Week 4: Asexual Reproduction (copy)

Reproduction

the process of an organism that overcomes the dying and perpetuation of species.

Syngamy

refers to the union of two gametes for the formation of a zygote

Sexual Reproduction

Involves gametes or sex cells for reproduction.

Asexual Reproduction

Does not involve gametes; offspring are clones.

Gametes

Reproductive cells; include sperm and ova.

Fertilization

refers to the union of two gametes for the formation of a zygote

Isogamy

Sexual reproduction with similar-shaped gametes similar morphology (similar shape and size), differing in general only in allele expression in one or more mating-type regions.

Morphology

the branch of biology that deals with the form of living organisms, and with relationships between their structures.

*GAMETES ARE SIMILAR BUT HAVE DIFFERENT GENOTYPES

Heterogamy

Fusion of dissimilar gametes, e.g., sperm and egg.

*GAMETES ARE OF DIFFERENT SIZE

Male and female are either motile or non motile

Oogamy

fusion of large immotile female gamete with small motile male gamete

Haplontic Life Cycle

Multicellular haploid stage; diploid only fertilized egg.

EX:

All fungi

Some green algae

Many protozoa.

Meiosis

is a type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes

Gametophytes

produce gametes.

Diplontic Life Cycle

Multicellular diploid stage; haploid represented by gametes.

EX:

Animals

Some brown algae

Haplodiplontic Life Cycle

Includes multicellular diploid and haploid generations.

EX:

Fern plants

Plants

Flower

Reproductive structure with sepals, petals, stamens, carpels.

Receptacle (Torus)

– usually shortened, conical or disk shaped at the upper end of the stalk of the flower.

Accessory Organs

Calyx, corolla and receptacle

Essential Organs

stamen and pistil.

Calyx

Outermost green leaf-like structure of a flower.

Sepal

Lobe of Calyx

Corolla

Brightly colored petals inside the calyx.

Perianth

accessory part of the flower composed of petals and sepals.

Gamosepalous

sepals are united forming a tube.

Polysepalous

sepals are free from one another.

Gamopetalous

petals are united forming a tube.

Polypetalous

petals are free from one another.

Perigynous

corolla born on the calyx

Epigynous

corolla originates from top of the ovary.

Hypogynous

corolla arise from the receptacle below the ovary

Sepals

enclose the outer flower parts in the bud, generally green in color.

Petals

usually the conspicuous, colored attractive part of a flower

Stamens

Male reproductive part; the male germ cells/sperms/part of the flower; the grouping of the stamens is called androecium.

Filament

a stalk-like structure that attaches to the base of the flower and supports the anther the

Anther

the part of a stamen that produces and contains pollen.

Pistil

Female reproductive part; includes ovary, style, stigma. found at the center and the female part; collectively known as gynoecium.

Ovary

Contains ovules; base of the pistil.

Style

Slender structure on top of ovary.

Stigma

the enlargement at the tip of the style

The stigma receives a sticky substance which helps in pollination.

The style is the passage of the sperm of the nuclei in going to the ovary to fertilize the egg cell.

Carpel

Part of pistil; includes style, stigma, ovary. the carpel is the ovule bearing leaf-like part extending out to the style.

Monoecious Plants

Staminate and pistillate flowers are present on same plant.

ex. Squash and corn.

Dioecious Plants

Staminate and pistillate flowers are born on separate plants.

ex. papaya

Pollen Development

comprises three major stages: microsporogenesis, post-meiotic development of microspores, and microspore mitosis

Pollen

is produced within the anthers (microsporangia or pollen sacs) of the flower.

During its development from an undifferentiated mound of cells (anther primordium) the anther forms two general groups of cells.

Sporogenous Cells

give rise to the microspores and are formed from cells located centrally within the developing anther. The non-reproductive cells form discrete anther tissues layers and include the epidermal, cortical and tapetal cell layers surrounding the sporogenous cells.

Microsporogenesis

comprises the events which lead to the formation of the haploid unicellular microspores.

During microsporogenesis the diploid sporogenous cells differentiate as microsporocytes (pollen mother cells or meiocytes) which divide by meiosis to form four haploid microspores.

Each diploid meiocyte gives rise to a tetrad of four haploid microspores and microsporogenesis is complete with the formation of distinct single-celled haploid microspores.

Microspores

are small haploid structures that give rise to the male gametophyte. The function of sporogenous tissues is the production of pollen grains.

Meiocyte

- the cells that undergo meiosis to produce gametes

Gametophyte

it develops sex organs that produce gametes,

Pollination

Transfer of pollen from anther to stigma.

Self-Pollination

Pollen transfer within the same flower or plant.

ex:

Pea plant

Ground Nut

Barley

Cross-Pollination

Pollen transfer between different plants or flowers.

ex:

Sunflower

Date palm

Maize

Xenogamy

pollination between flowers of different genetic constitution is known as ______.

Entomophilous Flowers

Insect-pollinated flowers; often brightly colored.

Zoophilous Flowers

Pollinated by animals; adapted for animal transport.

Anemophilous Flowers

Wind-pollinated; small, inconspicuous, no nectar.

Hydrophilous Flowers

Water-pollinated; small and inconspicuous.