D3.1 Reproduction SL

Sexual reproduction

• contributes to genetic diveristy → good for adapating to a changing environemnt

Asexual reproduction

• produces genetically identical offspirng

• good for non changing environemnts

• faster, less energy can colonize a new area easily

Examples of asexual reproduction

• binary fission

• mitosis

• budding

• vegetative reproduction

Role of meiosis in sexual reproduction

• meisosi breaks up the parent alleles producing genetically diffrent cells

• the egg cell and sperm cell then fertilize leading to formations of new comibnations → genetic diversity

Egg cell vs sperm cell

Egg cell:

• large

• doesnt move

• stores nutrients

• has organelles

• only one per menstraul cycle

Sperm cell

• motile → flagellum

• very small

• no food reserves

• travels to the egg

• millions of sperms produced

Where are ovaries

Where is the vagina

Where is the cervix

Where is the uterus

Where is the oviduct

Where is the endometrium

Role of vagina

semen ejaculated there during sexual inetrcourse

Role of cervix

• sperm eneters there for fertilzation

• pathway for childbirth

Role of oviduct

transports egg from ovaries to the uterus

Role of uterus

• early embryo will be implanted there

Endometrium role

• highly vascual lining

Role of ovaries

• produce oestraidol

• produce the egg

• corpus luteum created there → secretes progestorne

• ovulation occurs there

Where is urethra

Where is scrotum

Where is testis

Where is the epididymis

Where is the vas deferens

Where is the urinary bladder

Where is the prostate gland

Where is the seminal vesicle

where is the erectile tissue of penis

Role of testes

• produce sperm in seminiferous tubules

Scrotum role

• sac that holds testes outside body for lower temp then that of the body

epididymis role

• sperm recieved, matures and gains motility

vas deferens role

tube that sends mature sperm from epididymis to urethra

seminal vesicles role

add seminal fluid to semen

prostate gland role

produces semen

penis

• erection

urethra

tube thorugh which semen and urine leave the body

Phases in menstural cycle

• follicular phase - first 14 days

• lutheal phase

Role of GnRH

• hypothalamus priduces GnRH

• the target tissue is next to pituitory galnd

• Results in secretion of FSH and LH → target tissue: ovaries

FSH and LH role

• increase production and secretion of oestradiol → target tissue: endometrium → increased density of blood vessels

• production of a Graafian follicle

• spike in LH and FSH → ovulation

Positive feedback loop: FSH, LH and oestradiol

• FSH and LH stimulate prodution of oestradiol

• oestradiol stimulates pituitaory to release more FSH and LH

• spike in FSH and LH → ovulation

Progesterone

• folicle begins secretion → follicle turns into corpus lutheum

• role of progestrone: maintains thickened highly vasuclar endometrium

Negative feedbak loop due to oestradiol and progestrone

• high levels of progestorne and oestradiol prevent hypothalmus of secretion of GnRH and hence FSH and LH

if No pregnancy what happends

• corpus lutehum breaks down

• decline in progestrone and oestradiol

• blood vessles of endometrium rupture → menstruation

Negative feedback → due to drop in oestrdaiol and progestorone

• progestorone and oestadiol drop

• increase in GnRh and hence FSH and LH

Ovarian cycle

control production and relase of egg

Uterine cycle

preparation and maintance of endometrium to recive fertilized egg

Process of fertilization

• sperm enter from vagina

• thorgh cervix into Fallopian tubes

• Release hydrolytic enzymes from acrosomes to get through the zona pellucida

• If one spermaoozon eneters vesicles reelased from egg that detroy mitochodnria and falgellum

• The sets of chromosmes remain seperated forming membranes - called pronucleus

• undego DNA rep

• Temporray membrane dissolves

• Mitosis begins

In vitro fertilization process

• medication that suspends normal menstural cycle

• female then taked meds including FSH to stimulate follicle growth - leading to superovulation

• Eggs are harvested surgically

• In lab combined with sperm

• One to three embroys implanted into uterus

Sexual reproduction in hermaphroditic plants

• hermaphroditic - which have both male and female parts its still sexual reproduction - selfpolination

• meiosis produces ovules and pollen grains which are haploid which then divide by mitosis

Cross polination

• petals that attarct pollinators

• anther positioned such that polinators come in contact without realising

• goes to stigma

• pollen when adheres to stigma will grow into pollen tube - with two male nuclei

• ovule - three haploid nuclei

• one and one fertilize

• one sperm and two eggs produce and endoserm which will nourish the embryo

Characteristics of insect pollinated flowers

• bright colours

• scent

• sticky pollen

• sticky stigma

Where is petal and sepal

Where is anther

Where is filament

Where is ovule

Where is stigma

where is stamen

where is ovary

where is carpel

where is style

Role of petal

attracts polinators

Role of sepal

proetcts developing flower

Role of anther

produces male gametes

Role of filament

holds anther

Role of stigma

pollen lands

role of style

holds stigma

role of ovary

contains one or more ovules

ovule

• female nuclei develop

Self incompatibility mechanisms

• when pollen lands on the same plant - the growth of pollen tube is reduced or stopped

Ways in which this occurs:

• pollen grain fails to germinate into pollen tube

• poleln grain germinates but cant enter through stigma

• can enter but pollen nuclei degerate before fertilization

• fertilization occurs but the embryo degenerates

Seed dispersal

• travel by wind

• by water

• can have pods which dry out and then they pop dispersing away from plant

• fruits consumed by animals when digested the coat reamins and give off in faeces far from plant

What is necesarry for seed gerimnation

• water

• oxygen

• approporiate temprature

Dormancy

• low metabolism

• low water content

• can last for years

• seed can sustain harsh conditions

Process of seed germination

1. Imbibition - seed uptakes water activates enzymes

2. enzymes digest food from endosperm tissue rasnfered by cotyledons which allow for cell respiration and proetin syntheis

3. First fill grow a radicle into the ground

4. The first structure that will emerge over the ground is the hypotocyl - against gravity → lifting cotyledons above ground