REPRODUCTION AND DEVELOPMENT IN PLANTS AND ANIMALS

ASEXUAL REPRODUCTION

ASEXUAL REPRODUCTION Unicellular organisms, many simple animals and many plants reproduce asexually, at least during one part of their life cycles. Because asexual reproduction takes place by mitotic cell division, each offspring show little variation and they are nearly identical to each other and to the parent. Asexual reproduction is rapid and results in large number of offspring.

A) BINARY FISSION It is the simplest form of asexual reproduction in which parent organism divides into two parts that are about equal. Each of the daughter cells becomes a separate individual and grows to normal size. It’s seen in bacteria, protozoa (ameba, euglena, paramecium) and many algae.

Binary fission occurs in width of Paramecium

Binary fission occurs longitudinally in Euglena

B) BUDDING Parent organism divides into two unequal parts in budding. New individuals develop as small outgrowths or buds on the outer surface of the parent organism. The buds may break off and live independently or they may remain attached, forming a colony. Budding takes place in yeast and hydra as well as sponges, some worms and some plants. NOTE: Both hydra and yeast can also reproduce sexually.

B) BUDDING

BUDDING IN YEAST

C) SPORE FORMATION It’s seen in some one-celled organisms such as fungi, algae and protozoa (ex: Malarial Parasite, Plasmodium) as well as mosses (karayosunları) and ferns (eğreltiotları). Spores can be formed sexually and asexually. The spores are formed by meiosis in spore cases and they are monoploid.

C) SPORE FORMATION Spores are resistant to unfavorable conditions like high temperature, drought etc. because of their outer covering In favorable conditions (heat, moisture, food), spores germinate and forms a new organism.

C) SPORE FORMATION Plasmodium is a parasite that causes malaria (sıtma) in humans. Plasmodium has reproductive stages that occur in mosquitoes and humans. Sexual reproduction takes place in the digestive tract of the mosquito, and the asexual reproduction takes place within the liver and bloodstream of the human. At one stage of the life cycle of Plasmodium, the spores invade red blood cells of the human host, multiply there, then break out and invade new cells. The destruction of the red blood cells releases toxic cell wastes into the blood that causes fever and chills.

C) SPORE FORMATION @

C) SPORE FORMATION

D) VEGETATIVE REPRODUCTION Roots, stems and leaves are called vegetative structures. When they gave rise to a new plant, the process is called vegetative reproduction. In vegetative reproduction, undifferentiated cells, such as cambium and epidermal cells, divide mitotically and differentiate to produce an independent plant. The new plant has the same hereditary characteristics as it’s parent.

D) VEGETATIVE REPRODUCTION Vegetative reproduction takes place naturally, but it can be brought about artificially. Cutting Layering Grafting Bulb Corm Tuber Rhizome Runner (stolon) Artificial vegetative reproduction Natural vegetative reproduction

D) VEGETATIVE REPRODUCTION Some plants such as tulips, onions and lilies reproduce by bulb which is a short underground stem. As the plant grows new bulbs sprout from the old one. Each bulb give rise to a new plant.

D) VEGETATIVE REPRODUCTION Tuber is a type of underground stem . White potatoes are tubers. There are some indentations called “eyes” on the surface of the tuber that can produce new potatoes if they are cut and plant in soil.

D) VEGETATIVE REPRODUCTION The parts of the blackberry plant that touches the ground can break apart from the parent plant and give rise to new plants

D) VEGETATIVE REPRODUCTION Strawberry plants and many kinds of grasses reproduce by runners. A runner is a stem that grows sideways and has buds. It usually grows along the surface of the ground. Where buds from a runner touch the soil, new independent plants develop.

D) VEGETATIVE REPRODUCTION Ferns, irises, cattails and water lillies, reproduce by rhizomes. A rhizome is a thick and fleshy stem that grows sideways underground. Buds produced on the upper surface of rhizome give rise to leaf-bearing branches. The lower surface produces roots.

E) REGENERATION

E) REGENERATION Regeneration is the ability of an organism to regrow lost body parts. Simple animals like hydra, planarian, starfish, earthworm can regenerate lost parts. A planarian can be cut into several pieces, each of which will grow into a complete worm. (starfish is also like that) The power of regeneration decreases as animals become more complex. Ex: Lizards regenerate their tails but not their legs.