ReproductionWays of reproducing

Chapter 6- Unit 1 Biology

Producing the next generationAsexual reproduction involves the formation of individuals whose genes all come from one parent.

There is no fusion of sperm and egg.

Sexual reproduction is the formation of offspring by the fusion of haploid gametes (sex cells).

Ovum: female gamete - usually large and nonmotile.Spermatozooan: male gamete - usually small and motile.

Sexual reproduction increases genetic variation among offspring.

Asexual Reproduction- Cloning!•Offspring are genetically identical to their parent.•An organism basically makes an exact copy of itself.

Fission: (similar to mitosis) in which a parent cell splits to form 2

identical daughter cells.Binary Fission of a Man

Bacterial Fission

Asexual Reproduction

Asexual Reproduction in Protozoa Binary fission begins with mitosis. Cytoplasmic division (cytokinesis) results in two identical cells. Binary fission is (a) longitudinal in some protozoans and (b) transverse in others.

2N

2N

2N

2N

2N

Sexual ReproductionDiploid female

sex organ

cells 2N

Haploid female sex

cells-gametes N

Diploid zygote 2N

Fertilization

Diploid male sex

organ cells 2N

Haploid male sex cells-

gametes N

Diploid embryo 2N

MITOSISMeiosis

Asexual Reproductions involves Mitosis Sexual Reproduction involves Meiosis

Other Types of Asexual Reproduction

BuddingFragmentationVegetative ReproductionParthenogenesisSpore formation

Budding:Development of a new organism from an outgrowth of the parent organism

Fragmentation:Individual cells or groups of cells from the parent organism can develop into a complete new organism eg sponges ,

flatworms

Parthenogensis: Egg development without

fertilization is possible in:◦ Many plants◦ Aphid◦ Daphnia◦ Honeybee◦ Whiptail lizard◦ Komodo Dragon◦ Hammerhead Shark

Spores:A reproductive cell that can grow into a new individual by mitosis

NN

2N

2N

2N

Mitosis

Fertilization

Meiosis

Forms of Vegetative Propagation:

Stems: Runners are stems that grow horizontally above the ground. They have nodes where buds are formed. These buds grow into a new plant.

Forms of Vegetative Propagation:A Corm is a short, vertical, swollen underground plant stem that serves as a storage organ used by some plants to survive winter or other adverse conditions such as summer drought and heat .

Forms of Vegetative Propagation:

Rhizomes are a stem that is usually found underground, often sending out roots and shoots from its nodes.

Tubers: Roots

Tubers Roots: New plants will grow out of swollen, modified roots called tubers. Buds develop at the base of the stem and then grow into new plants.

Bulbs:

Bulbs are an underground stem. Leaves are attached to the stem. These leaves contain much stored food. At the centre of the bulb is an apical bud. Also attached are lateral buds. The apical bud will produce leaves and a flower while the lateral buds will produce new shoots. As the plant grows and develops it will form a new bulb underground.

Leaves & Plantlets:Leaves: Leaves of some plants will grow into a new plant if they become detached from the parent plant. Other plants grow small plants called plantlets on the edge of their leaves.

Plant Cuttings:Small pieces of plant leaf or stem can strike roots and grow into a new plant.

Flowering Plant Sexual Reproduction

Flowers are the sexual organs of Angiosperms

Plant Reproduction : Fertilization

Can be either: SELF-POLLINATION – if the pollen attaches to the stigma of the same flower.CROSS-POLLINATION – if the pollen attaches to the stigma of a different flower.

Non Flowering Plant Reproduction

Non Flowering Plant Reproduction

Sexuality:Hermaphroditism versus Gonochorism

Acropora sp., a hermaphoditic coral

Fungia scutaria, a gonochoric coral

eggs

sperm packet

egg cloud

Hermaphroditism: both sexes in the same individualsGonochorism: sexes are separate

Internal and external fertilization both depend on mechanisms ensuring that

mature sperm encounter fertile eggs of the same species

External Fertilization: requires a moist habitat that will protect a developing egg from desiccation and heat stress.Specific mating behaviors assure that sperm and egg will be in the same place at the same time.

Brooding vs Broadcast Spawning

broadcast spawnerPocillopora damicornis, a brooder

planula in polyp

released gametes

Brooding: eggs develop to planula stage in gastrovascular cavity of parent polypBroadcast Spawning: eggs and sperm are shed into the water column where fertilization and development occurs

External Fertilization:Internal fertilization requires cooperative behavior that leads to copulation.

chemical signals released by one organism that influence the behavior of other individuals of the same species.

