in female include a period of release of matureovum called ovulation.

At ovulation time, they are sexually receptive tomales.

Mammalian placental female has recurringphysiologic changes that are induced byreproductive hormones called the estrous cycle andmenstrual cycle.

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REPRODUCTION IN MAMMALS

ESTROUS CYCLE MENSTRUAL CYCLE

Reabsorb the endometrium if conception does not occur during that cycle.

Shed the inner lining of their uterus followed by heavy bleeding.

Females are generally only sexually active during the estrous phase of their cycle.

Sexually active at any time in their cycle, even when they are not about to ovulate.

Examples: dogs, cows, horses, rats, goats, elephants

Examples: human and apes

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Mammals can be divided into three categories:

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REPRODUCTION IN MAMMALS

MONOTREMESEgg lying mammals

MARSUPIALSPouched mammals EUTHERIANS

Placental mammals

Monotremes are oviparous since that theylay eggs. The young hatch pink andunfinished as an embryonic stage toohelpless to fend for themselves.

The females have mammary glands but nonipples, so the young must lap up the milkas it oozes from their skin.

Examples of monotremes are platypus andspiny anteater.

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REPRODUCTION IN MONOTREMES

Marsupials are viviparous.

The marsupials young are born tiny, blind, andhairless but find their way to the motherspouch which is at her ventral surface.

There they were suckled and finish theirdevelopment in the pouch.

Examples are kangaroos and Tasmanian Devils.

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REPRODUCTION IN MARSUPIALS

Eutherians are viviparous.

Eutherians retain their young for a much longerperiod of development in the mothers uterus.

The young are nourished within the mothersuterus by the placenta which is a composite ofmaternal and fetal tissue.

It is the organ of exchange of nutrients andwastes between the maternal blood and the fetalblood.

embryos grow faster than marsupials do in theirpouch and the offspring are fully formed at birth.

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REPRODUCTION IN EUTHERIANS

Major types of protection to ensure offspring survival are:

i) Tough eggshell (Oviparous animals)

ii) Development of embryo within the mother (Ovoviviparous / Viviparous)

iii) Parental care ( Amphibian, Aves, Reptiles and Mammals)

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REPRODUCTION IN VERTEBRATE:

CONCLUSION

ASEXUAL SEXUAL

ADVANTAGE DISADVANTAGE

SEXUAL

Genetic diversity increase chances ofsurvival in an unstable environment

Costly because there is a need to produce gametes and make the gametes meet (time + energy )

ASEXUAL

Beneficial parental genotype can be preserved in a stable environment.

Genetic uniformity leads to susceptibility to diseases.

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Chapter 2_reproduction Part 1 201415 Latest