4[1].1 form 5

BIOLOGY FORM 5

LEARNING OUTCOMES• To explain the necessity for organisms to

reproduce;• To state types of reproduction;• To explain the necessity for the formation

of gametes;• To describe formation of sperm in

humans;• To describe formation of ovum in humans;• To compare the formation of sperm with

that of ovum.

THE NECESSITY FOR ORGANISMS TO REPRODUCE

• To ensure the continuous existence of their species

• To increase their numbers.

• REPRODUCTION = the production of new individuals of the same species.

TYPES OF REPRODUCTION

• ASEXUAL REPRODUCTION–Production of new individual from a single parent without involving gametes.

–Daughter cells/new individuals are genetically identical to the parent

–Binary fission, budding, spore formation, vegetative reproduction & regeneration

ASEXUAL EXAMPLEBinary fission Bacteria, Amoeba,

ParameciumBudding Yeast, HydraSpore formation

Fungi, mosses, ferns

Vegetative reproduction

Onion, ginger, potato

Fragmentation & rejuvenation

Sponges, flatworms, starfish

TYPES OF REPRODUCTION

•SEXUAL REPRODUCTION– Involves two parents male parents = male gamete, female parents = female gamete

–Male gamete + female gamete zygote new individual

–Formation of gametes gametogenesis.

• Human male gamete spermatozoon (plural : spermatozoa) @ sperm.

• The formation of sperm spermatogenesis

MALE REPRODUCTIVE SYSTEM

ORGAN FUNCTION

Testis Production of sperms & sex hormones.

Epidi-dymis

Sperm maturation site & sperm storage

Vas deferens

Transport of sperms from the epididymis to the urethra

Seminal vesicle & prostate gland

Secretion of a fluid for sperms to swim in as well as providing fructose as a source of energy

Penis Organ of sexual intercourse

• Spermatogenesis occurs at the wall of seminiferous tubules

• Germinal epithelium (outermost layer of cells @ seminiferous tubules) consists of germ cells formed sperms.

• The developing spermatozoa obtain their nutrients from Sertoli cells.

A mature spermatozoon• A large nucleus

carries genetic• Acrosome contain

enzyme to penetrate the ovum

• Tail to swim towards the ovum

• Middle piece – large number of mitochondria provide energy.

• The formation of ovum oogenesis

FEMALE REPRODUCTIVE SYSTEM

ORGAN FUNCTION

Ovary Production of ovum & sex hormones

Fallopian tube

Site of fertilisation; carries ovum from ovary to uterus

Uterus Site of implantation; chamber in which the embryo develops

Cervix Secretion of mucus that facilitates sperm movement

Vagina Organ of sexual intercourse; birth canal

• Oogenesis occurs at the germinal epithelium of the ovaries.

• A large number of oogonia (singular : oogonium) are produced only one ovum is formed at the end of the process.

• 1st stage : the female is still an embryo in her mother’s uterus born with all the oogonia.

• Clusters of cells in the ovary of a mature female primary follicles

• One of the cells is larger than the rest oogonium.

• The primary follicle develops (oogonium) primary oocyte.

• Mature follicle Graafian follicle (contain secondary oocyte at one side & a fluid-filled cavity. It may reach a size of 1cm diameter it now bulges at the surface of the ovary.

• Graafian follicle ruptures release its secondary oocyte.

• Female have a pair of ovaries each produce an ovum (secondary oocyte) every 28 days.

SIMILARITIESFormation of

spermFormation of

ovum• Both processes begin with repeated

mitotic division of the germ cells.

•Both processes involve meiosis.

•Both processes result in the formation of haploid reproductive cells

gametes.

DIFFERENCESFormation of

spermFormation of ovum

Every spermatogonium develops primary

spermatocyte

Only one oogonium develops primary

oocyte, others disintegrate.

1st meiotic division of the primary spermatocyte

cytoplasm divides evenly 2 secondary

spermatocytes

1st meiotic division of the primary oocyte uneven distribution of cytoplasm 1 bigger (secondary oocyte), 1 smaller polar body

No polar bodies are formed

1 to 3 polar bodies are formed.

Hundreds of thousands of sperms are formed in the

process.

Only one ovum is formed in the process.

EXERCISE 4.11. Define reproduction.2. Describe the formation of sperm in

humans.3. Compare the formation of a sperm

with that of an ovum.