Reproduction in Plants and Animals Practical Activities

​Examining the stages of mitosis

• About 2 mm of a root tip of onion bulb is cut off and placed on a microscope slide.
• A stain e.g. aceto-orcein is added and the root tip macerated using a scapel.
• A cover slip is added and observations made.
• Different stages of mitosis can be observed.

Examining the stages of meiosis

• An unopened bud of Tradescantia is obtained
• The anther is removed and placed on a microscope slide.
• A few drops of hydrochloric acid and acetic-orcein stain are added.
• A cover slip is placed on the anther.
• Pressing the cover slip gives a thin squash, which is observed under the microscope.
• Different stages of meiosis are observed.

To observe the structure of Rhizopus

• Rhizopus grow on moist bread left under suitable temperature
• A piece of moist bread is placed on a petri­-dish or enclosed in a plastic bag and observe daily for four days.
• Under a low power microscope the sporangia and stolons can be observed.

To examine spores on sori of ferns

• Obtain the fern plant.
• Detach a frond from the plant and observe the under-side using a hand lens to see the raised brown patches - the sori.
• Open up the sorus to observe the sporangia.

To examine spores on sori of ferns

• Obtain the fern plant.
• Detach a frond from the plant and observe the under-side using a hand lens to see the raised brown patches - the sori.
• Open up the sorus to observe the sporangia.

Examine insect and wind pollinated flowers

• Obtain insect pollinated flowers e.g. crotalaria, hibiscus/Ipomea, Solanum, incunum.
• Note the scent, colour and nectar guides.
• A description of the calyx, corolla, androecium and gynoecium is made.
• Obtain a wmd pollinated flower e.g.,' maize, star-grass, sugar-cane, Kikuyu grass.
• Observe the glumes, spikes and spikelet.
• Examine a single floret, and identify the androecium and gynoecium.

Classifying fruits

• Obtain different fruits - oranges, mangoes, maize, castor oil, bean pod, black jack .
• Observe the fruits, classify them into succulent, dry-dehiscent or indehiscent.

Dissection of Fruits

• Obtain an orange and a mango fruit.
• Make a transverse section.
• Observe the cut surface and draw and label the parts.
• Note that the fruit is differentiated into epicarp, mesocarp and endocarp.
• Obtain a pod of a legume.
• Open up the pod and observe the exposed surface.
• Draw and label the parts.

Note that the fruit wall is not differentiated.
Dispersal of fruits and seeds

• Obtain animal dispersal fruits, like oranges, tomatoes, black jack, sodom apple.
• Identify the way by which each is adapted to dispersal by animals.
• Obtain wind dispersed fruit/seed e.g. Nandi flame, Jacaranda Sonchus, cotton seed, Tecoma.

Nutrition 
The placenta facilitates the transfer of nutrients from maternal blood to foetus.
Excretion 
Placenta facilitates the removal of nitrogenous wastes from the foetus' blood to maternal blood.
Gaseous exchange 
Oxygen from the maternal blood diffuses into the foetal blood while carbon (IV) oxide from foetal blood diffuse into maternal blood.
Production of hormones 
Placenta produces progesterone and oestrogen. ​

​The period between conception and birth is called gestation.
In humans gestation takes nine months (40 weeks).
The embryo differentiates into tissues and organs during this period.
Week 1 to 3:
Zygote divides to form blastocyst.
Implantation takes place.
The three germ layers form endoderm, mesoderm and ectoderm.
Nervous system starts to form. 
Week 4 to 7:
Development of circulating and digestive systems.
Further development of nervous system, formation of sensory organs,
All major internal organs are developed.
At week 5, heartbeat starts.
Week 8 to 24:
All organs well developed including sex organs.
Hair, finger and toe nails grow.
Foetus move and eyelids open.
Week 25- 30:
The fully developed foetus responds to touch and noises and moves vigorously.
The head turns and faces downwards ready for birth.
Week 31-40:
Foetus increases in size.
Birth occurs. 

• Sexual reproduction involves the fusion of gametes.
• In animals two individuals are involved, a male and a female.
• Special organs known as gonads produce gametes.
• In males testes produce sperms while in females ovaries produce ova.
• The fusion of male gamete and female gamete to form a zygote is called fertilisation.

