GENERAL BIOLOGY 2
Reproduction
- Produce offspring or a new individual
- Passing of genetic material from parent/s to offspring
Asexual Reproduction
- Involves only one parent
- No need for gamete union
- Genetically identical to parent (Clone)
Types of AS Reproduction:
● BUDDING (PLANTS) → in which a new organism develops from an outgrowth or
bud due to cell division at one particular site.
● BINARY FISSION (BACTERIA) → is a separation of the parent cell into two new
daughter cells. Commonly observed in prokaryotes and a few single-celled
eukaryotes.
● PARTHENOGENESIS → involves development of a female (rarely a male) gamete
(sex cell) without fertilization.
● SPORULATION → whereby adult organisms produce single-celled diploid spores
that grow into adults themselves.
● REGENERATION → the organism is capable of regrowing certain body parts.
● VEGETATIVE PROPAGATION → taking a part of one parent plant and causing it to
regenerate itself into a new plant.
● FRAGMENTATION → in which a piece of the body, or fragment, of the parent
breaks off and develops into an independent offspring.
● POLYEMBRYONY → the splitting of one sexually produced embryo into many
offspring, which are genetically identical to each other but distinct from their
parent(s).
● AGAMOGENESIS → any form of reproduction that does not involve a male gamete.
● APOMIXIS → involves the production of seeds without the function of gametes,
which means avoiding the processes of meiosis and fertilization, leading to embryo
development.
AS Reproduction in PLANTS
- ADVANTAGE: when they are adapted to a particular environment and the genetic
variation among plant members is not a necessity
- STRATEGY: Vegetative Reproduction
→ is an asexual method of plant reproduction that occurs in its leaves,
roots and stem. The new plant that results from this type of reproduction is
identical to its parent plant.
AS Reproduction in ANIMALS
- are commonly found among lower forms of organisms such as protists, cnidarians,
hydra, amoeba, and some complex animals.
- Types:
a. FISSION → involves the division of the body into two or more equal parts.
b. BUDDING → a new individual arises as an outgrowth (bud) from its parent.
c. FRAGMENTATION → he body breaks into two or more parts, with each
fragment capable of becoming a complete individual.
Sexual Reproduction
- Involves two parents
- Gamete union; Sperm has to fertilize the egg
- Hybrids of parents; genetic combination of the two parents
Types of SX Reproduction:
● Mating
● Breeding
● Copulation
SX Reproduction in PLANTS
- occurs in the sexual organ of the flower.
Male organs of a Flower:
a. Stamen → male reproductive part of a flower
b. Anther → makes tiny grains called “pollen”, which contains male sex cells
c. Filament → holds up the anther
Female organs of a Flower
a. Carpel → female reproductive part
b. Stigma → traps the pollen
c. Style → joins the stigma and the ovary
d. Ovary → contains the female sex cells called ovules
SX Reproduction in ANIMALS
- Types:
a. GAMETOGENESIS → production of gametes
b. SPAWNING OR MATING → bringing gametes together
c. FERTILIZATION → fusion of gametes (external or internal fertilization)
ADVANTAGES OF AS REPRODUCTION:
● Only one parent is involved, thus inhibiting isolation to produce offspring without
finding mates. In plants, it eliminates the need for pollinating agents.
● The new generation produces the same characteristics as its parent. Plants with
desired characteristics can be cloned for economic reasons.
● A large number of offspring can be produced in a short time.
● The production of genetically identical offspring have well-adapted to an environment
of a particular(?)
DISADVANTAGES OF AS REPRODUCTION:
● The lack of genetic variability in a sexual reproducing population.
● The species may only be suited to one habitat.
● Disease may affect all the individuals in a population.
ADVANTAGES OF SX REPRODUCTION:
● Produces genetic variation in the offspring.
● The species can adapt to new environments due to variation, which gives them a
survival advantage.
● A disease is less likely to affect all the individuals in a population.
DISADVANTAGES OF SX REPRODUCTION:
● Time and energy are needed to find a mate.
● It is not possible for an isolated individual to reproduce.
Vegetative Propagation
- The process in which new plants are grown from the old parts of another plant like
roots, shoots and leaves, without involving any reproductive organ.
Examples:
● Rhizome → Bamboo, Bearded Iris, Canna Lilies, Ginger
● Tuber → Yams, Potato, Aroids, Cassava
● Bulb → Garlic, Onion, Spring Onion, Fennel
● Sucker → Red raspberry, Lilac, Blueberry
● Stolon/runners → Strawberries, Bermuda grass, Peppermint, Spider grass
● Leaf → Begonia, Bryophyllum
● Corm → Crocus, Titan anum (Amorphophallus titanum)
Alternation of Generation
- Also called metagenesis or heterogenesis, the alternation of a sexual phase and an
asexual phase in the life cycle of an organism.
- Two generation or life stages:
a. GAMETOPHYTE → haploid (one set of chromosomes (n) = 23) stage
b. SPOROPHYTE → diploid (two sets of chromosomes (n) = 46) stage
- Commonly occurs in fungi, algae, and plants.
- Moss and Ferns → Sporophyte and Gametophyte generation
Explanation:
In general, this is how alternation of generations works: a male gametophyte
(n) and a female gametophyte (n) produce gametes (sperm and eggs, respectively),
which combine in fertilization to form a diploid plant called a sporophyte (2n). This
sporophyte will grow and then produce spores, through meiosis, that will germinate
into a new gametophyte (n), thus the alternating cycle is complete.