Tag: reproduction in animals

Starfish (echinoderms) possess remarkable regenerative abilities and can regenerate lost body parts, including whole arms or even a new body from a single severed arm under certain conditions.

• There are different methods of asexual reproduction. 
• They include binary fission, fragmentation, and budding. 
• Binary fission occurs when a parent cell splits into two identical daughter cells of the same size.
• Fragmentation occurs when a parent organism breaks into fragments or pieces, and each fragment develops into a new organism. Starfish, like the one in Figure below, reproduce this way.
• Budding occurs when a parent cell forms a bubble-like bud. The bud stays attached to the parent cell while it grows and develops.

Regeneration is the ability to replace the lost or damaged body parts. Plants can regenerate all body parts from the precursor cells. Many trees, for example, can be cut off at the ground and in due course, sprouts appear. These go on to develop the new stem, leaves and flowers. So, regeneration is a process of restoration and growth and also a process of renewal.
Thus, the correct answer is option D.

Regeneration is the process of renewal, restoration, and growth of cells which lead to the renewal of lost or damaged parts or cells. All the cells of the body do not take part in the regeneration rather the cells involved in regeneration are cells which have immense potential to divide and differentiate. In lizards, the cells of blastema actively takes part in the regeneration and it is capable of growth composed of pleuripotent cells which retains memory of tissue origin. So, the given statement is true.

• The liver is the only internal organ that can regenerate itself.
• Hepatocytes are the liver cells that are responsible for the liver's ability to regenerate; they act as stem cells that can re-form liver tissue. The liver can regenerate after either surgical removal or after chemical injury. It is known that as little as 25% of the original liver mass can regenerate back to its full size.
• The lost portion of dissected liver regenerates by Compensatory hypertrophy i.e The growth which is a result of increased cell size.
• So, the correct answer is 'Compensatory hypertrophy'.

• The ability of the multicellular organism to repair certain damaged cells present in the Damaged parts and organs is called Reparative regeneration.
• Reparative regeneration is observed in both invertebrates and vertebrates.
• Hence Damaged parts and organs can be repaired by Reparative regeneration.
• So, the correct answer is 'Reparative regeneration'.

• Nemathelminthes  is a phylum of unsegmented, triploblastic, pseudocoelomic, cylindrical or thread-like worms which are covered by a body wall having cuticle and epidermis. They are commonly called threadworm or roundworm.
• The members of the phylum Nemathelminthes lacks the ability of regeneration because they do not have stem cells required for regeneration.
• So, the correct answer is 'Nemathelminthes'.

C- A mass of cell capable of growth and regeneration into organs or body parts is called as blastema that means these cells can grow in any type of cells except neurons.For the formation of blastema adult stem cells known as neoblasts are required before occurence of any regeneration.

• Regeneration process in higher animals involves a series of steps.1)Wound closure 2) Demolition and Defence 3)De-differentiation 4)Blastema Formation 5) Growth and 6)Re-differentiation.
• WOUND HEALING: Amputation or injury to organ results in exposure of the interior tissues to the outside. Some cells in the injured region get destroyed. There may be bleeding at the injured surface. The blood soon clots and blocks further flow of blood to the outside. Hence bleeding is stopped.
• Then the epidermal cells proliferate and migrate from all sides towards the center of the wound. Thus the epithelium forms a complete covering over the injured tissues underneath the blood clot. 
• Hence Wound closure step of regeneration stops the bleeding at the site of amputation.
• So, the correct answer is 'Wound closure'.