biology sexual and asexual reproduction

asexual reproduction

**a process resulting in the production of genetically identical offspring from one parent**

advantages of sexual reproduction

* species can multiply faster
* species can colonise faster and more efficiently

disadvantages of asexual reproduction

* minimal variation
* limited chance of survival in different and changing environments
* will not evolve as efficiently
* at a greater risk of extinction because of mutations and diseases

sexual reproduction

**a process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote and the production of offspring that are genetically different from each other**

haploid

what are the nuclei of gametes

diploid

what are the nuclei of gametes

advantages of sexual reproduction

* gives rise to variation
* higher chance of survival in different or changing conditions
* makes it easier to colonise new habitats
* evolution occurs efficiently
* a negative mutation takes longer to inflict a significant effect

disadvantages of sexual reproduction

* takes a long time to court
* takes a while to colonise new habitats
* requires two parents
* positive or favourable genes may not be passed o
* produces fewer offspring

ok

play a game to identify the parts of a flower

sepals

**a hard layer that protect the flower while it is a bud**

petals

come in different, often vibrant, colours to attract insects for pollination

anthers

contain pollen sacs. This is where pollen grains are formed. Pollen grains contain the male gametes (sex cells) required for fertilisation.

stigma

a sticky surface that catches the pollen during pollination.

ovaries

contain ovules. These develop into seeds when they are fertilised.

insect pollinated flowers

larger and heavier than grains from wind-pollinated flowers.

have pollen grains that are usually either sticky or spiky – this helps the pollen get stuck to insects, assisting the pollen in getting carried to another flower.

wind pollinated flowers

smooth and light pollen grains so that the wind can carry the pollen to other flowers without the pollen clumping together.

produce higher numbers of pollen grains than insect-pollinated flowers

pollination

**the transfer of pollen grains from the anther to the stigma**

agents of pollination

Animals, including insects; the wind; water.

fertilisation

occurs when a pollen nucleus fuses with a nucleus in an ovule.

insect pollinated flowers

petals are persent and colourfull, nectar produced by nectaries , stigmas are present inside flower and are often flat, stamen is present, smaller amount of pollen

wind pollinated flowers

petals are absent or small and green, nectar is absent, stigmas are large and feathery the filaments are long and there are larger amounts of pollen

testes

**production of male gametes (sperm)**

scrotum

**sac that holds the testes outside the body**

sperm ducts

**transfer sperm to the urethra**

prostate gland

**secrete fluids for sperm to swim in forming semen**

urethra

**carries urine and semen to vagina during sexual intercourse**

penis

**transfers semen to vagina during sexual intercourse**

ovaries

**release of female gametes (eggs)**

oviducts

**transfers egg to uterus and the site of fertilisation**

uterus

**where the fetus develops**

cervix

**ring of muscle at the opening of the uterus**

vagina

**receives penis during sexual intercourse**

fertilisation

**the fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell/ ovum)**

male gametes

very small, mobile, and millions of them

female gametes

very big, immobile, very few of them

adaptations of sperm

has a tail, which makes a whipping motion (Tail is called flagellum) posess digestive enzymes in a sac in its head

adaptations of egg cell

contains large enrgystores which provide nutrients for the embryo during early development, surrounded by a jelly coating called the zona pellucida, which changes to become impenetrable after fertilization

menstrual cycle

hormone regulated cycle.  On average, it lasts 28 – 35 days.

menstruation

During menstruation, follicles start to develop, and along with them, the oocytes they carry. The Endometrium lining starts getting repaired. The dominant follicle – i.e. the one that will release the egg in ovulation, will only finish developing after the end of menstruation.

ovulation

This marks the transition from the follicular phase to the luteal phase. In ovulation, the dominant follicle bursts and turns into a corpus luteum, and the oocyte is released into the oviduct. The luteal phase has begun.

zygote

In early development, it forms an embryo. An embryo is a ball of cells that implants into the wall of the uterus.

umbilical cord

takes blood from the foetus to the placenta, through the umbilical artery

placenta

bring the foetal blood and maternal blood very close, but don’t allow them to mix.

amniotic sac

enclosing the amniotic fluid and preventing the entry of bacteria.

amniotic fluid

supporting the foetus and protecting it from physical damage. It also absorbs excretory materials (urine) release by the foetus.

HIV

may lead to acquired immune deficiency syndrome (AIDS)

methods of HIV transmissions

* From infected mother to foetus across placenta
* Feeding a baby milk from an infected mother
* Unprotected sexual intercourse with an infected person
* Transfusion with unscreened blood
* Use of unsterilized surgical instruments
* Sharing hypodermic needles when taking drugs

spread of STIs control

* abstinenece
* having only one sexual partner
* wait and test
* get vaccinated
* use condoms and dental damd
* avoid drinking alcohool excessively
* communicate