THE LIVING WORLD
Characteristics of Living Organisms:
1. Cellular Structure
2. Metabolism
3. Growth
4. Reproduction
5. Consciousness
Other characteristics of living beings include:
- Adaptation
- Lifespan
- Homeostasis
- Healing and repair
- Movement and variation
Q. What is a defining feature?
A. A feature is said to be defining if it fulfills two criteria:
a) If it is unexceptionally present in all organisms.
b) It should not be part of non-living objects.
1. Cellular Structure: It is the structural and functional unit of life. Cells are present in all living objects. Cells are not present in non-living objects. Therefore, it can be said that cellular structure is a defining feature.
2. Metabolism: (Gk: metabole = change / conversion)
All the organisms are made of chemicals -- these chemicals are constantly being made. These changes are called chemical reactions. All chemical reactions occurring inside our body constitute metabolism.
Metabolism comprises of two events: Anabolism and Catabolism
=> These metabolic reactions can occur in vivo or in vitro.
- Metabolism is a characteristic feature of all living organisms and it is absent in non-living objects. It can, therefore, be said that metabolism is a defining feature.
3. Growth:
Growth is defined as an irreversible increase in mass or overall size of our cell / organ or the whole organism. In other words, growth is an increase in body mass.
Growth occurs due to net results of two components of metabolism:
If anabolism > catabolism --- It leads to growth
If anabolism = catabolism --- no growth will occur
If anabolism < catabolism --- it leads to negative growth
Q. Compare plants and animals + growth in living and non-living with respect to growth?
=> Since growth is a characteristic of both living and nonliving objects. Growth is, therefore, a non-defining feature.
4. Reproduction:
It is a process of formation / production of offspring having features more or less similar to parents.
Asexual Reproduction: It involves single parent, it is therefore, uniparental. Besides, it does not involve fertilization of gametes.
Types of asexual reproduction:
Fish -- Fission (eg: binary fission in bacteria)
Fry -- Fragmentation (eg: in filamentous algae)
Really -- Regeneration (eg: Planaria)
Very -- Vegetative reproduction
Spicy: sporulation (eg: algae, fungi, bacteria)
Buddy -- Budding (eg: yeast, unicellular fungi, hydra)
Sexual reproduction: It involves two parents = biparental. Besides, it involves the formation of gametes and their fusion.
=> In unicellular organisms, growth and reproduction are synonymous. For instance in bacteria and amoeba -- increase in cell number is associated with the growth. On the other hand, in higher plants and animals, growth and reproduction are mutually exclusive events. A Mutually Exclusive term is used to describe a situation where the occurrence of one event is not influenced or caused by another. Mutually exclusive events never occur at the same time.
- Reproduction is not present universally. For instance Mule (a cross between male donkey [Jack] and female horse [Mare]) and worker bee. Both mule and worker bees are sterile.
=> Since reproduction is somewhere associated with growth in unicellular organisms and since reproduction is not present universally -- it can be considered as a non-defining feature.
5. Consciousness:
It is the ability to sense stimulus / environment and response to it. External stimulus can be physical, chemical or biological. It is unexceptionally shown by all living organisms. It can, therefore, be considered as a defining feature.
1. Cellular Structure
2. Metabolism
3. Growth
4. Reproduction
5. Consciousness
Other characteristics of living beings include:
- Adaptation
- Lifespan
- Homeostasis
- Healing and repair
- Movement and variation
Q. What is a defining feature?
A. A feature is said to be defining if it fulfills two criteria:
a) If it is unexceptionally present in all organisms.
b) It should not be part of non-living objects.
1. Cellular Structure: It is the structural and functional unit of life. Cells are present in all living objects. Cells are not present in non-living objects. Therefore, it can be said that cellular structure is a defining feature.
2. Metabolism: (Gk: metabole = change / conversion)
All the organisms are made of chemicals -- these chemicals are constantly being made. These changes are called chemical reactions. All chemical reactions occurring inside our body constitute metabolism.
Metabolism comprises of two events: Anabolism and Catabolism
=> These metabolic reactions can occur in vivo or in vitro.
- Metabolism is a characteristic feature of all living organisms and it is absent in non-living objects. It can, therefore, be said that metabolism is a defining feature.
3. Growth:
Growth is defined as an irreversible increase in mass or overall size of our cell / organ or the whole organism. In other words, growth is an increase in body mass.
Growth occurs due to net results of two components of metabolism:
If anabolism > catabolism --- It leads to growth
If anabolism = catabolism --- no growth will occur
If anabolism < catabolism --- it leads to negative growth
Q. Compare plants and animals + growth in living and non-living with respect to growth?
=> Since growth is a characteristic of both living and nonliving objects. Growth is, therefore, a non-defining feature.
4. Reproduction:
It is a process of formation / production of offspring having features more or less similar to parents.
Asexual Reproduction: It involves single parent, it is therefore, uniparental. Besides, it does not involve fertilization of gametes.
Types of asexual reproduction:
Fish -- Fission (eg: binary fission in bacteria)
Fry -- Fragmentation (eg: in filamentous algae)
Really -- Regeneration (eg: Planaria)
Very -- Vegetative reproduction
Spicy: sporulation (eg: algae, fungi, bacteria)
Buddy -- Budding (eg: yeast, unicellular fungi, hydra)
Sexual reproduction: It involves two parents = biparental. Besides, it involves the formation of gametes and their fusion.
=> In unicellular organisms, growth and reproduction are synonymous. For instance in bacteria and amoeba -- increase in cell number is associated with the growth. On the other hand, in higher plants and animals, growth and reproduction are mutually exclusive events. A Mutually Exclusive term is used to describe a situation where the occurrence of one event is not influenced or caused by another. Mutually exclusive events never occur at the same time.
- Reproduction is not present universally. For instance Mule (a cross between male donkey [Jack] and female horse [Mare]) and worker bee. Both mule and worker bees are sterile.
=> Since reproduction is somewhere associated with growth in unicellular organisms and since reproduction is not present universally -- it can be considered as a non-defining feature.
5. Consciousness:
It is the ability to sense stimulus / environment and response to it. External stimulus can be physical, chemical or biological. It is unexceptionally shown by all living organisms. It can, therefore, be considered as a defining feature.
It does not matter if you are a biology student or not, we all should learn about animals and plants. This is very helpful. Thank you for sharing.
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