IGCSE Biology : Reproduction

Human sexual reproduction, sexual reproduction in plants, asexual reproduction

oviduct (fallopian tube)

oviduct (fallopian tube)

carries egg cells from the ovaries to the uterus

uterus lining (endometrium)

a blood-rich lining in which an embryo implants. This lining is lost every month

vagina

a muscular tube that leads from the cervix to the outside of the body

uterus

where the baby develops during pregnancy

ovary

contains hundreds of undeveloped egg cells. Every month, an egg cell matures and is released

cervix

a ring of muscle at the lower end of the uterus, which keeps the baby in place during pregnancy

Sperm duct

carries sperm cells from the testes to the urethra

testes

produce sperm and releases testosterone

gland

produces fluid to mix with sperm cells to make semen

urethra

tube that carries urine and semen, has a ring of muscle to separate the fluids

penis

allows urine and semen to pass out of the body

scrotum

bag of skin that contain the testes

why are the testes outside of the body?

to keep them cool, the higher the temperature the fewer sperm cells produced

sperm cells adaptation

• flagellum (tail) - allows it to swim through the female reproductive system

• haploid nucleus - contains half of the normal number of chromosomes

• mitochondria - many mitochondria to produce energy for the flagellum to move through the uterus towards the egg

labia

folds of skin at the opening of the vagina

vulva

what is visible outside of the body in women’s reproductive system

what does the cervix produce?

mucus that change during the menstrual cycle sometimes allowing sperm to pass through and other times not

acrosomes

sac of enzymes at the tip of the sperm cell

testosterone

male sex hormone secreted from testes

causes : growth until adult size, penis, testes, and scrotum growth, deepening of voice, etc

oestrogen

female sex hormone

causes: growth until adult size, breast growth, widening hips etc

where does fertilisation take place

in the oviduct

how is a zygote made?

during fertilisation, the nucleus of the sperm cell fuses with the nucleus of the egg cell forming a fertilised egg - zygote

menstrual cycle

sequence of changes that occur in women’s body monthly

what is the pathogen for chlamydia

bacteria

pathogen for gonorrhoea

bacteria

syphilis pathogen

bacteria

genital herpes pathogen

virus

genital warts (HPV) pathogen

virus

HIV pathogen

virus

hepatitis pathogen

virus

pubic lice (crabs) pathogen

parasite

trichomoniasis pathogen

parasite

haploid cell

cells which have one set of genetic information

diploid cell

cells that have 2 sets of genetic information

what cells do gametes have

haploid cells

why do zygotes divide repeatedly?

to create all the cells of the new organism (all these cells will be diploid)

what are some advantages of sexual reproduction?

• variety in offspring

• individuals that may be better adapted to different conditions

• survival of the species is more likely

disadvantages of sexual reproduction

• requires 2 parents

• takes time and energy

• takes longer to produce an offspring

define fertilisation

when the nucleus of a male gamete fuses with the nucleus of a female gamete to form a zygote

Stamen

male parts of the flower made up of the anther and held up on the filaments

anthers

produce male gametes in the form of pollen

sepals

protect the flower in the bud

petals

the part that attract insects

stigma

female part of the flower that collect pollen grains

ovary

• female part of the flower that produces female gametes in the form of ovules

• protects the female gametes from the dry outside air

nectary

sometimes present in places to produce sugary substance that aims to attract insects

carpel

the female part of a flower consisting of the stigma, style and ovary

style

female part of the flower that supports the stigma

what happens as the pollen grains matures?

• develops thick outer shell to protect the male gamete

• when they all mature, the anther splits open to release them

features of wind-pollinated flowers

• no scent

• no nectaries

• small or no petals so pollen dispersal is not obstructed

• green, inconspicuous or no petals

• stigmas large and feathery; hanging outside the flower to trap pollen

• external, loose anthers that easily release pollen grains

• lightweight pollen grains that are easily carried by the wind

features of insect-pollinated flowers

• often scented

• nectaries present base of the flower produce sugary liquid to attract insects

• large petals

• brightly coloured petals

• stigmas are small and held inside the flower

• a few smaller anthers usually held inside the flower

• sticky or spiky pollen grains

pollination

• initial step in the reproductive process of flowering plants

• transfer of pollen from the stamen to the stigma of the same species

fertilisation at the ovule

• one of the male sex cells fertilise the egg

• initiates the formation of a seed

what happens during asexual reproduction?

cells from an adult organism divide to produce the offspring that are genetically identical to the parent and each other

binary fission

a type of asexual reproduction where a single organism divides into two equal parts, each becoming a new organism

how does bacteria reproduce asexually

with binary fission

advantages of asexual reproduction

• one parent required

• often large numbers of organisms can be produced in a relatively short period

• offspring are identical to parents and each other

disadvantages of asexual reproduction

• lack of variation - any change in conditions will affect all equally

• not suited to moving away and exploiting environments with different conditions