Many act as male attractants.

male

Pheromones:

Internal fertilization usually results in the production of fewer zygotes than does internal fertilization.

However, the survival rate is lower for external fertilization than it is for internal fertilization.

Species with internal fertilization usually produce fewer zygotes but provide more parental protection than species with external fertilization

· The externally fertilized eggs of fishes and amphibians are surrounded by a gelatinous coat.

· The internally fertilized amniote eggs of birds, reptiles and monotremes are protected by calcium and protein shells.

· In most mammals the embryo is retained within the females reproductive tract.

· The least complex reproductive systems lack gonads.· Polychaete worms lack

gonads.· Eggs and sperm develop

from undifferentiated cells lining the coelom.

Some reproductive systems, such as that seen in parasitic flatworms, can be very complex.

Complex reproductive systems have evolved in many animal

phyla

Most insects have separate sexes with complex reproductive

systems.In many species the female reproductive system includes a spermatheca, a sac in which sperm may be stored for a year or more.

The basic plan of all vertebrate reproductive

systems are very similar.

However, there are variations.In many non-mammalian vertebrates the digestive, excretory, and reproductive systems share a common opening to the outside, the cloaca.Mammals have separate opening for the digestive and reproductive systems.Female mammals also have separate openings for the excretory and reproductive systems.

Human reproduction involves intricate anatomy and complex

behavior

Male Reproductive SystemThe scrotum and the penis are the external components of the reproductive system.The internal reproductive organs consist of gonads, accessory sex glands, and ducts.

Testes are located in the scrotum, outside the body cavity. This keeps testicular temperature cooler than the body cavity.Consists of many highly coiled seminiferous tubules surrounded by layers of connective tissue. Sperm form in seminiferous tubules.Leydig cells scattered between seminiferous tubules produce androgens (ex. testosterone).From the seminiferous tubules sperm pass to the coiled tubules of the epididymis.It takes about 20 days for sperm to pass through the tubules of the epididymis.In the epididymis sperm become motile and gain the ability to fertilize.

Testes are the male gonads.

Testes:

Seminiferous Tubules

Spermatogenesis

Mature Spermatozoa

Prostate gland:

Location- surrounds and opens into the urethra where it leaves the bladder. Secretion- slightly alkaline fluid that activates the sperm and prevents them from sticking together

Ejaculation propels sperm from the epididymis to the vas deferens.The vas deferens run from the scrotum and behind the urinary bladder.Here each vas deferens joins with a duct from the seminal vesicle to form an ejaculatory duct.The ejaculatory ducts open into the urethra.The urethra drains both the excretory and reproductive systems.A male usually ejaculates about 2 – 5 mL of semen; each milliliter containing about 50 –130 million sperm.

External structure of the penis:The shaft of the penis is covered by relatively thick skin.The sensitive glans penis is covered by thinner skin.The penis is composed of three layers of spongy erectile tissue.During sexual arousal the erectile tissue fills with blood from arteries.The resultant increased pressure seals off the veins that drain the penis.The engorgement of the penis with blood causes an erection.An erection is essential to the insertion of the penis into the vagina.

Female Reproductive TractExternal reproductive structures:• labia• clitoris • vaginal openingInternal reproductive structures:• ovaries• fallopian tube (uterine tube)• cervix• uterus• vagina• fimbrae

Female Reproductive Tract

Ovulation:OVULATION

Oogenesis in the Ovary

•Ovary- contains 400,000 oocytes; release about 500 in a lifetime•Ovary- under influence of FSH. The follicles mature every 28 days•Primary follicle produces estrogens•And primary oocyte completes its 1st division produces 2ndary oocyte and polar body

•Approx 1/2 way through the 28 day cycle the follicle reaches the mature Vesticular or Graffian follicle stage. •Estrogen levels rise and release LH and FSH and triggers ovulation.•The 2ndary oocyte travels down the uterine tube to the uterus.•If fertilized by sperm, it will produce a zygote

Hormone , Follicle & Endometrial Development :

Oogenesis

Ovarian Cycle

Ovulation, fertilization & implantation

Fertilisation

Fertilization & Embryonic Development

Fertilization & Embryonic Development

Gestation Period

After fertilisation the zygote is implanted onto the endometrium, this marks the beginning of pregnancy. The zygote is supplied with blood via the umbilical cord and the embryo develops. The umbilical cord connects to the placenta with is supplied with blood from the mother’s circulatory system. At 8 weeks the embryo is now a foetus. It will continue to grow for another 32-33 weeks.

Meiosis VideoMeiosis Square Dance