There are two types of fertilisation. External and internal. 
External fertilization

• Example in amphibians takes place in water.
• The male mounts the female and shed sperms on the eggs as they are laid.
• Eggs are covered by slippery jelly-like substance which provides protection.
• Many eggs are released to increase the chances of survival.

Internal fertilisation

• This occurs in reptiles, birds and mammals.
• Fertilisation occurs within the body of the female.
• Fewer eggs are produced because there are higher chances of fertilisation since sperms are released into the female body.

Structure of female reproduction system,  
​The female reproduction system consist of the following: Ovaries

• Are two oval cream coloured structures found in lower abdomen below the kidneys.

Oviducts.

• They produce the ova.
• Are tubes which conduct the ova produced by the ovaries to the uterus.
• Fertilisation occurs in the upper part of the oviduct.

Uterus

• The uterus is a hollow muscular organ found in the lower abdomen.
• The embryo develops inside the uterus.
• The inner lining endometrium supplies nutrients to embryo.
• The embryo is implanted into the inner uterine wall- the endometrium which nourishes the embryo.
• The thick muscles of the uterus assist in parturition.

Cervix

• Has a ring of muscles that separates the uterus from the vagina.
• It forms the opening to the uterus

Vagina

• Is a tube that opens to the outside and it acts as the copulatory and birth canal through the vulva.

Structure of male reproductive system
The male reproductive system consists of the following: 
Testis:

• Each testis is a mass of numerous coiled tubes called semniferous tubules.
• Each is enclosed within a scrotal sac that suspends them between the thighs.
• This ensures that sperms are maintained at a temperature lower than that of the main body.

Seminiferous tubules

• The lining of seminiferous tubules consists of actively dividing cells which give rise to sperms.
• Between the seminiferous tubules are interstitial cells which produce the male hormones called androgens e.g. testosterone.
• The seminiferous tubules unite to form the epididymis, which is a coiled tube where sperms are stored temporarily .
• Vas deferens (sperm duct) is the tube through which sperms are carried from testis to urethra.
• Seminal vesicle produces an alkaline secretion which nourishes the spermatozoa.  

Prostate gland

• Produces an alkaline secretion to neutralise vaginal fluids.

Cowpers' gland

• Secretes an alkaline fluid.
• All these fluids together with spermatozoa form semen.

Urethra

• Is a long tube through which the semen is conducted during copulation.
• It also removes urine from the bladder.

Penis

• Is an intro-mittent organ which is inserted into the vagina during copulation.

Fertilisation in Animals

• Fertilisation is preceded by copulation in which the erect penis is inserted into the vagina.
• This leads to ejaculation of semen.
•  The sperms swim through the female's genital tract to the upper part of the oviduct.
•  The  head of the sperm penetrates the egg after the  acrosome_ releases lytic enzymes t dissolve the egg membrane.
• The tail is left  behind.
•  Sperm nucleus fuses with that of the ovum and a zygote is formed.
• A fertilisation membrane forms around the zygote which prevents other sperms from penetrating the zygote.

Implantation:

• After fertilisation the zygote begins to divide mitoticaly as it moves towards the uterus.
•  It becomes embedded in the wall of the uterus a process called implantation.
• By this time the zygote is a hollow ball of cells called blastocyst or embryo.
• In the uterus the embryo develops villi which project into uterus for nourishment later the villi and endometrium develop into placenta.

Embryonic membranes

• Embryonic membranes develop around the embryo.
• The outermost membrane is the chorion which forms the finger-like projections (chorionic villi) which supply nutrients to the embryo.
• The amnion surrounds the embryo forming a fluid filled cavity within which the embryo lies.
• Amniotic cavity is filled with amniotic fluid.
• This fluid acts as a shock absorber and  protects the foetus against mechanical injury.
• It also regutates  temperature.
• The chorionic villi, allantois together with the endometrium from the placenta.
• The embryo is attached to the placenta by a tube called umbilical cord which has umbilical vein and artery.
• The maternal blood in the placenta flows in the spaces lacuna and surrounds capillaries from umbilical vein and artery.
• The umbilical cord increase in length as the embryo develops.

​In flowering plants, the flower is the reproductive organ which is a specialised shoot consisting of a modified stem and leaves. The stem-like part is the pedicel and receptacle, while modified leaves form corolla and calyx.

​The process by which mature individuals produce offspring is called reproduction. Reproduction is a characteristic of all living organisms and prevents extinction of a species.