Life Processes in Amoeba
Amoeba is a simple, single-celled organism found in freshwater environments. Despite
its simplicity, it performs all essential life processes required for survival, including
nutrition, respiration, excretion, movement, osmoregulation, irritability (response to
stimuli) and reproduction. Below is a detailed overview of each life process in amoeba.
1. Nutrition in Amoeba
Amoeba exhibits a holozoic mode of nutrition, meaning it ingests solid food particles.
The process involves several steps:
Ingestion: Amoeba feeds on microscopic organisms like bacteria and algae. It extends
its pseudopodia (temporary finger-like projections) to surround and engulf food
particles, forming a food vacuole inside its cytoplasm. This process is called
phagocytosis.
Digestion: Digestive enzymes are secreted into the food vacuole, breaking down
complex food into simpler substances.
Absorption: The digested nutrients are absorbed into the cytoplasm, providing energy
for the cell.
Assimilation: Absorbed nutrients are utilized for growth, repair, and energy production.
Egestion: Undigested waste is expelled from the cell by rupturing a part of the cell
membrane.
The entire process allows amoeba to obtain and utilize nutrients effectively for survival.
2. Respiration
Amoeba does not have specialized respiratory organs. Instead, it relies on simple
diffusion for gas exchange:
Oxygen from the surrounding water diffuses through the cell membrane into the
cytoplasm.
Carbon dioxide, produced as a waste product, diffuses out into the water.
This process is efficient because of the amoeba’s small size and large surface-area-to-
volume ratio.
3. Excretion
Amoeba, ingest food by endocytosis. The food vesicle fuses with a lysosome, which
digests the food. Waste is excreted by exocytosis.
Metabolic waste products such as carbon dioxide, ammonia, and urea diffuse out
through the cell membrane. Additionally, excess water and some wastes are collected in
a contractile vacuole, which periodically contracts to expel its contents outside the cell,
helping maintain internal balance.
4. Movement
Amoeba moves by extending its pseudopodia. The cytoplasm flows into these
extensions, allowing the cell to move in the desired direction. This method of movement
is called amoeboid movement.
5. Osmoregulation
Osmoregulation is the process by which amoeba maintains water balance:
Water continually enters the cell by osmosis.
The contractile vacuole collects excess water and expels it, preventing the cell from
bursting.
This function is crucial for survival in freshwater environments, where water constantly
enters the cell.
6. Irritability (Response to Stimuli)
Amoeba can sense and respond to changes in its environment, such as light,
temperature, and the presence of chemicals. For example, it moves away from strong
light and can encyst (form a protective cyst) in unfavorable conditions, such as drying
ponds or lack of food.
7. Reproduction
Amoeba reproduces asexually, mainly by binary fission:
The nucleus divides first, followed by the division of cytoplasm, resulting in two identical
daughter cells.
Under unfavorable conditions, amoeba forms a cyst (encystment) and undergoes
multiple fission or sporulation, producing many daughter cells that are released when
conditions improve.
Summary Table: Life Processes in Amoeba
Life Process Description
Nutrition Holozoic; ingestion, digestion, absorption, assimilation, egestion
Respiration Diffusion of gases through cell membrane
Excretion Diffusion of wastes; contractile vacuole expels water and waste
Movement By pseudopodia (amoeboid movement)
Life Process Description
Osmoregulation Contractile vacuole maintains water balance
Irritability Responds to stimuli; can encyst in adverse conditions
Binary fission (mainly); multiple fission/encystment in adverse
Reproduction conditions
Conclusion
Amoeba, though unicellular, efficiently manages all life processes necessary for survival.
Its ability to move, feed, respond to the environment, regulate water, excrete wastes,
and reproduce makes it a successful organism in its habitat. These processes highlight
the complexity and adaptability of even the simplest forms of life.
